ISHS Acta Horticulturae 779: International Symposium on Growing Media
DISEASE SUPPRESSIVENESS AND MICROBIAL COMMUNITIES OF FLAX STRAW COMPOST |
| Authors: | W. Wohanka, S. Bodenburg, H.-D. Molitor |
| Keywords: | bio-test, Pythium, Rhizoctonia, Linum, Pisum, actinomycetes |
| Abstract:
The objective of this study was to examine the disease suppressive properties of flax straw compost in comparison to a peat based growing medium by performing a bio-test with pea seedlings. Peas were sown in trays filled with either defined flax straw compost or a peat based growing medium (TKS 1). Both substrates were used either untreated or heat-sterilized. After germination, the pea seedlings of both marginal rows of each tray were inoculated with Pythium ultimum or Rhizoctonia solani. Such a position of "infector plants" enables the examination of efficacy against the spread of both diseases. After inoculation with P. ultimum, seedling fresh weight as well as the appearance of root damage revealed a significant disease suppressive effect of the flax straw compost as compared to the peat based medium. The portion of brown roots amounted to about 47% in peat and to about 28% in flax straw compost. Pea seedlings grown in flax straw compost produced a smaller number of plants with stem rot (caused by R. solani) in comparison to seedlings in the peat medium. While 34% of the seedlings in the peat based medium showed the typical symptoms, only 10% of the flax straw compost raised seedlings were infected. Microbiological analyses indicated a much higher microbial colonization of the flax straw compost compared to the peat based growing medium. The heavy colonization of the flax straw compost by actinomycetes (ca. 105 to 106 colony forming units per gram dry weight) is remarkable. In the peat mix, these micro-organisms were not detectable at the start of the experiment and only in very low densities at the time of termination. These findings suggest that particularly the actinomycetes contribute to the disease suppressive effects of the flax straw compost. | |
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