Submitted to: International Symposium on Septoria/Stagonospora Disease of Cereals
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/2003
Publication Date: 12/8/2003
Citation: Czembor, P.C., Arseniuk, E., Ueng, P.P. 2003. Field evaluation of quantitative trait loci (qtls) associated with partial resistance to phaeosphaeria nodorum in wheat seedlings. International Symposium on Septoria/Stagonospora Disease of Cereals. pp. 119-122. Interpretive Summary: Stagonospora nodorum blotch (SNB) is an important disease in cereals. Only partially resistant wheat cultivars are commercially available, and there is need to find ways to identify genes that can improve resistance to the disease. In a previous study on wheat seedlings, we had found the chromosomal locations of six disease resistance genes in two resistant wheat cultivars. In this paper we report that only three resistance genes are responsible for glume resistance in adult plants in the field condition. This new knowledge will aid in the breeding of wheat plants having enhanced resistance to SNB and will be of interest to plant breeders.
Technical Abstract: Six quantitative trait loci (QTLs) that were significantly associated with partial resistance to Phaeosphaeria nodorum blotch in the 5th leaf stage seedlings of two mapping populations were evaluated in adult plants in the field. The doubled haploid lines derived from crosses between a susceptible wheat cultivar, Begra, and two partially resistant wheat cultivars, Liwilla and Alba, were used. Disease severity on the plant leaves (_L) and heads (_H) was estimated by the area under the disease progress curve (AUDPC) method, and the association with six known QTLs was subjected to QTL analysis. In both mapping populations, none of previously detected QTLs in seedling stage were associated with leaf resistance in adult plants. However, some of the QTLs apparently were involved in resistance of heads in adult plants. Based on AUDPC_H, two QTLs on chromosomes 2B and 5D in wheat cultivar Liwilla had logarithm of likelihood ratio (LOD) values of 4.5 and 2.9, respectively, and each of them explained 22% of the phenotypic variance of the trait in one field trial. In wheat cultivar Alba, head resistance (AUDPC_H) was consistently associated with the QTL mapped on chromosome 6D. The LOD values were 3.9 for the first year (AUDPC_H1) and 4.5 for the second year (AUDPC_H2). The percentage of phenotypic variance explained by this QTL was 27% and 25% respectively in field trials during two years.