THE ROLE OF ANTAGONISTIC FUNGI AND BACTERIA LIMITING THE OCCURRENCE OF SOME PHYTOPATHOGENS INHABITING THE SOYBEAN SOIL ENVIRONMENT

Danuta Pięta, Elżbieta Patkowska

ABSTRACT

The object of the studies conducted in the years 1998-2000 was the rhizosphere soil of soybean, Mazovia cultivar, and the non-rhizosphere soil. The experimental plot was set in Czesławice near Nałęczów on grey-brown podzolic soil formed from loesses, which was the second complex of soil suitability (good wheat complex). The microbiological analysis showed a much greater number of microorganisms in the rhizosphere soil than in the non-rhizosphere soil. The proportion of pathogenic fungi in the non-rhizosphere soil was almost twice as high in comparison to the rhizosphere, and it was 48.4% and 25.6%, respectively. The dominating pathogenic fungi were Fusarium spp., Rhizoctonia solani and Sclerotinia sclerotiorum. On the other hand, bacteria Bacillus spp. (81 isolates) and Pseudomonas spp. (231 isolates) as well as fungi Trichoderma spp. (64 isolates) were obtained among the microorganisms distinguished by their antagonistic effect towards phytopathoge

Key words: pathogenic fungi, antagonistic fungi, Bacillus spp., Pseudomonas spp..

INTRODUCTION

Various reactions take place within the group of microorganisms and between microorganisms and plants. The highest activity is characteristic of rhizosphere soil. The composition of microorganisms in the root zone undergoes constant changes, for example under the influence of root exudates [17]. On the other hand, the chemical composition of the substances exudated by the roots is related to the genus, species, cultivar, the age of the plant as well as many other biotic and abiotic factors [13, 15, 18].

A huge role in limiting the occurrence of pathogenic fungi in the soil is played by antagonistic bacteria Bacillus spp. and Pseudomonas spp. as well as by fungi Gliocladium spp. and Trichoderma spp. [1, 6, 12].

Establishing the composition of antagonistic microorganisms towards soil-borne phytopathogens is especially important from the point of view of biological protection of plants. That is the reason why studies were undertaken whose purpose was to look for antagonistic microorganisms limiting the occurrence of pathogenic soil-borne fungi.

MATERIALS AND METHODS

The studies were conducted in the years 1998-2000 on the experimental plot located at Czesławice near Nałęczów. The object of the studies was the rhizosphere soil of soybean, Mazovia cultivar, and the non-rhizosphere soil formed from loesses, which was the second complex of soil suitability (good wheat complex).

In each year, samples of rhizosphere soil were taken at the anthesis of soybean plants. The samples of non-rhizosphere soil were taken from the belts mechanically maintained in black fallow. The manner of rhizosphere soil sampling and the laboratory microbiological analysis were in accordance with the method described by Martyniuk et al. [11]. The rhizosphere soil of soybean and the non-rhizosphere soil from the depth of 5-10 cm were taken to sterile Petri dishes. Next, a sterile soil solution with the dilutions from 10^-1 to 10^-7 was prepared in sterile laboratory conditions. Those dilutions were used to determine the total number of bacteria, the number of bacteria Bacillus spp. and Pseudomonas spp. as well as the total number of fungi in 1 g of d.w. of the examined soil samples [16].

The results concerning the number of bacteria and fungi were analyzed statistically, and the significance of differences was established on the basis of Tukey’s confidence intervals [14].

In each year of the studies, the bacteria isolated (100 isolated from Pseudomonas spp. and 100 isolated from Bacillus spp.) as well as all the isolates of saprophytic fungi from the genera of Gliocladium, Penicillium and Trichoderma were used to determine their antagonistic effect towards such pathogenic fungi as Botrytis cinerea, Fusarium culmorum, F. oxysporum f. sp. glycines, F. solani, Phoma exigua var. exigua, Rhizoctonia solani and Sclerotinia sclerotiorum according to the methods described by Martyniuk et al. [11], Mańka and Mańka [10] and Pięta [17].

