| Abstrakt: |
Abstract: Whereas experiments directed towards proving the infectious character of the hop curl disease did not give reliable proof of its virus character (we have not been able to transfer it neither by cuttings nor by graft), but made possible its differentiation from the English nettlehead hop virus disease, the practical experiences and results presented in this paper show that nutritional conditions essentially affect the known variability of the external manifestations of the hop curl disease. Especially such nutrients play a role which with the normal fertilising techniques are not returned to the soil in sufficient quantity. Since the hop curl disease was noticeably inhibited in a nutritional field experiment on application of the salts of some elements, predominantly of B, Mg, Mo, Mn, Ni, I and Zn, it appears possible to apply “symptomatic therapy” of the hop curl disease, which could have wide practical importance for limiting this disease. In order to supplement the provocation field experiments, comparative investigations of the chemical composition of the leaves from healthy and hop curl diseased plants were carried out. Quantitative analysis of the biogenic elements carried out by the usual methods and by polarography showed a regularly higher content of P, K, Ca and a lower content of Zn in the diseased plants as compared to healthy ones. The differences observed in the content of N, Na, Mg, S, Fe and Cu were not always in the same sense. Chemical analysis was accompanied by parallel spectral analysis of ash. This made it possible to obtain a considerably complete survey of the qualitative and approximately quantitative representation of a whole series of other elements in healthy and diseased plants; however, no characteristic differences were recorded. Finally the results obtained in the present work are confronted with the findings of other researches, especially from Germany, and discussed. |
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