| Maize(Zea mays L.)is an annual herbaceous grain crop in Gramimeae, Maudeae. It is one of the most important crops widely planted in the world. China has the second largest area planted to maize, only next to America. It is necessary for maize breeding to research the change trend of different period maize hybrids. It was researched for⑴changing trend of maize yield,⑵the relationship of heterosis change and yield,⑶correlation of parents yield and hybrid yield,⑷agricultural and ear characters affecting to yield,⑸genetic study of stem puncture resistence. The main results were as fallows:1. Twenty maize hybrids and their parents in different period utilized widely in China were chose as the materials. By split plot design over 3 sites, the results indicated that yield of hybrids and mid-parents increased gradually with the new varieties releast; yield of the earlier varieties showed decreasing for high plant density, while yield and plant density increased gradually for current varieties; the heterosis of hybrids presented the trend of"down"for high and"up"for low plant density, respectively, it didn't change for middle and average density; Investigation evaluated changes for plant traits showed that tassel branch numbers and leaf angle uppermost ear reduced gradually; rows per ear, ear diameter, kernel length, and 100-kernel weight increased gradually, but not changed in kernels per row, shelling percentage and unit weight; the relationship was not significant between yield and heterosis; rows per ear, ear diameter, kernel length, 100-kernel weight and yield of mid-parents were significant positive relationship with yield at 0.01 level; tassel branch numbers and leaf angle uppermost ear were negative significant relationship with yield at 0.01 level. The conclusion indicated that there was conflicting evidence to support the heterosis was the principal contribution to yield increase, the contribution of maize yield increase owed to the increase of mid-parents yield and plant density, optimization of plant type and ear traits, and decrease of tassel branch numbers.2. The research was made on correlation between corn lodging resistance and its stem puncture resistence-pull strength in the different growth period by the utilization of the puncture-pull equipment designed by ourselves with forty-one corn varieties. The result indicated that the puncture resistent strength of the varieties stem third-node over ground were significant negative relationship with its lodging resistance; also, the pull strength of varieties stem were significant negative relationship with its lodging resistance when the angle between the variety stem and level ground hold 45°; the variety planting density, stem puncture resistence, and stem diameter were the principal direct factors for variety lodging resistance. In hence, the strength of variety stem puncture resistence and pull were acted as the index for variety lodging resistance.3. Shendan 16 and Zhengdan 958'six generations, namely F1, F2, backcrosses BC1 and BC2 and their parents′P1 and P2 were used to study the inheritance of maize stem lodging with joint analysis of multiple generations. The results were the followings: the F2 population of two hybrids appeared two peaks distribution, the BC1 and BC2 populations of two hybrids appeared multi-peaks distribution, these results indicated that maize stem puncture trait was quantitative in nature and controlled by polygene; The inheritance of maize stem puncture trait fitted D model which was a pair of additive-dominance-epitasis major gene plus additive-dominance-epitasis polygene; The major gene heritability was 34.5% to 45.7%; The polygene heritability was 41.6% to 56.3%, their effects were important on maize stem inheritance and should be value on maize breeding.
|
PDF Full Text Request