Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 3, 1999
Publication Date: N/A
Technical Abstract: The development of hybrid rice and the use of high yielding foreign germplasm to develop new cultivars have been hindered by low milling quality (MQ). It is difficult to select for MQ early in the breeding process because of the large impact variable macro- and micro-environments have on this trait. Because long, thin kernels are known to break more readily during milling than do short, thick kernels, regardless of hardnes or other physicochemical properties, segregation for grain shape in an early breeding generation would further confound selection efforts. The purpose of this research was to identify genomic regions associated with MQ and with aspects of kernel morphology and chemistry known or hypothesized to be associated with milling quality in order to clarify the relationships between these kernel traits and MQ, and to identify molecular markers breeders can use for selecting for improved MQ. A population of 284 recombinant inbred lines (RILs) was developed from a Lemont x Teqing cross and characterized for 175 RFLP probes. In fissured seed samples harvested from two 1997 field replications were characterized for 3-dimensional kernel shape and MQ. Interval mapping identified a total of eight chromosomal regions associated with MQ. Two of these QTLs are of particular interest to us because they are apparently independent from grain shape. These loci each accounted for 6- to 8-percent of the total variance observed in percent head rice, which translates into a 4-percent increase in head rice resulting from the incorporation of a single gene into a new variety. The economic importance of a 4% increase in milling quality has been demonstrated to the rice industry by the variety 'Cypress'. MQ data collected from 1998 seed will be used to verify these putative QTLs.