| Due to the global climate change,agricultural production is facing many problems,such as adverse weather frequency,water shortage,environmental pollution and so on.Combined with population booming and socio-economic development,global food security is severely challenged.Wheat is one of the most important food crops in the world,whose sustainable high and stable production hold the promise for ensuring the food security in China and even all over the world.However,the genetic bottleneck effect in modern breeding program greatly reduces the genetic diversity of wheat,which limits the further breakthrough of genetic improvement of wheat yield.To better understand the relationship between wheat yield-related traits and provide the valuable germplasm,we made use of the representative tetraploid emmer wheat（including wild,domesticated and cultivated durum wheat）and hexaploid wheat（including landrace and variety）as material,and then comprehensively investigated and compared their spike-and grain-related traits.Furthermore,the correlations among these traits were systematically revealed and the spike traits highly associated with high yield together with the excellent germplasm were also identified,which provided the theoretical basis and material resources for high-yield breeding in wheat.The main results are as follows:（1）Comparative analysis of these spike traits,grain traits and other agronomic traits found that the variations of each trait in tetraploid wheat were larger than those of hexaploid wheat.In detail,the coefficient of variation of 1000 grain weight ranked the largest,with 13.4%for hexaploid wheat and 35.4%for tetraploid wheat while the coefficient of variation of grain diameter was the smallest,with the value of 4.9%for hexaploid wheat and 9.5%for tetraploid wheat.Among tetraploid emmer wheat,the variation of each traits showed that wild emmer wheat>domesticated emmer wheat>durum wheat.In addition,the correlation analysis showed that there were high correlation coefficients among all of these spike traits and grain traits.（2）Analysis of the effects of spike and grain traits on the three yield-related factors found that the 1000 grain weight（TGW）was mainly affected by grain length,grain width,grain perimeter,grain area,grain diameter and effective tiller number;the number of grains per spike was mainly affected by the number of spikelets and spike length;the spike number per unit area was mainly affected by spike density.Further direct path coefficient and indirect path coefficient analysis found that the spike and grain configuration with more effective tillers,wider grain,smaller grain length width ratio,larger roundness,larger grain area,longer spike length and more spikelets was crucial for wheat yield.The multiple linear regression models of the three yield factors were finally determined as follow TGW:y=–28.942–0.00896×X1+31.104×X2–60.192×X3;grain number per spike:y=–17.844–0.718×X1–0.0683×X2–0.0378×X3+2.615×X4–7.664×X5+29.290×X6;spike number per unit area:y=177.551–2.048×X1+0.342×X2+0.130×X3–1.247×X4–165.230×X5.In addition,41 hexaploid wheat and 30 tetraploid wheat were identified as the excellent resources for wheat spike and yield genetic improvement by evaluating the spike and grain traits.（3）The evolution of spike traits and grain traits in wheat was also analyzed and significant differences were found in grain traits during the process of wheat domestication,improvement and polyploidization,while the change of spike traits was scarce.Among them,1000 grain weight,grain width and roundness increased continuously,while the ratio of grain length to width decreased continuously.The plant height of tetraploid increased gradually from wild emmer to cultivated emmer,but decreased from hexaploid landrace to varieties,and the plant height of hexaploid varieties was the smallest.This study investigated and compared the spike and grain traits of tetraploid emmer wheat and hexaploid bread wheat,preliminarily defined the optimal spike architecture related to wheat yield,fitted the multiple linear regression model of three factors of high-yield wheat yield,and mined the excellent germplasm material,which can be used for wheat breeding with high and stable yield.The trend of spike morphology in wheat evolutionary process was also clarified to some extent.This study laid the foundation for the study of the evolution and breeding of yield related traits in wheat,and also provided the theoretical basis for the selection of yield related spike traits. |
