Identification of sources of Sclerotinia sclerotiorum resistance in a collection of wild cicer germplasm

Abstract

Sclerotinia sclerotiorum is an important fungal pathogen of chickpea (Cicer arietinum L.), and it can cause yield losses up to 100%. The wild progenitors are much more diverse than domesticated chickpea, and this study describes how this relates to S. sclerotiorum resistance. Initially, the pathogenicity of nine Australian S. sclerotiorum isolates was examined on three Cicer lines to develop a robust phenotyping assay, and significant differences in isolate aggressiveness were identified with six isolates being classed as highly aggressive and three as moderately aggressive. We identified two S. sclerotiorum isolates, CU8.20 and CU10.12, to be highly aggressive and moderately aggressive, respectively. A subsequent phenotyping assay was conducted using the two isolates to evaluate 86 wild Cicer accessions (Cicer reticulatum and Cicer echinospermum) and two C. arietinum varieties for resistance to S. sclerotiorum. A subset of 12 genotypes was further evaluated, and subsequently, two wild Cicer accessions with consistently high levels of resistance to S. sclerotiorum were examined using the initially characterized nine isolates. Wild Cicer accessions Karab_084 and Deste_063 demonstrated consistent partial resistance to S. sclerotiorum. There were significant differences in responses to S. sclerotiorum across wild Cicer collection sites. The Cermik, Karabahce, and Destek sites’ responses to the aggressive isolate CU8.20 ranged from resistant to susceptible, highlighting an interaction between isolate genotype and chickpea collection site for sclerotinia stem rot resistance. This is the first evidence of partial stem resistance identified in wild Cicer germplasm, which can be adopted in chickpea breeding programs to enhance S. sclerotiorum resistance in future chickpea varieties.