RESUMO
Milo disease in sorghum is caused by isolates of the soil-borne fungus Periconia circinata that produce PC-toxin. Susceptibility to milo disease is conditioned by a single, semi-dominant gene, termed Pc. The susceptible allele (Pc) converts to a resistant form (pc) spontaneously at a gametic frequency of 10(-3) to 10(-4). A high-density genetic map was constructed around the Pc locus using DNA markers, allowing the Pc gene to be delimited to a 0.9 cM region on the short arm of sorghum chromosome 9. Physically, the Pc-region was covered by a single BAC clone. Sequence analysis of this BAC revealed twelve gene candidates. Several of the predicted genes in the region are homologous to disease resistance loci, including one NBS-LRR resistance gene analogue that is present in multiple tandem copies. Analysis of pc isolines derived from Pc/Pc sorghum suggests that one or more members of this NBS-LRR gene family are the Pc genes that condition susceptibility.
Assuntos
Ascomicetos/patogenicidade , Genes de Plantas , Mapeamento Físico do Cromossomo , Sorghum/genética , Toxinas Biológicas/genética , Alelos , Sequência de Aminoácidos , Cromossomos Artificiais Bacterianos , Cromossomos de Plantas , Clonagem Molecular , Cruzamentos Genéticos , DNA de Plantas , Dosagem de Genes , Duplicação Gênica , Genes Dominantes , Marcadores Genéticos , Genótipo , Dados de Sequência Molecular , Polimorfismo Conformacional de Fita Simples , Recombinação Genética , Homologia de Sequência de AminoácidosRESUMO
We report a genetic recombination map for Sorghum of 2512 loci spaced at average 0.4 cM ( approximately 300 kb) intervals based on 2050 RFLP probes, including 865 heterologous probes that foster comparative genomics of Saccharum (sugarcane), Zea (maize), Oryza (rice), Pennisetum (millet, buffelgrass), the Triticeae (wheat, barley, oat, rye), and Arabidopsis. Mapped loci identify 61.5% of the recombination events in this progeny set and reveal strong positive crossover interference acting across intervals of
