Physiological Mechanism Of Maize Hybrids With Wide Adaptablity For Stress Tolerance And Stablity

ABSTRACT The main characteristics of maize hybrids with wide adaptability is of high and stable yield, small changes between years, extensive areas suitable for planting, planting large area yearly, even to be able to grow across ecological zones. They were often the main force to promote the replacement of maize varieties, were the most effective way to improve the level of maize yield. The adaptability of varieties is more important than heterosis. The level of maize production depends on its ability to adapt to local ecological conditions. Drought, inadequate fertility, low light were the main abiotic stress factors for yield and stability in maize producing areas of the Huanghuaihai maize belt and the maize producing area. In this study, under controlled conditions, the different maize varieties with adaptability were used to study the lack of fertility, the effect of flowering drought, low light stress factors and three double, triple Stress (7stresses, totally) on maize growth to explore physiological mechanism of the wide varieties with wide adaptability response to these stress factors. The main results are as follows:Low light on corn growth and yield was large than that of fertility and flowering drought. In this study,7Stresses decreased yield by13.62%～91.55%. The effect of7kinds of stress on the five yield of maize hybrids in order were shade> low fertility and shade>low fertility, drought and shade> drought and shade>low fertility>low fertility and drought> drought. Shading at flower period significantly reduced the yield of5varieties by84.48%than non-shading treatments. Low fertility and drought treatment caused51.23%and18.26%yield loss, respectively. Shading had a great influence on flowering time. The silking time of5varieties was delayed by more than7d in treatments of shade, low fertility and shade, drought and shade, low fertility, drought and shade.There were more significant interactions between the factors, not just the cumulative effect of single stress factors. The interactions of low-fat, flowering shade and drought on the yield of maize yield existed. Among the interactions of two factors, the interactions of fertility, drought, and shade were significant or very significant. The interaction had very obvious effect on characteristics of species. The resistance of Zhangyu-9to low fertility was significantly higher than other varieties. Shading significantly increased the degree of sensitivity of maize to fertility, Zhangyu-9was the most sensitive and its barren-resistant index changed from the highest to the lowest.The corn hybrids variety with wide adaptability had high resistance to stresses, and no obvious defects. The yield of Nongda108was the highest in the treatment of drought and shade, was the lowest in the treatment of drought, drought and low fertility. Zhang Yu-9yielded most in the treatment of low fertility, and yielded lowest in the treatment of shade and low fertility. The yield per plant Yuyu22in low-fertility and drought conditions was higher than Zhengdan958, and it was the second highest in high fertilizer and drought conditions. However, the yield per plant of Yuyu22was the lowest in the conditions of shade, drought and shade, low fertility conditions. Luoyu-4yielded lowest in the condition of low fertility, drought, shade. Zhengdan958yielded highestly in the conditions of shade, drought, and low fertility and drought-shade. And it yielded the second highestly in the other four stresses. Therefore, the wide adaptability of maize hybrids did not significantly sensitive to stress, showing a wide range of adaptability to stresses.The difference of dry matter of5corn hybrids at silking was small. From silking to harvest the dry matter accumulation of maize hybrids with wide adaptability Zhengdan958was faster10.4%to17.3%than other varieties. At silking and harvest, the dry matter per plant of maize hybrids with wide adaptability Zhengdan958changed smallest among7kind of stresses, and the variation coefficient were3.94%and8.34%respectively. Under normal conditions, plant growth rate of maize hybrids with wide adaptability Zhengdan958during seed formation critical period was the highest, being4.03g/(plant· d), higher27.57%～57.37%than other varieties.The maize hybrids with wide adaptability Zhengdan958was stronger ability for controlling matter distribution. In this study, stem was sink organs to accumulate storage material at pre-or pro-silking, and2weeks after silking, storage material in stem began to transport and redistribute in the treatment of drought, low fertility, drought and low fertility. During stresses the redistribution of the storage material in leaves was of great important for maize response to stresses. The maize hybrids with wide adaptability Zhengdan958transported only6.52%leaf material under normal conditions, while the transfer rate of the other four varieties changed from18.73%to30.58%. But under stress conditions, Zhengdan958could transported32.27%mostly of the material in leaves, and its regulatory capacity was much higher than the other four varieties.The organ development of maize hybrids with wide adaptability was influenced small under by stresses. The effect of stresses on dusting time of varieties with different adaptability was very small, less than2d; but its effect on silking time was very large. The silking time of wide adaptability Zhengdan958was put off0.75～7.95d by stresses, and its ASI increased1.15～6.60d. Their variation coefficients among7kinds of stresses were minimum in5varieties, being28.13%and22.89%respectively. Ear growth also showed the same characteristics. The ratio of ear to total ear (ear+bract) of Zhengdan958was34.66%under7kinds of stresses at2weeks after silking (third sample), ranking third among5varieties. The variation coefficient of Zhengdan958between stresses was only higher than Nongda108. The ratio of Zhengdan958was the highest at fifth sampling, being42.87%. its variation coefficient was also small and being in second place.Characteristics of carbon and nitrogen metabolism of maize hybrids with wide adaptability. After silking, the soluble sugar content, C/N in leaves, stem and ear, and total nitrogen content in leaves of5maize varieties changed as single-peak curve, and was the highest at3weeks after silking (5th sample). The performance of organs in order was stem> ear> leaf. The total nitrogen content in stem and ear was the lowest at3weeks after silking, and it was higher at harvest than at silking. The content of soluble sugar and total nitrogen in leaves and stem of the maize hybrids Zhengdan958with wide adaptability under normal conditions was higher. After stresses relieved, it could restored quickly than other varieties.