Suppression of hyphal growth of soil‐borne fungi by dune soils from vigorous and declining stands of Ammophila arenaria

Abstract

A study was carried out to determine whether expansion of marram-grass stands (Ammophila arenaria (L.) Link) on acidic inner Dutch coastal dunes was caused by suppressiveness of soils from these stands against three potential pathogenic fungi of marram grass, namely Fusarium culmorum (W. G. Sm.) Sacc., Phoma exigua Desm. and a Ulocladium sp. The suppressiveness of the acidic inner dune soils was compared with that of lime-rich dune soils from vigorous and declining marram-grass stands. Suppressiveness of the dune soils against the saprotrophic fungi Chaetomium globosum Kunze : Fr, Mucor hiemalis Wehmer and Trichoderma harzianum Rifai was also determined. All fungi had been isolated from marram-grass roots. Suppressiveness was determined by comparing the formation of hyphae from potato-dextrose agar discs into (layer method) or on top of (surface method) dune soils with that of controls consisting of sterile, acid-washed beach sand. The growth of the three root-infecting fungi was strongly inhibited in all soils regardless of the method used. Hence, there were no indications that the potential pathogenic fungi were selectively suppressed by the acidic dune soils and, consequently, the results did not give any indication for the involvement of a fungal component in the decline of marram grass. Growth of the saprotrophs C. globosum and M. hiemalis was much less inhibited than that of the root-infecting fungi. Growth of T. harzianum was strongly inhibited in alkaline soils but not in the acid ones. The suppression of fungal growth could be partly or completely eliminated by a microwave treatment, indicating that biological components of the soil were essential to suppressiveness. The suppression of the fungi by colonies of dune soil micro-organisms on water-agar differed considerably from soil alone. Yet, all methods indicated the occurrence of general suppressiveness against fungi by dune soils, irrespective of the origin of the soil samples. This suppressiveness was probably not due to direct competition with other soil micro-organisms for nutrients but to inhibiting compounds produced by the soil micro-organisms.

Cross-Site Soil Microbial Communities under Tillage Regimes: Fungistasis and Microbial Biomarkers

“…Fungistasis biotests were performed by using a surface method described previously by De Boer et al (17). Three replicate platings were used in the experiments, and when differences between treatments were observed, the experiment was repeated with four replicates.…”

Microbial Community Composition Affects Soil Fungistasis

“…The properties of the soil from Terschelling, sampled in February 2000, were: pH (water), 6.9; moisture, 6.2% (wt/wt); and organic matter, 12.5 g kg Ϫ1 . In a previous study, it was shown that soils from these locations suppressed hyphal growth of a wide range of fungi (8). Originally, it was planned to do all the experiments with the soil from Oostvoorne.…”

“…Hyphal extension of test fungi was measured by the method described by De Boer et al (8). This method tests the ability of a fungus to invade a nutrient-poor medium, such as soil, from a nutrient-rich spot.…”

“…Enumeration of bacterial and fungal CFU was performed with 1/10-strength tryptic soy broth-agar for bacteria and water-agar for fungi as described previously (8).…”

“…In general, plant pathogenic fungi appear to be more sensitive than saprophytic fungi (8,17). The sensitivity of plant pathogenic fungi to fungistasis is thought to protect them from germinating and initiating growth under unfavorable conditions (17,29).…”