Studies On Sorghum Density Tolerance And QTL Mapping Of Grain Dehydration Rate

In this experiment,sorghum varieties suitable for mechanized harvesting were selected as the goal,and sorghum density tolerance and preliminary QTL mapping for grain dehydration rate were studied.In 2017 and 2018,sorghum varieties（lines）of 6 domestic or overseas genotypes were used as materials to study the density tolerance of sorghum with 5density treatments.The density tolerance of sorghum was evaluated in terms of plant traits,leaf traits,crude protein content and yield traits.Two varieties Xinliang52 and Meiyin-20 with large difference in dehydration rate were selected as parents,and F₂ population was obtained by cross combination.Quantitative genetic analysis of dehydration rate was carried out.The preliminary QTL analysis of sorghum dehydration rate was carried out by interval mapping method using Map QTL 4.0 analysis software.The experimental results are as follows:1.Density has great influence on the main agronomic characters and crude protein content of sorghum varieties（lines）.The plant height of 6 varieties（lines）increased with the increase of density,and reached the highest at 120,000 plants/hm².Then the plant height decreased with the increase of density,but the decrease was not significant.Leaf angle,leaf area,flag leaf sheath length and other leaf traits are greatly affected by density.The change rules of six varieties（lines）are consistent in the two-year experiment.With the increase of density,leaf area,leaf angle and flag leaf sheath length all show a decreasing trend,reaching the lowest at a density of 150,000 plants/hm².2.The research shows that the yield increases first and then decreases with the increase of density.The yield of 6 varieties（lines）reaches the highest in D₄ treatment（120,000plants/hm²）.This study showed that ear weight was greatly affected by density,while1000-grain weight was less affected by density.According to the correlation analysis of yield and spike number,spike weight and 1000-grain weight,it can be concluded that the yield and spike number are positively correlated and reach a very significant level.The yield was positively correlated with spike weight and 1000-grain weight and reached a significant level.Correlation analysis showed that spike number was the most important factor affecting yield.3.The result of density tolerance evaluation shows that the 6 varieties（lines）used in the research have good density tolerance,but the order of density tolerance is Meiyin-185,Meiyin-65,Xinliang52,Sanchisan,Meiyin-31 and Meiyin-20 from high to low.The screening results of the density tolerance index showed that the density tolerance of sorghum was a complex character,which was influenced by many factors and was closely related to seven important agronomic characters.Among them,the density tolerance was positively related to four characters such as stem diameter,spike stalk length,leaf included angle and leaf area,and negatively related to three characters such as plant height,spike length and leaf sheath length.This study believes that sorghum’s density tolerance cannot be directly distinguished by single screening,and must be screened by comprehensive evaluation of its traits.4.In this study,Xin Liang-52 with fast grain dehydration rate and Mei Yin-20 with slow grain dehydration rate were used as parents to carry out quantitative genetic analysis on the dehydration rate of F₂ population.The results showed that the grain dehydration rate of mature sorghum was in accordance with the additive-dominant-epistasis hybrid genetic model.The calculated genetic rate of the main gene was 53.48%,which proved that the trait was controlled by two pairs of main genes and could be stably inherited.5.QTL Mapping for grain dehydration rate usedparents and 404 F₂derived from them as mapping populations.A sorghum genetic linkage map with 10 marker sites was constructed,covering 114.6c M of sorghum chromosome 5 genome with an average distance of 12.73c M between markers.Mapping QTL 4.0 software was used to locate a QTL locus for regulating grain dehydration rate in sorghum.The QTL locus was located between Xtxp023 and Sam79604 markers on chromosome 5 and was named qGDR-E-1.The contribution rate of this locus to its phenotypic traits was 10.37%.