Evaluation of the Effect of Pollen Irradiation on Karyotype Variability in M2 Cotton Plants

The karyotypes of biomorphologically abnormal cotton (Gossypium hirsutum L.) plants obtained in M₂ after pollination with pollen irradiated at dose rates 10, 15, 20, and 25 Gy were studied. Various genomic and chromosomal mutations were detected in 57 M₂ families. The primary monosomics isolated in M₂ were found to be cytologically more stable and more viable, since they had higher meiotic index, pollen fertility, and seed formation. In M₂, a decrease in the number of plants with multiple karyotype aberrations and interchromosomal exchanges with high frequency of multivalent formation was observed. The multivalent configurations had different types and chromosome disjunctions. Their pollen fertility was higher than in translocants found in M₁. Desynapsis often occurred in M₂, including plants with chromosome deficiency or rearrangements. The variation in the number of univalents in various cells was found to result from different expression of synaptic genes. The results indicate stabilization of karyotypes, increase in cytologic stability and viability, and the absence of sterility in aberrant plants.