Molecular mapping of the blast resistance gene, Pi44(t), in a line derived from a durably resistant rice cultivar

Abstract

 A recombinant inbred line derived from a cross between CO39 and ‘Moroberekan’, RIL276, was found to be resistant to lineage 44 isolates of Pyricularia grisea in the Philippines. One hundred F₂ individuals were obtained from a backcross of RIL276 and CO39. Phenotypic analysis showed that RIL276 carries a single locus, tentatively named Pi44(t), conferring complete resistance to lineage 44 isolates of P. grisea. RFLP probes, STS primers and AFLP markers were applied to identify DNA markers linked to Pi44(t). Neither RFLP nor STS-PCR analysis gave rise to DNA markers linked to the locus. Using bulk segregant AFLP analysis, however, two dominant AFLP markers (AF₃₄₈ and AF₃₄₉) linked to Pi44(t) were identified. AF₃₄₉ and AF₃₄₈ were located at 3.3±1.5 cM and 11±3.5 cM from Pi44(t), respectively. These markers were mapped on chromosome 11 using an F₂ population derived from a cross between ‘Labelle’ and ‘Black Gora’. The location of AF₃₄₈ on chromosome 11 was confirmed using another F₂ mapping population derived from IR40931-26-3-3-5/ PI543851. DNA products at the loci linked to Pi44(t) were amplified from RIL276, ‘Labelle’ and PI543851 using the same primer pairs used to amplify AF₃₄₉ and AF₃₄₈. Sequence analysis of these bands showed 100% identity between lines. This result indicates that these AFLP markers could be used for the comparison of maps or assignment of linkage groups to chromosomes.