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Utilization of endo-root fluorescent Pseudomonas of chilli for the management OF ROOT diseases of chilli

SAMRAH TARIQ¹, RUQQAYA KHAN², VIQAR SULTANA², JEHAN ARA³, AND SYED EHTESHAMUL-HAQUE¹

Abstract: Chili (Capsicum annuum) is an important vegetable and spice crop worldwide produced and consumed as fresh or processed. However production is increasingly constrained by chili plant diseases. The four diseases that lead to wilting in chili are Phytophthora root rot, Verticillium wilt, Rhizoctonia root rot, and Fusarium wilt. The association of Fusarium species with Rhizoctonia solani or root knot nematodes (Meloidogyne spp.) caused huge losses. In this study, seven strains of Pseudomonas aeruginosa were isolated from inner roots of healthy chili plants growing under field condition. In vitro test cell free culture filtrate of some strains showed nematicidal activity against Meloidogyne  javanica  root knot nematode by killing the 2^nd stage juveniles and by retarding the egg hatching.  In dual culture plate assay, one strain of  P. aeruginosa inhibited the radial growth of all the four test root rotting fungi Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and F. oxysporum by producing the zone of inhibition. While other strains caused growth inhibition of at least 2 or 3 test fungi. Some bacterial strains also caused lysis of fungal hyphae. In screen house, application of some of these bacterial strains caused significant suppressive effect on root rotting fungi and root knot nematode infecting chili roots. Some Pseudomonas aeruginosa strains also showed positive impact on plant growth by increasing the plant height and fresh shoot weight and were found to produce indole-acetic acid at varying degree.

¹Agricultural Biotechnology & Phytopathology Laboratory, Department of Botany,

²Biotechnology & Drug Development Laboratory, Department of Biochemistry,

³Post-harvest Technology Laboratory, Department of Food Science & Technology, University of Karachi, Karachi-75270, Pakistan