EFFECT OF SEED TREATMENT WITH UV RADIATION AND SOME COMPATIBLE COMPOUNDS ON PLANT RESISTANCE TO BIOTIC STRESS

Abstract

Biotic stress is considered one of the limiting factors for agricultural productivity. In the present study, Rhizoctonia solani was used as a model for biotic stress in plants. R. solani is known to be one of the most harmful pathogens that affect productivity of several crops. Many synthetic fungicides are recently used to control the disease despite their adverse consequences on human health and environment. Therefore, one of the pesticides alternatives is induction of plant resistance against a wide range of pathogens. In this study, green bean seeds were exposed to UV-C radiation for 60 min and/or treated with each of salicylic acid (SA, 5mM), glycine betaine (GB, 5mM), mannitol (5 mM) and mixed solution of all of the previous compounds for 24 hours to stimulate defensive mechanisms in seeds and grown plants against R. solani. To evaluate the effectiveness of these treatments, two experiments were designed as follows: 1- Green house experiment: in which control or treated seeds were sown in both sterilized and soil infested with R. solani. Therefore, the final design of experiment consisted of 20 treatment sets. After two weeks, root samples were collected to evaluate disease index (DI) and plant resistance machinery through determination of total phenols, antiradical activity of roots extracts, lipid peroxidation, proline concentration and some plant defensive enzymes activities. 2- In vitro experiment: which included testing the accumulation of phytoalexins in the germinated seeds after treatments through an antifungal assay using ethanolic extracts of treated germinated seeds against R. solani. Also, evaluation of the inhibitory effect of these extracts against cell wall degrading enzymes secreted by R. solani.