�����������������

Citation: Syamsudin, T.S.; Kirana, R.;

Karjadi, A.K.; Faizal, A.

Characteristics of Chili (Capsicum

annuum L.) That Are Resistant and

Susceptible to Oriental Fruit Fly

(Bactrocera dorsalis Hendel)

Infestation. Horticulturae 2022, 8, 314.

https://doi.org/10.3390/

horticulturae8040314

Academic Editors: Awraris

Derbie Assefa and

Minaleshewa Atilabachew

Received: 24 February 2022

Accepted: 5 April 2022

Published: 8 April 2022

Publisher’s Note: MDPI stays neutral

with regard to jurisdictional claims in

published maps and institutional affil-

iations.

Copyright: © 2022 by the authors.

Licensee MDPI, Basel, Switzerland.

This article is an open access article

distributed under the terms and

conditions of the Creative Commons

Attribution (CC BY) license (https://

creativecommons.org/licenses/by/

4.0/).

horticulturae

Article

Characteristics of Chili (Capsicum annuum L.) That AreResistant and Susceptible to Oriental Fruit Fly(Bactrocera dorsalis Hendel) InfestationTati Suryati Syamsudin 1,*, Rinda Kirana 2, Asih Kartasih Karjadi 2 and Ahmad Faizal 1

1 School of Life Sciences and Technology, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung 40132, Indonesia;afaizal@sith.itb.ac.id

2 Indonesian Vegetable Research Institute (IVEGRI), Jalan Tangkuban Parahu 517, Lembang 40391, Indonesia;rindakirana@gmail.com (R.K.); asihkk@yahoo.com (A.K.K.)

* Correspondence: tati@sith.itb.ac.id

Abstract: The response of chili (Capsicum annuum L.) to oriental fruit fly infestation (Bactrocera dorsalis)is highly variable among varieties. The differences in the resistance level of chili to oriental fruit flyinfestation are presumed to be determined by the characteristics of chili fruit. This study aims toevaluate the morphochemical characteristics of different resistance levels of chili fruits to orientalfruit fly infestation in field conditions. The field test was carried out at the research station of theIndonesian Vegetable Research Institute (IVEGRI), West Java, Indonesia. Six essential derivatives ofC. annuum from IVEGRI, consisting of three resistant and three susceptible varieties, were establishedin a prior investigation. The test population included 132 plants, with 22 plants planted for eachvariety. The resistance parameters observed were oviposition incidence, yield loss, fitness index,and chili fruit characteristics (morphology, nutrition, volatile compounds). The results showed thatthere were morphological and chemical differences between the varieties resistant and susceptibleto oriental fruit fly infestation. The morphological characteristics of the fruit (width, weight, andthickness of fruit flesh) and fruit shape at pedicel attachment had an impact on the resistance levelof fruit flies. Meanwhile, volatile compounds, water content, carbohydrates, and fiber content wereamong the chemical features that influenced oriental fruit fly infestation.

Keywords: antixenosis; Bactrocera dorsalis; morphology; nutrition; volatile compounds

1. Introduction

The oriental fruit fly (Bactrocera dorsalis) is a major insect pest in chili cultivation inIndonesia that has an economic impact. The damage begins when the female fruit flies layeggs on chili fruit. After two days, the eggs hatch into larvae and consume the fruit flesh,making the fruit rotten and unable to be sold, causing farmers to lose their crops. Severalstudies have reported that the rate of loss of chili fruits by fruit flies varies between 40 and60% and could reach up to 100% loss if there is no fruit fly control [1,2].

The resistance of chili fruits to fruit fly infestation varies across cultivars, as shown bythe deterrent index for antixenosis and the fitness index for antibiosis [3]. Experiments bySyamsudin et al. [3] on fifty chili varieties of fruit fly infestation in the laboratory showedthat the prevention of oviposition by the chosen method was in the range from 46.01% to100%; however, the no-choice method was in the range from 11.11% to 99.07%, while thefitness index of oriental fruit fly feeding on chili fruits was in the range from 0.03 to 6.74.These results indicate that the resistance of chili to oriental fruit fly infestation is determinedby variety. The difference in the resistance level of chili varieties to fruit flies might bedetermined by the characteristics of chili fruits. Bosland and Votava [4] reported thatchili fruits exhibit a wide range of morphological and chemical features. Morphologically,chili fruits have a high degree of variability in their characteristics (shape, color, and size).

Horticulturae 2022, 8, 314. https://doi.org/10.3390/horticulturae8040314 https://www.mdpi.com/journal/horticulturae

Horticulturae 2022, 8, 314 2 of 15

Meanwhile, based on their chemical composition, chili fruits vary in terms of water content,carbohydrates, fats, amino acids, proteins, fragrances, anthocyanins, antioxidants, vitamins,carotenoids, and capsaicinoids. Several studies have shown that the chemical compositionof chili changes according to the variety [5,6]. As a result, the diversity of chili fruit traitsmay have an influence on the resistance level of varieties to fruit flies.

Chili fruits can be protected from oriental fruit fly infestation if they are able to preventfemale fruit flies from laying eggs and inhibit larval growth and development. A previousstudy has identified resistant and susceptible varieties of oriental fruit fly infestation andestablished a correlation between fruit morphological characteristics and the resistancelevel of fifty chili varieties to fruit flies. Large-fruited chili varieties from the species ofC. annuum (large chili) are more sensitive than small-fruited chili varieties from C. annuum(curly chili) and C. frutescens (cayenne pepper) species [3]. The resistance level of largechili and curly chili varieties to fruit fly infestation can be determined by the differencesin the characteristics of each variety. This study aims to evaluate the morphochemicalcharacteristics of different resistance levels of chili fruits to oriental fruit fly infestationin field conditions. This in-depth study is expected to help in the understanding of themechanism behind chili resistance to oriental fruit fly infestation and hopefully serve asthe basis for the initiation of plant breeding programs for chili resistance to fruit flies.

2. Materials and Methods2.1. Study Site

The research was conducted at the research station of the Indonesian Vegetable ResearchInstitute (IVEGRI) (6◦47′57′′ S, 107◦39′01′′ E), at 1250 m above sea level (West Java, Indonesia).

2.2. Plant Materials

Six essential derivatives of IVEGRI chili varieties from the species C. annuum wereused for these experiments, consisting of three resistant varieties (RK-1, RK-2, and RK-3)and three susceptible varieties (RK-4, RK-5, and RK-6) identified from previous research [3].Each variety was planted in a plot measuring 1 m × 6 m. Each plot was planted with22 individual plants, resulting in a total plant population of 132 plants. The chili cultivationtechnique followed the recommendation of IVEGRI [7]. Chili seeds were sown in a nurserytray using a mix of sterile soil medium and organic fertilizer (1:1). Subsequently, one-month-old seedlings were transplanted into planting plots in the field. Plants were maintainedby regular weeding, watering, fertilizer application, pest control against thrips, aphids,and mites using a commercial pesticide containing profenofos (1 mL/L), imidacloprid(0.25 mL/L), and mancozeb (2 g/L).

2.3. Resistance of Chili to Infestation of Fruit Flies

In the field, the resistance of chili fruit to oriental fruit fly infestation was determinedby counting oviposition incidence, yield loss, and fitness index. Fruit fly ovipositionincidence was determined by the number of infested plants divided by the total numberof plants. Yield loss was calculated at the harvest period based on the number of infestedfruits divided by the total number of harvested fruits. Infested fruits were identified bythe presence of ovipositor punctures and/or larvae inside the fruits. The fitness index wascalculated using the number and respective weight of pupae, the duration of egg to pupa,and the duration of egg to imago, as described by Syamsudin et al. [3].

