Chromosome counts and cytomixis in two species of Trigonella L.

Abstract

Chromosome counts, detailed meiotic course, microsporogenesis, and pollen fertility studies have been carried out in two species of Trigonella, T. emodi Benth. and T. pubescens Edgew. ex Baker collected from the Kinnaur and Chamba districts of Himachal Pradesh (India). Both of the species from Kinnaur have been studied cytologically for the first time. T. pubescens which showed a diploid count of w=8 is recorded chromosomally for the first time worldwide. Both of the species depicted the occurrence of chromatin transfer involving 2-12 pollen mother cells (PMCs) in 15.88-62.88% cases. The partial or complete chromatin transfer resulted in the formation of hypoploid-, hyperploid, and enucleated PMCs. Also, the migration of nucleolus along with chromatin material resulted in PMCs with supernumerary nucleoli. In addition to the migration of chromatin, PMCs also showed late disjunction of some bivalents, lagging of chromosomes, and chromatin bridges during anaphases/telophases. Consequent to these meiotic irregularities, sporads with micronuclei, pollen sterility (9-62.00%), and apparently fertile pollen grains of two different sizes were obtained. In both the species, the occurrence of cytomixis has been reported for the first time and it seems to be a natural phenomenon under direct genetic control. © 2013 The Japan Mendel Society.