Вплив температури на ріст та розвиток гриба Diaporthe (Phomopsis) helianthi M.

Abstract

The main condition for successful plants cultivation is their ability to adapt to a complex of environment factors. Climatic parameters (temperature, precipitation, humidity of air) takes a significant role in formation of soil processes, since water-air and thermal regimes of the soil, and, accordingly, the direction of biological processes are closely linked with them. In order to successfully grow sunflower Helianthus annuus L. it is necessary to know features of development most dangerous diseases – Phomopsis helianthi Munt , development of which depends on climatic conditions of the region and technology of growing this crop. In this regard, it is relevant to determine the optimal temperatures that contribute to development of Phomopsis helianthi Munt. on sunflower, annually in the Southern region ofUkraine. Under natural conditions, mushrooms are able to adapt to changes in environmental factors. Special effects on growth and development of the fungus are caused by temperature conditions that have a seasonal and daily fluctuation pattern. Therefore, there is a need to determine the most favorable and critical temperatures for development certain types of given pathogen in laboratory conditions in vitro . The aim of study was to determine the effect of temperature on growth and development of Diaporthe (Phomopsis) helianthi M. The isolation of Phomopsis helianthi M. in a pure culture and its identification was carried out at department of the Kherson regional phytosanitary laboratory. Potato glucose agar (PGA) was used in pure culture to isolate Phomopsis helianthi M. For inoculation of substrates, were used 2 weeks age cultures. The mycelium was sown in Petri dishes to the center surface of a dense nutrient agar with a small piece of the inoculum, about 5 ×5 mm in size, always of one density and age. Petri dishes were incubated in a thermostat with temperature of 0 °C; +5; +10; +15; +20; +25; +30 and +35 °C. It has been established that in culture vegetative growth of fungus Diaporthe (Phomopsis) helianthi M. occurs in a wide range of temperatures. Differences in the rate of mycelia growth are determined. The lower limit, which marked the growth of mycelium, is +5 °C, and the higher – + 30 °C. The temperature of 0 and + 35 °C did not reveal a growth of mycelium. In vitro, the least intense growth of the fungus culture was detected under temperature conditions of +5 °C and +10 °C. The beginning of Phomopsis helianthi M. growth occurred at 5 and 4 days, respectively. More intense of mycelium growth was noted for temperature regimes of +15 °C and + 20 °C. It has been shown that optimal temperature for isolates of Diaporthe (Phomopsis) helianthi growth is + 25 °C. Under these conditions, on the 8th day of incubation, complete colonization of the substrate in the Petri dish was recorded. After increasing temperature to + 30 °С, the intensity of growth of mycelium of the fungus decreased. Thus, the average monthly air temperature in the summer (20–23.8 °С) simultaneously with irrigation can contribute development of Diaporthe (Phomopsis) helianthi M. fungus on sunflower plants.