Virulence Phenotypes on Chili Pepper for Phytophthora capsici Isolates from Michoacan, Mexico

Phytophthora blight of vegetables caused by Phytophthora capsici causes significant economic losses in production of Solanaceae and Cucurbitaceae crops in Mexico. The development of universal resistant chili pepper cultivars is challenging due to the diverse virulence phenotypes produced by P. capsici. The objective of the study was to characterize the diversity of phenotypic interactions for P. capsici isolates recovered from production fields in Michoacan, Mexico, to facilitate the development of resistant cultivars. Virulence phenotypes were characterized for 12 isolates of P. capsici using 26 Capsicum annuum New Mexico Recombinant Inbred Lines (NMRILs) in greenhouse conditions. Criollo de Morelos CM-334 and California Wonder were used as resistant and susceptible controls, respectively. Seedlings at the four to eight true leaf stage were inoculated with 10,000 zoospores per seedling and disease severity was evaluated at 20 days post-inoculation. Two of the P. capsici isolates did not infect any pepper host even though the isolate was less than a year old. The 10 virulent isolates were designated in 10 virulence phenotypes. The information generated by this study is of utmost importance for efforts of producing resistant cultivars specific for Michoacan producers.