凡纳滨对虾野生群体F_1与近交群体杂交和自交子代的抗逆、生长性状比较

A comparative study on stress resistance and growth among the inbred and hybrid offsprings of wild population F_1 and inbreeding population of Litopenaeus vannamei

为了探究野生群体的引入对凡纳滨对虾(Litopenaeus vannamei)近交群体子代性状的影响,利用源自厄瓜多尔海区的野生群体群选F_1(EC)与自建的全同胞兄妹近交群体(ZG)双列杂交,构建了EC♂×EC♀(EE)、ZG♂×ZG♀(GG)、EC♂×ZG♀(EG)、ZG♂×EC♀(GE) 4个子代群体,并对4个群体的仔虾进行了急性低盐度、亚硝酸盐暴露下的存活率和急性微囊藻毒素(MC-LR)暴露下的抗氧化酶活性分析,同时进行了养殖生长性状测试。结果显示:4个群体仔虾急性低盐度暴露下的存活率、急性MC-LR暴露下的抗逆性和生长性状都表现为EE>GE>EG>GG,急性亚硝酸盐暴露下的存活率GE>EE>EG>GG;杂交群体GE在急性低盐度、亚硝酸盐暴露和生长性状的杂种优势率分别为31.83%、77.01%和2.77%;而EG群体的杂种优势率分别为-19.21%、-8.01%和-8.14%,性状弱于双亲中值。4个群体的抗逆、生长性状总体表现为EE>GE>EG>GG。研究发现:凡纳滨对虾杂交群体的性状以母本遗传占主导优势,近交群体的性状衰退可能是导致以其为母本的杂交子代性状退化的主因;凡纳滨对虾选育工作可能需要每年补充外源基础群体,才能保持选育群体的优势性状。

Litopenaeus vannamei, which is also known as white shrimp, is one of the main farmed shrimp species in China. It is native to the coastal line of Central and South America and was, instead of Fenneropenaeus chinensis, introduced into China in the 1990’s. The yield of white shrimp increases annually significantly because of its fast growth, adaptability to a wide range of salt and temperatures, strong disease resistance and low demand for dietary protein. However, in recent years, the success rate of white shrimp farming in China has declined because almost 70% of white shrimp seedlings are from inbreeding produced by hatchery farm without systematic selection, resulting in inadequate growth performance and stress resistance. The very small quantity of quality broodstock imported from abroad is unable to meet market demand. Meanwhile, the dominant trait of broodstock selected by other research institutes in China is not stable. The selection of high-quality broodstock is critical to improving shrimp farming in China. Collection of different basic populations is the basis for white shrimp selective breeding and inbreeding should be avoided. In this study, in order to analyse the effect of wild population introducing on the growth trait and stress resistance of the L. vannamei inbreeding population offspring, we used wild population F1 which was imported from Ecuador （EC） and an inbreeding population （ZG） using a complete diallel cross to construct four F1 populations including EC♂×EC♀ （EE）, ZG♂×ZG♀ （GG）, EC♂×ZG♀ （EG）, ZG♂×EC♀ （GE）. The survival rate of post-larvae after exposure to acute low salinity or nitrite, the antioxidant enzymes activities under microcystin-LR （MC-LR） exposure and the growth speed were compared between these four F1 populations. The results showed that the survival rates under acute low salinity （from 30‰ to 2‰） for 24 h to 48 h were significantly different between the four F1 populations （EE〉GE〉EG〉GG, P〈0.05）, with the sur-vival rate of the EE population as the highest and the GG population as the lowest. The survival rates of the four F1 populations under acute nitrite treatment （35 mg/L） after 60 h were different （GE〉EE〉EG〉GG）, with GE as the highest and GG again as the lowest. After exposure to 8 mg/L MC-LR, the antioxidant enzyme activities of SOD and CAT were significantly upregulated at 24 h or 36 h; activities of GPX, GST and GR, which are involved in removing secondary metabolites such as H2O2 and ROOH, were also up-regulated; the GSH contents in hepato-pancreas decreased because of consumption and the resistance to MC-LR was significantly different between the four F1 populations （EE〉GE〉EG〉GG）. The growth trait analysis showed that the growth speed of the EE and GE populations during 0？40 d was slower than the other two populations, while these two populations showed higher growth speed during 40？83 d, and the EE population had the best growth trait after 83 d （EE〉GE〉EG〉GG）. The heterosis rates of hybrid population GE under acute low salinity, nitrite or MC-LR treatment were 31.83%, 77.01%, and 2.77%, respectively, and the performance was better than the mean values of the parents. While the heterosis rates of the EG population were ？19.21%, ？8.01% and ？8.14%, the performance was weaker than the mean values of the parents. In conclusion, the stress resistance and growth trait of the four F1 populations was EE〉GE〉EG〉GG. The results revealed that maternal inheritance was dominant for hybrid populations; the trait depression in hybrid offspring could be caused by using female individuals from inbreeding population; and im-proving the dominant traits depended on more and more basic populations for white shrimp selective breeding.