Genetic diversity in relation to heterosis in maize (Zea mays L.)
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Date
2014
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Punjab Agricultural University
Abstract
The present investigation was conducted to estimate the magnitude of general and specific combining ability of inbred lines and crosses, respectively; mid-parent heterosis for yield component characters of maize and the association of the heterotic valve with the dissimilarity coefficient values derived from the diversity analysis using SSR markers. Forty eight crosses were made in a line x tester model by using twelve lines and four testers and all crosses with their parents were evaluated. The data was recorded on thirteen characters. The lines 1123, 1135 and 1137 were good general combiners for most of the characters studied. The estimates of gca effects revealed that inbreds 11102, 11166, 1123, 11103, 11100, LM 11 and LM 14 were good general combiners for grain yield/plant. The hybrids 1135 X LM 5, 1137 X LM 5, 1140 X LM 5, 1123 X LM 11, 1123 X LM 14, 1140 X LM 11 and 11102 X LM 11were found to be good specific combiners for most of the characters. The best crosses for per se performance and mid- parent heterosis were 1123 X LM 14, 1137 X LM 5, 11109 X LM 11, 1123 X LM 11, 1135 X LM 11 and 1135 X LM 5, 11109 X SE 546, 11109 X LM 11, 11166 X SE 546, 1137 X LM 5, respectively. Unweighted pair group method with arithmetical averages (UPGMA) available in diversity analysis computer software DARwin 5.0 was used to group the inbred lines in different clusters. Dendrogram constructed grouped the inbred lines in three clusters (C-l, C-2 and C-3). A set of thirty seven SSR primers dispersed throughout the maize genome were used to assess the genetic diversity at the molecular level. A total of one hundred and thirteen alleles were detected and polymorphism information content (PIC) value ranged from 0.218 to 0.778 with an average value of 0.565. SSR primers with di-repeats revealed a maximum mean PIC value of 0.62, followed by tetrarepeats (0.57) and tri-repeats (0.50). In order to predict the hybrid performance, utilizing SSR markers, genetic distances were calculated among the inbred lines. Correlation coefficients calculated between the genetic distances of inbred lines and mid parent heterosis and specific combining ability for various yield and yield component characters of maize were non-significant. Thus it seems rather difficult to make a generalized conclusion regarding the prediction of hybrid performance especially for grain yield, based on genetic distance measures.
Keywords: Maize, combining ability, heterosis, genetic diversity.
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livestock, diseases