Genetic Analysis and Mapping of Genes for Culm Length and Internode Diameter in Progeny from an Interspecific Cross in Rice

In this study, two near-isogenic lines (NILs) were selected from a series of chromosome segment substitution lines developed from an interspecific cross between Oryza sativa ssp. japonica cultivar ‘Hwaseongbyeo’ as a recipient parent and wild rice (Oryza grandiglumis) as the donor parent. Compared with Hwaseongbyeo control, one NIL (CR222) had reduced plant height and the other NIL (CR7501) displayed thicker basal and first internodes leading to increased lodging tolerance in the field condition. QTL analysis using progeny from crosses between Hwaseongbyeo and the NILs indicated that QTL for culm length and internode diameter leading to erect panicle were located on chromosomes 1 and 2, respectively. The major QTL for culm length on chromosome 1 was allelic to sd1 locus and the NIL showed the same sequence as the sd1 mutant cultivar ‘Reimei’. The QTL for the internode diameter was delimited to a 1-Mbp region on chromosome 2 and this QTL region harbors GW2 gene controlling grain width. The NIL with thick internode trait showed no undesirable pleiotropic effects and therefore has potential value for rice breeding for increasing lodging resistance.