DEVELOPMENT OF A TESTING METHOD FOR CERCO SPORA-RESISTANCE OF SUGAR-BEET VARIETIES UNDER FIELD CONDITIONS - FIRST RESULTS

In 7 field trials, each with 12 varieties, varying from resistant to e xtremely susceptible, all varieties have been systematically inoculate d with C. beticola. For comparison purposes 5 trials were laid out und er natural attack and 8 trials without any attack, using the same asso rtment. In 12 additional trials, using 5 varieties, the effects of tim e of inoculation and of origin of C. beticola were tested. The evaluat ion of Cercospora attack was carried out from 4 to 5 weeks after closi ng of the canopy respectively 20 days after inoculation in a two weeks rhythm. Systematical inoculation led to a quick and equal infestation of C. beticola. In these trials the differentiation of varieties was more distinct than under natural attack. The ranking of the varieties was nearly the same in both types of infestation. The relative yield a nd quality were lowered extremely with the susceptible varieties but i t increased in the resistant ones in relation to non-attack conditions . The systematical inoculation had a much stronger effect on yield and quality than the natural attack. There was no reciprocal reaction to be found between varieties and time of inoculation or between varietie s and the origin of tile fungi C. beticola.