Development and Identification of Introgression Lines from Cross of Oryza sativa and Oryza minuta

Introgression line population is effectively used in mapping quantitative trait loci (QTLs), identifying favorable genes, discovering hidden genetic variation, evaluating the action or interaction of QTLs in multiple conditions and providing the favorable experimental materials for plant breeding and genetic research. In this study, an advanced backcross and consecutive selfing strategy was used to develop introgression lines (ILs), which derived from an accession of Oryza minuta (accession No. 101133) with BBCC genome, as the donor, and an elite indica cultivar IR24 (O. sativa), as the recipient. Introgression segments from O. minuta were screened using 164 polymorphic simple sequence repeat (SSR) markers in the genome of each IL. Introgressed segments carried by 131 ILs covered the whole O. sativa genome. The average number of homozygous O. minuta segments per introgression line was about 9.99. The average length of introgressed segments was approximate 14.78 cM, and about 79.64% of these segments had sizes less than 20 cM. In the genome of each introgression line, the O. minuta chromosomal segments harbored chromosomal fragments of O. sativa ranging from 1.15% to 27.6%, with an overall average of 8.57%. At each locus, the ratio of substitution of O. minuta alleles had a range of 1.5%-25.2%, with an average of 8.3%. Based on the evaluation of the phenotype of these ILs, a wide range of alterations in morphological and yield-related traits were found. After inoculation, ILs 41, 11 and 7 showed high resistance to bacterial blight, brown planthopper and whitebacked planthopper, respectively. These O. minuta-O. sativa ILs will serve as genetic materials for identifying and using favorable genes from O. minuta.