Characterization of Historic South African Wheat Cultivars for Seedling Resistance to Cereal Rusts

Wheat rusts caused by various Puccinia fungi (P.graminis, P.triticina and P.striiformis) remain important diseases of bread wheat worldwide. The deployment of host plant resistance is one of the most sustainable breeding strategies that has been shown to be effective in establishing resistance to various cereal rusts. This study encompasses efforts to characterize the rust resistance capacity of various South African historic wheat cultivars for further use as sources of resistance or for re-introduction purposes in new germplasm developments. More than 260 cultivars were evaluated for seedling resistance to some rust races that are quite prominent in South Africa such as the 6E22A+ yellow rust race, 3SA144, 3SA145 and 3SA146 leaf rust races. The presence of Sr2, Sr24, Sr26 and Lr34 was also detected in some of the cultivars by Marker Assisted Selection. The Sr2 gene appeared to be more prevalent in the cultivars, with more than 60% of the accessions showing the presence of the gene. Some cultivars had a combination of multiple genes per cultivar. Intriguingly, most cultivars with the (Sr2 + Lr34) gene combination appeared to be susceptible to most of these leaf rust races. Nonetheless, some level of diversity was seen amongst these cultivars, with more than 20 cultivars showing resistant to moderate resistance to at least 2 or more of the races evaluated. Cultivars showing seedling resistance with a few adult plant resistance genes would be systematically isolated for further development of cultivars deploying a durable resistance strategy to target known and emerging rust races.