2.4. Morphological Characteristics of Chili Fruit

Analysis of chili morphological characteristics focused on 22 fruit traits accordingto the International Plant Genetic Resources Institute [8]. Observation of morpholog-ical characteristics was conducted based on 22 characteristics of chili fruits. The fruitcharacteristics were number of days until fruiting (D), anthocyanin spots or stripes (A),fruit color before at intermediate stage (FC), fruit set (FS), fruit-bearing period (FB), fruitcolor at maturity stage (FCM), fruit shape (FSH), fruit length (FL), fruit width (FW), fruit

Horticulturae 2022, 8, 314 3 of 15

weight (FWG), fruit pedicel length (FP), fruit wall thickness (FWT), fruit shape at pedicelattachment (FSHP), neck at base of fruit (N), fruit shape at blossom end (FSHB), fruit blos-som end appendage (FBA), fruit cross-sectional corrugation (FCS), number of locules (N),fruit surface (FSU), ripe fruit persistence (RFP), placenta length (PL), and varietal mixturecondition (VM).

2.5. Analysis of Volatile Compounds

Volatile compounds were analyzed using gas chromatography–mass spectr-ometry (GC–MS) following the method described by Junior et al. [9] and Kirana et al. [10]with several adjustments. Fruit samples were extracted using the solid-phase microex-traction (SPME) method. Four grams of chili fruits was injected into a 40 mL SPME vialcontaining polytetrafluoroethylene (PTFE)/silicone septa and incubated at 30 ◦C for 30 min.Samples were taken using SPME fiber 50/30 mm divinylbenzene/carboxen/polydimethyl-siloxane-DVB/CAR/PDMS (Supelco Co., Bellefonte, PA, USA) and injected in spitless modeat 45 ◦C, held for 2 min, and increased to 250 ◦C in increments of 5 ◦C/min for 5 min. Columnseparation used DB-5 MS (Agilent, Santa Carla, CA, USA), and the carrier gas was helium ata rate of 1 mL/min.

Volatile compounds were identified based on the retention time on the GC (Agilent7890 A) and mass spectrophotometer (Agilent 5975 C) apparatus. The relative volatile com-pound content data were determined using the NIST08 library. Then, they were tabulatedand calculated for the presence index of volatile compounds as the ratio of the presenceof volatile compounds to the total detected volatile compounds. The detected volatilecompounds were selected based on the area and degree of similarity to the library [11,12].

2.6. Oriental Fruit Fly Response to Selected Volatile Compounds

Determination of selected volatile compounds was tested on oriental fruit fly responseusing the preference choice method [13,14] with several adjustments. The volatile com-pounds of interest were dissolved in 100 ppm methanol. A 200 µL volume of the solutionwas dripped on a black cloth attached to the artificial egg-laying place, while 200 µL ofmethanol was used as a control. Twenty-five pairs of fruit flies (28 days old) were placedin cages (20 cm × 20 cm × 20 cm). The number of ovipositions and the number of eggsoviposited were recorded. The test was repeated 16 times. Observation was conductedfrom 11.00 to 15.00 h West Indonesian Time.

2.7. Analysis of Nutritional Content

Chili fruits (without seeds and placenta) were grounded into powder and subjected tonutritional content analysis to determine water, carbohydrate, and fiber content [15].

2.7.1. Water Content

Two grams of the sample was dried in an oven at 105 ◦C until a constant weight wasreached. Water content (%) was determined by dividing the weight of the dried sample bythe weight of the sample before drying.

2.7.2. Carbohydrate Content

Five grams of the sample was placed into an Erlenmeyer flask, followed by the additionof 200 mL of 30%HCl solution, and then heated. After cooling, the solution was neutralizedwith 10% NaOH. The solution was then transferred to a volumetric flask with distilledwater added up to 500 mL and filtered. A total of 10 mL of the solution was pipettedand added to a 250 mL Erlenmeyer flask with Luff Schoorl solution (that was filtered andsupplemented with a few boiling stones), followed by the addition of 15 mL of distilledwater. Erlenmeyer flasks containing samples and blanks (without samples) were installedon a standing cooler before being heated. The heater was regulated so that the contents ofthe Erlenmeyer flasks could boil within ±3 min and were maintained for 10 min. It wasthen cooled rapidly under flowing water. Subsequently, 15 mL of 20% I2KI solution and

Horticulturae 2022, 8, 314 4 of 15

25 mL of 25% H2SO4 were unhurriedly added. After the reaction was complete, titrationwas carried out with thiosulfate (Na2S2O3) 0.1 N solution and starch solution indicator.Carbohydrate content was calculated using the formula (At × Fp)/g) × 0.90 × 100), whereAt is the number in the Luff Schoorl table, Fp is the dilution factor, and g is the sampleweight (mg).

2.7.3. Fiber Content

Two grams of the sample was weighed on a preweighed glass. The glazed glass wasattached to the extraction heater, and 50 mL of 1.25% H2SO4 was added and boiled for30 min. Then, it was rinsed with hot water before adding 50 mL of 3.25% NaOH andboiling for 30 min. Subsequently, it was rinsed with 96% ethanol and heated in an ovenat 105 ◦C for 1 h. The sample was removed from the oven and cooled in a desiccator for30 min. Drying and cooling were repeated until a constant sample weight was reached.Fiber content (%) was obtained by calculating the weight of the sample after drying dividedby the weight of the sample before drying.

2.8. Data Analysis

Differences in observational parameters between varieties were tested using theKruskal–Wallis statistical test. Multivariate analysis among parameters used principalcomponent analysis. Data analysis used the PAST program version 3.14 [16] and Metabo-Analyst 5.0 [17].

3. Results3.1. Resistance Characteristics

Resistant varieties RK-1, RK-2, and RK-3 showed lower incidence, yield loss, and fitnessindex values than susceptible RK-4, RK-5, and RK-6 varieties (Figure 1). The average oviposi-tion incidence of fruit flies was higher in susceptible varieties (25.9–41.6%) than in resistantvarieties (12.8–17.2%) (Figure 1a). Susceptible varieties also had higher yield loss (17.1–36.5%)than resistant varieties (2.4–7.5%) (Figure 1b). Furthermore, the average fitness index washigher in susceptible varieties (1.9–8.2) than in resistant varieties (0.3–0.9) (Figure 1c). RK-5was the most susceptible variety, with an average fitness index of 8.2.

3.2. Morphological Characteristics of Chili Fruit

Observation of 22 characteristics of fruits revealed that 10 characteristics differedacross varieties, while the other 12 characteristics showed no variation among the sixvarieties tested. Eight of the ten characteristics showed a significant difference amongvarieties, while the other two did not (Supplementary Table S1). The fruit morphologicalcharacteristics that are capable of discriminating resistant and susceptible varieties includewidth, weight, fruit set, fruit wall thickness, fruit shape at pedicel attachment, and fruitsurface (Figures 2 and 3). In comparison to susceptible varieties, resistant varieties had asignificantly narrower fruit width (Figure 2a), significantly lighter fruit weight (Figure 2b),significantly higher fruit set (Figure 2c), significantly smaller fruit wall thickness (Figure 2d),significantly smaller fruit shape at the pedicel attachment (Figure 2e), and significantlyrougher fruit surface (Figure 2f).

