青海干旱地区蚕豆根瘤菌耐旱性研究

A Study on Drought Tolerance of Rhizobia Strains of Faba Bean(Vicia faba L.)Isolated from Drought Regions in Qinghai Plateau

【目的】蚕豆是重要的粮饲草肥兼用豆科作物,根瘤菌的共生不仅能进行生物固氮而且可以提高作物的抗逆性。干旱环境能孕育出在逆境中生长繁殖并结瘤、固氮的耐旱根瘤菌,为探究和发掘青海干旱地区耐旱蚕豆根瘤菌资源。【方法】在人工模拟干旱胁迫的PEG6000高渗透环境下对青海省干旱地区采集分离获得的49份蚕豆根瘤菌进行耐旱性鉴定分析。【结果】干旱胁迫对蚕豆根瘤菌生长存活的影响差异极显著(P<0.001),采用平均连锁法(UPGMA)法把49份菌株的耐旱能力分为3类群,并且不同胁迫条件下供试菌株表现为3种生长模式:第一种生长模式,在低浓度PEG条件下3种菌株的生长不但没有被抑制,其浊度值反而高于CK;第二种生长模式,在中等浓度PEG条件下6个菌株一方面存在一个中间致死渗透势,而在更高浓度PEG条件下存活数量又增高;第三种生长模式,在高浓度PEG条件下32个菌株随着渗透势的下降,培养液的浊度值也随之下降。【结论】干旱地区蚕豆根瘤菌对干旱的耐受能力表现出多样性,除了同一地区不同土壤环境中分离的不同菌株的耐旱性表现差异性外,同一土壤不同耕作方式、不同施肥方式下的菌株的耐旱能力也存在较大差异。最终筛选获得5株比较耐干旱的菌株为下一步共生结瘤实验提供菌株材料。

[Objective]Faba bean is an important legume crop which is used as grain,forage and fertilizer.Symbiontic rhizobia not only allow biological nitrogen fixation but also increase stress resistance of plants.The dry environment can breed the drought-tolerant rhizobia which can grow and reproduce,at the same time,they can form nodules and fix nitrogen in the adverse conditions.This study was to explore and discover faba bean Rhizobium resources of drought-tolerance in arid region in Qinghai.[Method]The drought resistance of 49 strains of faba bean rhizobia were evaluated under the condition of artificially simulated drought stress.[Result]There was a significant difference in growth and survival of faba rhizobia under drought stress(P<0.001).The average linkage method(UPGMA)was used to divide the drought-tolerant ability of the 49 strains from arid areas in Qinghai into three groups. At the same time,the strains showed three growth patterns under different stress conditions.In the first growth mode,the growth of the three strains under the low concentration PEG condition was not inhibited,but the turbidity value was higher than that of CK.In the second growth mode,six strains had an intermediate lethal osmotic potential under medium PEG concentration,but the number of viable strains increased under higher PEG concentration.In the third growth mode,the turbidity value of the culture medium decreased with the decrease of osmotic potential of 32 strains under high PEG concentration.[Conclusion]Those used strains showed a diversity of drought tolerance in the arid regions.Those different strains isolated from the same region but different soil environments showed a diversity of drought tolerance. The different strains from the same soil under different tillage and fertilization pattems had different drought resistance capability.In the end,five drought-tolerant strains were screened to provide strain materials for the next stage of symbiotic nodulation experiments.