THE GROWTH OF NEMATODE TOLERANT AND INTOLERANT SOYBEANS AS AFFECTED BY PHOSPHORUS, GLOMUS INTRARADICES AND LIGHT

The effects of the vesicular-arbuscular mycorrhizal (VAM) fungus, Glom us intraradices, and the soyabean cyst nematode (SCN), Heterodera glyc ines, were studied singly and in combination on two soyabean cultivars , cv. Bragg (nematode intolerant) and cv. Wright (moderately nematode tolerant) grown in the greenhouse in soils with low (35 mu g/g) and hi gh (70 mu g/g) Phosphorus (P). Cultivar Wright grew better than cv. Br agg, showing a greater response to P and VAM, and was damaged less by SCN. These differences were not apparent, or were reversed, when the s ame cultivars were grown in growth chambers where lighting was sub-opt imal. Cultivar Wright had a larger shoot:root ratio than cv. Bragg. Th is finding and the observed growth responses indicate that cv. Wright has a more efficient root system than cv. Bragg. This, we suggest, is the basis of both the greater VAM response observed in, and the greate r nematode tolerance ascribed to, cv. Wright compared to cv. Bragg.