پرآزاری برخی قارچ‌های عامل لکه برگی برنج در استان ایلام

The rice is one of the oldest cultivated plants in the world. Rice occupies the largest cultivated area of the world after wheat and it has a significant role in feeding the people of the world and Iran. The fungi that cause rice leaf spot diseases are one of the most important factors that cause damage and reduce yield in the rice growing areas of Ilam province. In this study, in order to determine the degree of pathogenicity of disease agent species, 44 fungal isolates of genera, Curvularia spp. and Alternaria sp. obtained from infected rice were inoculated on four leaf stage of the rice (Tarem-Mahali cultivar) using fungal suspensions including 4×104 spores, under humidity of about 95% and temperature degree of 28-30 °C in greenhouse conditions. The data analysis ANOVA (Analysis of Variance) was conducted using of the SAS software version 9.6 in completely randomized design (CRD) with 45 treatment in three replicates. Leaf spot symptoms appeared four days after inoculation and were fully visible until ten days after that. After ten days leaf spot symptoms were evaluated using the scoring scale (scores 0-9) suggested by Horsfall & Barratt (1945) and the formula (Dr = ∑[(N1× 1) + (N2×2) +…+ (Nt×t) / ∑ (N1+ N2+ …+Nt). The results of the analysis of variance and compare means showed that there is considerable diversity in terms of virulence among isolates and all fungal isolates had pathogenicity. All isolates belonged to genus, Alternaria had medium disease severity. Finally, the maximum disease severity was belonged to C. muehlenbeckiae and the lowest disease severity was related to species, C. lunata.