Horticulturae 2022, 8, 314 5 of 15Horticulturae 2022, 8, x FOR PEER REVIEW 5 of 15

(a) (b)

(c)

Figure 1. Resistance of six chili varieties to oriental fruit fly infestation in the field, as shown by (a)

oviposition incidence, (b) yield loss, and (c) fitness index. RK-1, RK-2, and RK-3 are resistance vari-

eties; RK-4, RK-5, and RK-6 are susceptible varieties. Different letters above each column indicate

significant differences between the mean values.

3.2. Morphological Characteristics of Chili Fruit

Observation of 22 characteristics of fruits revealed that 10 characteristics differed

across varieties, while the other 12 characteristics showed no variation among the six va-

rieties tested. Eight of the ten characteristics showed a significant difference among vari-

eties, while the other two did not (Supplementary Table S1). The fruit morphological char-

acteristics that are capable of discriminating resistant and susceptible varieties include

width, weight, fruit set, fruit wall thickness, fruit shape at pedicel attachment, and fruit

surface (Figures 2 and 3). In comparison to susceptible varieties, resistant varieties had a

significantly narrower fruit width (Figure 2a), significantly lighter fruit weight (Figure

2b), significantly higher fruit set (Figure 2c), significantly smaller fruit wall thickness (Fig-

ure 2d), significantly smaller fruit shape at the pedicel attachment (Figure 2e), and signif-

icantly rougher fruit surface (Figure 2f).

Figure 1. Resistance of six chili varieties to oriental fruit fly infestation in the field, as shown by(a) oviposition incidence, (b) yield loss, and (c) fitness index. RK-1, RK-2, and RK-3 are resistancevarieties; RK-4, RK-5, and RK-6 are susceptible varieties. Different letters above each column indicatesignificant differences between the mean values.

Horticulturae 2022, 8, x FOR PEER REVIEW 6 of 15

(a) (b)

(c) (d)

(e) (f)

Figure 2. Characteristics of chili fruits against oriental fruit fly infestation, as shown by (a) fruit

width, (b) fruit weight, (c) fruit set, (d) fruit wall thickness, (e) fruit shape at pedicel attachment,

and (f) fruit surface. Different letters above each column indicate significant differences between the

mean values.

Figure 2. Cont.

Horticulturae 2022, 8, 314 6 of 15

Horticulturae 2022, 8, x FOR PEER REVIEW 6 of 15

(a) (b)

(c) (d)

(e) (f)

Figure 2. Characteristics of chili fruits against oriental fruit fly infestation, as shown by (a) fruit

width, (b) fruit weight, (c) fruit set, (d) fruit wall thickness, (e) fruit shape at pedicel attachment,

and (f) fruit surface. Different letters above each column indicate significant differences between the

mean values.

Figure 2. Characteristics of chili fruits against oriental fruit fly infestation, as shown by (a) fruit width,(b) fruit weight, (c) fruit set, (d) fruit wall thickness, (e) fruit shape at pedicel attachment, and (f) fruitsurface. Different letters above each column indicate significant differences between the mean values.

Horticulturae 2022, 8, x FOR PEER REVIEW 7 of 15

Figure 3. Morphological performance of chili fruits used in this. RK-1, RK-2, and RK-3 are resistant

varieties; RK-4, RK-5, and RK-6 are susceptible varieties.

The fruit morphological characteristics (width, weight, wall thickness, and base

shape of fruits) were positively correlated (value: >0.6) with the incidence, yield loss, and

fitness index (Figure 4). Based on the position of the variety in the quadrant, the most

susceptible variety to oriental fruit fly infestation was RK-5 since it was in the quadrant

with the resistance parameter, while the most resistant variety was RK-3, as it was in the

quadrant opposite the resistance parameter (Figure 5).

Figure 4. Correlation of morphological and resistance characteristics of chili fruits: days to fruiting

(D), fruit set (FS), fruit-bearing period (FBP), fruit color at maturity stage, fruit shape, fruit length

(FL), fruit width (FW), fruit weight (FWG), fruit pedicel length (FPL), fruit wall thickness (FWT),

fruit shape at pedicel attachment (FSHP), fruit surface (FSU), ripe fruit persistence, placenta length,

and varietal mixture condition. Oviposition incidence (OI), yield loss (YL), and fitness index (FI).

Figure 3. Morphological performance of chili fruits used in this. RK-1, RK-2, and RK-3 are resistantvarieties; RK-4, RK-5, and RK-6 are susceptible varieties.

The fruit morphological characteristics (width, weight, wall thickness, and base shapeof fruits) were positively correlated (value: >0.6) with the incidence, yield loss, and fitnessindex (Figure 4). Based on the position of the variety in the quadrant, the most susceptiblevariety to oriental fruit fly infestation was RK-5 since it was in the quadrant with theresistance parameter, while the most resistant variety was RK-3, as it was in the quadrantopposite the resistance parameter (Figure 5).

Horticulturae 2022, 8, 314 7 of 15

Horticulturae 2022, 8, x FOR PEER REVIEW 7 of 15

Figure 3. Morphological performance of chili fruits used in this. RK-1, RK-2, and RK-3 are resistant

varieties; RK-4, RK-5, and RK-6 are susceptible varieties.

The fruit morphological characteristics (width, weight, wall thickness, and base

shape of fruits) were positively correlated (value: >0.6) with the incidence, yield loss, and

fitness index (Figure 4). Based on the position of the variety in the quadrant, the most

susceptible variety to oriental fruit fly infestation was RK-5 since it was in the quadrant

with the resistance parameter, while the most resistant variety was RK-3, as it was in the

quadrant opposite the resistance parameter (Figure 5).

Figure 4. Correlation of morphological and resistance characteristics of chili fruits: days to fruiting

(D), fruit set (FS), fruit-bearing period (FBP), fruit color at maturity stage, fruit shape, fruit length

(FL), fruit width (FW), fruit weight (FWG), fruit pedicel length (FPL), fruit wall thickness (FWT),

fruit shape at pedicel attachment (FSHP), fruit surface (FSU), ripe fruit persistence, placenta length,

and varietal mixture condition. Oviposition incidence (OI), yield loss (YL), and fitness index (FI).

Figure 4. Correlation of morphological and resistance characteristics of chili fruits: days to fruiting (D),fruit set (FS), fruit-bearing period (FBP), fruit color at maturity stage, fruit shape, fruit length (FL),fruit width (FW), fruit weight (FWG), fruit pedicel length (FPL), fruit wall thickness (FWT), fruitshape at pedicel attachment (FSHP), fruit surface (FSU), ripe fruit persistence, placenta length, andvarietal mixture condition. Oviposition incidence (OI), yield loss (YL), and fitness index (FI).

Horticulturae 2022, 8, x FOR PEER REVIEW 8 of 15

Figure 5. Morphological and resistance characteristics of chili fruits based on PCA: days to fruiting

(D), fruit-bearing period (FB), fruit length (FL), fruit width (FW), fruit weight (FWG), fruit pedicel

length (FP), fruit wall thickness (FWT), fruit shape at pedicel attachment (FSHP). Oviposition inci-

dence (OI), yield loss (YL), and fitness index (FI).

