| The maize is the largest grain crop in China.Innovation and utilization of germplasm resources are beneficial to increase maize yield,improve quality,and enhance disease resistance.The introduction of foreign germplasm,continuous genetic improvement,and aggregation of good genes are important ways to enrich the germplasm resources in China.This study used maize Non-Reid excellent inbred lines of PH4 CV,PHB1M,KW6F513,M5972 as the basic materials,and carried out two rounds of genetic improvement for the resistance and main traits of leaf blight in order to obtain high yield and resistance lines,and provide theoretical reference and material basis for resistance breeding and the expansion of germplasm resources.This experiment is based on different Non-Reid group germplasms PH4CV(high susceptibility),PHB1M(high resistance),M5972(high resistance),KW6F513(medium resistance),and bred the first round of improved lines J9D207,J1577 and the second round of improved lines J1673,J1630,J1791,J1778,so as to study the effects of genetic improvement on the resistance,yield traits,and plant type traits of leaf blight.Firstly,the paper uses SSR molecular marker technology to analyze the genetic diversity of the basic line and the improved line,and then studies the genetic improvement effect of each trait of the Non-Reid basic line and the two rounds of improved line;finally,the paper uses the basic line and the improved line as the male parent,selects the corresponding 5 excellent inbred lines of Reid group as female parent,makes 5×10 incomplete dillel crosses to study the heterosis,genetic parameter analysis and correlation.The experimental results are as follows:1.The genetic diversity analysis showed: the genetic differences between the basic lines are large,and there are genetic differences between the basic lines and the improved lines.When the threshold is 0.25,10 inbred lines can be divided into four categories.2.The effect of genetic improvement showed: after two rounds of genetic improvement,we have obtained the first round of improved line J9D207 and the second round of improved line J1630 with high resistance and stable yield traits,providing theoretical references and material basis for the improvement of maize inbred lines against leaf blight.Each round of improved line is superior to the basic line in different traits,and there are significant or extremely significant differences between the basic line and the improved line.The second improved J1630 is better and reaches the optimal value in traits such as single plant yield,100-seed weight,shaft thickness,and grain depth.Comprehensive disease resistance,yield traits,ear traits and grain traits,J1630 is the best quality inbred line with the best improvement effect.It provides theoretical and material basis for improving disease-resistant inbred lines and assembling disease-resistant high-yield hybrids.3.The heterosis analysis showed : the combination with the highest heterosis per plant yield is PH6WC×J9D207(97.00%),J1596×J1791(81.84%),PH6WC×J1577(80.32%),J1595×J1577(80.07%),and PH6WC×C1 have the highest yield heterosis per plant.The combination with the greatest heterosis of 100-seed weight is PH6WC×J9D207(30.14%).Therefore,the improved line is easy to produce a high yield.4.Combination analysis showed: the yield per plant and 100-seed weight of the improved lines J1630 and J1673 are generally the highest;the general combination of the grain depth is the best;the combination of J9D207 and J1577 have good thickness.J1630 and J1673 has better effect on improving ear length,and J1778 and J1791 has the best effect on improving shaft thickness.The combinations with the largest SCA yield per plant are PH6WC×J9D207,J1590×J1778,and the largest SCA yield of improved lines are PH6WC×C1,J1596×C2;the highest 100-seed SCA weight of improved lines are PH6WC×J9D207,J1596×J1673,the largest 100-seed SCA of improved lines is PH6WC×C1.5.Correlation showed: ear length and yield traits are significantly positively correlated,and the correlation coefficient with yield per plant is as high as 0.773;shaft diameter is significantly negatively correlated with yield per plant and 100-seed weight.There is a very significant positive correlation between grain traits and yield traits,and the correlation coefficient is relatively large.There is a significant or extremely significant correlation between ear traits and grain traits,and the correlation coefficient between ear length and grain depth is 0.681;yield traits are closely related to grain traits and ear traits,but there is no significant correlation between plant height,ear position,stem thickness and other traits.6.Genetic parameters showed: plant height,ear position,ear length,and grain depth are controlled by additive effect genes,which also means that the heritability is large and early generation can be carried out. |
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