Forty-eight years of rice improvement in Texas since the release of cultivar bluebonnet in 1944
Information on the contribution of plant breeding to changes in yields and other agronomic traits is useful for optimizing selection gains; thus, this study aimed to determine the contribution of Texas rice (Oryza sativa L.) breeding to changes in cultivars released during the 48 yr since the release of ‘Bluebonnet’ in 1944. Twenty-three cultivars were evaluated in three environments and two N levels. Days to heading, plant height, whole and total milled rice percentages, and grain yield were measured. Significant variation among cultivars was found for all traits evaluated, while N affected all traits except milled rice. There was a linear decrease in days to heading in cultivars released from 1944 to 1992. Plant height decreased at 1.28 and 1.10 cm yr–1 for the 190 and 95 kg ha–1 N levels, respectively, mainly due to the incorporation of the semidwarf gene in many cultivars starting in 1981. Plant heights of recently released cultivars were more stable across N levels and less susceptible to lodging. Although whole and total milled rice percentages increased at 0.06 and 0.03% yr–1, respectively, environmental factors limited their genetic advances. Grain yield increased at 42.0 and 26.3 kg ha–1 yr–1 under the 190 and 95 kg ha–1 N levels, respectively, demonstrating that newer releases responded well to higher N. These show the remarkable progress in the Texas rice breeding program from 1944 to 1992.