Classification Of Low Temperature Tolerance Ability Of Sorghum Germplasm Resources And The Effect Of Low Temperature On The Physiological Mechanism Of Sorghum Seedlings

Sorghum is widely distributed in China,and the northeast is one of the main production centers.Because of its strong tolerance to waterlogging,high temperature,salt and alkali,it plays an important role in dry farming in northern China.However,with global climate change,the northeast region is prone to low temperature damage and late spring cold in spring.Low temperature stress has become the main factor limiting the growth,development,and yield of sorghum.seed germination,as the first step in morphogenesis,plays a crucial role in the entire growth cycle,and improving the stress tolerance during seed germination is of great significance for sorghum production.This study selected 50 main sorghum varieties grown in Northeast China and set up four different temperature treatments(5 ℃,10 ℃,15 ℃ and 25 ℃ as controls)to calculate germination potential and germination rate,while measuring indicators such as radicle and embryo length.Based on the performance of cold tolerance characteristics of different sorghum varieties during germination,identification and classification were conducted through methods such as analysis of variance,principal component analysis,cluster analysis,and comprehensive evaluation of D-values.The main research findings are as follows:1.There is a significant correlation between the germination potential,germination rate,radicle length,and embryo length of sorghum varieties during the germination period under low temperature stress,and all of them are highly significant positive correlations(P<0.01).With the decrease of germination temperature,the germination potential and germination rate of 50 sorghum varieties were inhibited to varying degrees,especially the variation of relative root length and relative bud length.After principal component analysis,the four intion were conducted through methods such as analysis of variance,principal component analysis cluster analysis,and comprehensive evaluation of D-values.The main research findings are as follows:dependent cold resistance indicators with significant relationship were synthesized into one.From the comparison of positive contribution rate,the relative germination rate in the comprehensive indicators was the largest,which can be used as the key indicators for comprehensive evaluation of sorghum cold resistance,and the relative germination potential,relative germination rate,relative root length and relative bud length all played a positive role.By cluster analysis,50 sorghum varieties can be divided into 3 types: cold tolerant(18%),general(62%)and sensitive(20%).Among them,9 varieties such as’ Zhongshuhui 1 ’and’replanted sorghum ’are cold tolerant,accounting for 18%‘ 31 varieties,such as seven leaf sorghum ’and’ white sorghum ’,are of general type‘ Soft sorghum ’,’ Wa Watou ’and other 10 varieties are sensitive.2.The comparison of morphological indicators,protective enzyme activity,membrane oxidation degree,osmotic regulation,and root activity of sorghum seeds during the seedling stage showed that under low temperature stress treatment,there were significant differences in seedling length,fresh weight,dry weight,SOD,POD,CAT enzyme activity,MDA content,proline content,and root activity among different organs and cold tolerant varieties.Low temperature stress can significantly inhibit the growth of sorghum seedlings,with a decreasing trend in seedling length,root length,fresh weight,and dry weight indicators.Moreover,varieties with strong stress tolerance(GPR148 and Zhongshuhui 1)are less affected than varieties with weak stress tolerance(Soft Sorghum and 866R).As the degree of low temperature stress increases,the SOD,POD,CAT enzyme activity,MDA content,and proline content of each variety show an upward trend,while the root activity shows a downward trend.Except for MDA,all other indicators showed that the root system was more sensitive to low temperature stress than the leaves.Stress tolerant varieties have stronger osmotic regulation ability than sensitive varieties to resist the damage of low temperature stress to plants,and their root activity value is higher than that of sensitive varieties,with a smaller decrease and stronger cold tolerance.This has led to differences in the tolerance of difference types of sorghum varieties to low temperature stress.