Alien invasive legumes and Allelopathy: A case study at Gangetic West Bengal, India

Alien legumes exert major influence in modulation of sustainable agriculture and crop productivity in diverse ways. An investigation was carried out in inventorizing alien legume plants and their invasive nature in districts of Nadia, Hooghly, Howrah, 24 pgs (N) and Kolkata in Gangetic West Bengal during 2005-2011. As many as 40 alien species were documented, of which 14 species are highly invasive in nature and the tree Leucaena leucocephala was the worst invasive in nature. About 40% of plants have been used by local people as food and fodder, 20% in medicinal, and rest 40% as biomass fuel, manuring and in other diverse economic and commercial purposes. Allelopathic effect of an invasive legume on crop legume was ascertained by studying germination, growth traits and root-tip mitotic activity of Lathyrus sativus L., treated with leaf aqueous extracts of Leucaena leucocephala in different concentrations (0, 10, 20, 30 and 40%). A dose-dependent reduction in germination and plant dry weight was accompanied with significant (P<0.05) decrease in mitotic index and enhancement of mitotic abnormalities in Lathyrus plants. While 10% extract dose had no significant effect, concentrations of 20% onwards were found highly inhibitory to growth, and induced chromotoxicity in Lathyrus genomes.