RFLP ANALYSIS OF GENOMIC REGIONS ASSOCIATED WITH COOKED-KERNEL ELONGATION IN RICE

As a result of earlier breeding efforts, portions of the genome of ''B asmati 370'' have been introgressed into a rice breeding line, B8462T3 -710. Cooked-kernel elongation was increased in this breeding line to a level equal to that of ''Basmati 370''. The objective of this study was to identify and locate quantitative trait loci (QTLs) associated w ith cooked-kernel elongation in an F3 population derived from a cross between B8462T3-710 and the reduced-elongation recurrent parent variet y, Dellmont. DNA from the parental lines and ''Basmati 370'' as a cont rol, were screened for RFLPs using 170 clones chosen to cover the rice genome at intervals of 8 cM on average. Eighteen markers identified R FLPs common to Basmati 370 and B8462T3-710, but different from Dellmon t, suggesting possible associations with kernel elongation. The B8462T 3-710/Dellmont F3 population was analyzed for segregation of those RFL Ps and for kernel elongation. Analysis of variance of the kernel elong ation ratio revealed that two markers, 14.6 cM apart on chromosome 8, are significantly associated with this trait (RZ323 P less-than-or-equ al-to 0.005, RZ562 P less-than-or-equal-to 0.05). Interval mapping sug gests a single QTL with a close proximity to RZ323. This QTL was teste d in F6 lines derived from the same cross and the presence of the B846 2T3-710 segment detected by RZ323 caused a highly significant increase of the kernel elongation ratio (P less-than-or-equal-to 0.04). In add ition, the QTL for kernel elongation and a gene for aroma, which are m ajor components of the grain quality characteristics of Basmati-type r ices, showed linkage. The availability of linked markers to the QTL ma y facilitate early selection for kernel elongation in rice breeding pr ograms.