Genetic Analysis of Phytophthora Root Rot Race-specific Resistance in Chile Pepper

Abstract

<jats:p> <jats:italic>Phytophthora capsici</jats:italic> Leon., causal agent of phytophthora root rot, is one of the most devastating pathogens attacking chile pepper (<jats:italic>Capsicum annuum</jats:italic> L.) plants. Many studies have tried to better understand phytophthora resistance, but the genetic behavior is not completely understood. To determine if phytophthora root rot resistance in chile pepper is controlled by multiple alleles at a few loci, or multiple genes at different loci, five recombinant inbred lines (RILs) were evaluated. The resistant accession, Criollo de Morelos-334, and the susceptible cultivar, Early Jalapeno, were hybridized to develop multiple RILs. After seven generations of selfing using the single seed descent method, four RILs were selected based on their phenotypic response to inoculation by five <jats:italic>P. capsici</jats:italic> isolates. The RILs were hybridized to each other to obtain F<jats:sub>1</jats:sub> and F<jats:sub>2</jats:sub> populations. The F<jats:sub>2</jats:sub> populations were inoculated with single and a pair of races of <jats:italic>P. capsici</jats:italic>. When the F<jats:sub>2</jats:sub> populations were inoculated with a single race, ratios of three resistant:one susceptible were obtained in the majority of the populations, indicating the action of an independent single gene. When the F<jats:sub>2</jats:sub> populations were inoculated with a combination of two races, segregation ratios of 15 resistant:one susceptible were observed in two populations out of the four populations. The presence of susceptible individuals in all of the F<jats:sub>2</jats:sub> population indicates that the resistant genes for the different <jats:italic>P. capsici</jats:italic> races are located at different loci. However, the rejection of the segregation ratio in one of the F<jats:sub>2</jats:sub> population under a single race inoculation and in two of the F<jats:sub>2</jats:sub> populations challenged with a combination of two races suggest a linkage phenomenon between some of the <jats:italic>R</jats:italic> genes. None of the RILs evaluated in this study displayed allelism for phytophthora root rot resistance.</jats:p>

Identification of isolate‐specific resistance QTLs to phytophthora root rot using an intraspecific recombinant inbred line population of pepper (Capsicum annuum)

“…The results confirm the gene‐for gene relationship between C. annuum and P. capsici for root rot resistance reported by Sy et al. (2008) and Monroy‐Barbosa & Bosland (2008). Thus, the results indicate that at least a few specific gene functions are important components of root rot resistance to different P. capsici races/isolates in the YCM334 × Tean population.…”

“…Broadly speaking, two types of resistance to phytophthora root rot are known. Specific resistance to phytophthora root rot is oligogenic, effective against particular pathogen isolates and follows a gene-for-gene relationship (Monroy- Barbosa & Bosland, 2008;Sy et al, 2008). Quantitative resistance is polygenic (Lefebvre & Palloix, 1996;Thabuis et al, 2003).…”

Evaluation of Commercial Bell Pepper Cultivars for Resistance to Phytophthora Blight (Phytophthora capsici)

“…While resistant bell pepper cultivars have been available for some time, the genetics controlling resistance to Phytophthora blight in pepper are not clearly understood. Evidence to date supports the hypothesis that multiple genes are involved, and that different genes are responsible for resistance to root rot, fruit rot, and leaf lesions (16,21).…”

CaDMR1 Cosegregates with QTL Pc5.1 for Resistance to Phytophthora capsici in Pepper (Capsicum annuum)

“…However, the genes underlying this resistance remain elusive to plant breeders. Early research suggested resistance was due to a single or a handful of dominant alleles based on complete resistance found in the F 1 and segregation ratios of the F 2 (Gil Ortega et al, 1992; Monroy‐Barbosa and Bosland, 2008; Saini and Sharma, 1978; Smith et al, 1967; Sy et al, 2005; Walker and Bosland, 1999). Conversely, other studies report a polygenic inheritance based on multimodal distributions that range between the susceptible and resistant parents and higher order epistasis effects in resistance (Barksdale et al, 1984; Bartual et al, 1991; Bartual et al, 1993; Bonnet et al, 2007; Lefebvre and Palloix, 1996; Minamiyama et al, 2007; Ogundiwin et al, 2005; Palloix et al, 1988; Pochard and Daubeze, 1980; Reifschneider et al, 1992; Thabuis et al, 2003; Truong et al, 2012).…”