Concurrence among four biomarkers for identification of elite neem (Azadirachta indica A. Juss) chemotypes of azadirachtin-A [India]
2005
Rao, N.D.R. (Sri Sathya Institute of Higher Learning, Andhra Pradesh (India). Dept. of Biosciences) | Anand, M.G. (Sri Sathya Institute of Higher Learning, Andhra Pradesh (India). Dept. of Biosciences) | Chary, P. (Sri Sathya Institute of Higher Learning, Andhra Pradesh (India). Dept. of Biosciences)
Azadirachtin-A is a potent biopesticide which is found in minuscule quantities in neem seed kernels. This work describes the utilization of four biomarkers to find elite neem varieties yielding high azadirachtin-A. It is a compilation and inference of the outcome of the findings obtained from a) two microenvironments and b) five ecogeographically different regions in Andhra Pradesh, India. The methods chosen towards obtaining this goal showed that: 1) Extremely-arid-alkaline regions with maximum soil pH (8.05) yielded trees with the highest Azadirachtin-A content. The soil mycoflora and microelements served as indicators. Both VAM and soil fungal diversity and frequency showed maximal values in this rhizosphere which exhibited the lowest values for percentage moisture and for most of the microelements analyzed (Zn, Fe, Cu, Mn, P2O5 and K2O). 2) Tissue culture studies on seeds bearing high and low azadirachtin-A content showed that explants from high azadirachtin-A containing seeds were sturdier and more viable. Furthermore, cotyledons from explants of seedlings with high azadirachtin-A content alone showed significant amount of azadirachtin-A as analyzed by HPLC. Influence of growth and other micro-environmental factors resulted in the variations of several secondary metabolites along with DNA patterns from different parts of a single in vitro plant. 3) Ecomorphometric studies using SPSS version 10.0 clearly indicated that at least 8 parameters (seed diameter, soil pH, percentage moisture, K20, P2O5, Zn, lower lobe serrations and upper lobe distance of leaves) were significantly related to the quantitative variations in azadirachtin-A. 4) Molecular analysis using DNA fingerprinting studies clearly showed that there was a habitat-based molecular concordance of ISSR and FISSR profiles with azadirachtin-A content among the neem chemotypes. This was based on dendrograms constructed by using UPGMA algorithm based on the similarity index values
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