بررسی مقاومت سه رقم برنج در مقابل بیماری پوسیدگی فوزاریومی ریشه و طوقه

Fusarium root rot disease of rice caused by Fusarium fujikuroi is one of the most important seed-borne disease of rice. The most characteristic symptom of this disease is excessively tall plants with light green (chlorotic) stems and leaves. the most effective and cost-effective approach to manage this seed-born disease is seed disinfection and cultivation of resistant or semi-resistant cultivars. In the present research, first, the seeds of three rice varieties including Hashemi (a common local variety), Khazar (a variety resistant to blast disease) and Kian (a variety resistant to drought) were inoculated separately with a suspension of fungal pathogen spores with a concentration of 2 × 106 spores per milliliter then the response of each variety to crown and root rot disease was investigated in laboratory and greenhouse conditions in four replicates. In all experiments, the natural seed of each variety was used as a control for that variety. In the laboratory, 25 seeds from each treatment were placed individually in sterile Petri dishes with a diameter of 15 cm on a double layer of moist sterile filter paper. Petri dishes were kept in the incubator at the temperature of 25±2°C and 15 days after cultivation, the percentage of infection, the percentage of germination and some growth indicators were measured. In greenhouse studies, contaminated and natural (control) seeds of each variety were grown separately in pots and on the 30th day after planting, the percentage of seedling infection was measured. The laboratory results showed that the seeds of all three Hashemi, Khazar and Kian cultivars naturally had 29, 5 and 20% seed contamination, respectively, and artificial infection in these cultivars caused an increase of 6, 17 and 6% seed infection, respectively. Seed germination in normal and infected Hashemi variety was equal, while in Khazar and Kian varieties, seed inoculation with the pathogen caused a 5 and 23% decrease in germination compared to their natural control. According to the obtained results, in all three cultivars, there was significant difference statistically at the five percent probability level between the average fresh and dry weight of the seedlings and the percentage of seed germination in the experimental treatments. The highest amount of fresh and dry weight of seedlings and the percentage of seed germination were measured in natural Hashemi, natural Kayan and natural Khazar treatments, respectively, and the lowest amount of the mentioned indicators were recorded in the treatment of infected Kian, infected Hashemi and infected Kayan, respectively. In greenhouse conditions, among the three investigated cultivars, Khazar cultivar with 26% infection was determined as the most susceptible cultivar and Hashemi with 18% showed the least infection compared to other cultivars