Abstract
ABSTRACT Powdery mildew of wheat (Triticum spp.) caused by Blumeria graminis f.sp. tritici (DC) E.O. Speer Em. Marchal is one of the most important bread wheat diseases in Egypt. All the Egyptian common bread wheat cultivars are susceptible to that disease at seedling and adult stages. Breeding of resistant cultivars is the most economical and environmentally safe method to eliminate the disease and reduce crop losses. Combinations of two or more effective resistance genes may lead to better, more durable resistance to that disease. Eight Pm genes i.e. Pm2, Pm6, Pm12, Pm16, Pm24, Pm35, Pm36 and Pm37 out of 21 powdery mildew monogenic wheat lines (Pm) were resistant to 42 individual isolates of powdery mildew collected from different governorates in the Nile Delta area, Egypt, at seedling and adult stages. Only four DNA specific SSR markers (Xgwm337, Xcfd7 linked to Pm24, Pm35 and Xgwm332, Xwmc790) linked to Pm37 resistance genes were selected to detect these genes in 13 Egyptian common bread wheat cultivars. This study reveals the absence of Pm24, Pm35 and Pm37 in all the 13 Egyptian bread wheat cultivars. These results gave evidence that the Egyptian cultivars are not having resistance genes and need to further incorporate one, two or more resistant genes in a single genotype as all commercial cultivars defeated by the pathogen.
Highlights
Powdery mildew of wheat, caused by the fungus (Blumeria graminis f. sp. tritici Marchal), is a common disease that spread all over the world
Molecular markers are known to be useful in the process of detection of the disease resistance genes, especially in genotypes where the genetic back ground has not been clarified as is the case for most commercial cultivars
The genes Pm2, Pm6, Pm12, Pm16, Pm24, Pm35, Pm36 and Pm37 have remained completely effective for all isolates (100% efficacy)
Summary
Powdery mildew of wheat, caused by the fungus (Blumeria graminis f. sp. tritici Marchal), is a common disease that spread all over the world. Molecular identification of specific DNA sequences can be used to identify the presence or absence of wheat powdery mildew (Pm) genes in wheat cultivars, their chromosomal location, the number of genes, and the way in which they are transmitted to progeny (Chen and Chelkowski, 1999). The availability of molecular markers, used for identifying, mapping, and cloning powdery mildew resistance genes, has greatly enhanced the development of molecular breeding. Molecular markers are known to be useful in the process of detection of the disease resistance genes, especially in genotypes where the genetic back ground has not been clarified as is the case for most commercial cultivars. The genes Pm24, Pm35, and Pm37 were approved to be effective genes against the disease in the regions with similar ecological condition as Egypt in the world (Huang et al, 2000; Langridge et al, 2001; Miranda et al, 2007; Perugini et al, 2008). This study was conducted to identify those powdery mildew resistance genes i.e. Pm24, Pm35 and Pm37 in 13 registered Egyptian bread wheat cultivars using SSR markers under the Egyptian conditions
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