BYRNE, KENNETH, DEREK MITCHELL & BRUCE OSBORNE.
Department of Botany, University College Dublin, Dublin 4, IRELAND.
The roots of most healthy plants are intimately associated with mycorrhizal fungi which form functional symbioses. However, incompatible mycorrhizal associations may occur and the effects of these on the host have received limited attention. Cranberry, which is ericoid endomycorrhizal, was used as the host plant and was grown in peat/sand (1:9) under environmental growth conditions. After inoculation with the compatible fungus (Hymenoscyphus ericae), cranberry seedlings showed a higher shoot phosphorus content compared with non-mycorrhizal controls but there were no differences in growth or photosynthesis. Either in their natural habitat or under propagation, cranberry may be growing in soils, which contain arbuscular mycorrhizal (AM) fungi. Cranberry inoculated with Glomus mosseae had a greater root length but a decrease in shoot mass, length and nitrogen content compared with uninoculated seedlings. Although G. mosseae has not been reported to infect cranberry, vesicles were observed within the root systems. Since G. mosseae is obligately mycorrhizal with other plant species, further studies are in progress on the growth of cranberry in the presence of a compatible association between Plantago lanceolata and G mosseae. As disturbed peatlands may be colonized by plantain, Calluna vulgaris and Vaccinium spp., similar experiments were carried out on seedlings of P. lanceolata inoculated with H. ericae. No infection was observed and growth was not affected. The effects of cranberry/ H. ericae on the growth of plantain are also being investigated. These studies have shown that infection by G. mosseae has a deleterious affect on the growth of cranberry.