Development And Evaluation Of Wheat Grain Weight QTL Near-isogenic Lines

Grain weight(GW)contributes greatly to wheat yield and is directly related to kernel size and shape.Although over 100 quantitative trait loci(QTLs)for GW have been reported in the literatures,few have been well characterized for their effects on the kernel traits.In this study,three GW QTLs identified in elite cultivar 'Nanda2419'('Mentana'),including QGw.nau-2D,QGw.nau-4B and QGw.nau-5A,were investigated through near isogenic line(NIL)development and evaluation.In four different field trials,these NILs consistently produced heavier kernels than the recurrent parents.QGw.nau-4B showed the largest effect on GW;its presence resulted in 0.4-0.5g increase of hundred-grain weight,depending on genetic backgrounds.QGw.nau-4B and QGw.nau-5A functioned additively in conditioning GW.These three QTLs showed pleiotropic effects on,or close linkage with genes for,spike length,plant height and flag leaf width,respectively,and acted differentially in determining the kernel dimensions.They all conditioned wider kernels with QGw.nau-5A displaying the largest effect.QGw.nau-4B and QGw.nau-5A also conditioned thicker kernels but had opposite effects on kernel length.Previous studies have found that Bihongsui,Zaoyangmai,Yangmai17,Nanda2419 and Chuanmai42 had different haplotype in QGw.nau-5A site,but their allelic variation effect on grain weight was not clear.In this study,four haplotype near isogenic lines(NILs)were developed through marker assisted selection of the grain weight QTL QGw.nau-5A with the genetic background of Chuanmai42.Bihongsui,Zaoyangmai,Yangmai17 and Nanda2419 were used as the donor parents.Grain weight evaluation showed that allelic variation in the site of QGw.nau-5A,Yangmai 17 and Zaoyangmai does not change Chuanmai 42 grain weight,Bihongsui allelic variation reduced Chuanmai 42 grain weight,Nanda2419 allelic variation increased Chuanmai 42 grain weight.The availability of GW NILs could facilitate cloning of GW genes and unraveling of kernel development mechanisms.