Resistance to Wheat streak mosaic virus- a survey of resources and development of molecular markers

Wheat streak mosaic virus (WSMV) has been newly documented in Australia. The vulnerability of contemporary Australian elite wheat germplasm prompted a survey for effective resistance against an Australian isolate, WSMV-ACT. This study confirms the effectiveness of previously reported sources of resistance and shows that new sources of resistance also confer protection. The resistance derived from Thinopyrum intermedium (Wsm1) as a 4D translocation and a new 4A translocation, and two bread wheat resistances, Wsm2 and the new source c2652, were effective against WSMV-ACT in glasshouse experiments. Wsm1 was effective at lower temperatures but ineffective above 20°C, a temperature sensitivity shared with many of the derivatives of Wsm2 except for one new selection which was effective at 26°C. True wheats c2652 and Wsm2 selection CA745, and amphiploids Zhong1, Zhong2, Zhong4, Zhong5, TAF46, Summer1, Ot38 and OK7211542 were uniformly resistant at 20, 25 and 28°C. New sources of resistance were identified in a Th. scirpeum-wheat amphiploid, B84-994, and in chromosome addition lines Z2, Z6 and TAi27, derived from wheat-Th. intermedium partial amphiploids. Several new, tightly linked SSR, RAPD and EST-ILP PCR markers were developed for tracking the various Th. intermedium translocations associated with Wsm1, including the smaller translocations on wheat chromosome 4AS and 4DS. Three markers for the 4A-Wsm1 translocation were validated on a segregating breeding population.