Abstract
Endophytic mycopopulation isolated from India’s Queen of herbs Tulsi (Ocimum sanctum) were explored and investigated for their diversity and antiphytopathogenic activity against widespread plant pathogens Botrytis cinerea, Sclerotinia sclerotiorum, Rhizoctonia solani and Fusarium oxysporum. 90 fungal isolates, representing 17 genera were recovered from 313 disease-free and surface sterilised plant segments (leaf and stem tissues) from three different geographic locations (Delhi, Hyderabad and Mukteshwar) during distinct sampling times in consequent years 2010 and 2011 in India. Fungal endophytes were subjected to molecular identification based on rDNA ITS sequence analysis. Plant pathogens such as F. verticillioides, B. maydis, C. coarctatum, R. bataticola, Hypoxylon sp., Diaporthe phaseolorum, Alternaria tenuissima and A. alternata have occurred as endophyte only during second sampling (second sampling in 2011) in the present study. Bi-plot generated by principal component analysis suggested tissue specificity of certain fungal endophytes. Dendrogram revealed species abundance as a function of mean temperature of the location at the time of sampling. Shannon diversity in the first collection is highest in Hyderabad leaf tissues (H' = 1.907) whereas in second collection it was highest from leaf tissues of Delhi (H' = 1.846). Mukteshwar (altitude: 7500 feet) reported least isolation rate in second collection. Nearly 23% of the total fungal isolates were considered as potent biocontrol agent. Hexane extract of M. phaseolina recovered from Hyderabad in first collection demonstrated highest activity against S. sclerotiorum with IC50 value of 0.38 mg/ml. Additionally, its components 2H-pyran-2-one, 5,6-dihydro-6-pentyl and palmitic acid, methyl ester as reported by GC-MS Chromatogram upon evaluation for their antiphytopathogenic activity exhibited IC50 value of 1.002 and 0.662 against respectively S. sclerotiorum indicating their significant role in antiphytopathogenic activity of hexane extract. The production of 2H-pyran-2-one, 5,6-dihydro-6-pentyl from M. phaseolina, an endophytic fungus is being reported for the first time.
Highlights
Endophytic fungi inhabit a unique biological niche and are categorized as highly diverse, polyphyletic group of primarily ascomycetous fungi, capable of colonizing tissues of plants asymptomatically without initiating any disease or overt negative symptoms [1], [2], [3]
All the fungal endophytes recovered in the present study belonged to phylum Ascomycota besides Rhizopus oryzae (4.4%: Mucormycotina) that belongs to phylum Zygomycota
The study reports noted plant pathogens such as Bipolaris maydis, Rhizoctonia bataticola and Chaetomium coarctatum in endophytic state harbored inside O. sanctum for the first time
Summary
Endophytic fungi inhabit a unique biological niche and are categorized as highly diverse, polyphyletic group of primarily ascomycetous fungi, capable of colonizing tissues of plants asymptomatically without initiating any disease or overt negative symptoms [1], [2], [3]. Fungal endophytes are believed to be a treasure of structurally and biologically unique natural products as documented previously in several reviews [9], [10], [11], [12], [13], [14]. Because of its well documented therapeutic potential, Ayurveda (Indigenous system of Indian medicine) describes O. sanctum as Sashemani Shwasaharani (antiasthmatic), Kaphaghna (suppressant drug) and believed to promote longevity [17], [18], [19]. It is mentioned as adaptogenic in nature, balancing different processes in the body and helpful for adopting to stress in Charaka Samhita [20]
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