|Title||Onderzoek over de door Phoma apiicola Klebahn veroorzaakte schurftziekte van de knolselderijplant, Apium graveolens L. en over synergetische vormen en locale rassen van deze zwam|
|Source||University. Promotor(en): H.M. Quanjer. - Wageningen : Veenman - 78|
|Publication type||Dissertation, internally prepared|
|Keyword(s)||apium graveolens var. rapaceum - knolselderij - celeriac|
|Abstract||Symptoms of Phoma apiicola on celeriac were described. Severe ones were like the Phoma rot described by Bennet (Mich. Agric. Exp. Stat. Tech. Bull. 53 (1921). Seed did not transmit P. apiicola but contained a second unidentified Phoma sp. with larger spores and not harmful to celeriac. Two isolates from different places near Venlo and Maastricht differed in ability of pycnospores to grow on Coons' liquid medium. On agar pycnospores yielded 2 forms differing in profusity of growth and in pycnospore size, forms macroforma and microforma. The new micro form was constant at room temperature but at 0' to 5'C yielded pycnospores of both forms.
In mixed culture it promoted pycnidial formation by the macro. The observations were explained not by heterothallism but by conjunct ('synergetic') growth of pycnidia. Inoculation experiments suggested that the micro form was identical with Phyllosticta apii. Only 2 of 20 varieties of celeriac showed any resistance to P. apiicola. On agar the macro form lost its virulence but occasional transfer to celeriac or culture with the micro form restored it.