Cytology studies in germplasm of Jatropha (Jatropha curcas L.)

Abstract

Chromosomes numbers and pollen studies were done in 27 germplasm accessions of Jatropha curcas. The analysis of gametic cells indicated that the species exhibits 2n=22 chromosomes. The chromosomes were paired in bivalents at first metaphase. At late pachytene, just before the transition to diplotene, chromosomes disjoin from their typical pericentromere clustering at zygotene and early pachytene, which makes this an optimal stage for meiotic chromosome pairing studies. Metaphase I was regular as expected, showing eleven bivalents with clear, stretched centromeres facing the poles, with each bivalent containing one chiasmata. Anaphase I/II showed balanced segregation with chromosome chromatid numbers of 11+11. The normal pollen mother cell formation ranged from 90.32-100%. Consequently, pollen fertility was also very high and ranged from 95-100%. The results suggest that the species is highly fertile and stable in its natural habitat. Accessions namely NRCJ-1, NRCJ-2, NRCJ-3, NRCJ-8, NRCJ-23 and NRCJ-25 showed up to 99% fertility. The pollen viability of accessions ranged from 92-96%. Accession NRCJ-7 was recorded for 98% pollen viability. These results suggest that pollen viability is not a limitation for seed development in Jatropha curcas. Cytological studies suggested that Jatropha curcas is fully fertile and stable at various geographical ranges where it has been naturalized.