Resistance of Capsicum annuum to Phytophthora blight is dependent on the genetic background of the resistance source and the Phytophthora capsici isolate, which poses challenges for development of generally applicable molecular markers for marker-assisted selection. In this study, the resistance to P. capsici of C. annuum was genetically mapped to chromosome 5 within a 1.68-Mb interval by genome-wide association study analysis of 237 accessions. In this candidate region, 30 KASP markers were developed using genome resequencing data for a P. capsici -resistant line (0601 M) and a susceptible line (77,013). Seven of these KASP markers, located in the coding region of a probable leucine-rich repeats receptor-like serine/threonine-protein kinase gene ( Capana05g000704 ), were validated in the 237 accessions, which showed an average accuracy of 82.7%. The genotyping of the seven KASP markers strongly corresponded with the phenotype of 42 individual plants in a pedigree family (PC83-163) developed from the P. capsici -resistant line CM334. This research provides a set of efficient and high-throughput KASP markers for marker-assisted selection of resistance to P. capsici in C. annuum .

KEY MESSAGE:Genome re-sequencing and recombination analyses identified Capana06g000193 as a strong candidate for the minor male fertility restoration locus Rf2 in chili pepper G164 harboring two dominant male fertility restoration genes. Male fertility restoration genes of chili pepper restorer line G164 (Capsicum annuum L.) were studied using molecular marker genotypes of an F2 population (7G) of G164 crossed with the cytoplasmic male sterility line 77013A. The ratio of sterile to fertile single plants in the F2 population was 1:15. This result indicates that chili pepper G164 has two dominant restoration genes, which we designated as Rf1 and Rf2. An individual plant recessive for Rf1 and heterozygous for Rf2, 7G-112 (rf1rf1Rf2rf2), was identified by molecular marker selection and genetic analysis, and a single Rf2 gene-segregating population with a 3:1 ratio of fertile to sterile plants was developed from the self-pollination of male fertile individuals of 77013A and 7G-112 hybrid progeny. Bulk segregant analysis of fertile and sterile pools from the segregating populations was used to genetically map Rf2 to a 3.1-Mb region on chromosome 6. Rf2 was further narrowed to a 179.3-kb interval through recombination analysis of molecular markers and obtained the most likely candidate gene, Capana06g000193.

Pepper ( Capsicum spp.) is one of the earliest domesticated crops, providing a unique pungent sensation when eaten. Through the construction of the first pepper variome, we describe the main groups that emerged during domestication and breeding of C. annuum , their relations and temporal succession, and the molecular events underlying the main transitions. The initial differentiation in fruit shape and pungency, increase in fruit weight, and transition from erect to pendent fruits, and the recent appearance of blocky, large, sweet fruits (bell peppers), were accompanied by strong selection/fixation of key alleles and introgressions in two large genomic regions. Furthermore, we describe the identification of Up , a key domestication gene controlling erect vs pendent fruit orientation, encoding a BIG GRAIN protein involved in auxin transport, and Flip1 associated with capsaicinoid content, encoding a protein involved in phospholipid flipping. The function of Up was confirmed by virus-induced gene silencing. These findings constitute a cornerstone for understanding the domestication and differentiation of a key horticultural crop.

Fertility restoration of cytoplasmic male sterility (CMS) in Capsicum annuum is controlled by multiple alleles of Restorer-of-fertility ( Rf ) genes. The isolation of additional Rf genes should therefore enrich the knowledge of CMS/ Rf systems and accelerate their exploitation in hybrid seed production. In this study, the fertility restorer gene CaRfm of ‘0601 M’, a non-pungent bell pepper, was genetically mapped to a 1.2-cM region flanked by KASP markers S761 and S183. CaRfm was then physically mapped to a 128.96-Kb interval predicted from 24 recombinants with two co-segregated markers, S423 and S424. CaPPR6 encoding a pentatricopeptide repeat (PPR) protein was suggested as the most likely candidate gene for the CaRfm locus on the basis of sequence alignment as well as genotyping of tightly linked markers. In addition, molecular markers S1597 and S1609, which are immediately adjacent to CaRfm at 15.7 and 57.8-Kb respectively, were developed and applied to marker-assisted selection. The results provided friendly markers for breeding pepper restorer lines and laid the foundation for elucidating the male fertility restoration mechanism.