EVALUATION OF PLANT EXTRACTS AS BIOCONTROL AGENTS AGAINST XANTHOMONAS AXONOPODIS PV CITRI THE CAUSE OF CITRUS CANKER

Abstract

Ten plant extracts;  Allium sativum L.,  Allium cepa L., Azadirachta indica, Capsicum Annum, Calotropisgi gantea , Dalbrgia sissoo , Eucalyptus camelduensis, Gardenia florida Melia azedarach  and Zingiber officinalis were tested in vitro at Standard dose S and S/2 against Xanthomonas axonopodis pv. citri. All the plant extracts at both the doses reduced the multiplication of Xac except Zingiber officinalis and Capsicum Annum. Allium sativumand Azadirachta indicaat doses (S, S/2) exhibited statistically significant inhibition zones as compared to other treatments, followed by Dalbergia sisso. Gardenia florida and Melia azedarach which produced similar effect and raked 4^th. Calotropisgi gantea ranked 5^th while Eucalyptus camelduensis (Sufeda) and Allium cepa L. inhibited the growth of Xacat a minimum level. Capsicum Annum and Zingiber officinalis produced no inhibition zone and showed similar results as a control. All the plant extracts at standard doses reduced the multiplication of Xac maximumas compared to S/2 except Allium cepa L., Dalbrgia sissoo, Eucalyptus camelduensis and Melia azedarach which showed similar effects at both doses. The most effective treatments proved in vitro then tested after combining with streptomycin sulphate in vitro and found that Streptomycin sulphate 1 % reduced the multiplication of Xac significantly, followed by Streptomycin sulphate in combination with Allium sativum L. and Streptomycin sulphate in combination with Azadirachta indica at standard dose. These treatments then tested in greenhouse the results confirmed the findings of invitro trials. There is a need to promote research in the field of plant extracts usage as biocontrol agents and find out plants having toxicity against plant pathogens, as the plant extracts are environment friendly and cheaper.