Tolerance to virulence phenotypes of phytophthora capsici in pasilla pepper cultivars

Abstract

Phytophthora capsici is the most important limiting factor in the production of chile pepper in Mexico. This pathogen presents virulence phenotypes capable of infecting diverse cultivars of this crop. The search and development of resistance in chile pepper is an excellent alternative for the management of P. capsici. The objective of this work was to evaluate the response of four pasilla pepper cultivars to infection with five virulence phenotypes of P. capsici. Pasilla pepper landraces PAS-1, PAS-2, PAS-3, and PAS- 4 were inoculated with P. capsici isolates MX-1, MX-2, MX-7, MX-8, and MX-10. Two experiments were conducted under greenhouse conditions from April through June 2017 and April through June 2018. 'California Wonder' was included as a susceptible control, and uninoculated plants were included as a negative control. In each experiment, groups of six 56-day-old plants from each pepper cultivar were inoculated with each virulence phenotype. Disease severity was evaluated 20 days after inoculation using an individual plant severity scale. All pepper cultivars were classified as resistant 5 R, moderately resistant (MR), tolerant (T), moderately tolerant (MT), or susceptible (S), according to the frequency of resistant plants (severity 0-1). 'California Wonder' and 'PAS-4' were susceptible to all five virulence phenotypes. The rest had different responses to the virulence phenotypes, but 'PAS-2' and 'PAS-3' were susceptible to only one of the five virulence phenotypes. Pasilla peppers with low severity exhibited a slow rate of infection, which is a mechanism we have called "slow wilting." The pasilla pepper cultivars PAS-1, PAS-2, and PAS-3 could be used in plant breeding programs as sources of genetic tolerance and moderate resistance against P. capsici.