Identification of common root-lesion nematode (Pratylenchus thornei Sher et Allen) loci in bread wheat

Abstract

Plant parasitic nematodes are a major biotic cause of wheat-yield loss in temperate wheat-growing regions. A major strategy to develop resistance to root-lesion nematodes (RLNs) in wheat is to assess and then exploit their natural genetic variation. This study examines RLN (Pratylenchus thornei) resistance in 1 Middle Eastern landrace (AUS4930 7.2) and 1 synthetic hexaploid wheat, CROC_1/AE. SQUARROSA (224)//OPATA (CROC), using F2 and F9 populations generated by crossing AUS4930 7.2 and CROC with the susceptible cultivar Pastor, and inoculating these crosses with P. thornei in greenhouse trials. Wheat microsatellite markers linked to previously identified quantitative trait loci (QTLs) for resistance to P. thornei and P. neglectus were used to screen both populations. In the AUS4930 7.2 x Pastor population, resistance loci on chromosomes 1B, 2B, and 6D were detected. Similarly, in the CROC x Pastor population, 2 resistance loci, located on chromosomes 1B and 3B, were identified. Interestingly, a resistance locus located on chromosome 6D was not detected. More detailed mapping is required in these 2 populations, developed using new RLN resistance sources, to determine whether the QTLs identified on these chromosomes are the same, are allelic, or are linked to different resistance loci from those previously identified, and to determine whether these 2 sources contain other novel resistance loci.

Diploid and tetraploid progenitors of wheat are valuable sources of resistance to the root lesion nematode Pratylenchus thornei

“…Neither of the corresponding B-genome chromosomes has been identified in QTL analysis of P. thornei resistance in landrace bread wheats and synthetic hexaploid wheats. The addition lines DA2S, DA3S and DA4S had an intermediate level of resistance, more susceptible than A. speltoides but more R than Chinese Spring (Sheedy et al 2008a), with chromosome 2B and/or 3B commonly identified in QTL analysis of hexaploid wheat (Schmidt et al 2005;Toktay et al 2006;Zwart et al 2006Zwart et al , 2010. Chromosome 1B has been reported to have both susceptibility (Schmidt et al 2005) and resistance (Toktay et al 2006) loci but the DA1S addition line was more susceptible than Chinese Spring (Sheedy et al 2008a).…”

“…However, many genes conferring resistance to diseases and pests have been transferred using direct hybridization (Cox 1991(Cox , 1998Friebe et al 1996), including CCN resistance from T. monococcum to durum and bread wheat cultivars (Singh et al 2010). Previous studies on moderately P. thornei R hexaploid wheats from the West Asia and North Africa (WANA) region have used single marker regression and QTL analysis to identify resistance loci on chromosomes 2B, 3B, 6D and 7A (Schmidt et al 2005), 1B, 2B and 6D (Toktay et al 2006) and a susceptibility locus on 1B (Schmidt et al 2005). Similar studies on synthetic hexaploid derived populations have identified P. thornei resistance loci on chromosomes 6DS and 6DL (Zwart et al 2005), 1B and 3B (Toktay et al 2006) and 2BS, 6DS and 6DL (Zwart et al 2006(Zwart et al , 2010.…”

“…Previous studies on moderately P. thornei R hexaploid wheats from the West Asia and North Africa (WANA) region have used single marker regression and QTL analysis to identify resistance loci on chromosomes 2B, 3B, 6D and 7A (Schmidt et al 2005), 1B, 2B and 6D (Toktay et al 2006) and a susceptibility locus on 1B (Schmidt et al 2005). Similar studies on synthetic hexaploid derived populations have identified P. thornei resistance loci on chromosomes 6DS and 6DL (Zwart et al 2005), 1B and 3B (Toktay et al 2006) and 2BS, 6DS and 6DL (Zwart et al 2006(Zwart et al , 2010. It is not surprising that virtually all the resistance loci have been identified on the B and D-genomes, considering all of the A. speltoides accessions examined in this study were at least moderately R to P. thornei, as were 16% of A. tauschii accessions screened by Thompson and Haak (1997).…”

“…The addition lines DA2S, DA3S and DA4S had an intermediate level of resistance, more susceptible than A. speltoides but more R than Chinese Spring (Sheedy et al 2008a), with chromosome 2B and/or 3B commonly identified in QTL analysis of hexaploid wheat (Schmidt et al 2005;Toktay et al 2006;Zwart et al 2006Zwart et al , 2010. Chromosome 1B has been reported to have both susceptibility (Schmidt et al 2005) and resistance (Toktay et al 2006) loci but the DA1S addition line was more susceptible than Chinese Spring (Sheedy et al 2008a). Given there may be up to five genes controlling the P. thornei resistance in A. speltoides (Sheedy et al 2008a) and that many studies of hexaploid wheat have concluded that P. thornei resistance is polygenic with additive gene action (Schmidt et al 2005;Thompson and Seymour 2011;Toktay et al 2006;Zwart et al 2004Zwart et al , 2005Zwart et al , 2006Zwart et al , 2010, it seems reasonable to expect that P. thornei resistance in the diploid relatives of wheat may also be polygenic.…”

Resistance of winter wheat to Heterodera filipjevi in Turkey

“…Their results indicated no complete resistance and no relationship between H. filipjevi and P. thornei resistance. These most likely have quantitative resistance genes against both CCNs and RLNs (Toktay et al, 2006;Sheedy et al, 2012). However, it is clear that while the Cre genes provide resistance to H. avenae, they do not confirm resistance to the H. filipjevi Turkish population.…”