USE TRICHODERMA SPECIES FOR BIOLOGICAL CONTROLE OF FUNGAL PATHOGENS BY GROWING CONIFER SEEDLINGS IN FOREST NURSERIES OF MIDDLE SIBERIA
Gromovykh V.S., Makhova E.G. (SibSTU, Krasnoyarsk, RF)
Применение биопрепарата на основе аборигенного изолята Trichoderma asperellum «MG» G. Samuels, полученного в процессе биоконверсии лигнинсодержащих отходов древесины, привело к увеличению выхода сеянцев лиственницы на 17.6 % по сравнению с контролем.
The Siberian forest nurseries are faced with many challenges in their efforts to provide the quality seedlings for reforestation. Every year it is lost about 30% seedling. Seedling losses occur in conifer nurseries despite of the best efforts employed by nurserymen and foresters in disease control. Fungal diseases are widespread throughout Krasnoyarsk region. Main pathogens such as Fusarium, Pithium, Rhizoctonia, Alternaria, Phoma are widespread causing seedling losses in nurseries.
With an increasing demand for forest products, the forest nurseries have turned toward more intensive management practice to increase seedling quality. One of the most acceptable and environmentally-conscious approaches to solving these problems is the use of biological method. Biological methods are based in the suppression of pathogenic microorganisms by biological antagonists. And the selection of biological antagonists determines their safety. Nowadays a considerable part of microbiological products for plant protection is represented by fungal organism. The leading place among the fungal antagonists for biological activity against plant diseases belongs to the fungi in genus Trichoderma Pers.
The main economic impotence of Trichoderma spp. in biocontrol is recognized because of their production of enzymes, antibiotics or user as biocontrol agents. Using these fungi in biological control determines the selective suppression of pathogenic microorganisms in soil, without causing negative changes in microbiocenoses.
We have collected Trichoderma culture collection of approximately 250 aborigine strains from soils of several nurseries of Middle Siberia. First of all, antagonist properties of selected strains were tested in artificial light laboratory. Beneficial microorganisms specifically selected for forest nurseries are being evaluated for suppression of damping-off and root rot pathogens of conifer seedlings. Great positive effect was reached except for one isolate, which is a Trichoderma asperellum (G. Samuels), strain MG-97, obtained from forest soils in 1997.
Soils of Mininsky nursery was treated through a sprayer before of suspension (contained spore and pellet of fungus) 1.8x10 11/per square meters.
The effect of a Trichoderma strain was estimated as quantity of healthy seedlings compared to non-treated control. When applied strain MG improved seed germination on 9.4 % and reduced the fungal contaminants. Yield of larix seedling on second year on treated soil increased on 17.6 %.
The future management for applying biocontrol organisms exploration of various methods and form of biopreparation on the basis of different plant residuals.
Perhaps the most effective way is the use of organic compound with wide proportion N:C, such as hydrolysis lignin, bark and other carbohydrate residuals.
It was established that treatment of organic compounds consisted lignin increased the soil resistance. Positive effect can also be achieved by the capacity of conifer bark to suppress the growth of pathogens.
There is also great deal to be learned about the possibility of Trichoderma fungi to utilize such substrate and give high yield of spore. Our another goal is to make technology for creating new cheapest and ecological safety preparation Trichodermin on the basis of carbohydrate residuals, namely larix bark and hydrolysis lignin.
For this purpose we selected forth isolate of aborigine Trichoderma asperellum strains showed antagonistic and cellulase activity. Before using all substrate was tested on toxic activity toward conifer seedlings such as larix, pine seedlings and spruce in artificial light laboratory. It was established that substrate have non-toxic effect on plants. Than, substrate was inoculated with suspense of spores 1 X 10 6 spore per g.
can utilize larix bark and hydrolize lignin. Maximum of yield of spores was obtained for strain O-97 on lignin substrate and for MK on larix bark.
However, for applying such preparation it will be demand to increase biotechnology indexes, especially yield of spore until 1 X 10 11 .