Pollen morphology of Asian Vigna species (genus Vigna; subgenus Ceratotropis)from India and its taxonomic implications

The pollen morphology of 22 Asian Vigna [subgenus Ceratotropis (Piper) Verdc.] species, including wild and cultivated taxa from India, was investigated with light microscopy and scanning electron microscopy. The quantitative data were analyzed by descriptive statistics and multivariate statistics. The pollen grains are prolate spheroidal in shape with equatorial diameter of 36.06-116.33 μm and polar diameter of 36.31-120.96 μm in equatorial view. The small pollen dimensions were observed in Vigna hainiana, V. trilobata, and V. indica and the largest in V. vexillata. The pollen grains have reticulate-homobrochate and reticulate-heterobrochate types of pollen sculpture. The lumina are psilate or granulate with penta-hexagonal, penta-polygonal, and irregular shape. The muri are sinuous, straight, or narrow-straight. Pair group method using arithmetic averages analysis was used to divide the main pollen taxa into four groups based on pollen morphology. Statistically distinctive taxa were identified using principal component analysis. In the present investigation, the taxa studied demonstrated sufficient pollen polymorphism in their sizes, equatorial views, lumina shapes, and muri widths.