Wheat leaf rust resistance in selected Triticum turgidum accessions

[摘要] English: In wheat, the depletion of genes for rust resistance necessitates the search foralternative sources of diversity. Species related to wheat, e.g. Triticum turgidum,provide such a source of new and hopefully durable resistance genes to Pucciniatriticina. In an effort to exploit this source, T. turgidum ssp. dicoccum var. arras, T.turgidum ssp. durum var. aestivum, T. turgidum ssp. durum var. murciense and T.turgidum ssp. polonicum, were crossed with the leaf rust-susceptible cultivar 8ST55.The F1 progeny from all crosses were susceptible in the adult-plant stage, suggestingrecessivity of resistance. F2 tests indicated that two recessive genes may beresponsible for resistance in T. turgidum ssp. dicoccum var. arras and T. turgidumssp. durum var. aestivum, respectively. Segregation ratios suggested a singlerecessive gene in T. turgidum ssp. durum var. murciense. T. polonicum progenydeviated from both single and two-gene Mendelian models. To further characterize the resistance in T. turgidum, accessions wereinoculated with six pathotypes (UVPrt2, 3, 5, 9, 13 and 17) of P. triticina. Since allwere susceptible to UVPrt5 but resistant to the other isolates, it appeared that theseaccessions have race-specific (vertical) resistance to P. triticina. From fluorescencemicroscopy of resistance components it was found that prestomatal exclusion did notplay a significant role. In T. turgidum ssp. dicoccum var. arras, T. turgidum ssp.durum var. aestivum and T. turgidum ssp. durum var. murciense early abortion ofstructures seemed important. T. turgidum ssp. polonicum and Morocco (control) hadfew, if any, early aborted structures and subsequent colonies were large incomparison to the other lines. T. turgidum ssp. dicoccum var. arras, T. turgidum ssp.durum var. aestivum and T. turgidum ssp. durum var. murciense showed varying degrees of host cell necrosis which is typical of a non-durable, hypersensitiveresponse. No necrosis was detected in leaf rust colonies in T. furgidum ssp.polonicum. AFLP analysis was used to follow the introgression of resistance into domestichexaploid wheat from T. turgidum ssp. dicoccum var. arras, the F1 hybrid andsusceptible and resistant F2 plants. It was found that 12 AFLP markers were solelyintrogressed from T. turgidum ssp. dicoccum var. arras into the resistant F2 plants.Certain markers, however, introgressed from T. turgidum ssp. dicoccum var. arraswere not present in all the resistant F2plants (although not present in the SST55 andthe susceptible F2 progeny). This suggests that these markers are possible linked toeither flanking regions of the introgressed segment or to only one of the two genesresponsible for resistance. Contrary to what was expected, more polymorph ismswere detected in tetraploid T. turgidum ssp. dicoccum var. arras than hexaploidSST55, suggesting an unequal contribution of genetic material from the respectiveparents in susceptible. and resistant F2 progeny. Furthermore, the frequency ofintrogression into F2 plants, especially into the resistant F2 progeny, was higher fromT. turgidum ssp. dicoccum var. arras than from SST55. Further research is, however, necessary to fully evaluate the statistical significance of this data.

[发布机构] University of the Free State