| Breeding for Phytophthora capsici resistant chile pepper would relieve worldwide chile pepper growers from the devastating losses suffered each year. The existence of physiological races of this pathogen and the complex genetics of the resistance complicate the situation. Fortunately, sources of resistance do exist, and among them, the accession 'Criollo de Morelos-334' ('CM-334') is considered the most promising source of resistance. This accession was used to generate a population of Recombinant Inbred Lines (RILs) to study the genetics of resistance and to characterize the resistance with molecular markers.; The first part of this dissertation used the RIL population to develop a set of host differentials that aid in characterizing isolates of P. capsici into races. Eight RILs, NMRIL A, NMRIL B, NMRIL F, NMRIL G, NMRIL H, NMRIL N, NMRIL X, and NMRIL Z characterized isolates of P. capsici into races.; In the next part, hybridizations were made among resistant and susceptible accessions in order to have a better understanding of the genetics of resistance in 'CM-334.' The analysis of the genetic ratios in the segregating populations, challenged with different races of P. capsici suggested the existence of a gene-for-gene interaction within the P. capsici-Capsicum spp. system. An unexpected result when 'CM-3 34' was hybridized with the susceptible accession 'NMCA 10399,' was that resistance was unusually controlled by a single recessive gene, suggesting the presence of epistatic gene(s) in 'NMCA 10399.' A gene-for-gene model in which 13 genes were identified (Prr-1 through Prr-13) was proposed.; The last part of this dissertation reports on the use of 300 RAPD primers to find possible molecular markers linked to resistance to phytophthora root rot. One primer, OPM-4, revealed one marker, OPM4.310, associated with resistance to phytophthora root rot. |
