Evaluation On Drought Resistance Of Ten Soybean Germplasm Resources During R3 Period In Karst Regions

Soybean(Glycine max L.),containing high levels of fat,protein,vitamin and amino acid,is honored as“green milk”,and becomes one of China's major food crops and main economic crops.Guizhou Province of China is known for its karst rocky desertification land forms,featured with quite a few dry slopes in the mountainous areas,low soil organic content,severe groundwater leakage,uneven distribution of water resources and frequent seasonal drought,which greatly affect the growth of soybeans,leaving issues as "pods without seed" or "more leaves with less pods" and so on,resulting in soybean production is generally low.In this experiment,10 kinds of soybean germplasm in Guizhou Karst area were tested by pot experiment to study the drought resistance in R3 period.The aim of this study was to provide comprehensive drought resistance evaluation,and basic data for screening high drought resistance germplasm suitable for soil cultivation in karst area.The main findings are as follows.1.The contents of proline(Pro),soluble sugar(SS)and soluble protein(SP)in 10 soybean germplasm of R3 period were positively correlated with the water treatment gradients(P<0.01),increased as drought stress aggravated,and approached the maximum value under the severe drought stress.And the increase of Pro was generally higher.The correlation coefficient(R)of them are greater than 0.80.2.The stress coefficient of three osmotic adjustment substances(Pro,SS,SP)in 10 soybean germplasm of R3 period were higher than 1,and increased as drought stress aggravated,and almost approached the maximum value under the most severe drought stress.The stress coefficient of Pro is generally large,mostly over 2.And the three osmotic adjustment substances play a regulatory role in order,Pro> SS> SP.3.The leaf membrane permeability and malondiadehyde(MDA)content of leaves of 10 soybean germplasms were positively correlated with the water treatment gradients(P<0.01),and both increased gradually with the drought stress aggravated,and reached the maximum value under the severe drought stress.The correlation coefficient of them are greater than 0.84.4.Under drought stress,the membrane damage rate and MDA stress coefficient of leaves of 10 soybean germplasm were higher than 1,and increased with the drought stress aggravated,and reached the maximum under severe drought stress.The plasma membrane approached to the upper threshold of tolerance under heavy drought stress.5.The activities of superoxide dismutase(SOD),ascorbate peroxidase(APX),peroxidase(POD)and catalase(CAT)in 10 soybean germplasms were increased under mild drought stress.The activity of SOD,POD and CAT were increased in a few germplasms under moderate and severe stress,and the changes of activity in most germplasm were increased first and then decreased,as is the APX activity of 10 soybean germplasm.6.The stress coefficients of POD,SOD,CAT,APX and other enzymes were higher than 1 under mild and moderate drought stress.Under heavy drought stress,the antioxidant enzyme stress coefficient of several germplasm was lower than 1;And CAT played a greater role in resisting severe drought stress,followed by APX.7.Under drought stress,the contents of Chal-a,Chal-b and carotenoids were significantly negatively correlated with the water treatment gradients(P<0.01).The contents of three photosynthetic pigments were increased with drought stress The dynamic change showed a decreasing trend,and the coercivity coefficient decreased uniformly,lower than 1.The correlation coefficient of them are less than-0.87.8.Under drought stress,the plant height,pod number of single plant and 100-seed weight of 10 soybean germplasm decreased,and decreased with the aggravation of stress.The root length increased under slight stress,while decreased under the severe drought stress.And the four ecological indexes were negatively correlated with the water treatment gradients.The plant height,the number of pods per plant and the 100-seed weight were significantly negatively correlated.The correlation coefficient of them are less than-0.72.9.Under drought stress,the stress coefficient of the plant height,plant pod number and 100-seed weight in 10 soybean germplasms were lower than 1,and decreased with the increase of stress.The root stress coefficient increased firstly and then decreased under different drought stress,which is higher than 1 under mild drought stress and decreased drastically to a level lower than 1 under severe drought stress.10.In this study,the results of comprehensive drought resistance evaluation of 10 soybean germplasm in Guizhou were: 175?189?166> 172?174?177> 164> 186?188?165.