## 1 Introduction  
The oriental fruit fly (_Bactrocera dorsalis_) is a major insect pest in chili cultivation in Indonesia that has an economic impact. The damage begins when the female fruit flies lay eggs 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. Several studies have reported that the rate of loss of chili fruits by fruit flies varies between 40 and 60% 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 by the deterrent index for anitkenosis and the fitness index for antibiosis [3]. Experiments by [PERSON] et al. [3] on fifty chili varieties of fruit fly infestation in the laboratory showed that the prevention of oviposition by the chosen method was in the range from 46.01% to 100%; however, the no-choice method was in the range from 11.11% to 99.07%, while the fitness 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 determined by variety. The difference in the resistance level of chili varieties to fruit flies might be determined by the characteristics of chili fruits. [PERSON] and [PERSON] [4] reported that chili 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).  
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 composition of chili changes according to the variety [5; 6]. As a result, the diversity of chili fruit traits may 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 prevent female fruit flies from laying eggs and inhibit larval growth and development. A previous study has identified resistant and susceptible varieties of oriental fruit fly infestation and established a correlation between fruit morphological characteristics and the resistance level of fifty chili varieties to fruit flies. Large-fruited chili varieties from the species of _C. 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 large chili and curly chili varieties to fruit fly infestation can be determined by the differences in the characteristics of each variety. This study aims to evaluate the morphochemical characteristics of different resistance levels of chili fruits to oriental fruit fly infestation in field conditions. This in-depth study is expected to help in the understanding of the mechanism behind chili resistance to oriental fruit fly infestation and hopefully serve as the basis for the initiation of plant breeding programs for chili resistance to fruit flies.