Shade-endurance Among Different Maize Varieties And High-yielding Population Structure

Study the effect of different stages shading treatment and density in different areas on spring maize growth and development, physiological and biochemical characteristics by the field experiment; analysis of the resistant differences among varieties, explore the relationship between the physiological and biochemical indicators and shade resistance of spring maize and make mechanisms for shade resistance clear; selected shade resistance varieties, provide the theoretical basis and technical support to improve the output efficiency of spring maize shade breeding. Comparing the main conclusions are as follows:1. The actual shade resistance of varieties followed from strong to weak are:Xianyu335, Zhengdan958, Beiyu288, Zhongdan909, Liaodan565, Dondan90, Danyu39, Shenyu21, Danyu402, Danyu405. Uses the result of systematic cluster analysis and yield difference comparison of selected10spring maize varieties are divided into shade resistant varieties-Xianyu335, Zhengdan958, Beiyu288, Zhongdan909and Weak shade resistant varieties-Liaodan565, Dondan90, Danyu39, Danyu402, Danyu405, Shenyu21.2. The degree and reasons of maize yields decreasing resulted from shade stress vary in different stages. The results we study under shade treatments at different stage show that two shade treatments may cause maize yields decreasing, and grain shading treatment was more serious than ear shading treatment. Ear shading treatment processing in jointing stage, inhibited the growth of maize leaf, plant height, dry matter accumulation decreased, root growth slowing and vegetative growth is seriously affected. Grain shading streatment processing was conducted at thg beginning of the the spinning tasseling stage, shade treatment which resulted in loosed powder to silking(ASI)prolonging,spike grain number decrease, the kernel abortion increase, and even non synchronous flowering, production seriously.3. Ear shading treatment, the photosynthetic rate can be maintained at a high level in highly shading resistance varieties and higher than the normal illumination treatment. Short-term period of grain shading, at the same time can keep high light use efficiency, and the photosynthetic rate significantly lower than normal light treatment in the weak shading resistance varieties, also the light use efficiency is low. Light compensation point (LCP) and light saturation point (LSP) is reduced after ear shading treatment, leaf photosynthetic ability decreased too.Graing shading treatment decreased the photosynthetic rate of maize leaf, LCP and LSP were decreased, shading treatment make the maize leaf can better use weak light, decrease of light utilization ability, and strong shading resistance varieties has a better adaptability to low light environment in the varieties relatively weak shading resistance varieties.4. Compared with normal light, the initial fluorescence (Fo), maximal fluorescence (Fm), variable fluorescence (Fv) increased significantly after ear shading treatment; after the end of the shade, fluorescence parameters showed increasing trend, the shading treatment significantly cut the primary photochemical activity of PS Ⅱ, the reaction center is damaged; Maximum photochemical quantum yield (Fv/Fm) reduce more illustrates this point. Graing shading treatment30d Fv/Fm is obviously increases, continue to shading decreased, showed that long time shading PS Ⅱ reaction center was destroyed, and highly shading resistance maize has strong photochemical activity, small damage degree, short shading at late growth was good for photosynthesis.5. Electron transport rate (ETR), photochemical quenching (qP) and PS Ⅱ practical quantum yield Y (Ⅱ) decreased after shading treatment, and the photochemical quenching (NPQ) increased. qP decline shows that PS Ⅱ reaction center open proportion to drop, PS Ⅱ potential activity inhibition degree to strengthen, the increase of NPQ indicates the potential of PS Ⅱ heat dissipation ability strengthen, excess light energy wasted in the form of the photochemical quenching, avoid or mitigate for PS Ⅱ absorbing excess light energy damage of photosynthetic mechanism. The ETR and Y (Ⅱ) below the normal light after shading treatment, this shows that shade processing make actual photosynthetic ability drops, decrease in proportion for photochemical reaction part, reduces the photosynthetic electron transport rate.6. Compared with the normal illumination, chlorophyll content and chlorophyll a/b ratio decreased significantly after shade treatment,shade treatment lessened chlorophyll biosynthesis ability, causes the maize leaf accumulated a large amount of active oxygen, led to the chlorophyll to speed up the decomposition. After shade treatment of maize leaf by lowering the content of chlorophyll, avoid the absorption of excess light energy, damage of photosynthetic mechanism. Ear shade treatment significantly reduced at the same time, heading the carotenoid content of maize leaf, after the return to normal light, each type of carotenoid increased significantly, shade treatment, hindered the photosynthetic electron transport. 7. Ear shading treatment significantly increased the MDA content of maize leaves, but in the shade after processing, the MDA content significantly lower than normal light. Grain shading treatment can obviously reduce the ear leaf MDA content. After shade treatment, maize protective enzymes SOD and POD in the body the decrease trend overall, but highly shading resistance varieties has slightly increased at the beginning of the shade, the ability of scavenging free radicals is stronger. Highly shading resistance of maize varieties protection enzyme system has strong ability of scavenging free radicals, can protect the cell membrane from damage or destruction, to a lesser degree, in the restoration of normal light has a certain resilience.8. Maize varieties of resistance to negative and close relationships. The best planting density of Xiongyue is61259plants/hm2, followed by Fuxin57245plants/hm2, Tieling a minimum of56543plants/hm2. The best planting density in a slightly different performance among regions, the overall trend for tightness strong varieties resistant to Xianyu335, Zhengdan958, Beiyu288, Zhongdan909, Liaodan565is significantly higher than Danyu39, Danyu402, Danyu405, Dongdan90and Shenyu21. The tightness good resistant varieties adapted to grow in light and rainwater enough, tightness of poor resistance varieties should be planted in poor light conditions to give full play to the variety of yield advantage.