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Discolored kernels are but one component of rice (Oryza saliva L.) quality that requires attention by rice breeders. Discolored kernels are most often caused by damage from rice stink bugs [Oebalus pugnax (Fabricius)] and kernel smut disease (Tilletia barclayana Bref.), but other pathogens and physiological disorders can also contribute to kernel discoloration. Our objective was to further understand the inheritance and genotype x environment (GE) interactions for discolored rice kernels to improve rice kernel quality characteristics. Thirty-seven genotypes, representing southern U.S. rice germplasm, were evaluated for susceptibility to all causes of discolored kernels in field tests conducted during 1993 and 1994 at three Arkansas locations: Stuttgart, Tupelo, and Rohwer. Traits were inherited quantitatively, with single-plot heritability values of 0.07, 0.18, and 0.33 for rice stink bug damage, kernel smut, and other discolorations, respectively. The GE interactions were significant for all traits. Closer inspection of the GE interaction revealed that the causes were primarily related to magnitude changes but also included genotype rank changes. The bias of GE interaction during selection could be reduced by multi-year and multi-location testing. Phenotypic correlations among traits were low, indicating that selection for lower levels of one trait would not adversely raise the levels of another trait. Cultivars, such as Katy, Kaybonnet, and Drew, were identified as having stable, low susceptibility to rice stink bug damage, kernel smut, and other discolorations. Although breeding for improved kernel quality traits will have certain difficulties because of low heritability, the availability of good germplasm and a proper screening program should minimize this problem. |
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