Screening Of Partial Interspecific Hybrid Combinations Between Asian Rice And African Rice And Evaluation Of Heterosis In Yield-related Traits

The heterosis of hybrid rice tends to be stronger with the increase of genetic differences between their parents.The use of introgression lines between Asian rice and African rice as parents can enrich the genetic basis of parents and increase genetic differences between parents,which could be a new effective way for breeding high-yield hybrids rice.In this experiment,116 partial interspecific hybrids rice were produced via crosses using 20 NERICA（New rice for Africa）and 38 IRLs（Introgression restore lines）as male parents,ST1 and GZ63S as female parents in 2018 and 2019 respectively.Evaluation was made on nine agronomic traits such as days to heeding,plant height,panicle length,number of panicle per plant,number of spikelet per panicle,seed setting rate,thousand-grain weight,grain length-width ratio,and yield per plant based on field experiments of parental lines and F1 hybrids rice.Strong heterotic combinations and strong heterotic groups were screened and identified.Meanwhile,the proportions of O.glaberrima genome（PGG）of 49 ILs were estimated.The main results are as follows:1. A total of 13383 polymorphic SNPs were detected.The average PGG of Introgression Lines was 15.29%,ranging from 1.22%to 47.53%.The average PGG of New Rice for Africa was 15.29%,ranging from 11.79%to 49.71%,while,the average PGG of Introgression Restore Lines was 3.55%,ranging from 1.22%to 15.02%.2. For the partial interspecific hybrids produced from crosses between ST1 and the ILs,grain yield per plant（44.2%）,plant height（9.2%）,number of panicle per plant（3.8%）,number of spikelet per panicle（2.0%）,panicle length（1.2%）and thousand-grain weight（0.8%）of partial interspecific hybrids showed positive average heterobeltiosis,while grain length-width ratio（-3.7%）,days to headings（-9.5%）and seed setting rate（-21.0%）showed negative average heterobeltiosis.Among the partial interspecific hybrids produced by GZ63S and ILs,grain yield per plant（41.3%）,number of spikelet per panicle（32.4%）,plant height（13.0%）,seed setting rate（4.7%）,panicle length（4.3%）and thousand-grain weight（2.2%）of partial interspecific hybrids showed positive average heterobeltiosis,while grain length-width ratio（-0.1%）,days to heading（-4.7%）and number of panicle per plant（-10.7%）showed negative average heterobeltiosis.3. The principal component analysis found that four principal component factors were obtained in each year.The cumulative contribution rates of four principal component factors reached 80.328%and 75.268%,respectively.Two regression equations were obtained by stepwise regression analysis between grain yield per plant and four principal component factors,included Y=11.6X₂+7.4X₁+2.2X₄-1.5X₃+42.5 in 2018and Y=8.5X₁+7.2X₂-1.5X₄+40.6 in 2019.4. The competitive advantages of 116 hybrid combinations were identified.The control variety was Fengliangyouxiang 1.The results showed that the strong heterotic combinations in 2018 were Y17,Y16,Y52 and Y21,with competitive advantages of35.7%,33.9%,24.1%and 22.3%,respectively.Y16 and Y17 were hybrid combinations between ST1 and NERICA varieties,and Y21 and Y52 were hybrid combinations between ST1 and IRLs.The strong heterotic combinations in 2019 were Z15,Z38 and Z7,with competitive advantages of 20.3%,14.7%and 14.2%,respectively.Z7 and Z15 were hybrid combinations between GZ63S and NERICA varieties,and Z38 was a hybrid combination between GZ63S and IRL.5. Four heterotic groups were identified by UMPGA based on heterobeltiosis of nine agronomic traits in 2018,namely group 1,group 2,group 3 and group 4,respectively.Five heterotic groups were identified in 2019,included group a,group b,group c,group d and group e.The discriminant analysis was performed on the heterosis groups for further verification.The results showed there were distinct differences between the heterotic groups.Two strong heterotic groups were selected through multiple comparisons,including group 3（2018）and group e（2019）.