熊本牡蛎多嵴和无嵴品系F3生长性状的连续选择效应

Sustained response to selection of growth traits to the third generation for two strains of Kumamoto oyster Crassostrea sikamea

为进一步检测熊本牡蛎(Crassostrea sikamea)多嵴和无嵴品系F3的连续选择反应,以2个品系F2上选组为材料,开展2个品系F3混合上选研究,评估2个品系F3生长性状的选择反应、现实遗传力及遗传改进量,解析选育过程中选择效应、品系效应及二者交互作用对生产性状的影响。结果表明:多嵴品系F3生长性状具有较高的现实遗传力,表现出较好的遗传改良效果;无嵴品系F3表现出中等现实遗传力水平,但仍具有一定程度的遗传改良潜能。养成期360日龄时,多嵴品系子代壳高、鲜重的选择反应分别为0.70、0.76;现实遗传力分别为0.40、0.43;遗传改进量分别为7.02%、12.29%;无嵴品系的选择反应分别为0.36、0.33;现实遗传力分别为0.20、0.19;遗传改进量分别为3.74%、5.72%。经过双因子分析模型检测发现:品系来源是影响F3生长性状的主要因子,选择效应是次要因子,二者间不存在明显的交互作用。由此可见,随着连续选择的进行,选择反应逐渐降低,品系来源作用增强,本研究为熊本牡蛎遗传改良和新品系培育奠定了基础。

At present,for aquatic animals,successive selection is mainly used in the breeding of fish and shrimp species.However,there are some relevant research studies on bivalves,and many attempts have been made and have obtained positive and encouraging results.Specifically,in oyster,all selection experiments on growth characteristics were successful in altering the selected trait in the direction of selection.For other bivalves,positive or successful responses to selection have also been observed in catarina scallop Argopecten ventricosus,bay scallop A.irradians,Japanese scallop Patinopecten yessoensis Jay,coot clam Mulinia lateralis,hard clam Mercenaria mercenaria,pearl oyster(both Pinctada martensii and P.maxima),and other species.The Kumamoto oyster Crassostrea sikamea is an important wild oyster resource in Southeast Asia,including China,Japan,and Korea.They not only occur naturally in China but also live in abundance over a wide geographical distribution,ranging from Jiangsu to Guangxi,including Hainan Island.Traditionally,this oyster was a wild fishery resource;farmers captured these oysters from the reef or stones in the inter-tidal zone.Although the artificial breeding of this oyster was successfully conducted,little relative information for genetic improvement was found.A selective breeding program for improving growth rate in Kumamoto oyster was initiated in China in2012after the breakthrough of large-scale artificial breeding.To compare differences in growth between two strains,mass selection for the first and second generation selection between two strains was performed from2012to2014.As expected,a relatively higher response to selection and realized heritability was obtained for two populations after the first two generations.To investigate whether the response to selection after one generation of selection among different strains was sustained,we examine responses to selection,realized heritability,and genetic gain for growth traits of cultchless Kumamoto oyster taken from the third generation in southern China.The selection effect,strain origin,and their interaction were evaluated using multi-ridge and non-ridge strains by selecting the largest10%of the oysters from the second generation parents for the selected groups,while an equal number of the parents were randomly chosen as the control groups before the removal of parents for truncation selection.The results show that the realized heritability of growth traits of multi-ridge strains was higher than those of non-ridge strains with a high genetic improvement level,while the non-ridge strains showed moderate heritability at a realistic level with a certain degree of genetic improvement potential.During grow-out for the adult stage,shell height and total weight of response to selection,and realized heritability and genetic gain were0.70,0.76;0.40,0.43;and7.02%,12.29%for multi-ridge strains;and these indices were0.36,0.33;0.20,0.19;and3.74%,5.72%for non-ridge strains,respectively.Growth traits were mainly affected by strain origins;a second factor was selection effects,and no interaction was found during the whole process.Hence,the selection response of the two strains continually decreased with increasing generations.This study provides an excellent base for new variety culture of Kumamoto oysters.