近交导致的种质退化严重影响虾夷扇贝养殖产业.为探明虾夷扇贝近交衰退的现象及遗传调控机理,在表型水平上,构建近交系数分别为0.5、0.25和0的自交组、近交组与自然群体对照组,追踪不同近交系数下虾夷扇贝幼虫期到成体期530日龄的性状差异,同时选取7个适合度性状,利用主成分分析法构建基于近交衰退的适合度指标评价方法;在基因组水平上,利用1个自交家系的亲本及其21个子代进行全基因组重测序,开展标记偏分离分析.试验结果显示:针对存活率性状,在幼虫期,自交组近交衰退率是近交组的1.31~3.05倍;在成体期,自交组近交衰退率是近交组的0.97~7.29倍.而生长性状,在幼虫期,仅有自交组保持较低的近交衰退率(1.65%~2.56%);在成体期,自交组与近交组几乎未发生衰退.基于重测序分型得到1 253 519个单核苷酸多态性用于偏分离统计,约99%在子代中发生了显著的偏分离,其中23%属于配子偏分离、77%属于合子偏分离,合子偏分离中有89%为杂合子过剩,即超显性效应起作用,仅10%受显性效应影响为纯合子缺失.试验结果表明,超显性效应及偏分离作用在虾夷扇贝F1子代存活率性状的自交衰退中起主要作用,为近交衰退的机理提供更有力证据的同时,也为虾夷扇贝种质遗传改良提供了有效思路.
In order to clarify phenomenon and genetic regulatory mechanism of inbreeding depression in yesso scallop Patinopecten yessoensis in the phenotypic level,experimental groups and control groups of yesso scallop with inbreeding coefficients of 0.5,0.25,and 0 were constructed.At the same time,seven fit-ness traits were selected through tracking from the larval stage to the 530 days old adult stage,and a fit-ness index evaluation method based on inbreeding depression was constructed using principal component a-nalysis.In the genomic level,whole-genome resequencing was performed on the parents of a self-fertiliza-tion lineage and 21 offsprings for segregation distortion analysis.It was found that the inbreeding depres-sion rate in the self-fertilization group was 1.31-3.05 times during the larval stage,higher than that in the inbred group.In the adult stage,the trend was similar to that in the larval stage,with the inbreeding de-pression rate of 0.97-7.29 times in the self-fertilization group,higher than that in the inbred group.How-ever,only the self-fertilization group maintained a low inbreeding depression rate(1.65%-2.56%)in growth traits during the larval stage.In the adult stage,the self-fertilization group and most of the inbred groups did not experienced any depression,indicating that inbreeding depression mainly occurs in survival traits.A total of 1 253 519 SNPs were genotyped for biased segregation analysis,with 99%of the SNPs exhibiting significant segregation distortion in the offspring,23%of gametic segregation,and 77%of zy-gotic segregation.In zygotic segregation,89%was due to heterozygote excess,indicating that overdomi-nance effect was at work,and only 10%was affected by dominant effects as a result of homozygote loss.The findings indicate that overdominance effect and segregation distortion play a dominant role in inbreed-ing depression of yesso scallop F1,not only explores biased segregation in self-fertilized offspring of yesso scallop,but also provide important reference for the genetic mechanism of inbreeding depression in aquatic animals.