There were tested and screened, in vitro and in vivo, for the first time in Romania, nine respectively six plant extracts manufactured by Hofigal S.A. against Alternaria alternata (strain Aa 20) isolated from blackcurrant (Ribes nigrum L.). The highest in vitro activity (efficacy between 70% and 100%) was recorded for Satureja hortensis and Valeriana officinalis extracts at 20 and 10% concentrations. A good inhibitory activity on mycelial growth (efficacy between 54.3 and 88.6%) has been noticed for Allium sativum, Mentha sp. Rosmarinus officinalis, Tagetes patula extracts (at 10 and 20%). No efficacy was noticed for Artemisia dracunculus ‘sativa’. The extract obtained from Hyssopus officinalis inhibited the mycelial growth of A. alternata only at 20%, with 57.1% efficacy. In field trials, Valeriana officinalis and Satureja hortensis extracts have been very effective in limiting Alternaria disease severity in blackcurrant applied at 10%, compared to untreated control. This data confirmed their strong antifungal potential, both in vitro and in vivo. Based on our results, plant extracts with highly efficacy could be an alternative in the protection of blackcurrant as medicinal crop against Alternaria leaf spot and fruit rot especially in organic horticulture system.

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