Rice pyriculariasis: monitoring, prognosis of its spread in the Krasnodar Territory

Blast (causative agent — ascomycete fungus Pyricularia oryzae Cav.) is the most dangerousand harmful disease of rice, widespread in most rice-growing regions of the world, includingRussia. For 10 years (2013–2022), the condition of rice crops was monitored in ricegrowing farms of the Krasnodar Territory. At the infection site, under artificial infection, theimmunological properties of 13,158 variety samples transferred by breeders of the FederalRice Research Center and the Collection of Genetic Resources of Rice, Vegetable and MelonCrops were studied. The resistance was assessed on a ten-point scale of the InternationalRice Institute (IRRI) using visual and immunological diagnostics, as well as phytopathologicalobservation. The ranges and optimal values of environmental factors contributing to variousstages of the Pyricularia oryzae life cycle were established. It has been shown that for theeffective germination of conidia, the formation of apressoria and the penetration of thepathogen into plant tissues, the temperature in the range of 25–28 °C, relative humidity (above89%) and prolonged moistening of the leaf surface (at least 6 hours) are of key importance.The analysis showed that among the studied variety samples, 11.3% are resistant to blast,38.4% are moderately resistant, and 50.3% are susceptible. The paper presents a quantitativepredictive model reflecting the transformation of the varietal composition of rice classified bythe level of resistance to the fungus Piricularia oryzae, which serves as a scientific basis for thedevelopment of an adaptive breeding strategy. Of particular importance in this strategy is theselection of resistant varieties that provide built-in protection, reducing the need for chemicalfungicides and contributing to a stable yield. A promising direction is the creation of genotypescarrying R-genes of a wide range of resistance.

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