Azadirachtin-A content of seeds of Neem Ecotypes in relation to the Agroecological Regions of India

The azadirachtin-A content of the seed kernels of the neem, Azadirachta indica A. Juss, ecotypes from 11 of the 21 agroecological regions of India has been investigated in relation to the agroecological-factors such as ecosystem and climate, growth period (the period of continuous plant growth in a year) arid soil. The azadirachtin -A content ranged from 0.14 -2.02% w/w of kernel with an average of 0.68%. The ecotypes growing in the regions with coastal, arid and semiarid ecosystems showed high (>0.72%) and those from the regions with subhumid ecosystem showed very low (0.27%) average azadirachtin -A contents. The growth period upto 150 d appeared to be more conducive for azadirachtin -A content under arid and semiarid ecosystems. The ecotypes growing in the agroecological regions with red soil had higher azadirachtin -A content as compared to those growing in other soil types; the highest azadirachtin -A content being recorded in the samples from red soil falling under the rain-shadow areas of south-west monsoon.