Screening of Diverse spp. Highlights New Resistances to .

Stem rot caused by is a serious and sometimes devastating disease of lupin ( spp.). A total of 236 lupin accessions from across 12 species were screened against the prevalent isolate MBRS-1 (pathotype 76). accession 21655 and var. accession 20589 showed immune and "near-immune" responses, respectively. Thirteen accessions of , three accessions each of and var. , and a single accession each of var. , , , and (totaling ∼4%) showed a highly resistant (HR) response. A further 19 accessions of , 2 accessions each of and , and a single accession of (totaling ∼10%) showed a resistant (R) response. The reactions of 16 (15 , 1 ) of these 236 accessions were also compared with their reactions to a different isolate, Walkaway-3 (WW-3; pathotype 10). Against this isolate, five accessions showed an HR response and four showed an R response, and the accession showed a moderate resistance response. Overall, isolate WW-3 caused significantly ( 0.05) smaller lesions than MBRS-1 across tested accessions in common. In addition, 328 plants in a "wild" naturalized field population of were screened in situ in the field against isolate MBRS-1. Five (∼1.5%) of the 328 plants of wild lupin showed an immune response, 63 (∼19%) showed an HR response, and 146 (∼45%) showed an R response. We believe this is the first examination of diverse spp. germplasm responses to a prevalent pathotype of . Lupin genotypes exhibiting high-level resistance to Sclerotinia stem rot identified in this study can be used as parental lines for crosses in lupin breeding programs and/or directly as improved cultivars to reduce the adverse impact of this disease on lupin crops.