High Pollen Sterility Relatable to Structural Heterozygosity, and SEM Study in Poison Devil Tree (Alstonia venenata R.Br.)

Abstract

Alstonia venenata R. Br. (Family: Apocynaceae), a paleoendemic under ex situ conservation in north India has been cytologically investigated for chromosome counts. This study recorded chromosome count (n=11) for the species. The species existed at the diploid level. Most chromosomes were involved in the bivalent formation (67.65%) of the pollen mother cells (PMCs) observed at meiosis. However, two additional types (7_ll+2_IV and 9_II+1_IV) of chromosome association (multivalents) were observed in 32.35% of PMCs. The quadrivalents formed as a consequence of reciprocal translocations are either ring or chain type. Chiasma frequency is also studied. PMCs with more multivalents depicted relatively higher chiasma frequency than others. These chromosome associations resulted in high pollen sterility (80.33%). Scanning electron microscope (SEM) analysis has also been performed in pollen grains. Here in this paper, we are also presenting first time analysis of the meiotic course and occurrence of multivalents in an accession of the species. We also discuss the previous cytological studies done in the genus Alstonia. In spite of the occurrence of high pollen sterility, seed setting is normal which shows that the species has acclimatized to a greater extent in north India climatic conditions.