Reporting of B-Chromosomes in Trachyspermum ammi (L.) Sprague (Ajwain)

Resumo

To the best of our knowledge this is the first study regarding the reporting of B chromosomes in this plant species. During the meiotic study of Trachyspermum ammi (L.) Sprague, maximum two B chromosomes were reported in diploid plants which were retained in induced autotetraploid after the treatment of 0.2% colchicine at seedling stage. In the present study, the meiotic behaviour of B-chromosomes was analyzed in Trachyspermum ammi (L.) Sprague. The presence of B chromosomes and their number in the plant species of higher ploidy level is controversial. The existence of B chromosomes in polyploids varies from species to species. In the present case, no change has been observed in the number of B chromosomes despite the duplication of A chromosomes in autotetraploid plant. The unaffected number of B chromosomes represents their peculiar behaviour of inheritance. The plant species show adaptive mechanism for their retention in population. In the present study, significant changes (p < 0.05) have been observed in the chiasma frequency and pollen fertility of both diploid carrier plant as compare to non-carrier ones. Furthermore, the chromosomal associations have also been considered with observed number of B chromosomes in autotetraploid carrier plant. In autotetraploid carrier plant, the frequencies of multivalents were found to be quite low in comparison to diploid carrier plant.