ABSTRACT
Cultivars of upland cotton, Gossypium hirsutum L., have very few pigment glands in the calyx crown area of the bud (square) where early instar of larvae of the Heliothis complex feed. NDH-118, NDH-121, and NDH-128 are doubled haploids which have many glands in the calyx crown and are tolerant to the Heliothis complex. We crossed these with -Stoneville 213, (ST 213), and Stoneville 213 glandless (ST 213gl). ST 213 has oly a few glands and ST 213gl has no glands in the calyx crown. We also crossed the three doubled haploids together. Fl and P2 data from all 9 crosses and backcross data from 6 crosses were evaluated. Glands in the calyx crown were counted under a 4X power magnification. Count data were transformed into square roots for analysis. The Fl hybrids from crosses with ST 213 were glanded and had numbers of glands near the respective midparent value; whereas, the Fl hybrids with ST 213gl were glandless. Based upon Fl expression and F2 and backcross segregation ratios we developed a hypothesis for inheritance of gland expression in the calyx crown. We propose the number of glands in the calyx crown is controlled by at least three genes; Gl(2), Gl(3), and an inhibitor (I) gene. The number of glands is a relative to the combination of these three genes. Glands are produced when there are one or more dominant alleles at the Gl(2) or Gl(3) loci with the inhibitor homozygous recessive (ii) or when more than two dominant alleles are present with the inhibitor in the heterozygous (Ii) condition. When the inhibitor is homozygous dominant (II) the number of glands is like the ST 213 parental type we call this type A and it has less than 10 glands in all lobes of the calyx crown. The inhibitor is homozygous dominant in ST 213 and ST 213gl; whereas, it is homozygous recessive (ii) in the three double haploid lines. Modifiers are present in the lines and affect the absolute number of glands present in glanded plants. The elucidation of genetic control of calyx glands in cotton will allow researchers to develop this phenotype in breeding materials for potential use as a source of tolerance to larvae of the Heliothis complex.
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