Identification of quantitative trait loci conferring resistance to tan spot in a biparental population derived from two Nebraska hard red winter wheat cultivars

Tan spot, caused by Pyrenophora triticirepentis (Ptr), is a destructive foliar disease in all types of cultivated wheat worldwide. Genetics of tan spot resistance in wheat is complex, involving insensitivity to fungal-produced necrotrophic effectors (NEs), major resistance genes, and quantitative trait loci (QTL) conferring race-nonspecific and race-specific resistance. The Nebraska hard red winter wheat (HRWW) cultivar ‘Wesley’ is insensitive to Ptr ToxA and highly resistant to multiple Ptr races, but the genetics of resistance in this cultivar is unknown. In this study, we used a recombinant inbred line (RIL) population derived from a cross between Wesley and another Nebraska cultivar ‘Harry’ (Ptr ToxA sensitive and highly susceptible) to identify QTL associated with reaction to tan spot caused by multiple races/isolates. Sensitivity to Ptr ToxA conferred by the Tsn1 gene was mapped to chromosome 5B as expected. The Tsn1 locus was a major susceptibility QTL for the race 1 and race 2 isolates, but not for the race 2 isolate with the ToxA gene deleted. A second major susceptibility QTL was identified for all the Ptr ToxC-producing isolates and located to the distal end of the chromosome 1A, which likely corresponds to the Tsc1 locus. Three additional QTL with minor effects were identified on chromosomes 7A, 7B, and 7D. This work indicates that both Ptr ToxA-Tsn1 and Ptr ToxC-Tsc1 interactions are important for tan spot development in winter wheat, and Wesley is highly resistant largely due to the absence of the two tan spot sensitivity genes

Registration of ‘Juniper’ Wheat

‘Juniper’ (Reg. No. CV-1021, PI 639951) is a hard red winter wheat (Triticum aestivum L.) developed by the Idaho Agricultural Experiment Station and released in February 2006. Juniper was tested under the experimental numbers A91013W-1 and IDO575. It is a full-stature wheat released for very low rainfall, crop-fallow rotations of the Intermountain West and was released for its improved resistance to stripe rust (Puccinia striiformis Westend) and dwarf bunt (Tilletia controversa Kühn in Rabenh) and bread-baking quality compared with current full-stature cultivars. Juniper had an average yield in rainfed trials of 3290 kg ha−1, compared with the other tall cultivars for this region, ‘Weston’ and ‘Bonneville’, which had grain yields of 3050 and 3180 kg ha−1, respectively. Weston has undesirable baking quality due to short dough mixing time. Juniper has nearly a full minute longer mixograph mixing time compared with Weston (p \u3c 0.01). Juniper also has similar snow mold tolerance (causal organism Typhula spp.) to Bonneville without the undesirable characteristic of late heading date and maturity. Juniper heads 3 d earlier than Bonneville

Registration of ‘UI Darwin’ Wheat

‘UI Darwin’ (Reg. No. CV-1022, PI 639953) is a hard white winter wheat (Triticum aestivum L.) developed by the Idaho Agricultural Experiment Station and released in February 2006. UI Darwin (pedigree IDO445/‘Manning’) was tested under the experimental numbers A93151W-85 and IDO604. It is a tall semidwarf wheat released for crop-fallow rotations of the Intermountain West, where few hard white wheat cultivars are available. UI Darwin has improved resistance to stripe rust (Puccinia striiformis Westend.) relative to ‘Bonneville’ hard red winter wheat with resistance to dwarf bunt (Tilletia controversa Kühn in Rabenh) at similar levels to Bonneville. In 16 rainfed yield trials grown in Idaho from 2001 to 2005, UI Darwin had an average grain yield of 3200 kg ha-1, similar to Bonneville (3050 kg ha-1) and ‘Weston’ (3190 kg ha-1) but less than ‘Gary’ (3560 kg ha-1 UI Darwin has improved bread baking quality compared with current hard white winter wheat cultivars and has excellent color in akaline noodle products. UI Darwin had an average pup-loaf volume of 1075 mL, similar to hard red winter wheat cultivars Bonneville (1044 mL) and Weston (1064 mL) but greater than the hard white wheat cultivar Gary (963 mL)

Identification of quantitative trait loci conferring resistance to tan spot in a biparental population derived from two Nebraska hard red winter wheat cultivars

Tan spot, caused by Pyrenophora triticirepentis (Ptr), is a destructive foliar disease in all types of cultivated wheat worldwide. Genetics of tan spot resistance in wheat is complex, involving insensitivity to fungal-produced necrotrophic effectors (NEs), major resistance genes, and quantitative trait loci (QTL) conferring race-nonspecific and race-specific resistance. The Nebraska hard red winter wheat (HRWW) cultivar ‘Wesley’ is insensitive to Ptr ToxA and highly resistant to multiple Ptr races, but the genetics of resistance in this cultivar is unknown. In this study, we used a recombinant inbred line (RIL) population derived from a cross between Wesley and another Nebraska cultivar ‘Harry’ (Ptr ToxA sensitive and highly susceptible) to identify QTL associated with reaction to tan spot caused by multiple races/isolates. Sensitivity to Ptr ToxA conferred by the Tsn1 gene was mapped to chromosome 5B as expected. The Tsn1 locus was a major susceptibility QTL for the race 1 and race 2 isolates, but not for the race 2 isolate with the ToxA gene deleted. A second major susceptibility QTL was identified for all the Ptr ToxC-producing isolates and located to the distal end of the chromosome 1A, which likely corresponds to the Tsc1 locus. Three additional QTL with minor effects were identified on chromosomes 7A, 7B, and 7D. This work indicates that both Ptr ToxA-Tsn1 and Ptr ToxC-Tsc1 interactions are important for tan spot development in winter wheat, and Wesley is highly resistant largely due to the absence of the two tan spot sensitivity genes