University of Delhi South Campus, New Delhi, 110021, India.
Theor Appl Genet. 2011 Apr;122(6):1091-103. doi: 10.1007/s00122-010-1515-2. Epub 2010 Dec 29.
Oil content and oil quality fractions (viz., oleic, linoleic and linolenic acid) are strongly influenced by the erucic acid pathway in oilseed Brassicas. Low levels of erucic acid in seed oil increases oleic acid content to nutritionally desirable levels, but also increases the linoleic and linolenic acid fractions and reduces oil content in Indian mustard (Brassica juncea). Analysis of phenotypic variability for oil quality fractions among a high-erucic Indian variety (Varuna), a low-erucic east-European variety (Heera) and a zero-erucic Indian variety (ZE-Varuna) developed by backcross breeding in this study indicated that lower levels of linoleic and linolenic acid in Varuna are due to substrate limitation caused by an active erucic acid pathway and not due to weaker alleles or enzyme limitation. To identify compensatory loci that could be used to increase oil content and maintain desirable levels of oil quality fractions under zero-erucic conditions, we performed Quantitative Trait Loci (QTL) mapping for the above traits on two independent F1 doubled haploid (F1DH) mapping populations developed from a cross between Varuna and Heera. One of the populations comprised plants segregating for erucic acid content (SE) and was used earlier for construction of a linkage map and QTL mapping of several yield-influencing traits in B. juncea. The second population consisted of zero-erucic acid individuals (ZE) for which, an Amplified Fragment Length Polymorphism (AFLP)-based framework linkage map was constructed in the present study. By QTL mapping for oil quality fractions and oil content in the ZE population, we detected novel loci contributing to the above traits. These loci did not co-localize with mapped locations of the fatty acid desaturase 2 (FAD2), fatty acid desaturase 3 (FAD3) or fatty acid elongase (FAE) genes unlike those of the SE population wherein major QTL were found to coincide with mapped locations of the FAE genes. Some of the new loci identified in the ZE population could be detected as 'weak' contributors (with LOD < 2.5) in the SE population in which their contribution to the traits was "masked" due to pleiotropic effects of erucic acid genes. The novel loci identified in this study could now be used to improve oil quality parameters and oil content in B. juncea under zero-erucic conditions.
油含量和油质分数（即油酸、亚油酸和亚麻酸）受油菜籽中芥酸途径的强烈影响。种子油中低水平的芥酸可将油酸含量增加到营养上可接受的水平，但也会增加亚油酸和亚麻酸分数，并降低印度芥菜（芥菜）的油含量。本研究通过回交育种，对高芥酸印度品种（Varuna）、低芥酸东欧品种（Heera）和零芥酸印度品种（ZE-Varuna）进行了油质分数表型变异分析，结果表明，Varuna 中亚油酸和亚麻酸水平较低是由于活性芥酸途径引起的底物限制，而不是由于较弱的等位基因或酶限制。为了鉴定可在零芥酸条件下用于提高油含量和维持油质分数的理想水平的补偿基因座，我们在两个独立的 F1 加倍单倍体（F1DH）作图群体上进行了上述性状的数量性状基因座（QTL）作图，该群体是由 Varuna 和 Heera 杂交产生的。其中一个群体包含芥酸含量（SE）分离的植物，以前用于构建芥菜的连锁图谱和几个产量相关性状的 QTL 作图。第二个群体由零芥酸个体（ZE）组成，本研究中构建了基于扩增片段长度多态性（AFLP）的框架连锁图谱。通过对 ZE 群体的油质分数和油含量进行 QTL 作图，我们检测到了对上述性状有贡献的新基因座。与 SE 群体不同，这些基因座没有与脂肪酸去饱和酶 2（FAD2）、脂肪酸去饱和酶 3（FAD3）或脂肪酸延长酶（FAE）基因的图谱位置共定位，而在 SE 群体中，主要 QTL 与 FAE 基因的图谱位置一致。在 ZE 群体中鉴定的一些新基因座可以在 SE 群体中作为“弱”贡献者（LOD<2.5）被检测到，因为它们受芥酸基因的多效性影响，其对性状的贡献被“掩盖”了。本研究中鉴定的新基因座现在可用于在零芥酸条件下提高芥菜的油质参数和油含量。
