Chromosome Localization of the Semigamy Mutant of Pima Cotton and the Production of Nulli-Haploids

J. Jefferson Gwyn and David M. Stelly


 
ABSTRACT

The purpose of this study was to associate the semigamy locus with a chromosome or chromosome segment, and ultimately with a linked marker gene(s) to expedite chromosome manipulations. Intermediate materials generated in this study were also used in an attempt to isolate nulli-haploids that could subsequently be chromosome-doubled to form nullisomics. First, semigamous hypoaneuploid stocks were established by crossing monosomic, monotelodisomic, and duplicationdeficient stocks as female parents with a homozyqous semigamous male line. These semigamous aneuploids were then backcrossed as male parent to a normal female line. Five BC1 plants per semigamous aneuploid were self-pollinated and progeny tested. Only BC1 plants involving deficiencies for chromosome four or the short arm of chromosome four failed to segregate for the seynigametic trait indicating that the related semigamous aneuploid was hemizygous for semigamy. our results indicated that the semigamy gene is localized in the short arm of chromosome four, i.e., linkage group VIII. Attempts to associate the semigamy locus with morphological and biochemical marker genes is ongoing. Concomitantly, semigamous aneuploids were self-pollinated and progeny-tested in an attempt to isolate nulli-haploids. Approximately 25,000 progenies were evaluated. Although more that 45 putative nullihaploids were extracted, meiotic analyses failed to positively identify any nulli-haploid plants.



Reprinted from 1990 Proceedings: Beltwide Cotton Production Research Conferences pg. 70
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998