3.3. Characteristics of Volatile Compounds

Fifty-eight types of volatile compounds were detected through GC–MS analysis.

Chromatogram profiles between resistant and susceptible varieties of chili showed a dif-

ference except for RK-1. The presence of volatile compounds was more varied in suscep-

tible chili varieties than in resistant varieties (Figure 6). Seventeen of the fifty-eight volatile

compounds detected by GC–MS had an area greater than 2% (Table 1). Further analysis

of the 17 dominant volatile compounds showed that 8 volatile compounds (furan, 2-me-

thyl-; formic acid, 2-methylbuthyl ester; furan, 3-butyltetrahydro-2-methyl-, trans-; 1,9-

decadiyne; trans-3-decene; 4-octene, 2,6-dimethyl-, [S-(E)]-; cis-2,6-dimethyl-2,6-octadi-

ene; β-cis-ocimene) were correlated with oviposition incidence (Figure 7), and two com-

pounds had a quality value above 90%. Interestingly, β-cis-ocimene was only detected in

susceptible variety RK-5 in a significant amount (Table 1).

Figure 6. Presence of volatile compounds released resistant and susceptible varieties of chili fruit.

Different letters above each column indicate significant differences between the mean values.

Figure 5. Morphological and resistance characteristics of chili fruits based on PCA: days to fruit-ing (D), fruit-bearing period (FB), fruit length (FL), fruit width (FW), fruit weight (FWG), fruitpedicel length (FP), fruit wall thickness (FWT), fruit shape at pedicel attachment (FSHP). Ovipositionincidence (OI), yield loss (YL), and fitness index (FI).

Horticulturae 2022, 8, 314 8 of 15

3.3. Characteristics of Volatile Compounds

Fifty-eight types of volatile compounds were detected through GC–MS analysis. Chro-matogram profiles between resistant and susceptible varieties of chili showed a differenceexcept for RK-1. The presence of volatile compounds was more varied in susceptible chili va-rieties than in resistant varieties (Figure 6). Seventeen of the fifty-eight volatile compoundsdetected by GC–MS had an area greater than 2% (Table 1). Further analysis of the 17 dom-inant volatile compounds showed that 8 volatile compounds (furan, 2-methyl-; formicacid, 2-methylbuthyl ester; furan, 3-butyltetrahydro-2-methyl-, trans-; 1,9-decadiyne; trans-3-decene; 4-octene, 2,6-dimethyl-, [S-(E)]-; cis-2,6-dimethyl-2,6-octadiene; β-cis-ocimene)were correlated with oviposition incidence (Figure 7), and two compounds had a qualityvalue above 90%. Interestingly, β-cis-ocimene was only detected in susceptible varietyRK-5 in a significant amount (Table 1).

Horticulturae 2022, 8, x FOR PEER REVIEW 8 of 15

Figure 5. Morphological and resistance characteristics of chili fruits based on PCA: days to fruiting

(D), fruit-bearing period (FB), fruit length (FL), fruit width (FW), fruit weight (FWG), fruit pedicel

length (FP), fruit wall thickness (FWT), fruit shape at pedicel attachment (FSHP). Oviposition inci-

dence (OI), yield loss (YL), and fitness index (FI).

3.3. Characteristics of Volatile Compounds

Fifty-eight types of volatile compounds were detected through GC–MS analysis.

Chromatogram profiles between resistant and susceptible varieties of chili showed a dif-

ference except for RK-1. The presence of volatile compounds was more varied in suscep-

tible chili varieties than in resistant varieties (Figure 6). Seventeen of the fifty-eight volatile

compounds detected by GC–MS had an area greater than 2% (Table 1). Further analysis

of the 17 dominant volatile compounds showed that 8 volatile compounds (furan, 2-me-

thyl-; formic acid, 2-methylbuthyl ester; furan, 3-butyltetrahydro-2-methyl-, trans-; 1,9-

decadiyne; trans-3-decene; 4-octene, 2,6-dimethyl-, [S-(E)]-; cis-2,6-dimethyl-2,6-octadi-

ene; β-cis-ocimene) were correlated with oviposition incidence (Figure 7), and two com-

pounds had a quality value above 90%. Interestingly, β-cis-ocimene was only detected in

susceptible variety RK-5 in a significant amount (Table 1).

Figure 6. Presence of volatile compounds released resistant and susceptible varieties of chili fruit.

Different letters above each column indicate significant differences between the mean values.

Figure 6. Presence of volatile compounds released resistant and susceptible varieties of chili fruit.Different letters above each column indicate significant differences between the mean values.

Table 1. Dominant volatile compounds from six chili varieties detected by GC–MS.

No. RT 1

(min.)Volatile Compounds Q 2 (%)

Relative Area (%)

RK-1 RK-2 RK-3 RK-4 RK-5 RK-6

1 4.36 Furan, 2-methyl- 91 0 0 0 10.52 12.43 02 4.6 1-Hexyne, 5-methyl- 38 11.7 0 0 0 0 03 5.87 Silanediol, dimethyl 2 5.21 0 0 17.26 0 04 6.03 Acetamide, 2-fluoro 3 10.26 3.91 0 0 0 05 6.19 Formic acid, 2-methyl butyl ester 35 0 0 0 0 0 28.46 9.52 Furan, 3-butyltetrahydro-2-methyl-, trans- 9 0 0 0 0 0 5.367 11.41 1,9-Decadiyne 27 0 0 3.33 0 0 08 11.84 trans-3-Decene 37 0 0 0 0 0 3.29 12.19 4-Octene, 2,6-dimethyl-, [S-(E)]- 64 0 0 0 0 0 2.75

10 13.14 cis-2,6-Dimethyl-2,6-octadiene 80 0 0 0 0 5.19 011 14.5 β-cis-Ocimene 91 0 0 0 0 17.81 0

12 21.74 1,4-Benzenedi-methanethiol, 2TBDMSderivates 36 0 2.36 0 0 0 0

13 42.25 2-Tetradecanol 35 0 0 0 2.78 0 014 43.1 1-Octadecene 35 7.23 0 0 0 0 015 43.61 Butyl dodecyl ether 35 7.51 0 0 4.07 0 016 44.26 Isobutyl nonyl carbonate 50 0 0 0 2.25 0 017 46.38 1-Decanol, 2-hexyl 22 12.67 0 0 0 0 0

1 RT = retention time; 2 Q = quality.

Horticulturae 2022, 8, 314 9 of 15

Horticulturae 2022, 8, x FOR PEER REVIEW 9 of 15

Table 1. Dominant volatile compounds from six chili varieties detected by GC–MS

No. RT 1

(min.)

