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Genetics of tassel morphology in maize

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Item Summary

Title: Genetics of tassel morphology in maize
Authors: Huang, Yu
Keywords: maize
Issue Date: May 2013
Publisher: [Honolulu] : [University of Hawaii at Manoa], [May 2013]
Abstract: My research focused on tassel branching in maize and it encompassed studies of genetic and environmental factors affecting this trait. The maize tassel provides indispensable pollen in the process of reproduction, but it also competes with ears for photosynthetic products and can produce significant shade to leaves below. Thus newly developed corn hybrids have drastically reduced numbers of tassel branches compared to the ancient races of maize and tropical populations. My initial study involved analysis of branch numbers in 215 indigenous races of maize from ten countries through its regions of origin. Branch numbers ranged from 2.8 to 58.2 with an overall average of 27.0. In contrast a survey of 73 modern inbred lines, grown at Waimanalo Research Station, ranged from 2.5 to 36.5 branches with an overall average of 14.4. The difference was concluded to reflect long-term selection by maize breeders favoring smaller tassels.
Genetic studies of variation in near-isogenic lines of Hawaii's Hi27 revealed a major co-dominant gene, named Brta ("Branched tassel"). This gene essentially doubled branch numbers from 11 to 20. The Brta locus was found to be linked closely to the floury 1 and virescent 4 genes on Chromosome 2. Diallel analyses of several sets of progenies revealed high heterosis (>30%) for F1 hybrids and extensive variation in advanced progenies. A high ratio of 15.7 was observed for GCA:SCA (General:Specific combining ability), indicating that genetic control was largely due to additive gene action.
Three sets of recombinant inbred lines (RILs) were evaluated for tassel branch numbers, each having one parent with about 5 branches and the other about 20 branches. The RILs averaged about at the midpoint between these parents, ranging widely with minimal transgressive segregation. The data were almost normal in distribution and were best interpreted as involving four QTLs (quantitative trait loci) acting additively.
Environmental effects on branching were great from the low-light, cool winter to the warm, high-light summer, and these appeared to correlate directly with plant growth. Tassel branch numbers of one series of inbreds increased from 14.3 in December to 15.2 in February and 15.6 in April. A single significant GxE interaction involved the mutant ra2 (ramose tassel), which had more branches in winter than in summer, but it was clearly an exception.
Description: M.S. University of Hawaii at Manoa 2013.
Includes bibliographical references.
Appears in Collections:M.S. - Tropical Plant and Soil Sciences

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