J. Katan

Both soil solarization and Trichoderma reduce incidence of many diseases
due to their direct detrimental effect on pathogens. In the present work, we
studied induced systemic resistance following solarization and/or Trichoderma
treatments. In our system, only the roots were in contact with the
solarized soil or Trichoderma preparation, while the foliage was inoculated
with pathogens. Strawberry, cucumber and common bean grown on treated
soil or growth coconut substrate showed significant reduction in disease after
leaf infection with Botrytis cinerea or with Sphaerotheca fuliginea, hence
indicating induced resistance. For example, the percentage disease coverage
on foliage of cucumber caused by S. fuliginea was 25.0, 12.8, 11.4 and 12.7,
in nontreated, solarization, Trichoderma and combined treatments, respectively.
Attempts are being made to find the relationship between indigenous
populations of microorganisms in the rhizosphere and disease control.

For this purpose we use a molecular approach based on 16S-rDNA and
denaturating gradient gel electrophoresis (DGGE). The above-mentioned
treatments resulted in changes in the DGGE patterns of soil and substrate
populations. Induced resistance by soil solarization corresponds with previous
studies demonstrating physiological changes in foliage of plants growing in
solarized soil, and with higher population of fluorescent pseudomonads
(known as resistance inducers) in the rhizosphere of the plants in solarized
soils.

P. S59-S60