Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2001
Publication Date: N/A
Interpretive Summary: Scab is a destructive disease of wheat that can significantly reduce wheat grain yield and quality, resulting in billions of dollars in crop losses annually. It is caused by a fungus named Fusarium graminearum that also infects barley, oats, and rye, and causes stalk rot in corn. In addition to damaging wheat kernels, the fungus produces mycotoxins that limit the consumption of infected grain by humans and livestock. Even though fungicides can control the disease, they usually are not cost effective. If scab resistant wheat varieties were developed, they could represent effective and economically viable means of limiting losses caused by the disease. However, producing scab resistant wheat varieties by traditional breeding methods has been difficult because of the genetic complexity of scab resistance and the variability of environmental conditions that influence the development of the disease. The objectives of this study were to produce molecular probes for scab resistance genes that could be used to rapidly identify wheat lines containing the genes. In a previous study, we produced molecular markers linked to two genes that confer scab resistance in a Chinese wheat variety. In this study, we used those markers to develop rapid PCR tests that could be used to screen hundreds of plants for scab resistance genes. The results of these studies will be of interest to researchers who are working to produce new scab resistant wheat varieties, which should reduce economic losses to wheat producers and reduce the levels of mycotoxin within harvested grain.
Technical Abstract: Previous molecular analyses conducted in 133 recombinant inbred lines (RILs) derived from Ning 7840 (resistant) x Clark (susceptible) identified EcoRl- and PstI-AFLP markers linked to scab resistance in wheat. The objective of the present work was to convert the AFLPs into non-radioactive allele-specific PCR markers. Twelve markers including 9 EcoRI-AFLPs, and 3 PstI-AFLPs were cloned and sequenced. Sequence comparisons with databases showed similarity to a number of plant cDNAs. For a simple and rapid PCR based screening procedure, three sequence-tagged sites (STSs), and a single nucleotide polymorphism (SNP) were developed from 4 low-copy AFLP markers. In the Fl generation, two markers, SNPmaj and STSmaj flanking a major QTL explained 35.2% and 36.6% of the phenotypic variation respectively, with significant P values (< 0.001) in F5, F6, F7, and Fl generations. Another marker, STSmod1 linked to a second QTL explained 9.1% of the phenotypic variation in the Fl generation. The effect of allele substitution at these three loci (STSmaj, SNPmaj, and STSmod1) was significant at 0.01 to 0.001 level probability, showing tight linkage to the resistance QTL. In marker implementation on crossing block parents with varying genetic backgrounds, the STS and SNP markers detected the expected parental alleles. They are being used in marker-assisted selection for scab resistance.