The results of the cultivation experiments of different hybrids, different fertilizing ways and different planting densities were studied The results showed that the 3 hybrids, Dongnong249, Sidan 19 and Benyu 9 could ripen normally in Linzhi, Tibet at an elevation of 3000 meters, the grain yield could reach 7 500～12 000 kg/ha The nitrogen fertilizer could be based or top fertilized The suitable plant densities were 55 000～60 000 plants/ha
In this paper, we have described the aspect of maize rough dwarf disease occurring in China and conducted a systemic failure analysis of the disease system composing of different factors such as virus, vectors, host and environmental factors, and so on Thus, IPM systems for controlling maize rough dwarf disease were proposed based on the principles of agricultural sustainable development
It was analysed to the resistance to the maize inbred lines and hybrids with the artifical inoculation test during the year of 1999～2000 The results indicated that the resistance of maize inbred lines to maize head smut was commonly affected by the genetics features and soil with germ The genetic features of resistance belong to nuclear inheritance,but isn't under the control of cyto_plasmtic particulates The resistances of hybrids are bound up to its parental pair.
Salt stress damages the functions of plasma membrane and induces stoma-closing, photosynthesis-decreasing, over energy-consuming and unbalance of unorganic ion absorbing in plants. Many salt-inducible genes have been cloned,and there are some hypotheses on molecular mechanisms of salt-stress tolerance, such as osmotic adjustment,salt-resistence, compartmentation, regulated potassium transport system, regulated water channel and converted photosynthesis pathway.Some salt-inducible genes have been transformed into plants,and it was evidenced that exogenous matters can enforce the ability to tolerate salt stress.
Analysis and evaluation on fresh ear yield, quality characters, agronomic traits and resistance to diseases of 12 supersweet maize new hybrid combinations from Guangdong provincial regional trials of supersweet maize varieties during 1999～2000, which were conducted in the present time The results showed that these new hybrid combinations have higher fresh ear yield and a better resistance to diseases ,and were bred in recent years However, the advancement on the quality improvement of supersweet maize was still slower The introduction of new elite varieties resources, organic combination of biotechnology breeding and conventional breeding methods, which should be carried out in the present time, in order to breed some good hybrid combinations with top-quality, high-yielding and multi-resistances
Sweet corn, N×T, is short, high quality, and edible like fruit, which is suitable for high density cultivation (79 500～90 000 seedlings/ha). Seedlings should be grown in greenhouses 25～30 days before late frost, and transplanted to field covered with plastic film 1～2 days after late frost. Accumulated temperature 1 751℃·d can be reached within 55 days. So it can be sold at the earliest time, and make net profit of 27 000 RMB/ha.
The responses of maize plant to drought stress depend on metabolism,morphology and growht stage.When drought stress occurs before or during flowering time,it strongly reduces grain yield in maize.The heritability and genetic variance for grain yield usually decrease as yield levels fall,wihile experimental variances remain the same or increase ,resultiing in efficient selection directly for grain yield .Under these conditions,selection for secondary traits,such as anthesis silking interval and ear per plant,may increase the selection efficiency.Breeding for drought tolerance is to improve the reaction of genotype to drought stress,and to reach high yielding ability.The convetional breeding approach combined with MAS for drought tolerance may efficently work based on the major feature of target area.At present,identiifcation and utilization of Chinese eltie and CIMMYT drought germplasm is the fast and efficient way for maize breeding for drought tolerance in China.
Resistance of 100 maize germplasms to the strain B of maize dwarf mosaic virus(MDMV_B) was evaluated by artificial inoculated and natural infection in the field.Among them,13 maize lines were resistant,they are:543,2125,2026,CY119,Shenshi29,87_1×L105,444×87_1,Dan408_2 and Jidan321.Comparison of resistance assay for some maize lines was conducted by inoculated at seedling in greenhouse and at adult in field ,the incidence in greenhouse appears to be more about one time than that in field ,however,the resistance for few maize lines in greenhouse was consistent with that in field.The evaluation for resistance inoculated in the field should be combined with the evaluation in greenhouse ,so that the evaluation may be quick and reliable.The resistance appearance of maize germplasms should be different at different sowing time in the field for a same maize line,the later they were sowed,the severer they were diseased.The incubative stage was longer and the symptom emerged slower in resistant maize lines.
Anthesis and silking of maize were always not at the same time, that caused the occur of anthesis-silking interval (ASI) The elongation of ASI caused the decrease of kernel numbers per ear, and resulted in the decrease of grain yield For the same variety, ASI may be elongated by stress,but the reactions of different varieties were not the same This paper studied the underlying causes of the relationship between anthesis-silking interval and kernel numbers in the following aspects: the contest internal and external plants, the relationship Between kernel number and ASI, pollen supply and the fitness of spikelet
Overdose of nitrogen (N) fertilizer may cause not only less economic benefit, but also more nitrate leaching into groundwater, therefore, catches more attention than anytime before Nitrogen efficient maize cultivars provide a promising way to solve the problem In this experiment, eight hybrids were used to analyze agronomic characters in relation to N use efficiency (grain yield / N supplied) under high (200 kg N/hm 2), and low (no N) N levels It was suggested that, for selecting high yielding hybrids under high N supply, grain rows per ear, grain number per row on the ear, grain weight, biomass at silking stage, and the total area of the three leaves near the ear can be taken as selection indices For selecting N-efficient hybrid under low N supply, such characters as big ear weight, more grain rows per ear, big biomass at maturity and big area of the three leaves near the ear should be taken into consideration
Basing on the study of high yield experiment and demonstrate of semi-compact maize S9914, the results showed that it was suitable planting semi-compact hybrid maize S9914 in the special ecological condition of mountain area of northwest Guizhou The yield was 9 050～10 717 5 kg/ha in large area and 11 797 8～12 994 55kg/ha in small area The results of density experiment showed that the suitable density of S9914 was 61 500～85 500 plants/ha The yield comments were 59 603～78 035 spikes/ha, grain numbers 475～444 per spike, 1000-grain weight was 347～312 5g The maximum LAI was 4 27～5 48 The biological yield was 17 205～21 876 kg/ha and economic coefficient was 0 6～0 49 The characteristics of growth development and physiology were investigated, determined, analyzed during the period of total growth, such as height of plant, total leaf numbers, leafs area, weight of dry matter LAD, NAR,chlorophyll, photosynthetic rate, transpiration rate, also observed and determined relative climate resources and field microclimate We researched integration and composition of high yield cultivation techniques of semi-compact maize at the same time
