| Maize is one of the three major crops in China.Drought is the main abiotic stress factor to reduce maize yield.The distribution of water resources in China is uneven and the water shortage in some areas is serious.Therefore,how to identify and improve the drought tolerance of maize has important theoretical and practical value.In this experiment,9 maize varieties were used to simulate drought stress with PEG during seed germination,and pot culture was used to control water stress at seedling stage.The indexes of drought resistance of maize were evaluated and analyzed by using membership function method.The varieties with different drought resistance were selected.By spraying brassinolide(BR)to improve drought resistance of maize,the physiological and molecular mechanisms of BR regulating drought resistance of maize were studied,which provided theoretical and practical basis for drought resistance selection,cultivation and genetic improvement of maize.The main results are as follows:1.Five-star evaluation method was used to determine drought resistance of different maize varieties during germination period.The sequence is: Zheng Dan 958 >Shandan620 > Xianyu 335,Xin Yu 47 > Jin Tong 152 > Xin Yu 108 >Shandan628>Nine saint s692>KX3564?2.The correlation analysis of seed germination indexes to 6 varieties showed thatsprouting potential and germination rate,the length of the germ and the transfer rate of the storage substances,highly significant positive correlation.There was a significant positive correlation between germination index and storage matter transfer rate,germination index and germ length.3.The morphological indexes such as plant height and leaf area decreased with the in crease of drought degree,and the physiological indexes such as osmotic adjustment factors and protective enzymes increased with the increase of drought degree.Usingthe membership function method,according to membership value of different varieties,from strong to weak,the order of drought resistance at seedling stage was as follows:Shand an620 > Jintong 152 > Zheng Dan 958 > Xianyu 335 >Nine saints 692 > Xin Yu 108 > Xin Yu 47 >Shandan628>KX3564?4.By means of principal component analysis(PCA),14 kinds of the growth andphysiological indexes,were analyzed and determined.SOD?MDA,seedling dry weight,POD,chlorophyll,relative water content,leaf area,seedling height,root dry weight,and soluble protein,can be used as the important indexes to screen different varieties.5.Using strong drought resistance of Jin Tong152,medium drought resistance of xianyu335 and weak drought resistance of Shandan628 as material,pot experiments were carried out.6.BR could make stress sensitive Index(SI)down and drought resistance coefficient(DI)rise,including the SI and DI of seedling height,seedling dry weight,leaf area and etc.Under moderate drought conditions,the decrease of SI and the increase of DI increased by BR were bigger.For different varieties,the effects of BR on SI and DI were different under different drought degree.For example,under moderate drought conditions,using seedling height as an indicator,Jintong152 had the highest decrease in SI and the highest increase in DI after spraying BR.If using dry weight of seedling as indicator,SI of Shandan628 decreased most and DI increased most.Under severe drought condition,SI of Jintong 152 decreased most and DI increased most when leaf area was taken as the index.On the other hand,if the seedling height is used as the index,then SI and DI of Shandan628 changed most.Comprehensive comparison of the experimental results of seed germination period and seedling stage,we could draw a conclusion that Zheng Dan958 and Shan Dan620 were stronger drought resistance varieties,while Shan Dan628 and KX3564 were weaker drought resistance varieties,and the drought resistance of other varieties were moder ate.Using principal component analysis(PCA),10 kinds of drought resistance identification indexes of maize,such as SOD,were selected and determined at seedling stage.Spraying BR at maize seedling stage could effectively increase drought resistance coefficient,decrease drought stress sensitivity index and improve maize ability to adapt to drought stress.The results of this paper will provide theoretical and practical basis for selection of drought-resistant maize varieties and drought-resistant cultivation. |
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