Breeding and On-Farm Evaluation of New Chili Pepper (Capsicum annuum L.) Lines Against Pepper Yellow Leaf Curl Thailand Virus (PepYLCTHV)
Abstract
This study investigated the genetics of resistance to Pepper yellow leaf curl virus (PepYLCTHV) in advanced lines of chili peppers (Capsicum annuum) and generated new chili pepper populations resistant to PepYLCTHV disease. Experiments were conducted in three phases between May 2020 and October 2024 at three locations in Thailand. Three crosses were developed, involving PepYLCTHV-resistant (PEP6) and susceptible Jindanil 80 (JD), PP0437-7506, and Yodsonkeam 80 (YS) parents; PEP 6 was used as a common male parent. The segregation of resistant and susceptible plants was studied in F2, F3 and F5 generations, and yield components of selected F5 lines were recorded and analyzed. The parental line PEP6 exhibited a segregation ratio of resistant (R) to susceptible (S) plant (1R:1.5S), while PP0437-7506 fit a 1R:15S ratio. The F1 generations were completely susceptible, confirming that resistance is a recessive trait. The resistant-to-susceptible ratio from F2 to F5 generations was increased, suggesting that advanced-generation selection for resistance is effective. The population of YS/PEP6 showed an increase in resistance across generations, with ratios changing from 1R:15S in the F2 to 1R:1S in the F5. These results suggest that resistance to PepYLCTHV was under the control of multiple recessive genes. Evaluations of new breeding lines regarding disease severity and index (DI%) confirmed that the resistant parent PEP6 had low disease severity (1.1) and DI% (22%). In contrast, commercial and local varieties were highly susceptible. Two promising F5 lines, PF2 and PF8, derived from PEP6 developed during this study, displayed high levels of resistance with low DI% values of 24.67% and 18.67%, respectively. These lines are improved sources of PepYLCTHV-resistant chili pepper for further evaluation and direct release as PepYLCTHV disease-resistant cultivars in the Thai market segment and could be used as an improved source of resistance for breeding programs.