SELECTION OF APPROPRIATE NUTRIENT MEDIUM FOR CULTIVATION OF PYRENOPHORA TERES DRECHSLER

Net blotch (Pyrenophora teres Drechsler) is the dominant pathogenic complex of barley leaf diseases worldwide. The study of various methods of controlling hemibiotrophic fungus requires careful preparation and development of a sufficient amount of pathogenic inoculum. The aim of our research was to select appropriate nutrient medium for obtaining P. teres inoculum with maximum aggressiveness parameters (colony growth rate, sporulation, short latency period) and ergonomics in preparation. Three nutrient media were used: carrot-beet agar (CBA), potato-glucose agar (PGA), Czapek's medium for standard methods and cultivation conditions. The selection consisted of 10 isolates for each nutrient medium and had statistically significant differences among the experimental variants. It was found that appropriate combination of parametres such as growth rate (5.3±0.5 mm/day), colony diameter (53.4±1.1 mm), latent period (4 days), sporulation intensity (4100 conidia in 1 ml) was observed in case of cultivation of P. teres isolates on carrot-beet agar on the 6th day. When cultivating the fungus on potato-glucose agar, rather high growth rates (5.2±0.8 mm/day), colony diameter (52.0±2.9 mm), sporulation intensity (3700 conidia per 1 ml) were revealed, the latent period was the longest among the studied variants, the first sporulation was detected on the 6th day. In case of usage of the standard Czapek medium, the minimum aggressiveness of P. teres isolates was revealed (growth rate - 3.2 ± 0.3 mm/day; colony diameter - 31.6 ± 1.9 mm; latent period - spores were revealed on the 4th day in 1 cup; the intensity of sporulation was 500 conidia per 1 ml). It was noted that there is a larger range of morphological types of colonies on carrot-beet agar, including morphotypes of isolates which grow on other media. Almost all experimental variants cultivated on CBA medium had a clear structured mycelium with a dark color, which indicates a sufficient availability of nutrients in the culture medium. Thus, it is reasonable to use carrot-beet agar in order to obtain P. teres inoculum with maximum aggressiveness parameters and low labor costs when using standard cultivation methods.