Antifungal effect of some plant extracts and their combination with Moncut fungicide on sugar beet root rot

Abstract

Sugar beet (Beta vulgaris L. Chenopodiaceae) has become the first Egyptian crop for sugar production because it contributed with 59.5% of total sugar production. Sclerotium rolfsii is a soil-borne plant pathogenic fungi incident of southern sclerotium rot in sugar beet. The aim of the present study was to investigate the effect of some plant extracts in different solvents as inhibitory control agents against the growth plant pathogen S. rolfsii. Five plant extracts; Roselle, pomegranate, rosemary, black pepper and chamomile were evaluated as inhibitors for Sclerotium rolfsii of sugar beet root rot under laboratory and greenhouse conditions during 2016/2017 growing season at Gemmeiza Agricultural Research Station, (ARC). The results indicated that all tested plant extracts caused remarkable growth inhibition of S. rolfsii compared with control. However, black pepper extract was the most effective against S. rolfsii (recorded 93.33% inhibition). On the other hand, Pomegranate extract in methanol solvent showed also high inhibition percentage (93.30%). All plant extracts mixed with Moncut fungicides demonstrated an antagonistic effect. The pomegranate and black pepper treatments showed the lowest disease severity compared with control. Furthermore, the pomegranate and black paper treatments recorded the highest root weight, root yield/plot, total soluble solids percentage and sucrose content. Also, pomegranate and black pepper treatments reflected the highest amount of total phenols, free phenols, and conjugated phenols. Additionally, the interaction of pomegranate and black pepper treatments with S. rolfsii pathogen, showed the highest activity of oxidative enzymes peroxidase and polyphenol oxidase. This study recommends the application of pomegranate and black pepper as natural alternative fungicides against Sclerotium rolfsii plant infection.