EVALUATION AND IMPROVEMENT OF CEREAL GERMPLASM FOR DISEASE RESISTANCE AND WINTER-HARDINESS
Location: Plant Science Research
Title: MlAB10: a Triticum turgidum subsp. dicoccoides derived powdery mildew resistance gene identified in common wheat
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 10, 2010
Publication Date: September 27, 2010
Citation: Maxwell, J., Lyerly, J., Srnic, G., Parks, W.R., Cowger, C., Marshall, D.S., Brown Guedira, G.L., Murphy, P.J. 2010. MlAB10: a Triticum turgidum subsp. dicoccoides derived powdery mildew resistance gene identified in common wheat. Crop Science. 50:2261-2267.
Interpretive Summary: A soft red winter wheat line developed by North Carolina State University in 1997 has remained effective against natural populations of powdery mildew. The line, which is called NC97BGTAB10, has mildew resistance from wild emmer wheat. The resistance in NC97BGTAB10 was previously shown to be due to a single gene. In this research project, the resistance was mapped to the tip of the long arm of wheat chromosome 2B. A map of genetic markers was developed for that region of the 2B chromosome, so that wheat researchers can determine if the gene is present by using the markers. The gene is located in the same chromosomal region as two other mildew resistance genes from emmer wheat, MlZec1 and Pm33. Until tests can be carried out to determine whether the new resistance gene in NC97BGTAB10 is at the same locus as MlZec1 and Pm33, or simply near those genes on the same chromosome, a temporary name of MlAB10 is proposed.
Powdery mildew is an economically important disease in wheat growing areas with a cool maritime environment. Host genetic resistance is the most economical, consistent, and environmentally sound method of control. NC97BGTAB10 is a germplasm line containing powdery mildew resistance introgressed from wild emmer wheat (Triticum. turgidum subsp. dicoccoides (AABB; 2n = 28)). The objectives of this research were to genetically characterize the powdery mildew resistance in NC97BGTAB10, identify SSR markers closely linked to the resistance gene, and provide evidence that the gene is a novel T. turgidum subsp. dicoccoides-derived powdery mildew resistance gene. One hundred thirty nine F2:3 lines developed from the cross NC97BGTAB10 / Saluda were evaluated in the field and greenhouse for reaction to powdery mildew. The population segregated in an expected 1:2:1 (resistant : segregating : susceptible) ratio, typical of a monogenic trait. A bulked segregant analysis using 25 F3 families per bulk was conducted using Diversity Arrays Technology (DArT). The DArT analysis identified a polymorphism between the resistant and susceptible bulks on chromosome 2BL. The population was genotyped with SSR markers that were specific to chromosome 2B and a linkage map was developed for this region. The SSR marker Xwmc445 mapped 7 cM proximal to the resistance gene and no marker could be mapped distal to the gene. The markers all mapped to the most distal deletion bin (0.89-1.00) of chromosome 2BL. It was concluded that the resistance gene lies in the tip of chromosome 2BL. The powdery mildew resistance genes Pm6, Pm33 and MlZec1 have also been mapped to chromosome 2BL. A detached leaf test with two powdery mildew isolates indicated the resistance gene in NCAB10 was different from MlZec1. No allelism test could be conducted to determine the relationship between NCAB10 and the Pm33 or MlZec1 genes at this time. Thus, this gene has been given the temporary designation MlAB10.