The Influence of Stage of Host Development on Vesicular‐arbuscular Mycorrhizae and Endogonaceous Spore Population in Field‐grown Vegetable Crops I. Summer‐grown Crops

SUMMARY The pattern of mycorrhizal infection of roots of several fully grown vegetable crops showed three phases, a lag phase, a phase of rapid development and a constant phase. Twenty‐one days after sowing or transplanting, 0–24% of the roots were infected, but the proportion then increased rapidly to a more or less constant value of 55–92%. With musk melon (Cucurbita moschata L.), tomato (Lycopersicon esculentum Miller, Goed) and bringel (Solarium melongena L.), no constant phase was observed within the sampling period. During the first 4–8 weeks of crop growth, the Endogonaceous spore population of the soil decreased, but then increased to final harvest time. Three main types of endophytes were identified, two being members of Endogonaceae and one with very narrow, brown septate hyphae. The relationship between the different phases of mycorrhizal development, spore number in the soil and physiological changes in the host is discussed.