Antifungal and SAR potential of crude extracts derived from neem and ginger against storage carrot rot caused by Sclerotinia sclerotiorum

The in vitro and in vivo experiments were conducted to evaluate antifungal activity of crude extracts derived from neem (Azadirachta indica) leaves and ginger (Zingiber officinale) rhizomes against three isolates of Sclerotinia sclerotiorum, the causal agent of storage carrot (Daucus carota) rot. Ethyl acetate (EA) and ethanol were used as different solvents. Although plant extracts significantly reduced the mycelial growth of three isolates at volatile phase, highest inhibitory efficacy was observed at contact phase. Furthermore, all crude extracts were able to reduce carpogenic germination of sclerotia at concentrations 2 g/l. The isolate 2 was found to be more inhibited in in vitro tests. At volatile phase, EA and ethanol extracts of ginger meaningfully reduced myceliogenic germination of sclerotia in three isolates. However, all plant extracts decreased the myceliogenic germination of sclerotia at contact phase at the concentration 10 g/l. The results of in vivo tests showed that all plant extracts are able to decrease disease severity of carrot rot at the concentration 2 g/l. In addition, the enzymatic analyses of phenylalanine ammonia layse, polyphenoloxidase and peroxidase in inoculated carrots after application of plant crude extracts indicated that neem extracts can be considered as resistance inducers against Sclerotinia carrot rot.