Evaluation of Molecular Markers for Common Bunt Resistance Genes in Diverse Wheat Genotypes.

Common bunt (CB) (Tilletia laevis and T. tritici) is a seed and soil borne disease that can cause significant quality and yield losses in wheat (Triticum aestivum).  One of the most effective ways to control CB is with host resistance.  To date, 15 resistance genes have been identified (Bt1 to Bt15).  This study was conducted to evaluate previously identified molecular markers associated with Bt8, Bt10, Bt11, and Bt12 in 74 wheat genotypes of diverse origin. These lines included 15 isogenic CB differential lines, 24 lines with known Bt genes and the remaining lines were a mix of CB resistant and susceptible lines with unknown Bt genes. DNA was extracted from seed of each genotype and used for marker evaluation.  A total of eight markers were evaluated for their association with Bt8, Bt10, Bt11, and Bt12, including four SSR markers Xgwm264, Xgwm374, and Xbarc128 for Bt12, three RAPD markers 372, 196, and FDS-RSA for Bt10, one SSR marker Xgwm114 for Bt11, and one  RAPD marker Psg3 for Bt8.  Xbarc128 was the best marker among the three markers used in predicting the Bt12. Among 16 genotypes known to carry Bt12, 12 lines carried the target allele at Xbarc128 locus. The RAPD marker 196 was the best among the three used in predicting the Bt10. Among ten genotypes known to carry Bt10, seven lines carried the target allele at this locus.  However, the target alleles of Xbarc128 and RAPD 196 were also present in some genotypes known not to have the Bt12 and Bt10.  This suggests that more mapping studies should be conducted in order to identify molecular markers tightly linked to CB resistance genes.