Application of Yr52 Gene in Wheat Improvement for Stripe Rust Resistance

The objective of this study is to evaluate the application value of the high temperature adult plant (HTAP) resistance gene Yr52 in wheat production for improving stripe rust resistance. And wheat lines with good agronomic characters and high disease resistance were developed and selected. It laid a foundation for making full use of the existing HTAP resistance resources and improving the yield related traits.

The stripe rust resistance gene Yr52 was introgressed to Lunxuan 987 (LX987), Bainong Aikang 58 (AK58) and Han 6172 (H6172) by backcrossing and self-crossing combined with marker-assisted selection breeding. Adult-plant resistance of donor parent, receptor cultivars and their progeny lines were evaluated in the disease nursery fields at Mianyang, Sichuan and Yangling, Shaanxi by mixed endemic physiological races CYR32, CYR33 and CYR34. In comparison to the Chinese Spring reference genome, the flanking SSR markers Xcfa2040 (6.8 cm-Yr52) and Xbarc182 (1.2 cm-Yr52) of Yr52 were combined to search for markers of 35K SNP chip in the physical interval of target genes, and developed into derived cleaved amplified polymorphic sequences (dCAPS) and kompetitive allele specific PCR (KASP) markers. The resistance gene Yr52 was detected in BC₂F_5:6 progeny lines.

The evaluation of adult plant resistance and agronomic traits indicated that nineteen BC₂F_5:6 lines with LX987 background was obtained: Among of them, 11 were high resistance (IT=0-3, DS=1%-20%), 8 were moderate resistance (IT=4-6, DS=15%-30%), the average thousand kernel weight (TKW), kernels per spike (KPS), productive tiller number per line (PTN), plant height (PH) and spike length (SL) was 45.33 g, 46, 7, 113.26 cm and 10.05 cm, respectively. Four BC₂F_5:6 families with AK58 background: all showed high resistance (IT=0-3, DS=5%-25%); the average TKW, KPS, PTN, PH and SL were 44.67 g, 48, 7, 96.54 cm and 10.17 cm, respectively. Five BC₂F_5:6 lineages with H6172 background showed high resistance to stripe rust (IT=0-3, DS=5%-20%). The average TKW, KPS, PTN, PH and SL were 43.74 g, 49, 8, 109.72 cm and 10.06 cm, respectively. The detection rate of three simple sequence repeat (SSR) molecular markers Xbarc182, Xcfa2040 and Xwmc557 linked to Yr52, in offspring population were 78.57%, 66.67% and 66.67%, respectively. One dCAPS marker Xdcaps-Yr52-1 and one KASP marker Xkasp-Yr52-1 were successfully developed, and the detection rates were 73.68% and 41.67%, respectively. The agronomic traits of lines with high (IT=0-3) and medium (IT=4-6) resistance levels were compared. The results showed that the average TKW (P>0.05), PTN (P>0.05) and KPS (P<0.05) of lines with IT=0-3 were higher than those of families with moderate resistance level lines (IT=4-6). Five lines with disease resistance and stable agronomic traits were selected by evaluated of PH=80-105 cm, PTN≥6, KPS≥45, TKW≥42 g, SL≥8 cm.

Yr52 was found to be resistant to all of the present predominant races in the adult plant stage. After introgression Yr52 into the main susceptible Chinese wheat varieties, the progeny lines with good disease resistance and agronomic characters could be used for breeding resistance varieties with multi-gene polymerization, it is enriching for the diversity of disease resistance genes and achieving durable utilization. The development of molecular markers will facilitate detect the utilization of Yr52 gene in resistance identification of germplasm in the future.