New Zealand Journal of Crop and Horticultural Science abstracts
Selection of mycoparasites of sclerotia of Sclerotinia sclerotiorum
isolated from New Zealand soils
E. E. JONES*
A. STEWART
Soil, Plant and Ecological Sciences Division
P. O. Box 84, Lincoln University
Canterbury, New Zealand
email: Stewarta@lincoln.ac.nz
* Present address: Horticulture Research
International,
Wellesbourne, Warwick CV35 9EF, United Kingdom.
Abstract Seventy-four isolates of fungi including
Trichoderma spp. (18), Gliocladium spp. (12), Coniothyrium
minitans (39), Chaetomium globosum (3), Chrysosporium luteum
(1), and Fusarium sp. (1) were screened for ability to parasitise
sclerotia of Sclerotinia sclerotiorum. Seventeen isolates killed all
sclerotia after 4 weeks of incubation, with a further 15 isolates reducing
sclerotial viability to less than 20%. These 32 isolates were screened in a
second sclerotial parasitism test, where solid substrate (1% kibbled
maize:perlite colonised with antagonist) was incorporated into soil.
Twenty-four isolates significantly reduced sclerotial viability compared to the
untreated control, with C. minitans Conio, CH1, T5R4 2g, A69, and
T5R4 2i giving the greatest reduction. C. minitans isolates showed
considerable variation in their ability to parasitise sclerotia with some
showing high activity but others little or no activity. Two New Zealand
isolates (A69 and T5R4 2i) and two overseas isolates (CH1 and Conio) were
compared further. Increasing the length of the incubation period after
treatment of sclerotia with C. minitans resulted in a decrease in the
viability of sclerotia and an increase in the infection of sclerotia by C.
minitans. This effect was significantly greater for isolates CH1 and Conio
compared with A69 and T5R4 2i. Incorporation of spores of the four isolates
into soil (1 x 106 spores/g soil) reduced sclerotial viability, with
all isolates of antagonists surviving in the soil for the 2-week duration of
the experiment. Variation in the susceptibility of three S. sclerotiorum
isolates to sclerotial parasitism by C. minitans CH1 and A69 was
observed, with S. sclerotiorum isolate S9W1 the most susceptible and
isolate S35 the least.
Keywords Sclerotinia sclerotiorum; sclerotia;
biological control; Coniothyrium minitans; Trichoderma
viride; Trichoderma harzianum; isolation; parasitism
H99035
Received 22 September 1999; accepted 21 March 2000
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