小麦体细胞杂种渐渗系的遗传分析及外源DNA渐渗引起的遗传和表观遗传变异研究

Somatic hybridization, which could circumvent barriers of sexual hybridization, provides an alternative route to introgression. Broad phenotypic variations such as salt and drought tolerance, disease resistance, long spike, large grain, dwarfism, awnless and high quality were induced in derivatives of an asymmetric somatic hybridization involving bread wheat (Triticum aestivum cv. JN177) and tall wheatgrass (Thinopyrum ponticum Podp); however, how did these variations happened was unknown. Previous research indicated that except for the direct transfer of a few donor genes, the somatic hybridization also induced abundant variations to the genome of the introgression lines. Among those new traits induced by somatic hybridization, some controlled by QTL and others controlled by single gene variations. To explore the relationship between the novel traits of the introgression lines and the genetic and epigenetic variations induced by somatic hybridization, genetic analysis and preliminary gene mapping will be performed on some superior agronomic traits of 6 somatic hybridization introgression lines with different phenotypic traits, the variations in genomic sequences, gene expression and DNA methylation pattern of the 6 introgression lines will also be exploited by using a spectrum of DNA profiling techniques.

体细胞杂交可以克服远缘不亲和障碍, 是构建外源DNA渐渗系的有效方法。普通小麦"济南177"与UV照射的长穗偃麦草原生质体的非对称体细胞杂交产生了一系列具有新的农艺性状的渐渗系，包括耐盐、抗旱、抗病、大穗、大粒、矮秆、无芒、优质等。然而，这些性状是如何产生的目前还不清楚。前期研究表明体细胞杂交除了可以转移少量供体基因以外, 还诱导受体基因组产生大量的变异；体细胞杂种渐渗系不但可以产生由主效QTL控制的性状, 还诱导功能基因等位变异产生新性状。为了深入了解体细胞杂交渐渗产生的优异农艺性状与遗传和表观遗传变异的关系, 我们拟对6个具有不同重要性状的新种质进行遗传分析和渐渗/变异主效基因的定位；同时, 利用多种分子标记技术对这些具有不同农艺性状的体细胞杂种渐渗系的基因组序列、基因表达以及DNA甲基化修饰变异进行检测, 探讨由"体细胞基因组冲击"引起的遗传和表观遗传变异与小麦优异新种质形成的关系。

小麦与长穗偃麦草的非对称体细胞杂交产生了一系列具有新的农艺性状的渐渗系，包括耐盐、抗旱、抗病、大穗、大粒、矮秆、无芒、优质等。我们选取6种代表性渐渗系进行新性状的遗传分析并检测了渐渗系基因组的遗传和表观遗传变异。我们针对籽粒大小、耐盐碱、抗秆锈病、无芒等性状构建了遗传群体，利用SR3/济南17的DH群体检测到5个效应值较大的耐盐QTL，其中5A染色体上的QTL即之前定位到的耐盐主效QTL；发现SR3中1B和2B染色体上各有一个抗杆锈病基因；通过SR3/济南17的DH群体还定位到5A染色体末端的一个芒抑制基因B1。通过对6种渐渗系的遗传和表观遗传变异分析发现，渐渗系中存在广泛的遗传和表观遗传变异，主要包括序列丢失、基因表达调控改变、胞嘧啶甲基化修饰模式变化和逆转录转座子激活等，新表型的产生可能与外源遗传物质渐渗导致的遗传和表观遗传变异有关。