Genetic and Environmental Effects on Kernel Number and Ear Length in Corn (Zea Mays L.)
Files
Date
1980
Authors
Contributor
Advisor
Department
Instructor
Depositor
Speaker
Researcher
Consultant
Interviewer
Narrator
Transcriber
Annotator
Journal Title
Journal ISSN
Volume Title
Publisher
University of Hawaii at Manoa
Volume
Number/Issue
Starting Page
Ending Page
Alternative Title
Abstract
A 6-entry diallel set involving 3 temperate and 3 tropical corn inbreds was planted monthly in Hawaii during a 21-month period from August, 1977 to May, 1979 to study the effects of seasonal change in climatic factors on kernel number and ear length and the stability of these characters. Another 10-entry diallel set involving 5 temperate and 5 tropical corn inbreds was evaluated at different locations in temperate and tropical regions to study the effects of geographically diverse environments on kernel number and ear length and their relationships to grain yield. Also, generation mean analysis based on 6 crosses among 2 temperate and 2 tropical corn inbreds was carried out to study the genetics of kernel number and ear length. Under seasonal environments where cyclic changes in climatic conditions influence corn growth, the days to maturity of the corn plants were mainly determined by temperature and the vegetative growth of the corn plants was a function of the solar radiation available to the corn plants before silking. Corn plants were more sensitive to slight climatic changes during winter months than during summer months. Fifteen corn hybrids among 6 inbred lines did not differ significantly for almost all ear characters when seasonal environments were favorable for corn growth, but showed significant differences under unfavorable conditions. General combining ability (GCA) and specific combining ability (SCA) mean squares and GCA x month interaction mean squares were significant indicating that both additive and nonadditive genes contributed to the genetic variation in ear characters with a significant contribution by the additive x month interaction. Kernels per row, kernels per ear, cob length, filled ear length and grain yield followed the cyclical change in solar radiation, while floret number and row number were quite stable in seasonal environments. Average daily solar radiation during the 3rd month of the corn plant's growth explained 65 % of the variation in kernel number, ear length and grain yield. A non-linear asymptotic regression line showed that the expression of ear characters and grain yield was greatly influenced by a small change in solar radiation under unfavorable environments. Lower temperature during the winter season extended the growing period of the corn plants and compensated for the low irradiance, thus maintaining a grain yield higher than predictions based on solar radiation levels alone. The stable number of florets per row over season indicated that sink strength or limitations at the source rather than a limited sink size was responsible for lower grain yield in unfavorable seasonal environments. The stability of 15 hybrids, as estimated by regression analysis, was found to be different for kernels per row and filled ear length but not for grain yield. Additive genes were responsible for the stability of the corn hybrids. The relative stability of a hybrid could be predicted by the regression coefficients of combining ability effects. The response of GCA effects to environments was basically a response to the cyclical change in solar radiation in seasonal environments. Therefore, it would be possible to identify genotypes tolerant to light stress by testing a large number of genotypes and selecting genotypes with high stability in seasonal environments where solar radiation is a major limiting factor for corn growth. Under different geographic environments, growth of corn was influenced by temperature, day length and day length sensitivity of the genotypes. Average number of days to mid-silking of 45 hybrids ranged from 50 at Waimanalo, Hawaii to more than 80 at Kamuela, Hawaii and at the temperate areas of Ames, Iowa, and Suweon, Korea. Additive and non-additive genes contributed to the genetic variation of the ear characters with significant effects of additive x location interaction as in seasonal environments. The high GCA/SCA ratio for all ear characters and grain yield indicated that GCA was more important than SCA for all characters. In general, the temperate inbreds CI21E, Mol7 and 0h545 were good combiners for kernels per row and filled ear length, while the tropical inbreds CM105 and Tx601 were good combiners for kernels per ear with a high row number. Partial correlation coefficients indicated that kernel number was the most important determinant of grain yield at all locations. Hybrids among tropical inbreds had a high stability for kernels per row and filled ear length, while hybrids among temperate inbreds responded better to favorable environments. Several hybrids between temperate and tropical inbreds showed higher stability as well as higher kernel number, longer ear length and higher grain yield than hybrids among tropical or temperate inbreds alone. Regression analysis of GCA effects showed that all tropical inbreds contributed to high stability in their hybrids. The hybrid x location interaction was mainly due to the linear response of GCA effects to different locations while SCA effects appeared to be stable from location to location. Generation mean analysis of 6 crosses among 4 inbreds showed that the dominance gene effects were the most important contributors to the inheritance of floret number, kernels per row, cob length and filled ear length. Additive gene effects were of minor importance in 6 crosses studied. Genetic variances were smaller than environmental variance for all characters. Average narrow sense heritability estimates were 39 % for floret number and 22 to 27 % for other characters. The minimum number of genetic factors was 3 for floret number and 5 to 8 for other three characters.
Description
Keywords
Citation
Extent
Format
Geographic Location
Time Period
Related To
Related To (URI)
Table of Contents
Rights
Rights Holder
Local Contexts
Collections
Email libraryada-l@lists.hawaii.edu if you need this content in ADA-compliant format.