Mapping of a QTL contributing to cereal cyst nematode tolerance and resistance in wheat

Cereal cyst nematode (CCN; Heterodera avenae Woll.) is a root pathogen of cereals that can cause severe yield losses in intolerant wheat cultivars. Tolerance to CCN, measured as early vigour in CCN-infested plots, was mapped in a Trident/Molineux doubled-haploid (DH) population. A locus accounting for a significant proportion of the tolerance to CCN was mapped to chromosome 6B of Molineux by association with RFLP loci Xcdo347-6B and Xbcd1 and also by nullisomic/tetrasomic substitution line analysis, and has been designated Cre8. The linkage of CCN tolerance with Xcdo347-6B was validated using a Barunga/Suneca DH population. The Cre8 locus also contributed to CCN resistance in the Trident/Molineux population. The RFLP locus Xbcd175, which is diagnostic for the Aegilops ventricosa segment VPM1 of Trident, explained up to 18% of the variation for early vigour in CCN-infested soils in the Trident/Molineux population. However, the Trident/Molineux population also segregated for early vigour in the absence of CCN, with Xbcd175 explaining up to 7% of the variation for this trait. The VPM1 segment of Trident therefore provides early vigour that may contribute to CCN tolerance in this cultivar.K. J. Williams, J. G. Lewis, P. Bogacki, M. A. Pallotta, K. L. Willsmore, H. Kuchel and H. Wallwor