CALCIUM NUTRITION AND ITS EFFECT ON THE RECEPTIVITY OF CARNATION TO FUSARIUM OXYSPORUM F. SP. DIANTHI.

Tabel I: Comparison of high and low calcium treatment on infectious diseases and non-parasitic skin spots. x

	Low Ca	High Ca
Erwinia phytophthora ..........................	+ + + +	+
Rhizoctonia solani ...............................	+ + + +	+
Sclerotium rolfsii .................................	+ + + +	+
Botrytis cinerea ....................................	+ + + +	+ +
Fusarium oxysporum ...........................	+ + + +	+
Jonathan spot (non parasitic) ...............	+ + + +	+ +
Bitter Pit (non-parasitic) ......................	+ + + +	+ +

x The + mark means disease severity

From Z. KIRALY (1975).

This calcium effect is quite generally explained by the specific role of this element as a binding agent in the chains of pectic acids : the calcium pectate would increase the resistance of the cell wall to enzymatic degradation by pathogens.

Nevertheless this direct effect of calcium seems to have been largely underestimated as far as Fusarium oxysporum was concerned. J.P. JONES and S.S. WOLTZ (1970) on tomato, S.S. WOLTZ and A.W. ENGELHARD (1972) on chrysanthemum, observed both a decrease in the severity of the disease, with an application of lime and concluded to a direct effect of the treatment on the pathogen itself : the growth and the virulence of the pathogen would be limited by a decrease in the availability of minor elements induced by the

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