Bio-Efficacy of Decomposed Crude Eucalyptus Leaves Extract and Pseudomonas Species against Faba Bean Brown Spot Disease

Abstract

Brown spot disease is one of the most common diseases in faba bean. Many studies have focused on finding natural compounds and biological control agents that can help combat these diseases. This study focused on the study of the effectiveness of decomposed crude eucalyptus leaf extract and Pseudomonas species against brown spot disease in faba bean caused by Botrytis fabae Sard. A field study was carried out at Toshka Research Station, Desert Research Center, Aswan Governorate, Egypt, during the 2022 winter growing season. In this respect, eleven Pseudomonas isolates were evaluated for their potential to suppress the phytopathogenic fungus B. fabae. The most effective isolates were identified using 16S rRNA nucleotide sequence. Molecular identification data revealed that selected isolates are blast identical to P. stutzeri with 95% and P. fulva with 100%. The decomposed extract of eucalyptus leaves reduced the mycelial growth of B. fabae in a concentration-dependent manner. The HPLC profile of phenolic compounds in the fermented extract revealed that both hydroxybenzoic acids and hydroxycinnamic acids are more abundant and pyrocatechol was the major phenolic compound in the fermented extract. Under field conditions, the least severity was recorded from treated plants with
bioagents in combination with fermented eucalyptus leaf extract in the form of soil and spray applications. Treating faba bean plants with plant extracts and microbioagents improved most tested growth criteria, plant productivity and seed yield.