The effect of the abiotic factors researched on the interactions between fungi of Trichoderma genus and plant pathogens was defined based on individual biotic effect (IBE). The evaluation was based on the scale [17] in which “0” stood for a steady development of colonies of both fungi. The highest degree of the scale ‘+8’ stood for Trichoderma fungus colony totally inhibiting the pathogen development. Negative values were used whenever pathogenic fungi inhibited Trichoderma spp. development. The most powerful antagonistic properties of the Trichoderma genus fungi tested were noted towards F. solani and R. solani. However they inhibited B. cinerea growth less considerably. All the metal ions and pesticides tested least considerably affected the interaction between Trichoderma spp. and F. solani. Magnesium ions lowered the antagonistic activity of T. harzianum and T. viride towards B. cinerea, and slightly inc reased the value of IBE of T. pseudokoningii towards this pathogen (Table 1). The highest-applied concentration of zinc made antagonistic fungi lose completely their capacity to inhibit pathogens development (Table 2). T. harzianum isolate was the only one which, despite being treated with a high dose of zinc, still inhibited the growth of F. solani and R. solani. Zinc ions most considerably affected the activity of mycoparasites towards B. cinerea. Zinc weakened the effect of T. harzianum and T. pseudokoningii towards this pathogen, however, it strengthened the antagonism of T. viride.

Out of all the pesticides researched, Topsin M showed most unfavourable to the antagonistic activity of selected mycoparasites. Out of all the fungi tested, T. harzianum isolate was least susceptible to the preparations researched and maintained its antagonistic properties (Table 3). The herbicides applied decreased the activity of T. viride towards B. cinerea.

The results of the experiments into the effect of selected abiotic factors on effectiveness of Trichoderma genus fungi when pea seed-dressing was applied are given in Tables 4-6. Biological protection from all phytopathogens with antagonistic fungi was equally effective as the standard chemical dressing Oxafun T. The factors applied in the experiment modified the antagonistic effect of Trichoderma genus fungi applied in a form of seed dressing. The effect of the factors studied was considerably related to the saprophyte – pathogen relationship and the direction of changes depended on the fungus species as well as the factor kind. It was observed that in most objects the factors studied had a negative effect on the applicability of Trichoderma genus fungi to seed dressing. Magnesium ions treatment of selected saprophytic fungi showed an especially negative effect of pea seed dressing with T. harzianum and T. ps eudokoningii fungi against R. solani (Table 4). There was noted an unfavourable effect of zinc ions on the applicability of T. harzianum and T. pseudokoningii to pea seed dressing against B. cinerea. Zinc ions, on the other hand, showed a positive effect on the antagonistic activity of the saprophytes researched towards F. solani and R. solani (Table 5). The fungicides and herbicides researched significantly inhibited antagonistic properties of saprophytes towards the plant pathogens tested (Table 6).

DISCUSSION

The experiments presented showed that higher concentrations of the metal ions studied inhibited mycelium growth, weakened sporulation and spore germination of Trichoderma spp. isolates. All that is confirmed by the fact that metal ions of biogenic properties, including magnesium, manganese, zinc or copper show their toxicity in higher concentrations only [2]. Kowalski [10] observed that T. viride is a fungus especially susceptible to industrial emissions of zinc and lead. The author and his co-researchers [11] consider also Trichoderma polysporum and T. pseudokoningii fungi to be very susceptible to industrial pollution. A varied effect of mineral nutrition on T. viride was also noted by Sierota [27], observing a clearly inhibiting effect of zinc on the development of mycelium of that saprophyte and stimulation of sporulation by magnesium and manganese ions. Fungi pathogenic towards plants reacted to an increased concentration of zinc ions in the medium with a lowered growth rate, and zinc doses of 1000 and 3000 ppm showed a strong inhibition of pathogen development [6]. The highest susceptibility to zinc ions was observed in R. solani species.

Literature offers data which seem to confirm the present results showing a powerful fungistatic effect of Topsin M preparation on many fungi. Machowicz-Stefaniak [15] classified this fungicide as very fungicidal, falling into group one of the fungicidal activity as its ED₅₀ towards Botrytis cinerea was below 1 ppm of a.i. Higher concentrations of Topsin M showed fungicidal towards B. cinerea, while other reports inform of a low activity of Topsin M towards agaric pathogens and Phoma spp. and Pseudocercosporella herpotrichoides fungi [8,25,30]. Reports on the effect of fungicides on antagonistic fungi state that these microorganisms, similarly to pathogens, are susceptible to these substances. Powerful growth inhibitors for T. viride, following Klimach and Wieczorek [7], included the following fungicides: Seed Dressing T, Rizolex 50 WP, Dithane M-45 and Rovral 50 WP. Fungal development was not negatively affected only by Previcur 607 SL and Dress ing Marshal 25 ST. Machowicz-Stefaniak et al. [16], investigating 11 fungicides containing various active substances, observed that fungicides in the concentration of 100 ppm inhibited growth of T. harzianum colonies. Susceptibility of this fungus to the preparations researched differed, depending on the kind of fungicide. However for each preparation a decrease in the concentration of active ingredient was related to a loss of fungistatic activity. Reports by Appaiah et al. [1] showed, in turn, that inhibiting T. harzianum growth as a result of thiuram application was not proportional to an increase in substance concentration. The experiments reported by Sas-Piotrowska and Piotrowski [26] observed an increase in toxicity towards Trichoderma spp. fungi due to a combination of fungicides with Apron or Previcur. Out of all the species researched, the lowest susceptibility to the fungicides tested was observed in T. viride species. The authors showed also that T. viride and T. koningii species showed a higher resistance to fungicides than phytopathogenic fungi.

