Investigation on control of citrus blast disease by seed extract of Heracleum persicum (Golpar) and epiphytic yeasts

Citrus blast caused by species of Pseudomonas spp. is one of the most important citrus diseases in north of Iran. This disease causes considerable losses to citrus orchards in conducive climatic conditions. Due to restrictions on the use of antibiotics and chemical compounds, biological control and use of plant antimicrobial compounds can be an effective way to control citrus blast disease. In this study, performance of several epiphytic yeasts isolates and Golpar seed extract on bacterial blast of citrus were studied under in vivo and in vitro conditions. Antagonistic yeasts collected from citrus leaf samples were isolated from different regions of the Northern provinces. Also, Golpar seeds were collected from the highlands of the city of Babol (Mazandaran, Iran). The seed extract of Golpar showed significantly inhibited the growth of two pathogens on KB medium but none of the yeasts show significant growth inhibition. The results of greenhouse studies indicated that one of yeast isolate (Pichia sp.) reduces the severity of disease with average 78.8 percent. Also Golpar extract was able to reduce the pathogen populations by 60 percent in citrus fruit. The results showed that Pichia sp. and Golpar extract are effective for controlling the disease.