| Endophytic fungus are microorganisms that live within plant tissues without causing symptoms of disease. After a long time of evolution, endophytic fungus have established a symbiotic relationship with host plants. Studies in recent years show that endophytic fungus not only can protect plants from the damage of pathogens and consumers, but also can increase plants’tolerance of abiotic stress, such as heat, drought, salinity, heavy metals and so on. So it is valuable to research and exploit endophytic fungus. The objective of this thesis is mainly concerned about the isolation and idenfication of endophytic fungus in several saline plants collected from Xin Jiang province, then trying to search some endophytic fungus which can strengthen crop’s salt tolerance. The salient findings of the research are:1) A total of274isolates were recovered from5different saline plants and were classified into38taxon of different endophytic fungus using a combination of molecular and morphological identification methods. These isolates belong to3subphylums,6classes,10orders,12families,19genera. Among them, there were14endophytic fungus identified to species level, then there were19taxon were identified to genus level and5taxon were identified to families level based on the analysis of rDNA-ITS.2) The diversity index of endophtic fungus within five saline plants was Alhagi sparsifolia (H,1.76)> Sophora alopecuroides (H,1.49)> Suaeda glauca (H,1.48)> Phragmites australis (H,0.41), Populus euphratica (H,1.49). In the root tissue of Alhagi sparsifolia, Sophora alopecuroides and Phragmites australis, Fusarium, Alternari and Pleosporales were dominant taxon respectively, while Fusarium and Phoma dominant in the root tissue of Suaeda glauca. Meanwhile in the stem issue of Populus euphratica, Cladosporium was dominant taxa.3) Screening results showed that4endophytic fungus can promote salt tolerance of rice steadily on MS medium culture. Treated with200mM NaCl salt stress, the rice seedlings inoculated with endophyte strains KDZ-5、LTC-9、LTC-17、LTC-20growed better than those un-colonized. Compared with the un-colonized ones, their height increased12.3%、17.8%、21.2%,25.3%, respectively. The fresh weight and dry weight of rice seedlings inoculated with KDZ-5and LTC-9increased19.5%,11.1%and78.9%,15.3%, respectively.4) The results of hydroponic experiments showed, under salt stress, endophytic fungus KDZ-5and LTC-9had a growth-promoting effect on wheat seedlings. Under100mM NaCl salt stress, compared with the un-colonized ones, the fresh weight and dry weight of the wheat seedlings inoculated with endophytic fungi KDZ-5increased21.6%and13.0%; the ones inoculated with LTC-9increased16.7%and14.6%.5) The results of pot culture experiments showed, under salt stress, endophytic fungus KDZ-5, LTC-9and LTC-20have a growth-promoting effect on wheat seedlings. Under200mM NaCl salt stress, compared with the un-colonized ones, the fresh weight and dry weight of the wheat seedlings inoculated with endophytic fungi KDZ-5increased10.9%and12.5%; the wheat seedling inoculated with LTC-9increased3.6%and8.2%. Under250mM NaCl salt stress, compared with the un-colonized ones, the height, fresh weight and dry weight of the wheat seedlings inoculated with endophytic fungi KDZ-5increased51.4%,10.2%and18.5%; the wheat seedlings inoculated with LTC-9increased41.6%,17.9%and10.0%; the ones inoculated with LTC-20increased54.5%,14.6%and27.2%.6) The the differences of MDA, proline, Chloroyll contents between plants colonized and un-colonized by four endophytic fungus were measured. The results showed that under salt stress, compared with the un-colonized ones, the colonization of four endophytic fungus KDZ-5, LTC-9, LTC-17, LTC-20can reduce the concentration of MDA, but increase the concentration of proline in the leaves of wheat. These data above indicated that the tested endophytic fungus confered salt tolerance on wheat via balancing cell osmotic pressure and reducing the level of membrane lipid peroxidation of plants. |
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