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Variable Expressivity and Gene Action of Gland‐Determining Alleles in Gossypium hirsutum L. 1
Author(s) -
Wilson F. D.,
Smith J. N.
Publication year - 1977
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1977.0011183x001700040014x
Subject(s) - gossypol , diallel cross , biology , allele , hybrid , locus (genetics) , gossypium hirsutum , genetics , malvaceae , botany , gene
We studied the variable expressivity of gland‐determining alleles at three loci in stigmas and bolls of cotton ( Gossypium hirsutum L.) and their effects on the amounts of flower‐bud (square) gossypol that occur those glands. High levels of square gossypol provide resistance in the plant to certain insect pests. The alleles gl 1 and gl 1 y reduced stigma‐gland density and square gossypol content slightly but rendered bolls glandless, or nearly glandless. The Gl 2 allele was more expressive than Gl 3 for boll gland density and seed‐gossypol content, but less expressive for stigma‐gland density and square gossypol content. The relative potency of three alleles at the gl 3 locus was Gl 3 '> Gl 3 ru1 > Gl 3 . Judicious combinations of alleles should maximize gossypol content in the squares without changing it as much in the seeds. The alleles Gl 2 , Gl 3 , and Gl 3 rui repressed the gland‐determining action of the high‐potency Gl 3 ' because F 1 means were below the midparental value (MP) when any one of these alleles was present, but above MP when they were absent in combinations carrying Gl 3 '. All F 1 combinations carrying Gl 3 had lower amounts of square gossypol than MP. Additive genetic effects were similar and predominant in a halfdiallel set that included four parents and their hybrids carrying all combinations of Gl 2 , gl 2 , Gl 3 , and gl 3 , and in a diallel set to which had been added a fifth parent and hybrids carrying Gl 3 '. Nonadditive effects, however, differed for gland density, emphasizing the variable action of these alleles in different parts of the plant. The halfdiallel analysis showed only additive effects for square gossypol content, but the F 1 . —MP relationship indicated that nonadditive effects were also present. Thus, direct selection for high gossypol content, even though much more efficient than selecting for high gland density, could still present some breeding problems.