Analysis of nematodes and soil-borne fungi fromAmmophila arenaria (Marram grass) in Dutch coastal foredunes by multivariate techniques

Abstract

A survey was carried out at nine locations in the Dutch coastal foredunes to identify the species of soil borne fungi and nematodes associated with Ammophila arenaria (Marram grass). Ammophila arenaria is a sand binding grass that is very important for the stabilization of coastal foredunes. Degeneration of the plants occurs at stabilized sites and is supposed to be caused by a combination of soil-borne fungi and nematodes. Canonical correspondence analysis (CCA) and two-way indicator species analysis (TWlNSPAN) were used to examine which fungal and nematode species usually coexist in the rhizosphere of vigorous and early declining stands of A. arenaria. In total, 47 species of fungi and 10 genera of plant-parasitic nematodes were found. According to CCA, the community of soil organisms of stands that were more than 10 years old was significantly different from recently established stands of 3 years old. Also, the community of soil organisms isolated from calcareous locations differed significantly from that of lime-poor locations. No relationship between the vigour of the plants (vigorous vs. early declining) and the soil borne species composition was found, although in roots of vigorous stands, the number of nematodes was higher than that of early declining stands. A relatively large group of soil organisms occurred generally. This group possibly contains an ubiquitous pathocomplex that cause the growth reducing effects of biotic origin which generally occur in A. arenaria. Analysis of this group of nematodes and fungi by TWINSPAN resulted in 9 different combinations of concurring soil organisms of which 5 combinations were present at all investigated locations. Two of the latter combinations contained both nematodes and fungi. The first contained three endoparasitic nematodes (Meloidogyne maritima, Heterodera spp. and Pratylenchus sp.) that concurred with the fungus Mucor hiemalis. The second group contained Heterodera spp., Telotylenchus ventralis, Filenchus sp. together with the potentially plant-pathogenic fungi Microdochium bolleyi and Fusarium culmorum, as well as the fungi Mortierella sp. and Trichoderma harzianum, all in relatively high numbers.It is concluded that both CCA and TWINSPAN are valuable exploratory techniques, especially when used in combination, to detect possible combinations of soil organisms which may be involved in the degeneration of A. arenaria. Further identifications of harmful organisms should be obtained from experiments.

How Soil-Borne Pathogens May Affect Plant Competition

“…The specificity of soil pathosystems from successional foredune plants, although demonstrated by bioassays ( Van der Putten et al 1993) has not yet been elucidated. In both H. rhamnoides and A. arenaria, a number of plant parasitic nematodes and plant pathogenic fungi may be involved (Zoon et al 1993, De Rooij-Van der Goes et al 1995a). The competition experiments showed that sedentary endoparasitic nematodes (Heterodera avenae group) may contribute to the specificity of the pathosystem, as they formed cysts on roots of A. arenaria, but not on F. rubra.…”

“…Studies on soil-borne pathogens in natural vegetation are mainly confined to coastal sand dunes (Oremus and Otten 1981, Van der Putten et al 1993, Zoon et al 1993, De Rooij-Van der Goes et al 1995a, tropical rain forests (Augspurger 1990), and old fields (Bever 1994). The presence of specific soil pathogens in a successional sere of plants in coastal sand dunes (Van der Putten et al 1993) should have consequences for competitive interactions among the successive plant species (Crawley 1993).…”

“…arenaria takes over dominance in the vegetation Taylor 1979, Huiskes 1979). Plant-parasitic nematodes and pathogenic fungi in the root zone of A. arenaria are implicated in this degeneration (Van der Putten et al 1988, De Rooij-Van der Goes 1995, De Rooij-Van der Goes et al 1995a and F. rubra is relatively tolerant to the pathogens of its predecessor ( Van der Putten et al 1993).…”

Baiting of rhizosphere bacteria with hyphae of common soil fungi reveals a diverse group of potentially mycophagous secondary consumers

“…Bacterial inocula from both rhizosphere soils were prepared using the following protocol: 1 g Goes et al, 1995). In order to make sure that 163 no bacterial contamination was introduced together with the fungi, both fungi were pre-164 cultured on PDA containing oxy-tetracycline (50 mgL -1 ) and streptomycine (100 mgL -1 ).…”

Plant ectoparasitic nematodes prefer roots without their microbial enemies

“…They are able to strongly decrease the biomass of A. arenaria (de Rooij van der Goes 1995a), if not controlled by their microbial enemies (Piśkiewicz et al 2007). In the field T. ventralis usually does not reach population levels that can affect plant growth (van der Stoel et al 2002), but numbers vary locally (de Rooij van der Goes et al 1995b). In the present study, we examine if plant ectoparasitic nematodes T. ventralis are able to sense and avoid microbial communities that include their natural antagonists.…”