Camalexin Production in Camelina sativa is Independent of Cotyledon Resistance to Sclerotinia sclerotiorum

Abstract

Camelina sativa (L.) Crantz. has been proposed as a novel source of oilseed resistance to Sclerotinia rot (SR; causal agent Sclerotinia sclerotiorum (Lib.) de Bary). To assess factors likely important in determining the level of resistance to this pathogen, 30 diverse C. sativa genotypes were evaluated using a cotyledon test under controlled environmental conditions. Confirmed cotyledon SR-resistant (CS370) and SR-susceptible (CS2305) genotypes were assessed for camalexin production across time following inoculation at the 1-month vegetative stage of growth. There were significant differences among C. sativa genotypes in response to inoculation with S. sclerotiorum in terms of percent cotyledon disease index (%CDI), with the mean %CDI ranging from 30.9 to 69.4% across germplasm and confirmation screening, respectively. Genotype CS370 consistently showed low %CDI indicating high level of resistance to S. sclerotiorum, whereas CS2305 showed the highest %CDI value. These findings highlight the potential to develop highly SR-resistant cultivars of C. sativa by selection. Furthermore, liquid chromatographic analysis of leaves for both SR-resistant and SR-susceptible genotypes demonstrated that camalexin was produced when inoculated with S. sclerotiorum. However, camalexin production was not linked with disease severity in either genotype, indicating that SR resistance in C. sativa is independent of the level of camalexin production.