Screening for resistance of Allium species to Sclerotium cepivorum with special reference to non‐stimulatory resistance
Approximately 150 seed lots of Allium cepa and more than 30 different Allium species were tested in the greenhouse under strictly controlled conditions against Sclerotium cepivorum, the causal fungus of Allium white rot disease. The quantity and quality of the inoculum was determined using a simple and rapid test to achieve a high degree of standardization. Only the A. cepa cultivar “Sweet Sandwich’ and A. porrum, A. rotundum, A. sphaerocephalon and two further unidentified Allium species showed significantly lower disease incidence than the cultivar ‘Golden Bear’. The stimulatory effect of the root exudates on sclerotial germination was compared with that of diallyl sulphide. With the exception of A. species‘PI 249549′, extracts of all species that showed low levels of disease incidence in the greenhouse test stimulated sclerotial germination only weakly.