Species-specific tolerance patterns against major sucking pests in chilli (Capsicum spp.) under protected cultivation

Introduction

Protected cultivation systems offer controlled environmental conditions that support yearround cultivation, enhanced productivity and improved fruit quality. By regulating environmental factors such as temperature, light, wind speed and humidity, protected structures help in stable crop growth and increased economic returns (Kumar & Kumar, 2018; Singh et al., 2024; Jain et al., 2025) [7,14,5] . However, these conditions are also favourable for the rapid multiplication of sucking insect pests, especially mites, thrips, and whiteflies, which pose a major threat to chilli production (Yadav et al., 2022) [15] . These pests cause significant damage to crops by sucking plant sap, reducing photosynthetic efficiency, deforming leaves and fruits, and transmitting several viral pathogens, ultimately affecting yield and quality. Management of sucking pests in protected cultivation is mainly achieved through repeated application of chemical pesticides. Although it is effective in the short term, excessive application of pesticides has resulted in increased production costs, the development of pesticide-resistant pest populations, the disruption of beneficial insects, and the presence of pesticide residues in harvested produce (Logeswaran et al., 2023) [8] . Consequently, identification and deployment of host plant resistance have gained considerable attention as a sustainable component of integrated pest management strategies. Resistant cultivars reduce dependence on chemical inputs while contributing to environmentally safe and economically viable crop production (Sharma et al., 2019) [12] . The genus Capsicum exhibits wide genetic diversity, which is mainly expressed through variation in plant morphology, fruit characteristics, adaptation to different environments and resistance to biotic and abiotic stresses (Colonna et al., 2019) [3] . Differences among cultivated Capsicum species in their susceptibility to sucking pests have been attributed to variations in morphological characteristics such as trichomes, biochemical constituents, and underlying genetic factors (Barik et al., 2025) [1] . Despite the availability of diverse germplasm, information on species-level variation in resistance to sucking pests is still limited. With this background, the present investigation was carried out to assess the response of different Capsicum species to the major sucking pests, namely thrips, mites and whiteflies, under polyhouse conditions.

Materials and Methods

The present experiment was carried out at the Instructional Farm of Kerala Agricultural University, Thrissur, in a naturally ventilated polyhouse for two seasons from August, 2024 to January, 2025 and from March, 2025 to August, 2025. A total of 20 chilli (Capsicum spp.) genotypes comprising 11 accessions of C. annuum, five C. chinense and four C. frutescens were used in the investigation. The experiment was conducted in a Completely Randomised Design (CRD) with two replications. All recommended management practices were followed to ensure healthy crop growth (KAU, 2025) [6] . Pest response was evaluated through visual observation of characteristic damage symptoms associated with each pest (Fig. 1). Thrips infestation was recognised by the presence of upward curling of leaves, while mite damage was identified by downward leaf curling together with the characteristic rattail appearance of the foliage (Rai et [10,13,4] . Whitefly infestation was recorded based on the presence of whiteflies on the underside of leaves, honeydew deposits on leaves and leaf chlorosis (Senanayake et al., 2012; Yadav et al., 2022) [11,15] . Based on the observed symptoms, each genotype was categorised as either resistant or susceptible to each of the three sucking pests during the flowering stage. Chi-square (χ²) test of independence was performed to analyse the association between Capsicum species and pest response. For the analysis, genotypes belonging to C. annuum were considered as one species group, whereas C. chinense and C. frutescens were combined into a second group because these were genetically closely related (Carvalho et al., 2014) [2] . Resistance status (resistant or susceptible) served as the second categorical variable in the contingency analysis. Statistical significance was determined at the 5% probability level (P < 0.05).

Results and Discussion

The Chi-square (χ²) test of independence analysis revealed that species background significantly influenced the response of chilli genotypes to thrips, mites and whiteflies (Table 1), indicating that pest tolerance is closely associated with genetic background.

A major proportion of genotypes resistant to thrips belonged to the C chinense-C. frutescens group, whereas the majority of C. annuum genotypes were susceptible. But the genotype C.a. 653 has shown significant resistance to all three sucking pests, such as thrips, mites and whitefly. Thrips are one of the most devastating pests because they feed on tender plant tissues, resulting in leaf curling, deformation of young foliage and reduced plant growth. Thrips may also act as vectors for viruses in chilli (Dey et al., 2024) [4] . The resistance expressed by C. chinense and C. frutescens suggests that these species possess natural defence mechanisms that restrict thrips infestation and multiplication (Barik et al., 2025) [1] . Similar to the trend observed for thrips, resistant genotypes to mites were mainly identified in C. chinense and C. frutescens, while a higher proportion of susceptible genotypes occurred in C. annuum. The consistent resistance exhibited by C. chinense and C. frutescens against both thrips and mites suggests that these species may possess common defence mechanisms that protect against multiple sucking pests. These mechanisms may include structural barriers that hinder pest establishment or constitutive biochemical compounds that reduce pest survival and reproduction (Sharma et al., 2019) [12] . In contrast to thrips and mites, the pattern of resistance to whiteflies differed considerably among species. Resistant genotypes to whiteflies were predominantly represented by C. annuum. Whiteflies reduce crop performance through continuous sap extraction, induction of leaf chlorosis and deposition of honeydew, which encourages the development of sooty mould and limits photosynthesis (Parisi et al., 2020) [9] . The higher frequency of resistant genotypes within C. annuum indicates that the genetic basis of whitefly resistance differs from that governing resistance to thrips and mites. This contrasting response demonstrates that defence against sucking pests is highly pest-specific, and resistance to one pest cannot necessarily be expected to confer protection against another. Therefore, breeding strategies targeting multiple pests should consider the specific resistance profile of each donor parent.

Conclusion

The study revealed significant species-specific variation in tolerance to major sucking pests under protected cultivation. C. chinense and C. frutescens exhibited significantly higher tolerance to thrips and mites, whereas C. annuum demonstrated higher tolerance to whiteflies. The significant Chi-square associations confirm that pest response is strongly influenced by species background. These species can therefore serve as valuable donor parents in breeding programmes aimed at developing pest-tolerant chilli morphotypes suitable for protected cultivation.

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