Winter wheat genetic resistance to cephalosporium stripe disease and tolerance of aluminum toxicity

Paul S. Froese

This research was done to discover genomic regions of wheat (Triticum aestivum L.) associated with resistance to Cephalosporium stripe disease and aluminum (Al) toxicity tolerance in acidic soils, with the ultimate goal of improving wheat through targeted selection of favorable alleles at the loci herein revealed. The soilborne fungus Cephalosporium gramineum Nisikado and Ikata causes Cephalosporium stripe disease of winter wheat, reducing yields significantly in severe cases; complete resistance is unknown, and mapping efforts in wheat have been few. Al toxicity also reduces wheat yields in acidic soils, which are becoming more prevalent on the Palouse. There is natural variation in wheat Al tolerance and an Al tolerance gene on chromosome 4D named ALMT1 has been cloned and characterized. Much tolerance variation, however, is not explicable by known major tolerance loci, and the tolerance of regional germplasm is largely unknown. Two populations of winter wheat, one of 480 individuals (PopA), the other of 401 individuals (PopB), were used for association mapping (AM) of Al tolerance, whereas PopA and a population of 158 recombinant inbred lines (RILs) from ‘Finch’ and ‘Eltan’ parents were used to map Cephalosporium stripe resistance. All of these accessions were phenotyped in multiple field environments under respective stresses; PopB was also phenotyped hydroponically for Al tolerance. PopA was genotyped on a 90,000 single nucleotide polymorphism (SNP) chip, whereas PopB and the 158 RILs were genotyped on a 9000 SNP chip. PopB was also assayed with marker wmc331 for allelic state of ALMT1. Twelve Cephalosporium stripe resistance quantitative trait loci (QTL) were identified in Finch and Eltan, and more than 50 QTL were found via PopA AM. AM of Al tolerance identified 54 QTL, five of which were indicated in both PopA and PopB. Thirteen percent of PopB was found to carry the positive ALMT1 allele; however, AM with wmc331did not associate it with tolerance, and allelic correlation with tolerance score revealed only weak correlations, where significant. We believe that the unique germplasm examined in this study has novel sources of Cephalosporium stripe resistance and Al tolerance yet to be exploited in the development of superior wheat cultivars

Winter wheat genetic resistance to cephalosporium stripe disease and tolerance of aluminum toxicity

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