Evaluation Of Heterosis Of Important Agronomictraits In Partial Interspecific Hybrid Rice Combinations

Heterosis of hybrid rice depended on the genetic differences between their parental lines.Using the introgression lines carrying genomic genes of African rice to develop new combinations of partial interspecific hybrid rice,which can effectively broaden the genetic diversity between their parental lines,is a promising new way for high-yielding super hybrid rice breeding.In this study,8 African rice introgression lines and 10 restoror lines of different types as male parents and 4 cytoplasmic male sterile lines as females were used to produce the hybrid seeds.72 cross combinations were obtained using 4×18 incomplete diallel crosses(NCII design).Evaluation was made on the heterosis and combining ability of agronomic traits including duration from seeding to heading,plant height,flag leaf length,panicle length,effective panicles per plant,number of grains per panicle,seed setting rate,1000-grain weight,and yield per plant based on two years field experimants of all parental lines and F1 hybrids.The performance of the new hybrid rice combination with strong yield advantage was further screened;And the genetic diversity of 22 parental lines was analyzed.The main results are as follows:1.Most of the 72 combinations showed positive mid-parent heterosis in all traits except for seed setting rate.The percentages of lines with positive heterosis were69.17%,68.06%,95.83%,70.83%,98.61%,70.83%,69.17% and 81.94%,respectively.The competitive heterosis of 72 crosscombinations was analyzed using FenFLiangyouxiang 1 as the control,which showed that there were positive competitive heterosis in the yield-related agronomic traits including FLL,PL and SP.The percentage of combinations with positive competitive heterosis were 52.67%,54.17% and 77.78%,respectively;indicating most combinations had bigger panicle with more spikelets per panicle,and longer flag leaves as compared with the control.2.The analysis of the general combining ability of GYP showed that the general combining ability of the four female parents were as follows: C1> C4> C3> C2;the average yield of 18 male parents per plant was in descending order Is: Q3> Q7> Q13>Q12> Q8> Q1> Q18> Q5> Q10> Q4> Q17> Q14> Q9> Q15> Q11> relatively Q16>Q6> Q2.Among them,the general combining ability of the yields of the introgression lines Q7,Q13 and Q12 ranked 2-4,indicating that the introgression lines with African rice genes had relatively higher general combining ability.3.Correlation analysis showed that the correlation coefficients between mid-parent heterosis and SCA of combination,GCA of male parent,GCA of female parent,total GCA of both parents,SCA+GCA were significant at probability of 0.05 and 0.01,respectively.The correlation between mid-parent heterosis and SCA and SCA+GCA on plant height,the correlation between mid-parent heterosis and SCA+GCA on seed setting rate,and the correlations between mid-parent heterosis and SCA and SCA+GCA on grain yield per plant were significant at probability of 0.01.These parameters could be used for predicting mid-parent heterosis of related traits.4.Comprehensive screening of the F1 hybrid combinations resulted in four new high-yield hybrid combinations,C4×Q13,C1×Q18,C4×Q3,C4×Q4andC1×Q12..The yield of each of the four combinations showed a positive competitive heterosis against control variaty FenFLiangyouxiang 1,the competitive advantage of some of the interspecific hybrid rice combinations C4×Q13 was 37.85%.5.Genetic diversity of the parental lines was studied using the data of phenotypic traits,and the resulting UMPGA clustering map roughly matched the genetic lineage of the parental lines.It indicated that the analysis of genetic diversity based on phenotypic traits effectively representing the genetic differences between parental lines.