Effect of salicylic and ascorbic acids on growth of two pathogenic fungi of pepper pIants

This study was conducted to investigate the effectiveness of two types of acids, namely salicylic acid and ascorbic acid, against two fungi that are pathogenic to pepper plants, namely Fusarium oxysporum and Botrytis cinerea, under laboratory and greenhouse conditions.The results showed that the effect of salicylic acid increased with increasing acid concentration, as inhibition of the growth of the pathogenic fungus F. oxysporum increased, and when the acid concentration increased to 200 mg per liter, the fungal growth was completely inhibited.While the concentration of 300 mg/L of ascorbic acid completely inhibited the growth of the pathogenic fungus.It was also found that the dry weight of the pathogenic fungus F. oxysporum could reduce to 62 mg (or inhibition rate 53.73%) from 134 mg for spraying zero mg per liter salicylic acid with increasing the concentration of salicylic acid up to 50mg per liter.Raising acid concentration to 150 mg l (-1) resulted in dry fungal weight reduction to 14 mg (89.55% inhibition rate), whereas 200 mg l (-1) effectively inhibited growth.Both the selected compounds ascorbic acid had fully inhibited the dry weight of the pathogenic fungus in control conditions at a concentration of 300 mg/L.Tests showed that 100 mg/L of the acid concentration inhibited fungal growth to 42 mm (inhibition rate of 54.99%), inhibition increased to 86.43% at a concentration of 150 mg/L, and growth rate was limited to12.66mm; 200 mg per liter of salicylic acid completely suppressed fungal growth.The results also revealed that a 200 mg l (-1) concentration of the acid was enough to completely suppress fungal growth, with relative inhibition being 100%.Concerning ascorbic acid, the results showed that this effect was enhanced with increasing of concentration of acid, and resulted in decreasing the dry weight of Botrytis cinerea biomass.Growth was completely inhibited at 400 mg/L, as observed from the results.The results showed that the various treatments affected differently pepper plant growth parameters such as shoot and root length per plant, dry weight of plants and the percentage infected plants.The data indicated a clear impact of the tested pathogen Fusarium oxysporum in suppressing most plant growth and pathogenicity traits for the various treatments.It was obvious that the influence of salicylic acid and ascorbic acid to enhance the plant growth parameters and reduce percentage of Fusarium wilt diseases in comparison to various treatments.