Morphological And Genetic Diversity Of Wild And Cultured Stocks Of Macrobrachium Rosenbergii

Giant river prawn(Macrobrachium rosenbergii)is an important freshwater cultured shrimp in China.Since its introduction into China,the germplasm resources have declined due to the self reproduction of small stocks for many years.In this paper,Myanmar wild stock,Thailand and Vietnam cultured stocks of M.rosenbergii were collected to explore the effects of morphological characteristics of the three stocks on body weight.The SNP sites of the whole genome of M.rosenbergii were detected and identified by Super-GBS simplified genome resequencing technology,and the genetic diversity and genetic variation of the three stocks were explored.The results are as follows:The coefficients of variation of body weight were large in the three stocks of M.rosenbergii,showing great breeding potential,among which Myanmar wild stock had the greatest breeding potential;Except for the second uromere length,the coefficients of variation of other morphological characteristics among stocks were the largest in Myanmar wild stock and the smallest in Vietnam cultured stock.There were significant stock differences in morphological characteristics;The path coefficients of carapace width,the second uromere length and the second uromere width on body weight of Myanmar wild stock reached an extremely significant difference level(P<0.01);The path coefficients of the total length,carapace width and the second uromere length on body weight of Thailand cultured stock reached a significant difference level(P<0.05)or an extremely significant difference level(P<0.01);The path coefficients of carapace length and the second uromere width on body weight of Vietnam cultured stock reached an extremely significant level(P<0.01);In addition,the second uromere length of Myanmar wild stock and Thailand cultured stock were negatively correlated with body weight;The regression equations of morphological characteristics screened from each stock on body weight were established and regression relationships of equations reached an extremely significant level(P<0.01);The determination coefficients R2 of morphological characteristics screened from Myanmar wild stock,Thailand and Vietnam cultured stocks on body weight were0.982,0.941 and 0.933 respectively.In practical production,it can be based on the multiple regression equations of stock morphological characteristics on body weight,and the morphological characteristic whose path relationship reaches a significant or an extremely significant level on body weight of M.rosenbergii can be used as a directional breeding index.The expected heterozygosity(He),observed heterozygosity(Ho),polymorphism information content(PIC),effective allele number(Ne)and nucleotide polymorphism(π)of the genome of Myanmar wild stock of M.rosenbergii were significantly higher than those of Thailand and Vietnam cultured stocks.The genetic diversity of Myanmar wild stock was significantly higher than that of Thailand and Vietnam cultured stocks.The genetic differentiation coefficient between Myanmar wild stock and Thailand cultured stock was 0.033,and the degree of genetic differentiation was low.The genetic differentiation coefficients between Myanmar wild stock,Thailand cultured stock and Vietnam cultured stock were 0.094 and 0.088 respectively,and the degree of genetic differentiation were both medium.The genetic variation of the three stocks mainly came from within stocks,accounting for 87.45% of the total genetic variation,and the rest came from between stocks;The genetic distance of Reynolds between Myanmar wild stock and Thailand cultured stock is 0.034,which is the smallest and has the closest genetic relationship,but the genetic distance of Reynolds between Myanmar wild stock and Vietnam cultured stock is 0.099,which is the largest and has the farthest genetic relationship.The three stocks can be divided into two subgroups in terms of phylogeny.The Myanmar wild stock and Thailand cultured stock are clustered into one branch,and Vietnam cultured stock is clustered into one branch alone.The results of this study will provide a theoretical reference for the protection of genetic diversity and genetic structure in the breeding of improved varieties and seedling production of M.rosenbergii.