Screening new Trichoderma isolates for antagonistic activity against several phytopathogenic fungi, including Fusarium spp.

Abstract

Aims. To obtain and characterize new isolates of Trichoderma antagonistic to phytopathogenic fungi, including Fusarium spp., and 2) to determine their suitability for mass production under different cultivation conditions. Methods. Microbiological, cultural-morphological, statistical. Results. From plants affected by phytopathogenic fungi: cucumber (Cucumis sativus L.), tomato (Solanum lycopersicum L.), white cabbage (Brassica oleracea L.), winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.) in the Forest-Steppe of Ukraine (Kyiv re- gion) 11 new Trichoderma isolates were obtained. Preliminary, morphological determination allocated fi ve of them to T. viride (isolates CK, 165, 27, 49, 35), two of them to T. koningii (21, 64) and four of them to T. longibrachiatum (161, 162, 163, 164). All isolates showed moderate to high antagonistic activity towards 8 phytopathogenic fungal species (Fusarium oxysporum, Fusarium solani, Alternaria cucumerina, Colletotrichum phomoides, Botrytis cinerea, Trichothecium roseum, Penicillium sp., Cladosporium fulvum). In a dual culture experiment they showed generally similar or often higher activity to the above-mentioned fungi than the 8 control strains used in our study, belonging to T. viride (5 strains), T. koningii (2 strains) and T. harzianum (1 strain), which have been maintained since long time in our laboratory. The most active new isolate CK, (presumably) T. viride, showed comparable high activity towards all phytopathogenic fungi as compared to our most active control strain of T. viride, no. 23. The latter is the basis of a biocide Trichodermin, produced by biolaboratories of Ukraine, including the Institute of Plant Protection, NAAS, Kyiv. Chlamydospore production of all isolates and strains studied in submerged culture varied from 10 6 to 3 · 10 7 spores/ml, were T. viride isolates and strains were on the higher end. Isolates of ‘T. longibrachiatum’ did not produce chlamydospores in submerged culture. Upon superfi cial cultivation on barley grain, the strains and isolates of T. viride were also characterized by the highest production of spores (6 · 10 9 -9 · 10 9 spores/g) as compared to those of T. kon- ingii, T. harzianum (5.5 · 10 9 -6.8 · 10 9 spores/g) and T. longibrachiatum (1.3 · 10 8 -6.8 · 10 8 spores/g). In an in-vivo experiment under laboratory conditions the most promising antagonistic isolate CK was used to inoculate wheat seed and tested for protection against Fusarium root rot (inoculum a mixture of F. avenaceum, F. culmorum, F. gibbosum, F. oxysporum, in 4·10 4 spores/g), where it gave an 83 % reduction in root rot as compared to the non-inoculated con- trol. Conclusions. Five new isolates preliminarily (on the basis of morphological characteristics only) allocated to T. viride and four to T. longibrachiatum demonstrated in vitro the highest and widest antagonistic activity against the phytopathogenic fungal species Fusarium oxysporum, Fusarium solani, Alternaria cucumerina, Colletotrichum pho- moides, Botrytis cinerea, Trichothecium roseum, Penicillium sp., Cladosporium fulvum, as compared to new isolates, preliminarily allocated to - T. harzianum and T. koningii. New isolate CK (allocated to T. viride) showed a promising and similar high antagonistic activity as compared to our T. viride 23 strain, which is already successfully used in the biocide Trichodermin. Since this isolate CK also produced a high number of chlamydospores in submerged culture (3 · 10 7 spores/ml) and conidia (8 · 10 9 spores/g) when surface cultured on barley grain respectively, it is a potential new candidate for a biocide. When this CK isolate was studied in a small laboratory pot experiment, to control Fu- sarium root rot in wheat by preventive seed inoculation, it caused an 83 % reduction in this Fusarium root rot. Its usefulness under fi eld conditions and its effect on growth of plants will be investigated in future research