Quantitative trait loci mapping of adult-plant resistance to leaf rust in a Fundulea 900 x 'Thatcher' heat cross

Wheat leaf rust (LR), caused by the obligate biotrophic fungus Puccinia triticina (Pt), is a destructive foliar disease of common wheat (Triticum aestivum L.) worldwide. The most effective, economic means to control the disease is resistant cultivars. The Romanian wheat line Fundulea 900 showed high resistance to LR in the field. To identify the basis of resistance to LR in Fundulea 900, a population of 188F(2:3) lines from the cross Fundulea 900/'Thatcher' was phenotyped for LR severity during the 2010-2011, 2011-2012 and 2012-2013 cropping seasons in the field at Baoding, Hebei Province. Bulked segregant analysis and simple sequence repeat markers were used to identify the quantitative trait loci (QTLs) for LR adult-plant resistance in the population. Three QTLs were detected and designated as QLr.hebau-1BL, QLr.hebau-2DS and QLr.hebau-7DS. Based on the chromosome positions and molecular marker tests, QLr.hebau-1BL is Lr46, and QLr.hebau-7DS is Lr34. QLr.hebau-2DS was derived from 'Thatcher' and was close to Lr22. This result suggests that Lr22b may confer residual resistance on field nurseries when challenged with isolates virulent on Lr22b, or another gene linked to Lr22b confers this resistance from 'Thatcher'. This study confirms the value of Lr34 and Lr46 in breeding for LR resistance in China; the contribution of the QTL to chromosome 2D needs further validation.