RESULTS AND DISCUSSION

The microbiological analysis showed that the number of bacteria in 1 g d.w. of the rhizosphere soil ranged from 4.52ˇ10⁶ to 6.38ˇ10⁶ colonies, and those of the non-rhizosphere soil from 3.16ˇ10⁶ to 4.18ˇ10⁶ colonies (tab. 1). The mean numbers of bacteria Bacillus spp. in the rhizosphere and non-rhizosphere soil were similar and they were 1.73ˇ10⁶ and 1.13ˇ10⁶ colonies, respectively. The number of Pseudomonas spp. in the soil was higher (3.45ˇ10⁶ colonies, on average) as compared to the non-rhizopshere soil (2.06ˇ10⁶ colonies, on average). The total number of fungi in the rhizopshere soil of soybean was twice as high (mean 78.95ˇ10³ colonies) as in the non-rhizosphere soil (mean 37.44ˇ10³ colonies) (tab. 1).

The proportion of pathogenic fungi obtained from the non-rhizosphere soil was almost twice as high as compared to the rhizosphere soil and it was 48.4% and 25.6%, respectively (figs. 1 and 2). Fusarium spp., Rhizoctonia solani and Sclerotinia sclerotiorum dominated within the group of pathogenic fungi. The genus Fusarium was represented by F. culmorum, F. oxysporum f. sp. glycines and F. solani. Gliocladium spp., Penicillium spp. and Trichoderma spp. were most often isolated in the group of saprophytic fungi, and they were isolated twice as frequently from the rhizosphere soil of soybean as from the non-rhizopshere soil (figs. 1 and 2).

The increase of the number of microorganisms, especially in the rhizosphere soil of soybean, could have taken place under the effect of this plant’s root exudates. This fact is explained in numerous items of literature concerning the role of compounds exudated by the roots of different cultivated plants [4, 17].

Laboratory studies showed that the non-rhizosphere soil contained twice as few bacteria distinguished by their antagonistic effect towards the examined pathogenic fungi (103 isolates) as the rhizosphere soil (209 isolates) (tab. 2). Besides, almost three times as many antagonistic fungi were obtained from the soybean rhizosphere as from the non-rhizosphere soil. G. catenulatum spp., Penicillium spp. and Trichoderma viride dominated within the group of antagonistic fungi (tab. 2).

It should be supposed that a considerable number of antagonistic isolates of Bacillus spp., Pseudomonas spp., Gliocladium spp. and Trichoderma spp. could have had a significant influence on the decrease of the number of phytopathogens in soybean rhizosphere. This fact is confirmed in numerous items of literature [1, 6, 8, 12]. As stated by Księżak and Kobus [7], siderophores formed by fluorescent Pseudomonas inhibit the development of pathogenic fungi in the soil. Besides, antagonistic fungi and bacteria considerably limit the growth and development of pathogenic fungi not only by the exudated siderophores but also by antibiotics with fungicidal and fungistatic effect [2, 3, 5, 9]. On the other hand, the species of Trichoderma spp. are characterized by highly antagonistic effect on phytopathogens, and this effect is based on antibiosis, competition and parasitism [1, 6].

CONCLUSIONS

1. The proportion of pathogenic fungi in the non-rhizopshere soil was almost twice as high as in the soybean rhizosphere.

2. Antagonistic microorganisms included bacteria Bacillus spp., Pseudomonas spp., and fungi Gliocladium spp., Penicillium spp., Trichoderma spp.

3. The big numbers of antagonistic microorganisms in the rhizosphere of soybean can testify to their considerable biological activity, which contributes to the improvement of the phytosanitary condition of the soil.

1. Ahmed A. S., Sánchez C., Candela E. M., 2000. Evaluation of induction of systemic resistance in pepper plants (Capsicum annuum) of Phytophthora capsici using Trichoderma harzianum and its relation with capsidiol accumulation. Eur. J. Plant Pathol. 106, 9, 817-824.

2. El-Tarabily K. A., Soliman M. H., Nassar A. H., Al-Hassani H. A., Sivasithamparam K., Mc Kenna F., Hardy G. E. ST. J., 2000. Biological control of Sclerotinia minor using a chitinolitic bacterium and actinomycetes. Plant Pathol. 49, 5, 573-583.

