Development of chromosome segment substitution lines (CSSLs) of Oryza longistaminata A. Chev. & Röhr in the background of the elite japonica rice cultivar, Taichung 65 and their evaluation for yield traits

Oryza longistaminata (AA genome) is a wild rice species that is phenotypically inferior to cultivated rice but possesses useful alleles that can be used to improve agronomically important traits. Interspecific hybrids that are derived from cultivated rice and wild rice species with AA genome are important contributors of genetic diversity in rice. To illustrate the potential of wild rice relatives as a source of novel alleles for rice improvement, a total of 40 chromosome segment substitution lines (CSSLs) of O. longistaminata in the background of the elite japonica cultivar Taichung 65 were developed and evaluated for yield and various yield-related traits. A number of CSSLs carrying putative quantitative trait loci (QTLs) controlling different yield-related traits were identified during both dry and wet seasons. In particular, 10 major putative QTLs controlling early heading date, plant height, tiller number, panicle length, number of primary branches per panicle, grain number per panicle, grain width, and grain thickness were identified. Interestingly, one of the CSSL lines, LTSL26, with major putative QTLs on chromosomes 1 and 8 that increase grain number per panicle, showed pleiotropic effects on other traits such as plant height, days to flowering, tiller number, number of branches per panicle, and grain length. These results suggest that O. longistaminata is a good source of new alleles that can be used to improve yield-related traits in cultivated rice varieties.