Results are given of a survey on the occurrence of pathotypes (races) of Synchytrium endobioticum (potato wart) in both parts of re‐unified Germany. An assortment of six differential cultivars appears to be sufficient to distinguish between the seven presently important German wart pathotypes. A total of ten pathotypes was recorded. Two West and two East German pathotypes seem to be identical, based on the results obtained with presently available cultivars. In contrast to pathotype 1 (common race) which prior to 1945 was distributed over the whole German territory, the ‘new’ pathotypes seem to prefer the central and south German mountain areas.
A key for official assessment of potato cultivars for their resistance to Synchytrium endobioticum (potato wart) is presented. The margin between resistant and susceptible reactions is determined solely by the intensity of necrosis. Low numbers of ripe wart sori can be tolerated, if substantial necrosis occurs simultaneously. The key is a combination of the testing procedures of the two former German States and has been officially applied in Germany since 1992.
Using a modified crystal violet sodium polypectate (CVPB) double layer medium with 2,3,5-triphenyltetrazolium chloride and L-asparagine in the basal medium and bromthymol blue in the upper, both containing tryptone, gave red to pink colonies of Erwinia carotovora ssp. carotovora on a blue green background with cavity formation. The addition of 1.2 µg/ml polymyxin B sulphate to the upper layer inhibited the growth of Erwinia carotovora ssp. atroseptica, while 32 µg/ml erythromycin in the upper layer inhibited the growth of E. chrysanthemi. The addition of 35 µg/ml novobiocin inhibited the growth of Bacillus sp. Non-target bacteria such as Pseudomonas fluorescens , P. marginalis, Ralstonia solanacearum and E. herbicola formed pink, red, yellowish or white colonies without cavity formation. The growth of non-target bacteria on the semi-selective medium was one tenth of that obtained using CVPB medium.
A survey shows the present situation of the occurrence of potato wart (Synchytrium endobioticum) in the Federal Republic of Germany. By 1960 five different pathotypes (races) could be detected. Only 1 % of all foci identified after the Second World War belonged to the old pathotype 1 (← common race →). Questions of determination and emergence of new pathotypes as well as those of official restrictions on cultivar release are discussed.
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