长牡蛎中国群体和美国群体杂交效应与三倍体的优势

摘要

将长牡蛎中国群体二倍体分别与美国群体二倍体和四倍体进行杂交,实验共设置4组,分别为杂交二倍体组、杂交三倍体组、中国二倍体组和美国二倍体组,比较了各实验组卵裂率、D幼率、D形幼虫大小及幼虫期、稚贝期的壳高生长、存活率等生物学指标,并估算杂交二倍体的杂种优势率和杂交三倍体的三倍体优势率.结果表明,杂交二倍体幼虫壳高生长的杂种优势率不明显,平均杂种优势率为1.21%,幼虫的存活率及稚贝的壳高生长表现出明显的杂种优势,平均杂种优势率分别为34.47%和20.39%.杂交三倍体的D形幼虫大小、幼虫和稚贝的壳高生长、存活率均表现出三倍体优势,D形幼虫大小三倍体优势率为5.19%,幼虫期壳高生长和存活的平均三倍体优势率分别为4.00%和19.92%,稚贝壳高生长和存活的平均三倍体优势率分别为30.18%和54.43%,200日龄,杂交三倍体鲜体质量的三倍体优势率为202.96%,存活三倍体优势率为73.60%.此外,稚贝期的杂交二倍体生长性状的杂种优势率和杂交三倍体的三倍体优势率均高于幼虫期的优势率.研究表明,中、美两地理群体杂交获得的三倍体长牡蛎子代生长和存活性状都比二倍体优良.杂交三倍体的优良性状主要是三倍体优势,杂交优势的贡献率还有待进一步实验证实.%The Pacific oyster Crassostrea gigas is a major aquaculture species in China and around the world. A serious problem in Pacific oyster farming is the occurrence of summer mortalities. Heavy summer mortalities have been observed in cultured Pacific oysters in US, China and France. While the causes for the summer mortality are not well understood. The production and use of triploid oysters may help to reduce summer mortalities. The goal of this study is to determine if heterosis exists between US and China populations of the Pacific oyster and if the interstrain hybrid triploids have greatly improved performance compared to diploids. Hybrid crosses of Pacific oysters between diploids from China and diploids as well as tetraploids from America were conducted. Four groups were produced: Chinese diploid ♀ × Chinese diploid ♂ ,American diploid ♀ × American diploid ♂ , Chinese diploid ♀ × American diploid ♂ and Chinese diploid ♀ × American tetraploid ♂ Heterosis and triploid advantage of experimental groups were studied for traits such as fertilization and hatching success, survival, larval and juvenile growth. Our results show that heterosis in diploid hybrid progeny varied among traits and developmental stages:l. 21％ for larval growth,34.47％ for larval survival and 20.39％ for juvenile growth. The triploid advantage was significant for all traits and stages,except D larval size ( 5.19％ ) and larval growth ( 4.00％ ). Triploid advantages for larval survival,larval growth and juvenile survival were 19.92％ ,30. 18％ and 54.43％ ,respectively. The highest triploid advantage (202.96％)was observed in wet weight of juveniles at Day 200. Heterosis and the triploid advantage were stronger at juvenile stages than at larvae stages. Our results suggest that the hybrid tripioid Pacific oysters between Chinese diploid females and American tetraploid males have greatly improved growth and survival compared to all diploid groups. Production of triploids through interstrain crossing may be the best way for producing triploids for aquaculture. However, at Day 200 when the triploid advantage was 202.96％ in growth and 73.6％ in survival, the diploid heterosis was only 3.75％ and - 26.25％,respectively. This finding suggests that the superior performance of the triploids may not be caused by the same heterosis observed in diploids. It is possible that heterosis in triploids is different from heterosis in diploids. We did not have pure-line triploids as controls in this study. Further studies are needed to determine to what degree that heterosis contributes to the superior performance of hybrid triploids.