The Correlation Between 48 Pairs Of Molecular Fingerprinting SSR Markers And Heterosis In Rice

Heterosis is a ubiquitous biological phenomenon in crops.Since the 1970 s,the utilization of heterosis in rice has been rapidly promoted in China.The application of hybrid rice has made great contributions to the increase of grain yield and food security in China.However,the mechanism of rice heterosis has not been fully understood,which makes the selection of hybrid combination heavily depend on the breeders' experience in hybrid rice breeding.Therefore,it is urgent to develop a reliable method to address the challenge of rice heterosis prediction.Applying molecular markers as fingerprints of rice can well estimate the genetic differences among cultivars,which has a correlation with heterosis in rice.In this work,we choose a serial of materials,including 33 reference breeds(under industry standard of Ministry of Agriculture(NY/T1433-2014))with significant genetic differences,two male sterile lines(T91S and Pei'ai 64S),and the 66 cross combinations between them,to investigate mechanism of Heterosis in rice with the assistance of 48 pairs of SSR molecular markers.The results and conclusions are summarized as follows:1.According to the investigation of agronomic traits of the parent rice cultivars,it is found that there is a large variation range of agronomic traits of the two types of male parent.Especially,the variation range of Indica male parent is between 7.11%to 29.23%,and that of Japonica male parent is between 10.53% to 28.10%.The results reveal that the phenotypes of the parents rice are significantly different and have high heterosis research value.2.Based on the 48 pais of SSR molecular markers,the molecular fingureprints of the different tested rice cultivars are drafted,which facilitate the analysis of the genetic.The genetic distance between the two male sterile lines was 0.351,the heterozygosity was 0.468,and the genetic distance between the two male sterile lines was 0.269-0.456 and 0.322-0.423,respectively.It indicates that there are relatively profound genetic difference.Furthermore,based on the cluster analysis of the geneticsimilary coefficiency,the 33 refered rice cultivars can be categoried into three geneanolgies: one kind including 19 indica rice varieties,one kind including 12 japonica rice varieties and another kind including 2 indica rice varieties with japonica blood relationship.This result in in agreement with the genetic difference analysis based on the molecular figureprints of different rice cultivars.Therefore,It is indicated that the molecular fingprint based on the 48 SSR markers can exactly reveal the genetic differences among different rice cultivars.3.The analysis of the correlation between genetic distance and Heterosis of hybrid combinations showed that when the genetic distance between parents of T91 S and indica male parent combinations was between 0.269 and 0.300,the genetic distance was positively correlated with growth period and spike length heterosis,negatively correlated with 1000-grain weight heterosis,and reached a significant level,while the correlation between other agronomic traits and genetic distance was not significant.When the genetic distance between parents of hybrid combination Pei'ai64S and indica male parent was between 0.390 and 0.433,the growth period and genetic distance reached a very significant positive correlation,and spike length and genetic distance reached a positive correlation.Therefore,there is a certain correlation between molecular genetic distance and the agronomic traits of heterosis.4.According to the heterozygosity calculated from the molecular fingerprint of the rice and correlation analysis of heterosis,it showes that the heterozygosity of T91 S and indica hybrids was between 0.532 and 0.744.The correlation of super-parental advantage in growth period,plant height and ear length was significant.The heterozygosity of T91 S and indica hybrids was between 0.800 and 0.893.The correlation of super-parental advantage in ear length,total number of grains per panicle,number of grains per panicle,and yield per plant was extremely significant.The gene heterozygosity between Pei'ai 64 S and indica rice parental hybrids ranges from 0.447 to 0.691.The correlation of super-parental advantage in total number of grains per panicle was extremely significant.The correlation between the remaining agronomic traits and gene heterozygosity did not reach a significant level.The above results indicate that the heterozygosity of hybrid combination gene had somecorrelation with the main species in the main agronomic traits and the gene heterozygosity can be used as a figure-of-merit in hybrid combination.5.The correlation analysis between 48 pairs of SSR primers and heterosis of hybrid combinations indicate that major the agronomic traits showed strong heterosis with specific bands corresponding to some specific primers.The molecular fingerprint band type can provide guidanec in the prediction of heterosis.