A novel Effective Panicle Number per Plant 4 haplotype enhances grain yield by coordinating panicle number and grain number in rice

Increasing effective panicle number per plant(EPN)is one approach to increase yield potential in rice.However,molecular mechanisms underlying EPN remain unclear.In this study,we integrated mapbased cloning and genome-wide association analysis to identify the EPN4 gene,which is allelic to NARROW LEAF1(NAL1).Overexpression lines containing the Teqing allele(TQ)of EPN4 had significantly increased EPN.NIL-EPN4^(TQ) in japonica(geng)cultivar Lemont(LT)exhibited significantly improved EPN but decreased grain number and flag leaf size relative to LT.Haplotype analysis indicated that accessions with EPN4-1 had medium EPN,medium grain number,and medium grain weight,but had the highest grain yield among seven haplotypes,indicating that EPN4-1 is an elite haplotype of EPN4 for positive coordination of the three components of grain yield.Furthermore,accessions carrying the combination of EPN4-1 and haplotype GNP1-6 of GNP1 for grain number per panicle showed higher grain yield than those with other allele combinations.Therefore,pyramiding of EPN4-1 and GNP1-6 could be a preferred approach to obtain high yield potential in breeding.

Mapping of QTLs Controlling Panicle Length and Effective Panicle Number of Rice

Panicle length and effective panicle number of rice are closely related to yield. In this experiment, indica V20B as female parent was crossed with javanica CPSLO17 as male parent, recombinant inbred line （RIL） populations were obtained by single seed descent method, and with the RIL populations as mapping populations, QTL mapping and analysis were performed to the two panicle traits, panicle length and effective panicle. A high-density genetic map was constructed with SLAF labels, interval mapping was performed by software Map QTL5 under the threshold of 3.9, and 7 QTLs were detected on 3 chromosomes in total. Among the 7 QTLs, 5 QTLs controlling panicle length （qPLI-1, qPL1-2, qPL6-1, qPI_6-2 and qPL6-3） were located on chromosomes 1 and 6, respectively, and showed the contribution rates of 6.41%, 22.22%, 6.15%, 12.24% and 13.01%, respectively, their effect-increasing loci were mainly from CPSLO17, and qPL1-1 is a new QTL; and 2 QTLs controlling effective panicle number （qPN1 and qPN4） were located on chromosomes 1 and 4, respectively, and exhibited the contribution rates of 13.15% and 8.18%, respectively, and the effect-increasing loci were from parent V2OB. The marking of these loci lays a foundation for further cloning of genes controlling panicle length and effective panicle number and molecular marker-assisted selection.