Comparison of two methods of artificial inoculation of sunflower plants by pathogen of Phoma macdonaldii Boer. in greenhouses

During 2017, we had selected sunflower stems infected with Phoma rot in a breeding nursery of the All-Russian Research Institute of Oil Crops by Pustovoit V.S. (VNIIMK, Krasnodar), on field of the Armavirskaya experimental station (Krasnodar region), in Krasnogvardeysky district of the Stavropol region and sunflower seeds in the Volgograd region. We allocated monosporous cultures of disease pathogen Phoma macdonaldii Boerema on a medium oat agar. We determined aggressiveness of separated isolates on cotyledons leaves and hypocotyls fragments of sunflower hybrid Altair. The most aggressive isolates are: isolate No 19 collected in breeding field of VNIIMK (Krasnodar) and No 20 - from Krasnogvardeysky district of the Stavropol region. We tested two methods of artificial inoculation of sunflower plants in bottom of petiole in a phase of first pair of true leaves with isolates Phoma macdonaldii in greenhouse conditions: first one - introduction of 0.2 ml of a spore suspension by jab; second one - application of agar parts with mycelium, pycnidium and pycnospores. We presented the pictures of external symptoms of Phoma rot infection on sunflower plants for each methods of inoculation. Our results certify it is necessary to use both inoculation methods and comparing the infection grades to select genotypes having resistance to this disease both on external and internal tissues.