Abstract

Biocontrol of plant diseases through induction of systemic resistance is an environmental friendly substitute to chemicals in crop protection measures. Different biotic and abiotic elicitors can trigger the plant for induced resistance. Present study was designed to explore the potential of Pseudomonas aeruginosa PM12 in inducing systemic resistance in tomato against Fusarium wilt. Initially the bioactive compound, responsible for ISR, was separated and identified from extracellular filtrate of P. aeruginosa PM12. After that purification and characterization of the bacterial crude extracts was carried out through a series of organic solvents. The fractions exhibiting ISR activity were further divided into sub-fractions through column chromatography. Sub fraction showing maximum ISR activity was subjected to Gas chromatography/mass spectrometry for the identification of compounds. Analytical result showed three compounds in the ISR active sub-fraction viz: 3-hydroxy-5-methoxy benzene methanol (HMB), eugenol and tyrosine. Subsequent bioassays proved that HMB is the potential ISR determinant that significantly ameliorated Fusarium wilt of tomato when applied as soil drench method at the rate of 10 mM. In the next step of this study, GC-MS analysis was performed to detect changes induced in primary and secondary metabolites of tomato plants by the ISR determinant. Plants were treated with HMB and Fusarium oxysporum in different combinations showing intensive re- modulations in defense related pathways. This work concludes that HMB is the potential elicitor involved in dynamic reprogramming of plant pathways which functionally contributes in defense responses. Furthermore the use of biocontrol agents as natural enemies of soil borne pathogens besides enhancing production potential of crop can provide a complementary tactic for sustainable integrated pest management.

Highlights

  • Tomato (Solanum lycopersicum L.) is a member of family Solanaceae, cultivated worldwide, ranked first among the processing crops and second as a vegetable crop

  • Initial Screening of Metabolites Involved in induced systemic resistance (ISR) from Pseudomonas aeruginosa PM12

  • Searching of ISR Determinants from Extracellular Metabolites of Bacterial Strains. In this experiment extracellular metabolites/cell-free culture filtrates (CFCF) of P. aeruginosa PM12 were examined for the presence of ISR determinant/s

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Summary

Introduction

Tomato (Solanum lycopersicum L.) is a member of family Solanaceae, cultivated worldwide, ranked first among the processing crops and second as a vegetable crop. In Pakistan it is cultivated on about 58.196 thousand hectares with an annual production of 574.052 thousand tons (FAO, 2013). It contains valuable nutrients like vitamin A and C, calcium, phosphorus, potassium and magnesium. Induced Systemic Resistance against Fusarium Wilt (United States Department of Agriculture [USDA], 2009). It is a source of an antioxidant compound named lycopene that has been found helpful against cancer (Miller et al, 2002). Disease control strategies include use of resistant tomato varieties with cultural, chemical and biological control (Agrios, 2005; Pottorf, 2006). Used biological control employed induced systemic resistance (ISR) mechanism using rhizospheric plant growth-promoting bacteria against fungal pathogens (Pieterse et al, 2014)

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