Influence of matric potentials on carpogenic germination of sclerotia ofSclerotinia sclerotiorum. II. A comparison of results obtained with different techniques

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Abstract
Four techniques to study the influence of soil matric potential on carpogenic germination of sclerotia of Sclerotinia sclerotiorum were compared. These were the inclined box, polyethylene glycol, sealed jars, and tension plates. The inclined box technique showed that at high matric potential (-0.1 to -0.4 bar) percent germination was higher on the soil surface than at 1 cm depth, but the opposite occurred at potentials of less than-1 bar. All techniques showed that at matric potentials close to 0 bar, germination would occur only if sclerotia were on the soil surface and adequate oxygen was available; buried sclerotia failed to germinate and many rotted. The lowest matric potentials that appeared to induce carpogenic germination using the inclined box, polyethylene glycol, and sealed jar techniques were -4, -7, and - 15 bars respectively, With the latter two techniques the matric potentials are probably understated; thus, although sclerotia can germinate in soil well below field capacity, the lower limit is probably that shown by the inclined box technique. This technique provides the closest approximation to field conditions.