MYCORRHIZAL RESPONSES OF BARLEY CULTIVARS DIFFERING IN P-EFFICIENCY

The purpose of this study was to investigate how barley cultivars whic h are different in dry matter yield at low phosphorus (P) supply (i.e. they differ in agronomic P efficiency) respond to mycorrhizal infecti on. In a preliminary experiment, six mycorrhizal fungi were tested for their ability to colonize barley (Hordeum vulgare L.) roots at a soil temperature of 15-degrees-C. Glomus etunicatum was the most effective species and was used in the main experiment. The main experiment was conducted under glasshouse conditions in which soil temperature was ma intained at 15-degrees-C. Treatments consisted of a factorial arrangem ent of 8 barley cultivars, 2 mycorrhiza (inoculated and non-inoculated ), and 3 rates of P (0, 10 and 20 mg kg-1). P utilization efficiency ( dry matter yield per unit of P taken up) and agronomic P efficiency am ong the barley cultivars was significantly negatively correlated with mycorrhizal responses. However, the response to mycorrhizal infection was positively correlated with response to P application. Poor correla tion was observed between P concentration when neither mycorrhiza nor P were supplied and the percentage of root length infected. The extent of mycorrhizal infection among the barley cultivars in soil without P amendment varied from 8.6 to 28.6%. Significant interactions between cultivar and P addition, and between mycorrhiza and P addition were ob served for shoot dry weight but not root dry weight.