Development of introgression lines derived from Oryza rufipogon and O. glumaepatula in the genetic background of japonica cultivated rice (O. sativa L.) and evaluation of resistance to rice blast

Wild relatives of cultivated rice (Oryza sativa L.) are useful sources of alleles with economic value for rice breeding programs. To effectively identify such alleles, three sets of introgression lines (ILs) carrying one or more chromosome segments derived from wild relatives with the A genome in the background of japonica rice cultivars Koshihikari and Itadaki were developed using marker-assisted backcrossing. The donor wild species include two accessions of O. rufipogon (IRGC Acc. 104814 and 104812) and one accession of O. glumaepatula (IRGC Acc. 100968) while 2 japonica rice cultivars, Koshihikari and Itadaki, were used as recurrent parents. The two sets of ILs from O. rufipogon in the Koshihikari background consisted of 40 and 47 lines, respectively. The average proportions of recurrent parental genome were 94.3% and 96.0% in the ILs derived from accessions 104814 and 104812, respectively. The ILs from O. glumaepatula in the Itadaki background consisted of 47 lines, with an average proportion of recurrent parental genome of 91.0%. To demonstrate the potential of these ILs in identifying useful alleles, the two sets of ILs were screened for resistance to rice blast (Magnaporthe grisea). By substitution mapping, two new loci for partial resistance to rice blast were detected on chromosomes 3 and 11 of O. rufipogon (104812).