R. Priyanka ¹, S. Nakkeeran ¹, I. Arumuka Pravin ¹, A. S. Krishna Moorthy ¹, U. Sivakumar ²

Affiliations
1 Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore – 641003, Tamil Nadu, IN
2 Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, IN

Abstract

Biological control with bioagents is a cost effective alternate method for the management of crop diseases. The antagonistic bacterial strains were explored for the management of leaf blight of marigold which is caused by Alternaria alternata. The present study clearly proved that the mycelial growth of A. alternata was inhibited up to 83% by Bacillus subtilis subsp. spizizenii (MM19) in vitro. GC/MS analysis of partially purified extracts of B. subtilis subsp. spizizenii (MM19) revealed the presence of antifungal Phthalic acid esters which might be responsible for the inhibition of the pathogen. Foliar application of B. subtilis subsp. spizizenii (MM19) under field conditions suppressed leaf blight by 77%. This study highlighted the potential of B. subtilis subsp. spizizenii (MM19) for the management of Alternaria leaf blight.

Keywords

Alternaria, Bacillus subtilis Subsp. spizizenii, GCMS, PCR.

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P. R. Nithya ¹, S. Manimegalai ¹, S. Nakkeeran ², S. Mohankumar ³, S. Jayarajan Nelson ¹

Affiliations
1 Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore – 641003, Tamil Nadu, IN
2 Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore – 641003, Tamil Nadu, IN
3 Centre for Plant Molecular Biology and Biotechnology, Tamil Nadu Agricultural University, Coimbatore – 641003, Tamil Nadu, IN

Abstract

Entomopathogenic fungi are known to produce a multitude of low molecular weight secondary metabolites involved in different biological processes including fungal development, intercellular communication and interaction with other organisms in complex niches. In the present investigation, heterogeneity in metabolome profile of three isolates of Beauveria bassiana viz., MH590235 (TM), MK918495 (BR) and KX263275 (BbI8) were analyzed through GC-MS. Distinct differences in metabolite profile of the isolates were observed. A total of 63 metabolites were detected from all the isolates combined. Metabolites, 5-Oxotetrahydrofuran-2-carboxylic acid and undecane were found to be specific to BR isolate. Macrocyclic gamma lactones were detected in culture filtrates of BR and BbI8, oleic acid and hexadecanoic acid in TM and BR. An insecticidal compound, levoglucos an was detected in all the fungal isolates. Among the isolates, TM revealed higher variability in the metabolite production through PCA analysis. The metabolome of TM isolate contained compounds having several biological functions, viz., insecticidal and antimicrobial activity, lipid and fatty acid metabolisms and virulence enhancing factors.

Keywords

Beauveria bassiana, Biological Functions, GC-MS, Metabolome Heterogeneity, PCA Analysis.

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S. B. AKSHAYA ¹, A. S. KRISHNAMOORTHY ², S. NAKKEERAN ², U. SIVAKUMAR ³, G. THIRIBHUVANAMALA ²

Affiliations
1 College of Agricultural Sciences – SRM Institute of Science and Technology, Baburayanpettai – 603203, Chengalpattu, Tamil Nadu, IN
2 Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore – 641003, Tamil Nadu, IN
3 Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore –641003, Tamil Nadu, IN

Abstract

Plant diseases especially wilt disease caused by Fusarium spp. pose a major threat to the cultivation of vegetables. In the present study, experiments were undertaken to explore the potential antifungal metabolites produced by macro basidiomycetes viz., Lentinus edodes, Ganoderma lucidum and Schizophyllum commune against Fusarium oxysporum and F. solani causing wilt disease of cucumber and capsicum. Among these, the ethyl acetate fraction of Cell-Free Culture Filtrate (CFC) of L. edodes exhibited maximum per cent inhibition of the mycelial growth of F. oxysporum and F. solani (61.11 and 57.77 %, respectively) at a concentration of 2000 ppm. Characterization of antifungal metabolites of Cell Free Condensate (CFC) of ethyl acetate fraction of L. edodes observed as prominent bands in Thin Layer Chromatography (TLC) indicated with an RF value of 0.25 and 0.69. Further GC-MS characterization of TLC-eluted compounds from L. edodes indicated the presence of 14 different compounds including 2H-pyran-2-one 6-pentyl-, possessing antifungal activity. The Fourier-transform Infrared Spectroscopy  (FTIR) spectrum revealed the functional groups such as alcohol (O-H), amides (C-O), aliphatic polyes (CH₂), triazenes (N=N), silicon compounds (Si-O-Si), amines (C-N) and phosphorus (P=S). The comparison of metabolite distribution patterns by Principal Component Analysis (PCA) obtained from L. edodes (PC 1) showed a positive correlation between the compounds. This study infers that L. edodes possess antifungal activity against F. oxysporum and F. solani that can be explored for formulation and application of these antifungal compounds in plant protection.

Keywords

Antifungal activity, Cell-Free Condensate (CFC), FTIR, macro basidiomycetes, mycelial inhibition.

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