Introgression of chromosome 6PL terminal segment from Agropyron cristatum to increase both grain number and grain weight in wheat

Agropyron cristatum(2n=4x=28,PPPP),which harbours many high-yield and disease-resistance genes,is a promising donor for wheat improvement.Narrow genetic diversity and the trade-off between grain weight and grain number have become bottlenecks for increasing grain yield in wheat.In this study,a novel translocation line,WAT6501,was derived from the chromosome 6P addition line 4844-12,which can simultaneously increase both grain number per spike(GNS)and thousand-grain weight(TGW).Cytological analysis and molecular marker analysis revealed that WAT6501 was a 5BL.5BS-6PL(bin 12-17)translocation line.Assessment of agronomic traits and analysis of the BC4F2 and BC5F2 populations suggested that the 6PL terminal chromosome segment in WAT6501 resulted in increased grain number per spike(average increased by 14.07 grains),thousand-grain weight(average increased by 4.31 g),flag leaf length,plant height,spikelet number per spike and kernel number per spikelet during the two grow-ing seasons of 2020-2021 and 2021-2022.Additionally,the increased GNS locus and high-TGW locus of WAT6501 were mapped to the bins 16-17 and 12-13,respectively,on chromosome 6PL by genetic pop-ulation analysis of three translocation lines.In summary,we provide a valuable germplasm resource for broadening the genetic base of wheat and overcoming the negative relationship between GNS and TGW in wheat breeding.