Novosibirsk State Agrarian University
Siberian Research Institute for Plant Protection
About research work on the topic:
“Study of the fungicidal action of Stimulin”
Professor of the department of agroecology,
Doctor of biological sciences.
______________ L.N. Korobova
The purpose of this work was to study the effect of Stimulin on microscopic fungi, causative agents of seminal infections of spring wheat and barley.
- Isolate strains of pathogens (with medium or strong degree of pathogenicity) from the seed material;
- To study the fungicidal activity of Stimulina against Bipolaris sorokiniana Shoem., The causative agent of root rot, as well as the dark brown leaf spot and the “black germ” of the seeds;
- Evaluate the response to Stimulin of the phytopathogen Fusarium oxysporum Schlecht, the causative agent of root rot;
- To study the activity of the drug with respect to the conditionally pathogenic fungus, the causative agent of the “black seed germ”, Alternaria alternata (Fr.) Keissl.
1. Conditions and procedure for the laying of experiments
Fungicidal activity of the preparation was analyzed in laboratory experiments (in vitro) on the strains of those pathogens that always populate the grains of spring grasses. To cultivate the strains, Capeka-Doxa agar was used, where Stimulin was added. The effect of the drug was evaluated in 2 concentrations: the corresponding declared by the manufacturer and exceeded by 2 times.
The causative agents were isolated by the method of mycological analysis (according to Naumova) from the affected grain of spring wheat of the varieties Novosibirskaya 31 and Novosibirskaya 29 and barley Arna, after which their pathogenicity was verified. To assess the anti-fungal activity of Stimulin wheat strains of B. sorokiniana and F. oxysporum with moderately high and high aggressiveness were selected, and the barley strain A. alternata with medium aggressiveness.
After crossing the strains in sixfold repetition to Chapek’s medium (with the Stimulin concentration introduced and control), the diameter of the growing colonies was measured in dynamics at 3, 6 and 10 days, and the sporulation activity was measured.
Fungicidal activity of Stimulina against dark-colored B. sorokiniana fungus, the causative agent of root rot and dark brown patch, was high. The initial rate of development of the fungus was limited to more than 3 times (Pic 1, counting after 3 days).
Pic 1 Action of Stimulin on the initial growth of colonies B sorokiniana (left – control, right – Stimulin).
Stimulin continued to restrain the vertex growth of hyphae B. sorokiniana and later (Table 1), which resulted in a decrease in the diameter of its colonies by 10 days of recording more than 4.5 times.
In addition to the decrease in the rate of growth of the pathogen, against the background of Stimulin, a sharp decrease in sporulation of B. sorokiniana was noted, which manifested itself in a change in the dark color of the central part of the colonies and in the complete absence of conidia on their periphery (Pic 2):
Pic 2. The action of Stimulin on growth and sporification B sorokiniana (counting after 10 days) (left – control, right – Stimulin).
In relation to another dark-colored, microscopic fungus Alternaria alternat (conditionally pathogenic), the antifungal activity of the Stimulin preparation was also relatively high. The drug limited the growth of the colony (Table 1) and the formation of spores of asexual sporulation.
Table 1 – Stimulin’s anti-fungal activity in relation to virulent strains of cerebellar disease pathogens transmitted with seeds
|Variant||Colony diameter at 6 days|
|Fusarium оxysporum||Alternaria alternatа|
|cm||% from control||cm||% from control||cm||% from control|
At the same time, the fungicidal activity of Stimulin in relation to F. oxysporum, the causative agent of root rot was not high. Stimulin did not limit the initial growth rate of the colony at all, but changed the morphology of the developing fungus (Pic 3, Table 1).
In control, the aerial mycelium of strains F. oxysporum and stroma (mycelium immersed in nutrient agar) had a yellowish tinge. Under the influence of Stimulina, the stroma and aerial mycelium of the fungus became completely white.
The mycelium of the control fungus was more fluffy, and on the background of Stimulin it “stuck” to the substrate (Pic. 4). In this case, the test preparation limited approximately one-third the conidial sporulation of F. oxysporum, which resulted in a decrease in the number of both macro and microconidia.
An increase in the Stimulin concentration by a factor of 2 did not lead to a change in the growth rate of hyphae F. oxysporum. In this case, the expected decrease in the germination of spring wheat seeds occurred.
Pic 3. The effect of Stimulin on the initial growth of colonies F oxysporum (counting after 3 days) (left – control, right – Stimulin)
Pic 4. Effect of Stimulus on the growth and sporulation of F oxysporum
In general, the results of screening showed that in dark-colored fungi B. sorokinia and A. alternat. Stimulin at the recommended concentration reduces the rate of colonies growth and inhibits sporulation by at least half. In relation to fusariums, Stimulin shows slightly fungicidal properties, limiting only partial sporulation.
It can be assumed that the mechanism of fungicidal activity of Stimulina is associated with the suppression of the synthesis of the melanin pigment, which is phenolic in nature and protects the spore of dark-colored pathogens from the adverse effects of the environment.