Screening of Diverse Lupinus spp. Highlights New Resistances to Sclerotinia sclerotiorum .

Stem rot caused by Sclerotinia sclerotiorum is a serious and sometimes devastating disease of lupin ( Lupinus spp.). A total of 236 lupin accessions from across 12 Lupinus species were screened against the prevalent S. sclerotiorum isolate MBRS-1 (pathotype 76). L. angustifolius accession 21655 and L. albus var. albus accession 20589 showed immune and "near-immune" responses, respectively. Thirteen accessions of L. angustifolius , three accessions each of L. albus and L. albus var. albus , and a single accession each of L. albus var. graecus , L. mutabilis , L. palaestinus , and L. pilosus (totaling ∼4%) showed a highly resistant (HR) response. A further 19 accessions of L. angustifolius , 2 accessions each of L. albus and L. pilosus , and a single accession of L. mutabilis (totaling ∼10%) showed a resistant (R) response. The reactions of 16 (15 L. angustifolius , 1 L. digitatus ) of these 236 accessions were also compared with their reactions to a different isolate, Walkaway-3 (WW-3; pathotype 10). Against this isolate, five L. angustifolius accessions showed an HR response and four showed an R response, and the L. digitatus accession showed a moderate resistance response. Overall, isolate WW-3 caused significantly ( P < 0.05) smaller lesions than MBRS-1 across tested accessions in common. In addition, 328 plants in a "wild" naturalized field population of L. cosentinii 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 Lupinus spp. germplasm responses to a prevalent pathotype of S. sclerotiorum . 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.