Effects of hydrogen peroxide treatment on the germination, vigour and health of Zinnia elegans seeds

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 (H₂O₂) 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% H₂O₂ 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 H₂O₂, 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% H₂O₂ solutions for 60 and 20 min, respectively. Higher concentrations of H₂O₂ (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.