Meiotic anomalies in sodium azide induced tetraploid and mixoploid of Trigonella foenum-graecum

Abstract

Mutagen-induced polyploidy can be considered to be a system of increasing genotypic plasticity so that aberrations at the genic and chromosomal level are easily tolerated by the plants. A tetraploid and a mixoploid mutant was induced in Trigonella foenum-graecum by sodium azide. Healthy seeds of Trigonella were treated with different doses of sodium azide. In M 2 screening, we found variants at 0.15% treatment for 4 h and at 0.25% treatment for 2 h and they were studied for morphological characters, meiotic behaviour, pollen sterility and stomata frequency. They were confirmed as tetraploid and mixoploid respectively and their surviving M 3 progeny was further studied on the same line. Meiotic studies showed different types of abnormalities for both. In mixoploid, the RAR increased from M 2 to M 3 but in tetraploid plant it decreased in M 3 generation. The number of chiasma per chromosome was reduced in M 3 generation for both the mutants. A comparison of the different anomalies in 2 generations of the tetraploid and mixoploid helps us to understand the reason for very high pollen sterility and negligible seed set in the tetraploid. Stickiness was increased in both, but the relative increase was less in tetraploid. Stickiness has been considered as a natural method of ameliorating stress and hence may be responsible for better performance of mixoploid. Laggards and spindle disorientation was significantly higher in the tetraploid as compared to the mixoploid. © 2010 The Japan Mendel Society.