VERTICAL MIGRATION OF NEMATODES AND SOIL-BORNE FUNGI TO DEVELOPING ROOTS OF AMMOPHILA-ARENARIA (L.) LINK AFTER SAND ACCRETION

Ammophila arenaria benefits from regular burial of windblown beach san d as it allows escape from soilborne pathogens (nematodes and fungi). The present study was done to obtain more insight into the timing and order of migration of the soil organisms towards the newly formed root s. Accordingly, plants were grown in non-sterilized root zone soil, bu ried by 20 cm of beach sand and harvested periodically during one grow ing season. Plants were buried in November. After 17 weeks, the intern odes of the planted seedlings elongated and again 10 weeks later, in M ay, new roots began to develop. The majority of plant parasitic nemato des remained in the original core until root formation started in the deposited layer. Juveniles of Heterodera spp. successfully infected th e roots, formed cysts and produced an offspring in October, resulting in high numbers of larvae at the end of the experiment. In February, a t the first harvest of plants, fungi were isolated from soil and burie d shoots in the whole deposited layer, although it was still winter. D uring the growing season a shift in the community of fungi in soil and buried shoots occurred in both the original core and the deposited la yer. In both layers, the plant pathogenic fungi were gradually replace d by saprophytes. As all fungal and nematode species were able to colo nize the deposited sand layer within one year, we conclude that both f ungi and nematodes in the root zone of A. arenaria are very well adapt ed to sand deposition. Because of the fast migration rate of both path ogenic fungi and parasitic nematodes, the window for A. Arenaria to es cape in time from its soil-borne pathogens seems to be narrow. (C) 199 8 Elsevier Science B.V.