Identification of physiological races of Magnaporthe grisea in areas of rice irrigated in the State of Tocantins

Identification of physiological races of Magnaporthe grisea in areas of rice irrigated in the State of Tocantins In Brazil, the most important disease in rice is blast, which is caused by the fungus Magnaporthe grisea. This disease is considered to be a limiting factor for rice productivity. This work aimed to determine the prevalent races of the rice blast pathogen M. grisea in the state of Tocantins, in order to study the variability in the region and make it possible to develop and recommend blast-resistant rice cultivars. To assess this information, infected leaves were collected from three experimental sites, each consisting of multilines and a varietal mixture of irrigated rice in Tocantins state. A total of 250 monosporic isolates were obtained. Subsequently, these isolates were inoculated in the International Standard Differential (ISD). A total of 45 races were identified, where the most prevalent race was IA-1 (24.8% of the isolates), followed by IA-65 (11.2%) and IA-33 (6.4%), respectively. The highest number of races was found in the experimental site located at Lagoa da Confusao, followed by Formoso do Araguaia (Projeto Formoso) and Unitins-Agro, respectively. In the population of M. grisea under study, a high variability was found with prevalence of the race groups: IA, IB and ID.