Identification of sources of resistance in pepper germplasm against broad mite
Creators: name: Mendez, C
name: Ramasamy S, Othim S
Publisher: name: World Vegetable Center
Year: 2024
Subjects: subject: POLYPHAGOTARSONEMUS
subject: PEPPERS
subject: PEST INSECTS
subject: HATCHING
subject: MITES
subject: PLANT HAIRS
subject: SUSTAINABILITY
subject: BIOASSAY
subject: Broad mite
subject: Pepper plant
subject: Plant resistance
subject: Scoring scale

description: The broad mite, Polyphagotarsonemus latus (Acari: Tarsonemidae), is a significant pest affecting a wide range of plants, including economically important crops like peppers, tomatoes, and potatoes, as well as various ornamental plants. This pest’s life cycle is notably efficient, beginning with the deposition of translucent, oval eggs on the undersides of leaves. Within 2- 3 days, these eggs hatch into six-legged larvae, which immediately commence feeding on plant tissues. Following a brief larval stage, these mites molt into eight-legged nymphs that continue to target the young, tender parts of plants. Both nymphs and adults inject toxic saliva into the plant tissues, causing cellular disruption that manifests as leaf curling, bronzing, stunted growth, and necrosis. Such damage not only diminishes crop yield but also escalates production costs due to the increased need for control measures. Given the global impact of broad mites on pepper plants, there is a critical need to identify pepper lines with inherent resistance to this pest. In this study, 22 pepper germplasm lines were screened to evaluate their resistance to broad mite infestation. Over a 28-day period, the plants were monitored and assessed for damage using a scoring scale: 0 (no damage), 1 (slight bronzing on young leaves with mites present), 2 (crinkling on young and older leaves), 3 (death of young leaves), 4 (death of medium leaves), 5 (death of both young and older leaves) and 6 (Death). This study highlighted the significance of variability in the resistance of pepper germplasm lines to broad mite infestation. By Day 7, PBC115 was identified as more susceptible than the check line, making it unsuitable for breeding programs. On Days 14 and 21, PBC602 showed greater susceptibility among the 10 selected lines. However, PBC725 consistently demonstrated high resistance across the entire 21-day period, making it a strong candidate for breeding programs focused on developing broad mite-resistant pepper varieties. At 28 days post exposure, the performance of PBC725 (Line 16) was unexpectedly surpassed by PBC625 (Line 15), which showed the lowest odds ratio, indicating superior long-term resistance. This shift emphasizes the importance of extended evaluation periods in resistance studies. While these lines did not exhibit complete resistance, they show considerable promise. When integrated with other Integrated Pest Management (IPM) strategies, these lines could contribute significantly to effective pest management in pepper cultivation. Plant resistance to broad mites (Polyphagotarsonemus latus) has been observed in several species, indicating its potential as a viable strategy for reducing mite damage. Research by (Gibson and Valencia, 1978) identified that the wild potato Solanum berthaultii and S. polyadenium exhibited significant resistance, with less than 10% foliage damage. The resistance in S. berthaultii was attributed to trichomes with sticky tips, which effectively deterred mite feeding, whereas the resistance mechanism in S. polyadenium remains unstudied. Similarly, (Zaman and Karimullah, 1987) assessed various jute cultivars and found that Hibiscus cannabinus was minimally affected by broad mites, while Corchorus capsularis showed intermediate susceptibility, and C. olitorius was most severely infested. These findings suggest that incorporating plant resistance into pest management strategies can be an effective means of mitigating broad mite damage. Given the success of resistance observed in other plant species, exploring and developing resistant varieties in economically significant crops like peppers (Capsicum spp.) could be highly beneficial. Peppers are an important cash crop for smallholder farmers in developing countries, including Ethiopia, Nigeria, Ghana, China, India, Pakistan, Bhutan, Indonesia, Cambodia, and Thailand. Among the five cultivated species of the genus Capsicum (C. annuum, C. frutescens, C. chinense, C. baccatum, C. pubescens), C. annuum (both hot and sweet pepper) is the most widely cultivated. Hot pepper (chili) dominates the world spice trade today, while sweet pepper has become a popular vegetable in the tropics. Incorporating resistance into pepper varieties not only supports sustainable agriculture by reducing reliance on chemical pesticides but also enhances pest management (Edelstein et al., 2000; Gibson and Valencia, 1978; Levi et al., 2002). Further research into the inheritance and mechanisms of resistance is essential for developing commercially viable, pest-resistant pepper varieties (de Coss-Romero and Peña, 1998; Gerson, 1992; Grinberg et al., 2005; Jones and Brown, 1983). Given the significant impact of broad mite infestations on pepper plants, understanding and leveraging the genetic diversity within pepper germplasm is vital. Plant resistance has already shown promise in other species, and it emerges as a key strategy in integrated pest management (IPM) for peppers as well. This involves the breeding and selection of pepper varieties with inherent traits that reduce susceptibility to pest damage. Resistance to broad mites in pepper plants can be achieved through mechanisms such as antixenosis (Daryanto et al., 2017), where physical traits like thicker leaves and trichomes deter mites (Fernandes et al., 2015); antibiosis, which involves the production of harmful secondary metabolites (Sirikantaramas et al., 2008); and tolerance, enabling plants to maintain growth and yield despite mite damage. The objective of this study is to identify sources of resistance within 22 lines of pepper using a choice bioassay. This method assesses pest preference and plant susceptibility under controlled conditions, providing valuable insights into the mechanisms of resistance. By understanding these mechanisms, the study aims to support breeding efforts to develop resistant pepper lines, ultimately reducing the need for chemical pesticides and enhancing overall crop resilience.