Study On Density-resistant Maize Germplasm Materials

High-yield is the eternal goal in maize breeding. With the development of the breeding technology,it was reported depend on increasing the per plant yield to gain high yield is difficult.So increase the plant density is became a inevitable trend to increase the yield.And it is necessary to study the density-resistance and select the density-resistant hybrid. This study selected7inbred lines as the basis materials according to complete diallel cross produced49hybrid combinations. Planted these combinations in4densities (45000plants/hm2,60000plants/hm2,75000plants/hm2and90000plants/hm2).Analyzed the density-resistance, the results summarized as follow:1.Heterosis analysis indicated, among the average value of heterosis of all characters, the value of yield per plant is all greatest in4densities, the value is84.4%,78.3%,72.9%,53.3%.It indicated the average value of heterosis is decreased with the density increased, meanwhile this trend also performance on other characters.2. The results of analysis of combining ability indicated, on the GCA effect of yield per plant, the GCA of the inbred lines of6WC in4densities is30.92,33.41,36.92,39.85, the GCA of the inbred lines of4CV in4densities is2.17,10.09,16.21,18.34, the GCA of the inbred lines of J2067in4densities is10.32,15.28,20.97,28.61.But with the density increased, the GCA effect increased significantly. So these lines have better performance in high density, they can be used in breeding for density-resistant.3. Genetic parameter analysis indicated, plant height, ear height, ear weight, ear grains weight and ear rows, the inheritance of these characters influenced by gene additive effect; ear diameter, ear length, cob diameter, cob weight, kernels in a row, stalk diameter, hundred-kernels weight, kernel length and seed rate, the inheritance of these characters influenced by additive effect and non-additive effect combined action. The variance of heritability indicated, in4densities, the value of most of the characters more than50%,the narrow heritability and broad heritability of these characters(plant height, cob weight, ear diameter and cob diameter) are more than50%,the heritability of them is strong, these characters can be selected in early-generation;The broad heritability of these characters (ear height, ear weight, ear length, ear grains weight, ear rows, ear row kennels and100-kennels weight) is instability, so they cannot be selected in early-generation; the broad heritability of these characters (stalk diameter, kennel length and seed rate) is lower than50%, so they be selected in late-generation.4. Path analysis to the yield of hybrid in6density, rejected the indistinctive characters, the results showed that:in the density of60,000/hm2, the characters direct effect to the yield sored by size is hundred grain heavy>ear height>spike rough>seed rate, in the density of75,000/hm2, the characters direct effect to the yield sored by spike rough>size seed rate>spike long>hundred grain heavy>bald tip long, in the density of90,000/hm2,the characters direct effect to the yield sored by hundred grain heavy>spike long>ear height>spike rough>lodging rate.The analysis of characters and yield per plant indicated, the positive direct effect of100-kennels weight to yield per plant is the most significant, and negative direct effect of barren tip and lodging to yield per plant is significant. So if you want to get high yield per plant,should be considered the increase of100-kennels weight firstly, and the decrease of barren tip and lodging rate is also important.