SEED-BORNE ALTERNARIA BRASSICICOLA: DETECTION BY MEANS OF SYMPTOMS ON SEEDLINGS

Alternaria brassicicola, on seeds of Brassica oleracea var. botrytis is, very often, the only pathogen found. Two seed health testing methods suitable for the detection of the pathogen are recommended by ISTA: the blotter method (BM), that requires the use of the stereomicroscope to identify the fructification of the pathogen, and the agar plate method (APM), that reveals only the deep-seated inoculum. Both methods need, preferably, incubation under Near Ultra Violet (NUV) light. However, an other method, the deep freezing blotter method (DFBM), can be used, this is, in our experience, the most sensitive but it is even more time-consuming and requires experienced analysts.

To avoid the use of the stereomicroscope and the NUV light and to acquire information about the germinability of samples, it is possible to use the germination test (GT) on the Jacobsen apparatus, according to 1976 ISTA Rules, as seed health testing method.

Data obtained from the germination test that fits for producing reliable correlation coefficients either with the DFBM or the BM are those relative to the total percent infection (diseased seedlings + ungerminated, infected seeds) and to the percentage of seedlings with symptoms calculated on the basis of germinated seeds. Only the latter datum allow avoiding the use of the stereomicroscope.

Results of the agar plate method in comparison with the deep freezing blotter method indicate that the percentage of seeds with deep seated inoculum varies more than proportionally in comparison with the percentage of infected seeds.

All samples tested have not shown any influence of the fungus on seed germination.