Resistance of Brazilian wheat cultivars to blast under controlled condition/Resistencia de cultivares brasileiras de trigo a brusone sob condicoes controladas

• Published in: Ciência rural 2022-07, Vol.52 (7), p.1
• Main Authors: Maciel, Joao Leodato Nunes, dos Santos, Gustavo Bilibio, Pizolotto, Carlos Augusto, Kovaleski, Marcos, da Silva, Alieze Nascimento, Deuner, Carolina Cardoso, da Costa, Ivan Francisco Dressler
• Format: Article
• Language: English
• ISSN: 0103-8478
• DOI: 10.1590/0103-8478cr20210417

The first report of wheat blast in the world was in Brazil, in 1986. Since then, a great effort has been made towards the development of wheat cultivars resistant to this disease, which is caused by the fungus Pyricularia oryzae Triticum (PoT). The objective of this research was to (i) evaluate the resistance of wheat genotypes to blast and (ii) verify the correlation between disease severity on wheat spikes and sporulation rate of PoT on spike rachises. Plants of 40 cultivars grown in pots, at the flowering stage (stage 65 on the Zadoks scale), were inoculated with a suspension of conidia of a PoT isolate representative of the main variant of the fungus reported in Brazil. Severity of blast on the spikes at 5 and 7 days after inoculation (dai) and the rate of sporulation of the fungus on the rachis (conidia per g of rachis) were evaluated. Eighty percent of the cultivars that were classified in the group with the lowest sporulation rate were also classified in the group with the highest resistance at 7 dai. However, the correlation coefficients of the analysis established between the cultivar severity at 5 and 7 dai averages and the PoT sporulation rate averages were not significant (r=0.2464 and r=0.2047, respectively). Results obtained represent the updated characterization to blast of wheat cultivars in Brazil and constitute an important exploratory framework for the evaluation of the reaction of wheat genotypes based on the sporulation rate of PoT on their tissues. Key words: Pyricularia oryzae Triticum, severity, sporulation. O primeiro relato da brusone do trigo no mundo foi no Brasil, em 1986. Desde entao, tem-se realizado um esforqo muito grande com vistas ao desenvolvimento de cultivares de trigo resistentes a esta doenqa, a qual e causada pelo fungo Pyricularia oryzae Triticum (PoT). O objetivo deste trabalho foi de (i) avaliar a resistencia de genotipos de trigo a brusone e (ii) verificar a correlaqao entre severidade da doenqa em espigas e taxa de esporulaqao de PoT em raquis de espigas. Plantas de 40 cultivares brasileiras de trigo crescidas em vasos, no estddio de florescimento (estddio 65 da escala de Zadoks), foram submetidas a inoculaqao com uma suspensao de conidios de um isolado de PoT representativo da principal variante do fungo encontrada no Brasil. A severidade de brusone nas espigas aos cinco e sete dias apds a inoculaqao (dai) e a taxa de esporulaqao do fungo nas rdquis (conidios por g de rdquis) foram avaliadas. Oitenta por cento