Alternaria alternata and Alternaria radicina are fungal species that occur in several food crops and may produce mycotoxins and phytotoxins. The toxigenic profile of A. alternata and A. radicina isolated from carrot and other umbelliferous plants was determined by growing the fungus on rice and carrot discs. Most of the tested isolates of A. alternata produced the mycotoxins tenuazonic acid, alternariol, alternariol methyl ether and altertoxin–I on rice. Only alternariol and alternariol methyl ether were produced on carrot discs. When cultured on rice, none of the isolates of A. alternata from umbelliferous plants produced AAL toxins and fumonisins. AAL toxins, but not fumonisins, were instead produced by A. alternata f. sp. lycopersici isolate NRRL 18822 isolated from tomato. A. radicina produced the phytotoxic compounds radicinin, epi–radicinol and radicinol on carrot discs, whereas it produced radicinin and radicinol on rice. Although A. alternata has been frequently found in organic carrots, none of the above mycotoxins was detected in carrot roots or in carrot commercial products. The reduction of alternariol and alternariol methyl ether during carrot juice processing at laboratory scale was estimated to be >98%. Based on these findings and previous reports, it can be concluded that Alternaria mycotoxins in carrots do not represent a hazard for consumers.

The high infestation rate of zinnia (Zinnia elegans Jacq.) seeds with fungi, especially pathogenic Alternaria zinniae, has frequently resulted in a poor germination capacity associated with a high number of abnormal diseased seedlings. The effect of hydrogen peroxide (H ₂ O ₂ ) treatment on the germination, vigour and health of zinnia seeds was investigated. Two samples of zinnia seeds - sample I, characterised with a low germination capacity (39.5%) and a high level of seed infection with A. zinniae (76%), and sample II, with a high germination capacity (87%) and free from this pathogen - were tested. For treatment, seeds were soaked in 3%, 6%, 9% and 12% H ₂ O ₂ solutions for 10, 20, 30 and 60 min. Initially, the controls were seeds soaked in distilled water for 10, 20, 30 and 60 min, and then the results of selected treatments were compared with results obtained for untreated seeds and seeds treated with a fungicide (20% carbendazim and 45% thiram). The fungi Alternaria spp. and Fusarium spp. were frequently identified on tested seeds. The concentration of hydrogen peroxide affected the quality of zinnia seeds to a higher extent than the treatment time. However, all of the treatments applied, regardless of time and concentration of H ₂ O ₂ , positively affected seed health, significantly reducing seed infestation by fungi in both samples. Moreover, the lowest level of A. zinniae infection was observed if seeds were soaked in 6% and 9% H ₂ O ₂ solutions for 60 and 20 min, respectively. Higher concentrations of H ₂ O ₂ (9% and 12%) negatively influenced seed germination and vigour, especially in sample II. These findings suggested that the treatment of zinnia seeds with hydrogen peroxide can effectively improve germination mostly in samples heavily infected with pathogens, which means that it should be preceded by seed health evaluation.

The aim of the study was to evaluate the effect of microwave treatment on seed germination and health of carrot seeds using two seed lots naturally infected with the pathogens Alternaria dauci and A. radicina. Seeds of cv. Amsterdam and cv. Berlikumer varied in seed germination at the final count (50% and 29%, respectively), and seed infestation with A. radicina (38% and 5%, respectively). For treatment, seeds were placed in a Petri dish (dry treatment) or in a beaker with distilled water (wet treatment) and irradiated at power output levels 500, 650 and 750 W for 15, 30, 45, 60, 75, and 90 s. Germination and health were determined in treated and untreated (control) seed samples. Wet treatment controlled seed-borne fungi more efficiently than dry treatment. However, the exposure duration longer than 60 s frequently resulted in deterioration of seed germination. The highest seed germination in cv. Amsterdam was observed after microwave wet treatment at power output levels of 500 W for 75 s (81%), 650 W for 45 s (85%), and 750 W for 60 s (77%), whereas in the case of cv. Berlikumer this occurred when wet seeds were treated at 500 and 650 W for 60 s (46% and 43% respectively). Treating seeds soaked in water with microwaves for a period longer than 30 s, regardless of the power output, significantly decreased seed infestation with Alternaria spp. in both samples.

Priming is one of the most common methods of improving seed quality. The aim of this experiment was to study the effects of hydro- and osmopriming on the germination, vigour and hydrolytic enzymes (α-amylase, β-glucosidase, exopeptidase and lipases) activity of zinnia (Zinnia elegans Jacq.) seeds. Seeds of three cultivars: Jowita, Kirke and Orys, and Z. elegans fl.pl., a mixture of cultivars (Mix), were tested. The seeds were hydroprimed in a restricted volume of water (200 μl H₂O g⁻¹ seed, 24 h at 15°C) and osmoprimed in a polyethylene glycol solution (−1.0 MPa PEG 8000, 5 days at 20°C). Untreated seeds served as the control. The cultivars differed significantly in terms of seed quality as well as response to priming. On average, ‘Jowita’ seeds were characterised by the highest quality, expressed by the total number of germinating seeds (G_max) and germination at the 1^st and 2^nd counts. Mix seeds showed the lowest quality, expressed by germination at the 1^st and 2^nd counts and vigour. Generally, an increase in α-amylase activity and a decrease in lipase activity was found in hydroprimed and osmoprimed seeds, and α-amylase activity was significantly higher in ‘Jowita’ seeds than Mix seeds. The applied treatments did not affect β-glucosidase and exopeptidase activity in the tested seeds. Osmopriming accelerated seed germination and influenced α-amylase and lipase activity to a greater extent than hydropriming. Among the assayed enzymes, only the activity of α-amylase may be potentially useful for the seed industry as a physiological marker of zinnia seed vigour and the effectiveness of osmopriming.