CYTOGENETICS OF DISOMICS, MONOTELO- AND MONOISODISOMICS AND ml₁ st₁ MUTANTS OF CHROMOSOME 4 OF COTTON

J. E. Endrizzi ¹ and R. Bray ¹

¹ Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721

The linkage relationships and arm locations of the ml₁ and st₁ mutants of cotton were determined with the use of monotelodisomics, a monoisodisomic and disomics. The ml₁ st₁ mutants are more than 50 cM apart on chromosome 4. The ml₁ locus is in the short arm and 16 cM from the centromere, and st₁ is in the long arm and 48 or more cM from the centromere. Recombination in the monoisodisomic was twice the expected value and higher, but not significantly, than in its monotelodisomic counterpart. It was concluded that the increase indicates a greater frequency of proximal exchange in the monoisodisomic than in the monotelodisomic.