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

Abstract

Quantitative trait loci (QTL) for resistance to phytophthora root rot caused by Phytophthora capsici were investigated using two Korean P. capsici isolates and 126 F 8 recombinant inbred lines derived from a cross of Capsicum annuum line YCM334 (resistant parent) and local cv. Tean (susceptible parent). The experimental design was a split plot with two replications. Highly significant effects of pathogen isolate, plant genotype, and genotype · isolate were detected. QTL mapping was performed using a genetic linkage map covering 1486AE6 cM of the pepper genome, and consisted of 249 markers including 136 AFLPs (Amplified Fragment Length Polymorphisms), 112 SSRs (Simple Sequence Repeats) and one CAPS (Cleaved Amplified Polymorphic Sequence). Fifteen QTLs were detected on chromosomes 5 (P5), 10 (P10), 11 (P11), Pb and Pc using two data processing methods: percentage of wilted plants (PWP) and relative area under the disease progress curves (RAUD-PC). The phenotypic variation explained by each QTL (R 2 ) ranged from 6AE0% to 48AE2%. Seven QTLs were common to resistance for the two isolates on chromosome 5 (P5); six were isolate-specific for isolate 09-051 on chromosomes 10 (P10) and Pc, and two for isolate 07-127 on chromosomes 11 (P11) and Pb. The QTLs in common with the major effect on the resistance for two isolates explained 20AE0-48AE2% of phenotypic variation. The isolate-specific QTLs explained 6AE0-17AE4% of phenotypic variation. The result confirms a gene-for-gene relationship between C. annuum and P. capsici for root rot resistance.

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

“…Thabuis et al (2003) were among the first to report a resistance locus on P5 that confers the strongest resistance on different organs and at different stages of infection using three unrelated resistant pepper accessions. One of these accessions, CM334, was used as a parent in a different population to investigate race‐specific resistance QTL (Truong et al, 2012). That study found a disease resistance locus on P5 that conferred resistance to two Pc races.…”

“…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). The dissimilarities found between these studies may be due to environmental factors such as the use of different isolates, breeding lines, and the criteria used for scoring (Oelke et al, 2003).…”

“…Several sources of genetic resistance to Pc have been identified in peppers. One source of resistance is the well‐studied C. annuum landrace accession ‘Cdriollo de Morelos‐334’ (CM334) which has been reported to be completely resistant to multiple races of Pc (Glosier et al, 2008; Oelke et al, 2003; Thabuis et al, 2003; Truong et al, 2012). However, the genes underlying this resistance remain elusive to plant breeders.…”

“…There are numerous reports of QTL associated with resistance to Pc in pepper (Bonnet et al, 2007; Kim et al, 2008; Lefebvre and Palloix, 1996; Minamiyama et al, 2007; Ogundiwin et al, 2005; Pflieger et al, 2001; Sugita et al, 2006; Thabuis et al, 2003; Truong et al, 2012). However, many of these studies have been limited by the number of polymorphic markers employed and the use of segregating F 2 and F 3 populations that are limited in use for broad testing across environments.…”

Molecular Marker Application in Capsicum spp: A Supplement to Conventional Plant Breeding

“…So MAS is an effective and reliable approach. Specific geographic region isolates of pathogenspecific QTL controlling resistance is critical to breed for a cultivar with durable resistance (Truong et al, 2012).…”