Effect of Glomus mosseae on cucumber damping off caused by Pythium under salinity stress

Salinity stress is one of the most important abiotic factors that restrict the growth and yield of many plants. Salinity can increasingly influence the host susceptibility, occurrence and development of plant diseases due to its negative effects on the host plants. Mycorrhizal fungi are able to increase the tolerance of some plants to salinity. In this study, the biological effects of Glomus mosseae were studied against cucumber damping off caused by Pythium aphanidermatum. Subsequently the effects of different concentrations of salinity in the presence of AM fungus were assessed on the plant growth, the mineral nutrient uptake and also, the disease severity of cucumber damping off on seedlings. The results showed that G. mosseae significantly (P≤0.05) decreased the disease severity. The mean of disease severity caused by the pathogen was 56%, while in treatments inoculated to mycorrhizal showed a reduction to 28%. Furthermore, the plant growth parameters including root length and plant hight increased in treatments inoculated with mycorrhizal fungus as compared with non-mycorrhizal roots in salinity soil. It can be a consequence of more nutrient uptake by roots. Content of P and K was significantly reduced by increasing salinity, whereas the level of Na increased. The plants inoculated with mycorrhizal fungus increased the nutrient content of P and K as compared to non-inoculated treatment in all levels of salinity, but the content of Na decreased. These results showed that the colonization of cucumber seedling roots by G. mosseae can reduce the deterimental effects of salinity and damping off disease caused by Pythium.