NURSERY SURVEY OF ERICOID MYCORRHIZAS IN BLUEBERRIES

Current literature reports that commercially produced and cultivated highbush blueberry ( Vaccinium corymbosum ) are virtually non-mycorrhizal, while native populations of Vaccinium are highly infected with the ericoid fungal symbiont. To confirm this information, a nursery and grower survey was initiated in PA, MI, and NC. Percent infection was determined by presence/absence counts using a grid-line intersect method. Results from 5-plant samples of cultivars `Jersey', `Northland'. `Bluecrop', `Blueray', and/or `Berkeley' (all obtained from nursery sources) from which three root subsamples per plant were cleared and stained revealed that all plants were mycorrhizal. Infection rates ranged from an average of 9.4% for two year old plants to 55.5% on one year old plants. An inverse relationship occurred between rate of ammonium-N and infection rate. Data also indicated a significant difference in infection rate among cultivars with `Northland' most highly infected and `Berkeley' least. Plants propagated in woodchip/sand or peat/sand media developed ericoid mycorrhizas. Data from a current greenhouse experiment supports this observation. We are currently identifying the fungi involved in this symbiosis.