Inheritance And Correlation Studies In Corn

Author : Leon Afton Hansen
Publisher :
ISBN 13 :
Total Pages : 206 pages
Book Rating : 4.:/5 (945 download)

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Download or read book The Inheritance of Ten Quantitative Characteristics in Sweet Corn (Zea Mays L.) written by Leon Afton Hansen and published by . This book was released on 1975 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: The inheritance of ten characteristics of sweet corn was studied by quantitative genetic analysis. Characters studied were tassel date, silk date, plant height, ear height, shank length, husk extension, tip blanking, number of kernel rows, ear length, and weight of the first ear. Diallel crosses were made between seven inbred parents. The ten characters were measured on the seven parents and 21 F1 crosses in two years and on the 21 reciprocal F1 crosses and 21 F2 families in one year. A fixed model of the diallel analysis was used to partition genetic variation into general combining ability (GCA) and specific combining ability (SCA). F1 data were combined over years to evaluate genotype by year interactions. Regressions of progeny on parents were calculated to compare the results of covariance among relatives with results based on variance components. Combining ability effects and genotypic correlations between characters were also estimated. Both GCA and SCA were involved in the inheritance of all ten characters. This was consistent for the F1 crosses in both years and for the F2 families. Variance components were extracted from expectations of mean squares and expressed as ratios of V subscript [SCA]/V subscript [GCA] to compare the relative importance of GCA and SCA. SCA was more important than GCA for ear length and weight of the first ear in the F1. Ratios for these characters were slightly larger than 1.0. GCA was more important than SCA for all other characters in the F1. Ratios ranged from .047 for number of kernel rows to .566 for plant height. Variance ratios for most characters decreased in the F2. The failure of some ratios to decrease in the F2 was attributed to either differential interactions of GCA and SCA with the environment or inadequate sampling of the F2 families. Analyses of heterosis and inbreeding depression were in general agreement with variance component ratios. Genotype by year interactions influenced the expression of most characters. A greater portion of the genotype by year interaction was contained in estimates of SCA than in estimates of GCA. Heritability estimates from parent-progeny regression and from variance components were generally in close agreement, although those from regression were generally larger than those from variance components. This supports the use of the combining ability analyses in this study. Large positive genotypic correlations were found between tassel date and silk date, plant height and ear length, ear height and shank length, ear height and tip blanking, ear height and ear length, number of kernel rows and ear weight, and ear length and ear weight. Large negative genotypic correlations were found between plant height and husk extension, ear length and husk extension, and ear weight and husk extension. Characters with large genotypic correlations also had large phenotypic correlations. Reciprocal F1 crosses differed for all characters except weight of the first ear. These differences were large enough in some crosses to have important breeding implications. The cause of these reciprocal differences could not be definitely established in this study.