Volatile Com-

pounds

Q 2

(%)

Relative Area (%)

RK-1 RK-2 RK-3 RK-4 RK-5 RK-6

1 4.36 Furan, 2-methyl- 91 0 0 0 10.52 12.43 0

2 4.6 1-Hexyne, 5-me-

thyl-

38 11.7 0 0 0 0 0

3 5.87 Silanediol, dimethyl 2 5.21 0 0 17.26 0 0

4 6.03 Acetamide, 2-fluoro 3 10.26 3.91 0 0 0 0

5 6.19 Formic acid, 2-me-

thyl butyl ester

35 0 0 0 0 0 28.4

6 9.52 Furan, 3-butyltetra-

hydro-2-methyl-,

trans-

9 0 0 0 0 0 5.36

7 11.41 1,9-Decadiyne 27 0 0 3.33 0 0 0

8 11.84 trans-3-Decene 37 0 0 0 0 0 3.2

9 12.19 4-Octene, 2,6-dime-

thyl-, [S-(E)]-

64 0 0 0 0 0 2.75

10 13.14 cis-2,6-Dimethyl-

2,6-octadiene

80 0 0 0 0 5.19 0

11 14.5 β-cis-Ocimene 91 0 0 0 0 17.81 0

12 21.74 1,4-Benzenedi-me-

thanethiol, 2TBDMS

derivates

36 0 2.36 0 0 0 0

13 42.25 2-Tetradecanol 35 0 0 0 2.78 0 0

14 43.1 1-Octadecene 35 7.23 0 0 0 0 0

15 43.61 Butyl dodecyl ether 35 7.51 0 0 4.07 0 0

16 44.26 Isobutyl nonyl car-

bonate

50 0 0 0 2.25 0 0

17 46.38 1-Decanol, 2-hexyl 22 12.67 0 0 0 0 0 1 RT = retention time; 2 Q = quality.

Figure 7. Correlation of seventeen volatile compounds to oviposition incidence (OI) of oriental fruit

fly in chili fruit. The number at the horizontal axis represents the volatile compounds described in

Table 1.

Principal component analysis also mapped the position of resistant varieties and sus-

ceptible varieties in each quadrant. The volatile compounds released by RK-5 were similar

to those emitted during oviposition incidence, and RK-5 was identified as the variety with

the highest oviposition incidence (Figure 8).

Figure 7. Correlation of seventeen volatile compounds to oviposition incidence (OI) of oriental fruit flyin chili fruit. The number at the horizontal axis represents the volatile compounds described in Table 1.

Principal component analysis also mapped the position of resistant varieties andsusceptible varieties in each quadrant. The volatile compounds released by RK-5 weresimilar to those emitted during oviposition incidence, and RK-5 was identified as thevariety with the highest oviposition incidence (Figure 8).

Horticulturae 2022, 8, x FOR PEER REVIEW 10 of 15

Figure 8. Relationship of volatile compounds released by six chili varieties (RK1-RK6) with the ovi-

position incidence (OI) of oriental fruit fly.

A further test to confirm that insects were attracted to β-cis-ocimene showed that

female fruit flies responded to the volatile compounds (ocimene) by increasing the num-

ber of ovipositions (Figure 9a) and eggs laid (Figure 9b) compared to the control treat-

ment.

(a) (b)

Figure 9. Response of oriental fruit fly to β-cis-ocimene, as shown by the number of ovipositions (a)

and eggs laid (b). Note: β-cis-ocimene (O) and control (C). Different letters above each column in-

dicate significant differences between the mean values.

3.4. Nutritional Characteristics

In this study, the nutritional characteristics of chili were tested, including water, car-

bohydrates, and fiber content. The results showed that there were significant differences

in water content between varieties (p = 0.0004), as susceptible varieties had higher water

content compared to resistant chili varieties except for RK-5 (Figure 10a). The carbohy-

drate content of resistant chili varieties was significantly lower than susceptible chili va-

rieties (p = 0.0005) (Figure 10b). On the other hand, resistant varieties had a considerably

higher fiber content than susceptible chili varieties (p = 0.0004) (Figure 10c).

Figure 8. Relationship of volatile compounds released by six chili varieties (RK1-RK6) with theoviposition incidence (OI) of oriental fruit fly.

A further test to confirm that insects were attracted to β-cis-ocimene showed thatfemale fruit flies responded to the volatile compounds (ocimene) by increasing the numberof ovipositions (Figure 9a) and eggs laid (Figure 9b) compared to the control treatment.

Horticulturae 2022, 8, 314 10 of 15

Horticulturae 2022, 8, x FOR PEER REVIEW 10 of 15

Figure 8. Relationship of volatile compounds released by six chili varieties (RK1-RK6) with the ovi-

position incidence (OI) of oriental fruit fly.

A further test to confirm that insects were attracted to β-cis-ocimene showed that

female fruit flies responded to the volatile compounds (ocimene) by increasing the num-

ber of ovipositions (Figure 9a) and eggs laid (Figure 9b) compared to the control treat-

ment.

(a) (b)

Figure 9. Response of oriental fruit fly to β-cis-ocimene, as shown by the number of ovipositions (a)

and eggs laid (b). Note: β-cis-ocimene (O) and control (C). Different letters above each column in-

dicate significant differences between the mean values.

3.4. Nutritional Characteristics

In this study, the nutritional characteristics of chili were tested, including water, car-

bohydrates, and fiber content. The results showed that there were significant differences

in water content between varieties (p = 0.0004), as susceptible varieties had higher water

content compared to resistant chili varieties except for RK-5 (Figure 10a). The carbohy-

drate content of resistant chili varieties was significantly lower than susceptible chili va-

rieties (p = 0.0005) (Figure 10b). On the other hand, resistant varieties had a considerably

higher fiber content than susceptible chili varieties (p = 0.0004) (Figure 10c).

Figure 9. Response of oriental fruit fly to β-cis-ocimene, as shown by the number of ovipositions(a) and eggs laid (b). Note: β-cis-ocimene (O) and control (C). Different letters above each columnindicate significant differences between the mean values.

3.4. Nutritional Characteristics

In this study, the nutritional characteristics of chili were tested, including water,carbohydrates, and fiber content. The results showed that there were significant differencesin water content between varieties (p = 0.0004), as susceptible varieties had higher watercontent compared to resistant chili varieties except for RK-5 (Figure 10a). The carbohydratecontent of resistant chili varieties was significantly lower than susceptible chili varieties(p = 0.0005) (Figure 10b). On the other hand, resistant varieties had a considerably higherfiber content than susceptible chili varieties (p = 0.0004) (Figure 10c).

Horticulturae 2022, 8, x FOR PEER REVIEW 11 of 15

(a) (b)

(c)

Figure 10. Nutritional characteristics of six chili varieties (RK1–RK6) on (a) water content, (b) car-

bohydrate content, and (c) fiber content. Different letters above each column indicate significant

differences between the mean values.

Principal component analysis revealed a correlation between the nutritional charac-

teristics of chili fruits and their resistance level to oriental fruit fly infestation. Water con-

tent (WC) and carbohydrates (C) were positively correlated with the fitness index (IF)

(correlation coefficients were 0.79 and 0.90, respectively). Meanwhile, the fiber content (F)

was negatively correlated with the fitness index (correlation coefficient was −0.92) (Figure

11).

Figure 11. Correlation of water content (WC), carbohydrate content (C), and fiber content (F) with

the fitness index (FI) of oriental fruit fly in six chili varieties.

Figure 10. Nutritional characteristics of six chili varieties (RK1–RK6) on (a) water content, (b)carbohydrate content, and (c) fiber content. Different letters above each column indicate significantdifferences between the mean values.

Horticulturae 2022, 8, 314 11 of 15

Principal component analysis revealed a correlation between the nutritional charac-teristics of chili fruits and their resistance level to oriental fruit fly infestation. Water con-tent (WC) and carbohydrates (C) were positively correlated with the fitness index (IF) (cor-relation coefficients were 0.79 and 0.90, respectively). Meanwhile, the fiber content (F) wasnegatively correlated with the fitness index (correlation coefficient was −0.92) (Figure 11).

