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Hexaploid oat (Avena sativa L., 2n = 6x = 42) is a member of the Poaceae family and has a large genome (~12.5 Gb) containing 21 chromosome pairs from three ancestral genomes. Physical rearrangements among parental genomes have hindered the development of linkage maps in this species. The objective of this work was to develop a single high-density consensus linkage map that is representative of the majority of commonly grown oat varieties. Data from a cDNA-derived single-nucleotide polymorphism (SNP) array and genotyping-by-sequencing (GBS) were collected from the progeny of 12 biparental recombinant inbred line populations derived from 19 parents representing oat germplasm cultivated primarily in North America. Linkage groups from all mapping populations were compared to identify 21 clusters of conserved collinearity. Linkage groups within each cluster were then merged into 21 consensus chromosomes, generating a framework consensus map of 7202 markers spanning 2843 cM. An additional 9678 markers were placed on this map with a lower degree of certainty. Assignment to physical chromosomes with high confidence was made for nine chromosomes. Comparison of homeologous regions among oat chromosomes and matches to orthologous regions of rice (Oryza sativa L.) reveal that the hexaploid oat genome has been highly rearranged relative to its ancestral diploid genomes as a result of frequent translocations among chromosomes. Heterogeneous chromosome rearrangements among populations were also evident, probably accounting for the failure of some linkage groups to match the consensus. This work contributes to a further understanding of the organization and evolution of hexaploid grass genomes.

All cultures were maintained initially Pyricularia oryzae in the Philippines. Plant Disease 70:767-769. in prune agar slants. For long-term The rice blast pathogen, Pyricularia oryzae, was collected from various regions in the Philippines storage, sorghum grains were used as a and tested on widely grown Philippine cultivars and the International, Japanese, and Korean substrate. The grains were steeped, differential cultivar sets. Isolates with virulence to Philippine IR cultivars were common in samples boiled, and autoclaved on two consecutive from lowland areas, where such cultivars are widely grown, but virulence was rare among isolates days. The grains were seeded with the from Zamboanga del Sur, where upland rice is cultivated. Virulence to C22 was most frequent fungus and incubated at 25-28 C until all among Zamboanga del Sur isolates. Virulence to IR56, UPLRi3, and UPLRi5 was rare. Virulence grains were colonized. The colonized to the newly released cultivars IR58, IR60, and IR62 was present in the fungus population. IR60 grains were dried at 40 C for 24 hr, and IR62 showed a higher frequency of intermediate reaction types than other IR cultivars. None transferred to a vial of silica gel, and of the three differential sets could adequately differentiate agriculturally important isolates. stored at 4 C. These colonized grains Differential sets using established cultivars grown within a geographic region are recommended for were used as stock cultures for all retested

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