3. Fiddman P. J., O’Neill T. M., Rossall S., 2000. Screaning of bacteria for the suppression of Botrytis cinerea and Rhizoctonia solani on lettuce (Lactuca sativa) using leaf disc bioassays. Ann. Appl. Biol. 137, 3, 223-235.

4. Funck-Jensen D., Hockenhull J., 1984. Root exudation, rhizosphere microorganisms and disease control. Växtshyddsnotiser 48, 3-4, 49-54.

5. Goel A. K., Sindhu S. S., Dadarwal K. R., 2000. Pigment diverse mutant of Pseudomonas sp. ihibition of fungal growth and stimulation of growth of Cicer arietinum. Biologia Plantarum 43, 4, 563-569.

6. Kredics L., D., Dόczi I., Antol Z., Manczinger L., 2000. Effect of heavy metals on growth and extracellular enzyme activities of mycoparasitic Trichoderma strains. Biulletin of Environmental Contamination and Toxicology 66, 2, 249-252.

7. Księżniak A., Kobus J., 1993. Udział drobnoustrojów ryzosfery pszenicy, jęczmienia i owsa w produkcji sideroforów (The proportion of microorganisms of the rhizosphere of wheat, barley and oat in the production of siderophores) Pam. Puławski – Prace IUNG, 102, 77-90 (in Polish).

8. Łacicowa B., Pięta D., 1989. Szkodliwość grzybów z rodzajów Trichoderma i Gliocladium dla niektórych patogenów fasoli. [Harmfulness of the fungi from genera Trichoderma and Gilocladium to some pathogens of bean]. Zesz. Probl. Post. Nauk Roln. 374, 235-242 [in Polish].

9. Manwar A. V., Vaiganker P. D., Bhonge L. S., Chincholkar S. B., 2000. In vitro suppression of plant pathogens by siderophores of fluorescent pseudomonas. Indian J. Microb. 40, 2, 109-112.

10. Mańka K., Mańka M., 1992. A new method for evaluating interaction between soil inhibiting fungi and plant pathogen. Bull. OILB/SROP, XV, 73-77.

11. Martyniuk S., Masiak D., Stachyra A., Myśków W., 1991. Populacje drobnoustrojów strefy korzeniowej różnych traw i ich antagonizm w stosunku do Gaeumannomyces graminis var. tritici. [Populations of microorganisms of the root zone of different grasses and their antagonism towards Gaeumannomyces graminis var. tritici]. Pam. Puł. Pr. IUNG 98, 139-144 [in Polish].

12. McQuilken M. P., Gemmell J., Lahdenpera M. L., 2001. Gliocladium catenulatum as a potential biological control agent of damping off in bedding plants. J. Phytopathol. 149, 3/4 171-178.

13. Odham G., Tunlid A., Valeur A., Sundin P., White D. C., 1986. Model system for studies of microbial dynamics at exuding surfaces such as the rhizosphere. Appl. Environ. Microbiol. 52, 191-196.

14. Oktaba W., 1987. Metody statystyki matematycznej w doświadczalnictwie [Methods of mathematical statistics in experimental studies]. PWN, Warszawa [in Polish].

15. Parke J. L., 1990. Root colonization by indigenous and introduced microorganisms. In: The Rhizosphere and Plant Growth. D. L. Keister & P. B. Gregan, eds. Kluwer Academic Publishers, Durdrecht, The Netherlands, 33-42.

16. Patkowska E., 2001. Bacterial and fungal populations in the rhizosphere of various plants as related to root exudaties. J. Plant Prot. Res. 41, 3, 240-249.

17. Pięta D., 1999. Initial studies of populations of fungi and bacteria in the soil under influence of the cultivation of spring wheat and winter wheat in a growth chamber. Acta Agrobot. 52, 1-2, 161-166.

18. Schoruvitz R., Zeigler H., 1989. Interaction of maize roots and rhizosphere microorganisms. Z. Pflanzenkranch. Bodenh. 152, 217-222.

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed ‘Discussions’ in each series and hyperlinked to the article.