Garden City College, Bangalore, Karnataka 560049 India.
Physiol Mol Biol Plants. 2011 Mar;17(1):49-64. doi: 10.1007/s12298-010-0047-1. Epub 2011 Jan 26.
Azadirachtin-A (Aza-A), a tetranortriterpenoid, found in minuscule amounts in the Neem seed-kernels, has proved to be a potent biopesticide. Given the vast biodiversity of Azadirachta indica (Neem) in India, this study is an overview of four main aspects that corroborate with each other in identifying elite Neem chemotypes based on their Aza-A content. These biomarkers included mycofloral, tissue-cultural, ecomorphometrical and molecular analyses on accessions from five ecogeographically different regions in Andhra Pradesh, India, which high-lighted the characteristics of trees that yielded the highest Aza-A. In essence, extremely-arid-alkaline regions with maximum soil pH (8.05) yielded trees with the highest amount of this biopesticide. Likewise, both VAM and soil fungal diversity and frequency exhibited maximal values in their rhizosphere, whereas it exhibited the least values for percentage moisture and also for several micronutrients measured (P2O5, Zn, Fe and Cu). In vitro studies on seeds with high versus low Aza-A content gave sturdier seedlings in the former; with profusely coiled roots and fibirillar foliage in tissue-culture; in addition to these seeds being more viable. Furthermore, their cotyledons alone exhibited significant amount of Aza-A, as measured by HPLC. Besides this significant difference, the impact of growth factors culminated not only in the variations of several secondary metabolites, but also differences in DNA patterns from various parts of a single in vitro plant. Ecomorphometric analyses clearly indicated that at least eight parameters (seed diameter, soil pH, percentage moisture, K2O, P2O5, Zn, lower lobe serrations and upper-lobe-distance of leaves) were significantly related to the quantitative variations in Aza-A. Finally, PCR analyses exhibited a habitat-based molecular concordance of ISSR and FISSR profiles with Aza-A content among the Neem chemotypes. Their relatedness was based on dendrograms constructed by UPGMA algorithms using similarity-index-values.
印楝素-A（Aza-A）是一种四环三萜类化合物，在印楝种子的极小含量中被发现，已被证明是一种有效的生物农药。鉴于印度印楝的巨大生物多样性，本研究概述了四个主要方面，这些方面相互佐证，根据其 Aza-A 含量确定了优秀的印楝化学型。这些生物标志物包括来自印度安得拉邦五个生态地理区域的种质的真菌区系、组织培养、生态形态计量学和分子分析，这些分析突出了产最高 Aza-A 的树木的特征。本质上，土壤 pH 值最高（8.05）的极干旱-碱性地区产生了含有这种生物农药的最高量的树木。同样，VAM 和土壤真菌多样性和频率在其根际中表现出最高值，而在其根际中表现出最低的水分百分比值，并且在所测量的几种微量元素（P2O5、Zn、Fe 和 Cu）中也表现出最低值。高 Aza-A 含量与低 Aza-A 含量的种子的体外研究表明前者的幼苗更健壮；在组织培养中，根卷曲丰富，叶片纤维状；此外，这些种子的活力更高。此外，仅它们的子叶就表现出大量的 Aza-A，这是通过 HPLC 测量的。除了这种显著差异外，生长因子的影响不仅导致了几种次生代谢物的变化，而且还导致了单个体外植物不同部分的 DNA 模式的差异。生态形态计量学分析清楚地表明，至少有八个参数（种子直径、土壤 pH 值、水分百分比、K2O、P2O5、Zn、下叶锯齿和叶片上叶距）与 Aza-A 的定量变化显著相关。最后，PCR 分析显示基于 ISSR 和 FISSR 图谱的栖息地分子一致性与印楝化学型中的 Aza-A 含量有关。它们的相关性是基于使用相似指数值构建的 UPGMA 算法的聚类树图构建的。
