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

ABSTRACT

Stem rot caused by Sclerotinia sclerotiorum is a serious, and sometimes devastating, disease of lupin (Lupinus spp.). Two hundred and thirty-six 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 (totalling ~4%) showed a highly resistant (HR) response. A further 19 accessions of L. angustifolius, two accessions each of L. albus and L. pilosus, and a single accession of L. mutabilis (totalling ~10%) showed a resistant (R) response. The reactions of 16 (15 L. angustifolius, one L. digitatus) of these 236 accessions were also compared with their reactions to a different isolate, WW-3 (pathotype 10). Against this isolate, five L. angustifolius accessions showed a HR response and four showed a R response, and the L. digitatus accession showed a moderate resistance (MR) 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. cosentini 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 a HR response, and 146 (~45%) showed a 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 now 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.