Horticulturae 2022, 8, x FOR PEER REVIEW 11 of 15

(a) (b)

(c)

Figure 10. Nutritional characteristics of six chili varieties (RK1–RK6) on (a) water content, (b) car-

bohydrate content, and (c) fiber content. Different letters above each column indicate significant

differences between the mean values.

Principal component analysis revealed a correlation between the nutritional charac-

teristics of chili fruits and their resistance level to oriental fruit fly infestation. Water con-

tent (WC) and carbohydrates (C) were positively correlated with the fitness index (IF)

(correlation coefficients were 0.79 and 0.90, respectively). Meanwhile, the fiber content (F)

was negatively correlated with the fitness index (correlation coefficient was −0.92) (Figure

11).

Figure 11. Correlation of water content (WC), carbohydrate content (C), and fiber content (F) with

the fitness index (FI) of oriental fruit fly in six chili varieties.

Figure 11. Correlation of water content (WC), carbohydrate content (C), and fiber content (F) withthe fitness index (FI) of oriental fruit fly in six chili varieties.

Principal component analysis also mapped the position of the varieties tested. Basedon the quadrant position, the RK-5 variety was shown to be the most susceptible to orientalfruit fly infestation since it was in the same quadrant as the fitness index (Figure 12).

Horticulturae 2022, 8, x FOR PEER REVIEW 12 of 15

Principal component analysis also mapped the position of the varieties tested. Based

on the quadrant position, the RK-5 variety was shown to be the most susceptible to orien-

tal fruit fly infestation since it was in the same quadrant as the fitness index (Figure 12).

Figure 12. Relationship of water content (WC), carbohydrate content (C), and fiber content (F) with

the fitness index (FI) of oriental fruit fly in six chili varieties.

4. Discussion

In field conditions, there were variations in the resistance and susceptibility of chili

varieties to oriental fruit fly infestation. The obtained fitness index values were higher

than those reported by Jallow and Zalucki [18] for H. armigera in corn (0.2), cotton, and

cowpea (0.6), as well as in artificial media (1.2). The fitness index describes the ability of

fruit flies to complete one or more phases of their life cycle inside chili fruits. The results

of this research indicate that the fitness index of the oriental fruit fly is highly determined

by the chili variety. Based on the resistance characteristics, our findings also corroborate

previous studies stating that the variety impacts the resistance of chili to fruit fly infesta-

tion. In corn, resistant and susceptible varieties have been used as components of a push–

pull strategy in pest control [19]. Accordingly, the susceptible chili varieties identified in

this study have a pull characteristic capable of attracting fruit flies for oviposition. As a

consequence, breeding activities aimed at reducing the pull characteristic in susceptible

varieties should be able to minimize oviposition incidence.

In comparison to resistant chili varieties, susceptible chili varieties featured larger,

wider, and heavier fruit, thicker flesh, and a wider fruit base. The width and weight of the

fruits, as well as the thickness of the fruit flesh, are characteristics that determine the size

of bigger or smaller chili fruit. Meanwhile, the fruit shape at pedicel attachment is a qual-

itative characteristic following the fruit surface area. A chili fruit with a narrow surface

area may have a pointed base shape, while a chili fruit with a wider surface area may have

a rounded base shape. The fruit size is correlated with the resistance level since female

fruit flies mostly attack host plants with large fruits. Large fruit size can ensure the sur-

vival of oriental fruit fly larvae. According to Nufio and Papaj [20], oriental fruit fly imago

developed from larvae in larger fruit survive longer than larvae developed in small fruits.

Similar findings have also been reported, stating that there is a correlation between fruit

size and fruit fly attack levels of several commodities, such as in mangos, tomatoes, and

oranges [21–23]. The larger the fruits, the greater the likelihood that they will serve as a

host for insect pests such as fruit fly species.

Figure 12. Relationship of water content (WC), carbohydrate content (C), and fiber content (F) withthe fitness index (FI) of oriental fruit fly in six chili varieties.

Horticulturae 2022, 8, 314 12 of 15

4. Discussion

In field conditions, there were variations in the resistance and susceptibility of chilivarieties to oriental fruit fly infestation. The obtained fitness index values were higherthan those reported by Jallow and Zalucki [18] for H. armigera in corn (0.2), cotton, andcowpea (0.6), as well as in artificial media (1.2). The fitness index describes the ability of fruitflies to complete one or more phases of their life cycle inside chili fruits. The results of thisresearch indicate that the fitness index of the oriental fruit fly is highly determined by thechili variety. Based on the resistance characteristics, our findings also corroborate previousstudies stating that the variety impacts the resistance of chili to fruit fly infestation. In corn,resistant and susceptible varieties have been used as components of a push–pull strategyin pest control [19]. Accordingly, the susceptible chili varieties identified in this studyhave a pull characteristic capable of attracting fruit flies for oviposition. As a consequence,breeding activities aimed at reducing the pull characteristic in susceptible varieties shouldbe able to minimize oviposition incidence.

In comparison to resistant chili varieties, susceptible chili varieties featured larger,wider, and heavier fruit, thicker flesh, and a wider fruit base. The width and weight ofthe fruits, as well as the thickness of the fruit flesh, are characteristics that determine thesize of bigger or smaller chili fruit. Meanwhile, the fruit shape at pedicel attachment isa qualitative characteristic following the fruit surface area. A chili fruit with a narrowsurface area may have a pointed base shape, while a chili fruit with a wider surface areamay have a rounded base shape. The fruit size is correlated with the resistance level sincefemale fruit flies mostly attack host plants with large fruits. Large fruit size can ensure thesurvival of oriental fruit fly larvae. According to Nufio and Papaj [20], oriental fruit flyimago developed from larvae in larger fruit survive longer than larvae developed in smallfruits. Similar findings have also been reported, stating that there is a correlation betweenfruit size and fruit fly attack levels of several commodities, such as in mangos, tomatoes,and oranges [21–23]. The larger the fruits, the greater the likelihood that they will serve asa host for insect pests such as fruit fly species.

Several studies have shown an association between the volatile compounds of hostplants and insect activity. Female insects employ the volatile compounds emitted byhost plants to mark a place for oviposition and to choose male fruit flies [24–26]. Thevolatile compounds released by host plants can be detected by insects during the periodof searching and selecting host plant locations [27,28]. Chili releases various kinds ofvolatile compounds [5,29,30]. The composition of volatile compounds is assumed to becorrelated with the resistance level of chili to herbivore infestation such as fruit flies. Theresults of this study corroborated earlier findings that the volatile compounds generatedby host plants are directly correlated with the process of host searching by oriental fruitflies [10,14,19,25,31–33]. Susceptible chili varieties released volatile compounds, includingβ-cis-ocimene, which acted as an attractant for oriental fruit flies seeking oviposition,consequently indicating high oviposition incidence. Due to the high level of fruit flymobility, volatile compounds are detected by their antenna, and they use this informationto determine the existence of food sources and locations for ovipositing their eggs [34].Therefore, lowering the concentration of this dominant compound in susceptible chilivarieties will decrease the level of fruit damage caused by oriental fruit fly infestation.Farré-Armengol [35] stated that β-ocimene is one of the most ubiquitous volatile substancesin floral scents and plays multiple important roles in plants, which vary depending on theorgan and time of emission.

