Phyto-extracts Mediated Biological Control of Citrus Canker

Abstract

Citrus is second most important fruit crop and has significance economic importance in Pakistan. In Pakistan 2.17 million tonnes citrus was produced on area of 1.94 million acre. Citrus is mostly cultivated in Punjab and affected by different types of plant pathogens. Citrus canker is the most harmful disease among the major diseases of citrus which is caused by Xanthomonas axonopodis pv. citri. The copper based fungicides are mostly employed to manage the citrus canker in the field but excessive use of chemicals have negatively impacted the environment and warrant the need to find out organic solutions therefore the current study was aimed at identifying suitable plants extracts for the control of citrus canker bacterium. Isolation of the bacterium X.axonopodis was done through streaking on agar plate technique. Morphological and bio-chemical tests such as gram staining, KoH test, catalase test and starch hydrolysis test were performed to examine the bacteria X.axonopodispv. citri. Plant extracts were evaluated, in vitro, against the X.axonopodis pv. citri through paper disc method which showed the inhibition zone against the disease. The 100 percent extract of garlic, ginger, aloevera, moringa were used used along with the streptomycin as a positive control. The inhibition zone was 11.67mm and 10.83mm due to garlic and moringa extracts respectively while it was 16.67mm in case of positive control. The ginger and aloevera extracts proved ineffective against the citrus canker bacterium.The efficacy of garlic and moringa extracts were also checked against the X. axonopodis pv. citri under glasshouse conditions. The inoculum was sprayed on Kinnow plants, with three replicates, for each extract and data was recorded 15, 20, 25, 30 and 35 days post inoculation (dpi).The recorded disease severity percentage, after 35dpi, on garlic and moringa treated plants were 9.67% and  14.27% respectively while the 27% disease severity was recorded on control (plants sprayed with autoclaved distilled water). The garlic extract proved to be most effective followed by moringa extract which could be used as a potential organic solution to control citrus canker.