| Pears, which belongs to genus Pyrus L. in subfamily Maloideae of family Rosaceae, is one of the main cultivation fruit trees in China. There has been a long cultivation history of pears in China, and most of the oriental pears are originated from China. In order to adjust the variety structure of industrial, the government is promoting the cultivation of southern early-maturing pears. Due to the high temperature and drought in summer and autumn in the south of China, especially in Chongqing, some unhealthy phenomenons on the early-maturing pears such as flowering or branch germination appear frequently in autumn.Arbuscular Mycorrhizas(AM), which exist in plant generally, is a kind of mutual beneficial symbiote that is made up of the root of plants and the AM fungi belonging to order Glomales, class Zygomycete, phylum Zygomycota. Many researches indicated that AM fungi could promote the growth of fruit trees, and improve the nutritional status and water metabolism, as well as improve the resistant ability of drought and tolerance ability of high temperature for the fruit tree.In our work, AM fungi from three species(Glomus intraradices, Glomus mosseae, Glomus versiforme) and their mixture were inoculated to roots of Pyrus L. cv.’Cuiguan’ grafting seedlings, and the growth status was studied. To provide the technical basic to control the phenomenon such as flowering or branch germination in autumn on the early-maturing pears, physiology status and the resistance to stress of pears grafting seedlings under the drought stress with four levels (mild, moderate, severe and extreme drought) and the heat stress with four levels (the temperature40℃lasted one day, three days,and seven days and fourteen days, respectively) were studied. The results are as follows. 1We found that, after infection for200days by varieties of AM fungi, infection rates from high to low were62.5%(the mixed fungi)^47.06%(Glomus intraradices)、33.85%(Glomus mosseae) and23.92%(Glomus versiforme).The infection rates showed that the affinity between varieties of AM fungi and Pyrus was different.2Our results showed that, AM fungi could improve the survival rate, and increase leaf area and plant mass, as well as improve root system activity. So as to improve the N, P, K content of leaves and water status of the plant, enhanced photosynthesis level and CAT activity were found. The results initially proved that AM fungi could improve the growth of pears grafting seedlings.3Under drought stress, the water content of leaves and ratio of bound water to free water of mycorrhizal seedling were higher than control group. Comparied with the control seedling, and the activities of POD and SOD of mycorrhizal seedling were higher. Moreover, the content of free praline, soluble sugar and soluble protein increased, the MDA content、relative electric conductivity and damage degree also reduced. It was initially confirmed that under the drought stress AM fungi could ease the drought injury, and improve the drought resistance of pears seedlings.4It was initially proved that AM fungi could improve the heat tolerance under the high temperature stress.Compared with the control seedling, AM fungi could improve the activities of POD and SOD, and increase the content of free praline, soluble sugar and soluble protein, as well as reduce the content of MDA.5The effects of varieties of AM fungi on the growth, drought resistance and heat tolerance of Pyrus grafting seedlings are different. The pear seedlings inoculated by mixed fungi performed best on growth, drought resistance and heat tolerance, followed by Glomus intraradices, therefore Glomus intraradices might be the advantage infection fungus for Pyrus L. cv.’Cuiguan’grafting seedlings. |
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