Search

A broad panel of Capsicum spp. landraces, mostly originating in the Andean region, was assessed with thirteen molecular markers linked to disease resistance and pungency-related traits. Tsw and L4 were the most common loci observed within the collection, although resistant alleles associated to Pvr4, Phyto.5.2, and Cmr1 were also recorded in approximately 30% of pepper genotypes. South America and, namely the Andean region, revealed as a promising source of disease resistances, particularly against potyviruses. Clustering analysis split the collection into forty groups, each one carrying a distinctive combination of resistant alleles. Capsicum annuum and C. chinense showed the greatest variability, while the other Capsicum species generated homogeneous clusters with well-defined haplotypes. Capsicum chinense appeared as the most promising species for breeding purposes, with various accessions showing potential resistance to more than 80% of assessed diseases. PCoA analysis did not show a connection between those resistant genotypes and particular geographical regions. The pungency trait was predicted for 85.5% of pepper accessions. Markers linked to capsinoids content did not amplify or did not displayed polymorphism.

Pepper (Capsicum annuum L.) plants stressed by copper showed less disease symptoms after inoculation with Verticillium dahliae Kleb. We tested if such protection was accompanied of a defence response induced by copper stress by measurement of peroxidase and chitinase activity, phenolics and the expression of four genes related to plant defence. Peroxidase activity, but not chitinase, increased in roots, stem and leaves of copper-stressed plants. However, treating the plants with an ethylene perception inhibitor (MCP) before applying the copper stress, caused a synergic enhancement of both enzymes in stem and cotyledons. Phenolic compounds were also induced by copper but downregulated by MCP in stem. The expression of a peroxidase gene (CAPO1), a sesquiterpene cyclase gene (CASC1), a PR1 gene (CABPR1) and a β-1,3-glucanase (CABGLU) was highly upregulated by copper stress, but MCP neither suppresses nor enhances such an effect. Globally, copper stress causes an induction of defence mechanisms that may partially explain tolerance to Verticillium wilt.

This study investigated the expression pattern of genes encoding for a basic PR-1 protein, a basic beta-1,3-glucanase, a peroxidase, and a sesquiterpene cyclase involved in defense responses in three pepper cultivars with different levels of resistance to Phytophthora capsici. All genes were up-regulated in infected stems of the pepper cultivars, with expression being detected 8h post-inoculation. mRNA levels of these genes increased markedly by 24h post-inoculation, and maximal induction levels were observed for the PR-1 and sesquiterpene cyclase genes. PR-1, peroxidase, and sesquiterpene genes were always expressed at higher levels in resistant cultivars than in the susceptible cultivar, although up-regulation was observed in both, suggesting that the differences between these pepper genotypes in susceptibility and resistance are a matter of the timing and magnitude of the defense response.