Hafsi et al. [36] reported that the water content, carbohydrate content, and fiber contentof the host plant all contribute to the interaction between the host plant and oriental fruit flyspecies. Similarly, our result showed that resistant chili varieties have lower carbohydratecontent and higher fiber content than susceptible chili varieties. The nutrition content offruit on the host plant could influence larval growth and development as a food sourceafter the eggs hatch. It has also been reported that oriental fruit fly larvae thrive on fruitfrom the Solanaceae family [34,37]. The larval growth and development of Bactrocera zonata,

Horticulturae 2022, 8, 314 13 of 15

Ceratitis catoirii, C. capitata, and C. rosa were positively correlated with carbohydrate contentand fiber content but negatively correlated with water content. In contrast, the larvaldevelopment of Dacus demmerezi and Zeugodacus cucurbitae was positively correlated withwater content but negatively correlated with carbohydrate content. Meanwhile, the de-velopment of Neoceratitis cyanescens larvae was positively correlated with water contentand fatty acid content. According to Fontellas and Zucoloto [38], the fruit of the host plantwith a higher carbohydrate content was more suited for the larvae of Anastrepha obliquafrom the Tephritidae family, as the larvae move toward the carbohydrate-rich portion ofthe fruit. Fernandes-da-Silva and Zucoloto [39] also showed a correlation between femaleCeratitis capitata oviposition site selection and the carbohydrate content of the host fruits.This study supported the results of the above studies in which female flies chose fruit witha high carbohydrate content for oviposition.

Additionally, this study clarified the antixenosis mechanism of chili resistance to theoriental fruit fly. Antixenosis is the capacity of plants to resist insects by reducing orpreventing their ability to colonize. Because resistant chili varieties do not release attractivevolatile compounds, they are not selected by the female oriental fruit fly for oviposition and,therefore, exhibit a lower yield loss than susceptible chili varieties. Another antixenosismechanism is that resistant chili varieties have low water and carbohydrate content, whichprevents oriental fruit fly larvae from growing and developing in chili. This correspondsto the low value of the fitness index. This study provides a future direction for breedingprograms for chili varieties resistant to fruit flies. However, further research is requiredto strengthen the results of this study, including the use of biotechnology to isolate andcharacterize the genes involved in the production of ocimene volatile compounds and toidentify the chemical content of chili fruit, including primary and secondary metabolitesthat may affect the growth and development of oriental fruit fly larvae.

5. Conclusions

The characteristics of chili in the field, such as large fruit, ocimene (volatile com-pounds), high water content, high carbohydrate content, and low fiber content, may affectthe resistance level to oriental fruit fly (B. dorsalis) infestation. Chili uses an antixenosis de-fense mechanism modulated by volatile compounds to prevent oriental fruit fly infestation.Female fruit flies lay eggs in response to ocimene released by susceptible chili varieties.On the other hand, resistant chili varieties do not release this substance and hence preventfemale fruit flies from ovipositing their eggs. Thus, ocimene can be used as a chemicalmarker to identify chili resistance to oriental fruit fly attacks.

Supplementary Materials: The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/horticulturae8040314/s1, Table S1: Twenty two chili fruit charactersbased on IPGRI, AVRDC, and CATIE (1995).

Author Contributions: Conceptualization, T.S.S. and A.K.K.; Methodology, T.S.S., R.K., A.K.K. andA.F.; Data Analysis, T.S.S., R.K. and A.F.; Data curation, R.K.; Writing—original draft preparation,R.K.; Writing—review and editing, T.S.S., A.K.K. and A.F. All authors have read and agreed to thepublished version of the manuscript.

Funding: This work was supported by a grant from the Ministry of Research, Technology, and HigherEducation of the Republic of Indonesia to the first author and a scholarship to the second author.

Institutional Review Board Statement: Not applicable.

Informed Consent Statement: Not applicable.

Conflicts of Interest: The authors declare no conflict of interest.

Horticulturae 2022, 8, 314 14 of 15

References1. Said, A.E.; Fatahuddin, A.; Nasruddin, A. Effect of sticky trap color and height on the capture of adult oriental fruit fly, Bactrocera

dorsalis (Hendel) (Diptera: Tephritidae) on chili pepper. Am. J. Agric. Biol. Sci. 2017, 12, 13–17. [CrossRef]2. Hasyim, A.; Setiawati, W.; Sutarya, R. Screening for resistance to anthracnose caused by Colletotrichum acutatum in chili pepper

(Capsicum annuum L.) in Kediri, East Java. Adv. Agric. Bot. 2014, 6, 104–118.3. Syamsudin, T.S.; Faizal, A.; Kirana, R. Dataset on antixenosis and antibiosis of chili fruit by fruit fly (Bactrocera dorsalis) infestation.

Data Brief 2019, 23, 103758. [CrossRef] [PubMed]4. Bosland, P.W.; Votava, E.J. Peppers: Vegetable and Spice Capsicums; CABI: Boston, MA, USA, 2012.5. Wahyuni, Y.; Ballester, A.-R.; Sudarmonowati, E.; Bino, R.J.; Bovy, A.G. Secondary metabolites of Capsicum species and their

importance in the human diet. J. Nat. Prod. 2013, 76, 783–793. [CrossRef]6. Aliu, S.A.; Rusinovci, I.; Fetahu, S.; Kaçiu, S.; Zeka, D. Assessment of morphological variability and chemical composition of

some local pepper (Capsicum annuum L.) populations on the area of Kosovo. Acta Agric. Slov. 2017, 109, 205–213. [CrossRef]7. Prabaningrum, L.; Moekasan, T.K. Pest and disease management on hot pepper cultivation in high land. J. Hortic. 2014, 24,

179–188.8. IPGRI; AVRDC; CATIE. Descriptors for Capsicum (Capsicum spp.); International Plant Genetic Resources Institute: Rome, Italy;

The Asian Vegetable Research and Development Center: Taipei, Taiwan; The Centro Agronómico Tropical de Investigación yEnseñanza: Turrialba, Costa Rica, 1995; Volume 110.

9. Junior, S.B.; Tavares, A.M.; Teixeira Filho, J.; Zini, C.A.; Godoy, H.T. Analysis of the volatile compounds of Brazilian chilli peppers(Capsicum spp.) at two stages of maturity by solid phase micro-extraction and gas chromatography-mass spectrometry. Food Res.Int. 2012, 48, 98–107. [CrossRef]

10. Kirana, R.; Karyadi, A.K.; Faizal, A.; Syamsudin, T.S. Dataset on volatile compounds in susceptible and resistant chili variety tofruit fly infestation. Data Brief 2019, 22, 234–236. [CrossRef] [PubMed]

11. Luning, P.A.; de Rijk, T.; Wichers, H.J.; Roozen, J.P. Gas chromatography, mass spectrometry, and sniffing port analyses of volatilecompounds of fresh bell peppers (Capsicum annuum) at different ripening stages. J. Agric. Food Chem. 1994, 42, 977–983. [CrossRef]

12. Faizal, A.; Esyanti, R.R.; Aulianisa, E.N.; Santoso, E.; Turjaman, M. Formation of agarwood from Aquilaria malaccensis in responseto inoculation of local strains of Fusarium solani. Trees 2017, 31, 189–197. [CrossRef]

13. Jayanthi, P.D.K.; Woodcock, C.M.; Caulfield, J.; Birkett, M.A.; Bruce, T.J. Isolation and identification of host cues from mango,Mangifera indica, that attract gravid female oriental fruit fly, Bactrocera dorsalis. J. Chem. Ecol. 2012, 38, 361–369. [CrossRef][PubMed]

14. Aluja, M.; Arredondo, J.; Díaz-Fleischer, F.; Birke, A.; Rull, J.; Niogret, J.; Epsky, N. Susceptibility of 15 mango (Sapindales: Anacar-diaceae) cultivars to the attack by Anastrepha ludens and Anastrepha obliqua (Diptera: Tephritidae) and the role of underdevelopedfruit as pest reservoirs: Management implications. J. Econ. Entomol. 2014, 107, 375–388. [CrossRef] [PubMed]

15. Baedhowie, M.; Pranggonawati, S. Agricultural Product Quality Control Practice Guidelines; Department of Education and Culture:Jakarta, Indonesia, 1983; p. 129.

