Comparison And Analysis Of Salt Tolerance Of Rape Germplasm Resources In Tibet

Soil salinization restricts the development of agricultural production,and it is an severe problem in the agriculture development all over the world.It is one of the most direct,effective and ecological methods to cultivate and select salt tolerant halophytes.Tibet is located in the southwest of China,it is a typical low latitude and high altitude agricultural area in china.Tibetan wild rape resources are abundant,and the unique physiological environment forms a variety of complex physiological and genetic mechanisms of salt tolerance.In this study,42 kinds of rape seedlings from Tibet academy of agriculture and animal husbandry sciences were tested for salt tolerance at seedling stage,through the germination rate,biomass and other indicators of growth as well as photosynthesis,ion absorption and other physiological indicators to select salt tolerant rapeseed germplasm.The main results were as follows:(1)42 rape varieties under gradient salt concentration(NaCl)had different germination rate:15 C capital series including C 151 and C 153,and C093431-2 rape showed higher germination rate,while salt tolerance of J capital series were weak.With the increase of salt stress,the root length showed a decreasing trend,the plant height and fresh weight increased first,then decreased,but the decline of root length was greater than plant height and fresh weight.By comparison,it was found that C 151 and C 153 showed better salt tolerance than J 264 and J 436.(2)The hydroponics experiment was carried out under different salt stress concentration on salt tolerant varieties C 151 and C 153 and salt sensitive varieties J 264 and J 436,the results showed the salt damage index of J 264 and J 436 was significantly higher than the C 151 and C 153.Among the total root length,root diameter,root surface area and volume 4 indicators,the root surface area and volume were affected by salt stress more than root diameter.With the increase of salt stress concentration,C 151 and C 153 showed better salt tolerance because their root system index declined less than J 264 and J 436.(3)The sequence of fresh weight ratio from high to low was tape leaves,stems and roots when the salt concentration increased,leaf fresh weight proportion increased,relatively root and stem fresh weight ratio became smaller,suggested that salt stress has greater influence on the root and stem than leaf.In the analysis of the salt tolerance of J 436 and C 153 found the stem diameter,leaf length,leaf width and petiole length decreased with the increase of salt stress concentration,the decline in all indicators of J 436 were greater than the C 153.At the low salt concentration,the stem diameter,leaf length and plant biomass of C 153 increased;(4)When the salt concentration increased,the chlorophyll content and photosynthetic parameters of J 436 and C 153 two rape varieties showed a decreasing trend,proved the conclusion that salt stress inhibited rape photosynthesis.The photosynthetic rate of J 436 declined less than C 153,showed that the inhibitory effect of salt stress on J 436 was more obvious;The content of Na+ increased continuously in two rape,and the increase of Na+content in leaves was greater than in stems and roots,Na+ accumulates on the ground tissues.There was no significant change in K+,Ca2+ and Mg2+ contents in roots,but the contents were significantly decreased on the ground tissues.The above results showed that-two rape varieties C 151 and C 153 had better salt tolerance and has a high biomass accumulation.The effect of salt stress on their characters were small,and they can be further tried to grow in coastal saline alkali land.