Greenhouse Validation of Yield Component Transgressive Variation Effects of Wild Oryza Species Introgressions in an Elite US Rice Cultivar.

A number of global studies have been conducted which have shown that the wild ancestral species, Oryza rufipogon, possesses beneficial alleles that can be used to improve cultivated rice, O. sativa, for biotic and abiotic stress tolerance as well as yield.  Introgression lines (IL) were developed through backcrossing an O. rufipogon accession (IRGC 105491) with the recurrent parent, Jefferson, a US long grain variety. In a previous multi-location field trial, ILs having introgressions on chromosomes 1, 2, 3, 6, 8, or 9 were associated with yield increases as compared to Jefferson. In this study, greenhouse trials were conducted at four different times during the year to identify specific yield components affected by the QTL introgressions associated with field yield.  Eight introgression lines and Jefferson were grown in replicated pot studies with plant growth and yield parameters determined, including height, days to heading, days to maturity, tiller number, panicle number, panicle length, branch number, floret number, seed set ratio, grains per panicle, and total seed number. Digital images taken throughout the growth cycle of the plants were used to estimate leaf area index. Results indicated that the ILs differed significantly and positively from Jefferson for a number of yield components. Greenhouse data for yield QTLs yld2.1, yld6.1, yld8.1, and yld9.1 were associated with yield component QTLs which had been previously reported in field studies, including increases in seeds per panicle (spp2.1), percent seed set (pss6.1), grains per panicle (gpp8.1), and panicle length (pl9.1), respectively. This study demonstrated that the greenhouse environment can be used to clearly identify yield component traits that are related to field yield and may offer a more stable environment for identifying QTL associated with physiological pathways needed for improved crop productivity.