16. Hammer, Ø.; Harper, D.A.; Ryan, P.D. PAST: Paleontological statistics software package for education and data analysis. Palaeontol.Electron. 2001, 4, 9.

17. Pang, Z.; Chong, J.; Zhou, G.; de Lima Morais, D.A.; Chang, L.; Barrette, M.; Gauthier, C.; Jacques, P.-É.; Li, S.; Xia, J. MetaboAnalyst5.0: Narrowing the gap between raw spectra and functional insights. Nucleic Acids Res. 2021, 49, W388–W396. [CrossRef]

18. Jallow, M.F.; Zalucki, M.P. Relationship between oviposition preference and offspring performance in Australian Helicoverpaarmigera (Hübner)(Lepidoptera: Noctuidae). Aust. J. Entomol. 2003, 42, 343–348. [CrossRef]

19. Cook, S.M.; Khan, Z.R.; Pickett, J.A. The use of push-pull strategies in integrated pest management. Annu. Rev. Entomol. 2007, 52,375–400. [CrossRef]

20. Nufio, C.R.; Papaj, D.R. Superparasitism of larval hosts by the walnut fly, Rhagoletis juglandis, and its implications for female andoffspring performance. Oecologia 2004, 141, 460–467. [CrossRef]

21. Balagawi, S.; Vijaysegaran, S.; Drew, R.A.; Raghu, S. Influence of fruit traits on oviposition preference and offspring performanceof Bactrocera tryoni (Froggatt)(Diptera: Tephritidae) on three tomato (Lycopersicon lycopersicum) cultivars. Aust. J. Entomol. 2005, 44,97–103. [CrossRef]

22. Rattanapun, W.; Amornsak, W.; Clarke, A.R. Bactrocera dorsalis preference for and performance on two mango varieties at threestages of ripeness. Entomol. Exp. Appl. 2009, 131, 243–253. [CrossRef]

23. Muthuthantri, S.; Clarke, A.R. Five commercial citrus rate poorly as hosts of the polyphagous fruit fly Bactrocera tryoni (Froggatt)(Diptera: Tephritidae) in laboratory studies. Aust. J. Entomol. 2012, 51, 289–298. [CrossRef]

24. Nishida, R. Chemical ecology of insect–plant interactions: Ecological significance of plant secondary metabolites. Biosci. Biotechnol.Biochem. 2014, 78, 1–13. [CrossRef] [PubMed]

25. Prokopy, R.J.; Vargas, R.I. Attraction of Ceratitis capitata (Diptera: Tephritidae) flies to odor of coffee fruit. J. Chem. Ecol. 1996, 22,807–820. [CrossRef] [PubMed]

26. Syamsudin, T.S. Dampak konsumsi metil egenol terhadap perilaku dan keberhasilan perkawinan lalat buah Bactrocera carambolae(Diptera: Tephritidae). Indones. J. Plant Prot. 1999, 5, 114–119.

27. De Bruyne, M.; Baker, T.C. Odor detection in insects: Volatile codes. J. Chem. Ecol. 2008, 34, 882–897. [CrossRef] [PubMed]

Horticulturae 2022, 8, 314 15 of 15

28. Brevault, T.; Quilici, S. Flower and fruit volatiles assist host-plant location in the tomato fruit fly Neoceratitis cyanescens. Physiol.Entomol. 2010, 35, 9–18. [CrossRef]

29. Rodríguez-Burruezo, A.N.; Kollmannsberger, H.; González-Mas, M.C.; Nitz, S.; Fernando, N. HS-SPME comparative analysisof genotypic diversity in the volatile fraction and aroma-contributing compounds of Capsicum fruits from the annuum-chinense-frutescens complex. J. Agric. Food Chem. 2010, 58, 4388–4400. [CrossRef]

30. Pino, J.; Fuentes, V.; Barrios, O. Volatile constituents of Cachucha peppers (Capsicum chinense Jacq.) grown in Cuba. Food Chem.2011, 125, 860–864. [CrossRef]

31. Cornelius, M.L.; Duan, J.J.; Messing, R.H. Volatile host fruit odors as attractants for the oriental fruit fly (Diptera: Tephritidae). J.Econ. Entomol. 2000, 93, 93–100. [CrossRef]

32. Dudareva, N.; Martin, D.; Kish, C.M.; Kolosova, N.; Gorenstein, N.; Fäldt, J.; Miller, B.; Bohlmann, J.R. (E)-β-Ocimene andmyrcene synthase genes of floral scent biosynthesis in snapdragon: Function and expression of three terpene synthase genes of anew terpene synthase subfamily. Plant Cell 2003, 15, 1227–1241. [CrossRef] [PubMed]

33. Aluja, M.; Mangan, R.L. Fruit fly (Diptera: Tephritidae) host status determination: Critical conceptual, methodological, andregulatory considerations. Annu. Rev. Entomol. 2008, 53, 473–502. [CrossRef]

34. Fletcher, B. The biology of dacine fruit flies. Annu. Rev. Entomol. 1987, 32, 115–144. [CrossRef]35. Farré-Armengol, G.; Filella, I.; Llusià, J.; Peñuelas, J. β-Ocimene, a key floral and foliar volatile involved in multiple interactions

between plants and other organisms. Molecules 2017, 22, 1148. [CrossRef] [PubMed]36. Hafsi, A.; Facon, B.; Ravigné, V.; Chiroleu, F.; Quilici, S.; Chermiti, B.; Duyck, P.-F. Host plant range of a fruit fly community

(Diptera: Tephritidae): Does fruit composition influence larval performance? BMC Ecol. 2016, 16, 40. [CrossRef]37. Allwood, A.; Chinajariyawong, A.; Kritsaneepaiboon, S.; Drew, R.; Hamacek, E.; Hancock, D.; Hengsawad, C.; Jipanin, J.; Jirasurat,

M.; Krong, C.K. Host plant records for fruit flies (Diptera: Tephritidae) in Southeast Asia. Raffles Bull. Zool. 1999, 47, 1–92.38. Fontellas, T.M.d.L.; Zucoloto, F.S. Nutritive value of diets with different carbohydrates for adult Anastrepha obliqua (Macquart)

(Diptera, Tephritidae). Rev. Bras. Zool. 1999, 16, 1135–1147. [CrossRef]39. Fernandes-da-Silva, P.G.; Zucoloto, F.S. The influence of host nutritive value on the performance and food selection in Ceratitis

capitata (Diptera, Tephritidae). J. Insect Physiol. 1993, 39, 883–887. [CrossRef]