2018 ASHS Annual Conference

Since its introduction to New Mexico in the 1990s, powdery mildew, caused by Leveillula taurica (Lév), has been a major disease on chile peppers. Powdery mildew can lead to severe plant defoliation, resulting in significant quality and yield losses. Applications of fungicide can be effective in managing the disease; however, early detection and thorough coverage of the plant is required. The most economically and environmentally sustainable solution is breeding for resistance. The Chile Pepper Institute at New Mexico State University grows an annual Teaching Garden at the Fabian Garcia Science Center in Las Cruces, NM. During the 2017 growing season, environmental conditions were highly favorable for powdery mildew development, and severe infection was observed. Under natural infection, 152 accessions, including six Capsicum species, were evaluated for resistance. Of the 152 accession, 53 accessions would be considered resistant. When examining across species, 18 C. annuum accessions were resistant, as well as 11 C. baccatum, 16 C. chinense, 5 C. frutescens, 1 C. chacoense, and 1 C. rhomboideum accession. A disease index ranging from 0 to 5 was used to score individual leaves of the plant. Accessions were considered resistant if they scored a 0 or 1. In addition to the field study, characterization of a novel susceptibility gene, CaMlo2, was conducted in the resistant accession, HV-12, and the susceptible cultivar, ‘Maor’. A single nucleotide polymorphism (SNP) was identified and a marker was developed. Select accessions from the field study were screened. The marker identified all evaluated resistant accessions; however, was not accurate for all susceptible accessions. This study provides the first multiple species evaluation for powdery mildew resistance among Capsicum species in New Mexico. It also provides preliminary evidence for genetic control of resistance in Capsicum populations. The identified SNP can be used for early screening of resistant material. This study provides a valuable base for continued breeding efforts, especially in the more commercially significant, C. annuum.