A Novel Capsicum Gene Inhibits Host-Specific Disease Resistance to Phytophthora capsici

Abstract

A novel disease resistance inhibitor gene (inhibitor of P. capsici resistance [Ipcr]), found in the chile pepper (Capsicum annuum) variety 'New Mexico Capsicum Accession 10399' (NMCA10399), inhibits resistance to Phytophthora capsici but not to other species of Phytophthora. When a highly P. capsici-resistant variety was hybridized with NMCA10399, the resultant F1 populations, when screened, were completely susceptible to P. capsici for root rot and foliar blight disease syndromes, despite the dominance inheritance of P. capsici resistance in chile pepper. The F2 population displayed a 3:13 resistant-to-susceptible (R:S) ratio. The testcross population displayed a 1:1 R:S ratio, and a backcross population to NMCA10399 displayed complete susceptibility. These results demonstrate the presence of a single dominant inhibitor gene affecting P. capsici resistance in chile pepper. Moreover, when lines carrying the Ipcr gene were challenged against six Phytophthora spp., the nonhost resistance was not overcome. Therefore, the Ipcr gene is interfering with host-specific resistance but not the pathogen- or microbe-associated molecular pattern nonhost responses.

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

“…However, these alleles are shared by accessions Midal and Jeju which exhibit extreme susceptibility towards Pc (see Table 4). A recent study suggested that a resistance‐inhibitor gene, Ipcr , may mask the effects of resistance loci (Reeves et al, 2013). It may be speculated that although these accessions have the resistance factor at Pc5.1, they display a susceptible phenotype because they also have an active Ipcr gene.…”

“…This may explain why it has been challenging to transfer CM334‐based Pc resistance to large blocky type peppers. Pc resistance from CM334 has been reported by some to be dominantly inherited (Bosland and Lindsey, 1991; Reeves et al, 2013). However, there are reports of epistatic and semidominance effects of resistance to Pc (Bartual et al, 1993; Lefebvre and Palloix, 1996; Thabuis et al, 2003).…”

Mapping of a Novel Race Specific Resistance Gene to Phytophthora Root Rot of Pepper (Capsicum annuum) Using Bulked Segregant Analysis Combined with Specific Length Amplified Fragment Sequencing Strategy

“…capsici , was used as resistant parent (female) and NMCA10399, a P . capsici -susceptible accession [ 20 ], was used as susceptible parent (male). Derived from CM334 and NMCA10399, two BC 1 populations, (CM334×NMCA10399)×CM334, comprising 222 plants and (CM334×NMCA10399)×NMCA10399, of 372 individuals, respectively, and an CM334×NMCA10399 F 2 population of 259 plants were used for genetic analysis.…”

“…capsici ( Ipcr ) was found in a P . capsici -susceptible accession, NMCA10399 [ 20 ]. When the most P .…”

Evidence of recent increased pathogenicity within the AustralianAscochyta rabieipopulation

“…Whilst breeders have moved away from single source resistance to employing pyramided polygenic resistance (Thabuis et al, 2004;Reeves et al, 2013), longevity of newly deployed "resistant" cultivars remains dependent on the speed of isolate evolution and population adaptation (Moore et al, 2015;Mehmood et al, 2017). Accordingly, to assess this risk, variation in isolate aggressiveness has been assessed in many global regions including India (Vir and Grewal, 1974), the Palouse region of USA (Chen et al, 2004) Spain (Navas-Cortes et al, 1998), Pakistan (Jamil et al, 2000;Iqbal et al, 2004;Ali et al, 2012), Canada (Chongo et al, 2004), Syria (Atik et al, 2013;Imtiaz et al, 2015) and Australia (Mehmood et al, 2017).…”