高丹草高密度分子遗传连锁图谱构建及其低氢氰酸含量性状的QTL定位

Sorghum-sudangrass hybrid is the progeny derived from a wide cross between sorghum and sudangrass, which shows strong heterosis, high output and good quality, high tillering ability and strong regeneration. In additon, it also has resistance to drought, cold and salinity, as well as wide adaptability. Sorghum-sudangrass hybrid can be planted in North and South China, and used for more than one time, which is an important annual and excellent forage grass for developing livestock, especially the livestock in farming area and semi-pasturing areas. However, some young sorghum-sudangrass hybrid contain high hydrocyanic acid , which is susceptible to cause intoxication of livestock if eating too much. In recent years, to breed new sorghum-sudangrass hybrid varieties with low hydrocyanic acid content and good comprehensive agronomic characters, we hybridized loose spike sorghum which has low hydrocyanic acid content with red hull sorghum sudanense, and obtained the hybrid F1. Using the character of high pollen fertility in F1 hybrid, the F2 hybrid were then obtained by bagging selfing, which has important value for genetic research and breeding. In the present project, using the F2 hybrid as mapping population, we will construct a high density molecular linkage genetic map of sorghum-sudangrass hybrid based on AFLP and SSR markers, and locate the QTLs of low hydrocyanic acid content. The results will provide the basis for further study on the gene location, map-based cloning,functional analysis,molecular breeding and the efficient utilization of genetic resources, and promote the genetic breeding research level of forage in China.

高丹草是高粱和苏丹草种间远缘杂交产生的杂种类型，杂种优势强，产草量高，草质好，分蘖性和再生性强，较抗旱耐寒耐盐碱，适应性广，在我国北方和南方均可种植，可多次刈割利用，是发展畜牧业特别是农区和半农半牧区养殖业重要的一年生优良饲草。但其幼嫩茎叶含有氢氰酸，家畜采食过量易引起中毒。为培育氢氰酸含量低，综合农艺性状优良的高丹草新品种，近几年我们选择氢氰酸含量相对较低的散穗高粱和红壳苏丹草进行组配杂交，成功获得杂种F1代，并利用F1育性较高的特点，套袋自交得到了杂种F2种子。具有重要遗传研究和育种利用价值。本项目以杂种F2为作图群体，拟利用AFLP和SSR两种DNA分子标记技术，构建二倍体高丹草的高密度分子遗传连锁图谱，并定位低氢氰酸含量性状的QTL。为进一步开展高丹草低氢氰酸含量性状基因精细定位、图位克隆、功能分析、分子育种及遗传资源高效利用等奠定基础，促进我国饲草遗传育种研究水平的提升。

高丹草是高粱与苏丹草的种间杂交品种，其杂种优势很强，具有高粱产草量高、抗逆性和适应性强与苏丹草叶量大、分蘖多、适口性和营养品质好等优点。其不足点是茎叶鲜草氢氰酸含量偏高，家畜采食过量会引起中毒。为培育超低氢氰酸含量、优质高产的高丹草新品种，本课题组前期用散穗高粱与红壳苏丹草杂交，获得种间杂种F1代植株，并将F1套袋自交得到了F2分离群体。该项目以高丹草杂种F2代群体的305个分离单株及其亲本为作图材料，利用AFLP、SSR和SRAP三种分子标记技术和Join map 4.0作图软件构建其高密度的遗传连锁图谱，并采用两年两点的鲜草氢氰酸含量、单株产草量、种子产量、茎叶比等5个重要性状的测定数据的统计值和map QTL 4.0 定位软件进行QTL定位分析，以期为深入开展高丹草低氢氰酸含量、产量、品质等优异性状的QTL精细定位、相关功能基因图位克隆、分子标记育种等奠定基础。项目获得的主要研究结果：1）试验筛选出139对（个）适宜引物（含71对AFLP、57个SSR和11对SRAP引物）。用这些引物对高丹草305个杂种F2分离单株及双亲的基因组DNA进行大范围PCR扩增得到多态性标记位点1310个（含716个AFLP、346个SSR和248个SRAP标记位点），多态性位点百分率分别占81.6%、85.2%和93.6%。2）经卡方检验表明，在1310个多态性分子标记位点中，有1001个符合孟德尔3:1分离比例；有309个发生偏分离，其中含233个AFLP、43个SSR和33个SRAP标记，其平均偏分离比率占23.59%，可用于高丹草遗传作图。3）首次构建了一张含1310个标记、标记间平均图距为1.14cM的高密度高丹草分子遗传连锁图谱，其10个连锁群总长度为1488.5 cM。4）首次定位了控制高丹草鲜草氢氰酸含量、单株产草量及种子产量等5个重要性状的QTL 46个，其分布在10个连锁群上，每个连锁群平均为9.3个QTL，遗传贡献率变幅为9.6%～41.5%。发现遗传贡献率＞20%的主效QTLs有13个，其中低氢氰酸合量3个（Qcn1、Qcn3、Qcn4）、单株干重2个（Qdwp7和Qdwp8）、种子产量5个（Qyp2、Qyp3、Qyp7、Qyp8和Qyp12）、茎叶比1个（Qslrw3）。