Effects of osmo- and hydropriming on fungal infestation levels and germination of carrot (Daucus carota L.) seeds contaminated with Alternaria spp.

The purpose of this research was to study effects of priming on seed infestation with fungi and germination of carrot (Daucus carota L.) seed lots naturally contaminated with seedborne Alternaria spp. Three seed lots of two cultivars, 'Karita' and 'Nantes Topscore' Fl, varying in initial incidence of Alternaria spp., were primed in PEG 6000 or hydroprimed under laboratory conditions. The lots differed in their response to priming, both in terms of germination and presence of Alternaria spp. Priming resulted in a faster germination for all three seed lots. The uniformity of germination was improved in two lots. The overall percentage germination did not increase. Both osmotically and hydroprimed seeds gave rise to a decreased number of normal seedlings compared with untreated seeds. This decrease resulted from an increase in the number of seedlings with fungi and/or decays and dead seeds, which was related to a significant increase in the number of seeds contaminated with fungi after priming, In the seed lots with intermediate or high incidence levels of Alternaria dauci, A. radicina, or A. alternata, priming resulted in significantly higher levels of contamination. Moreover, fungi invaded inner parts of the seeds, especially after PEG priming. These findings indicate that the level of fungal contamination of seeds should be evaluated prior to the selection of seed lots for priming.