Studies On The Effects Of Pathogen Alternaria Tenuis Nees On Its Host Plant Trifolium Repens L. Under Cu Stress

The interactions between pathogens and their host plants in nature plant populations are very common and have been widely studied. The occurrence and expression of diseases caused by fungi in plant are closely related to environmental factors (both biotic and abiotic factors) which may affect not only host or pathogen individual but also their mutual interactions.In this paper, through long-term field investigations it was found that the pathogen Alternaria tenuis Nees was a parasitic fungus on its host plant Trifolium repens L. in nature. In the long-term co-evolution, they had set up steady relationship. The effects of A. tenuis on the physiological and biochemical characteristics of T. repens under Cu stress were studied. The results showed as below:(1) Through the isolation, inoculation, identification and pathogenicity test, combined with field survey, it was found that Alternaria tenuis Nees was the main pathogen that caused the disease in T. repens on the deserted land of Wugongli copper tailings in Tongling city. It was also showed that there were significant differences in resistance between two T. repens clones.(2) Through pot cultivation experiments of T. repens under Cu stress, we studied the effects of A. tenuis on the physiological and biochemical characteristics of two different populations of T. repens selected from a Cu-polluted area (marked as population I ) and a non-polluted area (marked as population II). The results showed that with Cu treatment, the infection of A. tenuis increased leaves' electric conductivity and MDA content of two populations with Cu concentrations from 0～1500mg·kg^-1, while electric conductivity was lower and MDA content higher than that of population II when Cu concentration was 2000mg·kg^-1. The infection also decreased chlorophyll and protein contents. In two inoculated populations, chlorophyll and protein contents declined with the increasing concentration, and chlorophyll content was negatively related to Cu concentration. The results also...