Fungistatic properties can be also attributed to herbicides [4]. The present paper reports on T. harzianum isolate being most resistant to herbicides. In vitro the highest fungicidal activity was recorded for Afalon 450 and Racer 250.

Similar results, to the present ones, showing an unfavourable effect of Afalon on pathogenic fungi were reported by Mazurkiewicz-Zapałowicz and Janowicz [18]. A negative reaction to Afalon was also noted in Trichoderma genus fungi. Nowak [21] observed an increased Trichoderma spp. colony growth inhibition intensity with increasing concentration of Afalon in the medium. As a result, with Afalon in the amount of 1000 mgˇdm^-3 of the medium, there was recorded a complete Trichoderma spp. mycelium growth inhibition. Growth of saprophytic fungi of Trichoderma genus can be also limited by other herbicides like Gesard 500 SC, Roundup or preparations containing atrazine, however they usually show a negative effect in higher concentrations only [5,7,31]. The group of preparations which even in higher doses show no inhibiting effect on the development of Trichoderma genus fungi included Aminopielik Super 464 SL and herbicides based on sulphorinate [5,7].

Trichoderma genus fungi are among most effective saprophytic antagonistic fungi, widely applied in protection of agricultural and horticultural plants and trees [9,22,23]. The experiments carried out confirmed the applicability of the Trichoderma genus isolates tested to plant protection against pathogens. The mycoparasites investigated in in vitro tests showed powerful antagonistic properties towards F. solani and R. solani, while B. cinerea growth inhibition was slightly lower.

The infection experiments reported in the present paper showed an effective protective effect of the Trichoderma spp. isolates studied on phytopathogens. Microbiological seed dressing with the saprophytic fungi species tested enhanced the pea seedling health status. The effectiveness of Trichoderma genus fungi towards all the pathogens used equalled the effectiveness of Oxafun T, a chemical seed dressing.

The application of Trichoderma spp. fungi as microbiological preparation components used for seed dressing is reported in numerous papers which cover protecting germinating seeds and then plant roots from infection with phytopathogens [12,14]. Clear protective effects of Trichoderma spp. under provoking conditions and exposed to a considerable inoculation potential of pathogenic fungi suggest that a similar effect can be obtained in the field. All that is confirmed by field experiments with pea and bean monocultures which showed that seed dressing with Trichoderma spp. enhances the emergence and inhibits plant infection with soil pathogens [13,24]. The application of Trichoderma spp. to seed dressing also makes significantly higher pea and bean yields possible.

The present results show that treating Trichoderma genus fungi with metal ions, fungicides or herbicides can change antagonisms of saprophytic fungi towards soil pathogens. Changes in the antagonistic or pathogenic activity in fungi as a result of environmental conditions were also recorded by other authors. Sierota [28] reports on magnesium, manganese and zinc in the concentration of 100 ppm enhancing the inhibitory effect of leachates of T. viride on brown root rot. All that can suggest that these elements participate in processes of antagonistic substances formation. It was observed that mutations of Trichoderma harzianum strains to obtain resistance to benomyl and iprodione fungicides, in general, decrease the mycoparasitic activity of strains towards a series of phytopathogenic fungi of Fusarium, Phytophthora, Rhizoctonia and Verticillium daliae genera [29].

The present results and the literature reports show that the effect of anthropogenic origin factor can significantly disturb ecosystem balance between pathogenic and antagonistic organisms conditioning plant health status.

CONCLUSIONS

1. The abiotic factors studied affected the Trichoderma genus fungi tested and the fungal reactions depended on the kind of factor, its concentration and on the fungal isolate.

2. Zinc ions applied in 1000 and 3000 ppm concentrations inhibited the growth and germination of Trichoderma genus fungi spores, while zinc ions in the doses of 50, 100, 200, 300 ppm of a.i. stimulated T. harzianum genus growth.

3. Topsin M 70 WP showed a fungicidal effect in the dose of 100 ppm of a.i, blocking mycelium growth and Trichoderma genus fungi spores germination.

4. In vitro experiments revealed strong fungistatic properties of Dispersive Afalon 450 SC and Racer 250 WP herbicides in the dose of 100 ppm of a.i. towards the Trichoderma spp. isolates tested.

5. Microbiological pea seed dressing against phytopathogens with Trichoderma genus fungi untreated with the abiotic factors researched enhanced the pea seedling health status.

6. The abiotic factors studied, including metal ions, fungicides and herbicides, deteriorated the antagonistic properties of Trichoderma genus fungi used as pea seed dressing against Botrytis cinerea, Fusarium solani and Rhizoctonia solani pathogenic fungi.

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