GREGOR HEINE, GEORGE TIKUM, WALTER HORST
University of Hannover, Institute for Plant Nutrition, Germany
Soil-borne plant pathogens are a major threat for the production of vegetables under conditions of protected cultivation. It has been shown that vegetable production in Thailand is especially limited by Pythium aphanidermatum, a root pathogen with a mainly tropical distribution. P. aphanidermatum mainly infects the roots of young plants causing poor plant growth and low yields.
Beneficial effects of silicon (Si) nutrition on plant health have been shown for many crops. Interestingly, so far most studies regarding silicon nutrition and plant health were conducted with silicon accumulator plants that are characterised by a high Si uptake as well as a high translocation rate to the shoots. In contrast, Si excluder plants discriminate Si at the plasma membrane leading to an accumulation of silicon in the root apoplast the site of Pythium infection.
In the present study Si effects on P. aphanidermatum disease were compared for a Si excluder and an accumulator plant, namely tomato (Lycopersicon lycopersicum) and bitter gourd (Mormodica charantia), respectively, under controlled conditions. Plants were grown in peat substrate low in silicon that was supplemented or not with Aerosil as a source of plant available Si. A pathogenic isolate of P. aphanidermatum originating from vegetable production sides in Thailand was used for inoculation.
For both species root length and shoot weight of three weeks old plants were reduced as a result of Pythium infection. In tomato, growth parameter did not differ between silicon treatments. On the other hand growth parameters of bitter gourd were clearly positively affected by addition of silicon. The results indicate that the beneficial effect of Si on plant resistance against Pythium is linked to symplastic rather than apoplastic effects of Si.
Keywords: Beneficial effects, Lycopersicon lycopersicum, Mormodica charantia, Protected cultivation, Pythium aphanidermatum, Silicon