Characterization of the crumpled-mottled mutation in Gossypium hirsutum L.

Abstract

Of the 62 chromosome translocations in Gossypium hirsutum that have been isolated, made homozygous, identified as to the chromosomes involved, and maintained as homozygous tester lines, only T8-12 is phenotypically abnormal. Homozygotes are dwarf with a mutant "crumpled-mottled" phenotype that includes negligible fertility in field-grown plants; heterozygotes have a more normal morphology and variable fertility. The mutation has been reported to be tightly linked with the translocation and has never been separated from it. Comparative pollen viability, quantitative morphological measurements, and segregation data were used to dissociate the mutant phenotype from the T8-12 breakpoint--and from the mimic mutant, Crp. The T8-12 breakpoint was also demonstrated to be independent of the semilethal locus Lf on chromosome 12. Homozygous T8-12 and Crp individuals were shown to be morphological, but not functional, equivalents. Heterozygous and homozygous Crp plants produced essentially normal pollen; T8-12 heterozygotes had significantly reduced mean pollen viability scores. Mean bracteole measures were significantly different between T8-12 and Crp heterozygotes. The fluorescein diacetate-based fluorochrome reaction identified both chromosomal and genic effects on pollen viability in this study; the potential usefulness of the FCR method was thus extended to the level of single mutant gene effects.