Genetic Analysis of Amylose Content, Alkali Spreading Score, and Grain Dimensions in Rice1

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Abstract
The inheritance and interrelationships in rice (Oryza sativa L.) of amylose content, alkali spreading score, and grain dimensions were studied in six crosses each involving a low amylose medium‐grain parental line. High amylose appeared to be controlled by a single dominant gene in four crosses and by two dominant complementary genes in a fifth cross. Evidence that amylose content was also influenced by modifying genes of minor effect was noted in these crosses. In the sixth cross, between two low amylose lines, control of amylose content was attributed to a few genes of small effect. Segregation patterns for alkali spreading scores in five crosses did not conform to any identifiable genetic model. In one cross alkali spreading score was probably controlled by a single gene. In the other crosses one or a few additive genes of major effect, along with modifier genes, were probably controlling alkali spreading score. Heritability estimates for alkali spreading score were very high. Kernel length and width appeared to be governed by quantitative genes. Transgressive segregation for kernel width was indicated in one cross. Heritability estimates suggested that selection for kernel length and width would be effective. Amylose content and mean alkali spreading score were not strongly correlated in these crosses. However, contingency tables showed a highly significant association between amylose content classes and alkali reaction types in three crosses. The linkage test between amylose class and alkali reaction type was highly significant in cross one, with an estimated recombination value of 0.34. Kernel length and width were negatively correlated in all crosses, with r values ranging from −0.36 to −0.58.