Abstract
Ten marine-derived fungi crude extracts, namely Emericella stellatus KUFA0208, Eupenicillium parvum KUFA0237, Neosartorya siamensis KUFA0514, N. spinosa KUFA 0528, Talaromyces flavus KUFA 0119, T. macrosporus KUFA 0135, T. trachyspermus KUFA0304, Trichoderma asperellum KUFA 0559, T. asperellum KUFA 0559 and T. harzianum KUFA 0631 were determined for their fungicidal activity against five rice pathogens in vitro. The results showed that the extracts of E. stellatus KUFA0208 and N. siamensis KUFA0514 exhibited the best antifungal activity, causing complete cessation of the mycelial growth of Alternaria padwickii, Bipalaris oryzae, Fusarium semitectum, Pyricularia oryzae and Rhizoctonia solani at 10 g/L. The N. siamensis KUFA0514 extract was fractioned and antifungal compounds were found in the fractions derived from petroleum-ether and chloroform (7: 3) evidenced by inhibition zones against the mycelial growth of A. padwickii around the disc containing each fraction. Moreover, in rice growth promotion tests, diluted cultural broth of T. asperellum KUFA 0559 and T. harzianum KUFA 0631 were found to strongly promote rice shoot and root elongation; however, higher concentrations of all marine fungal broths resulted in significantly reduced rice seedling growth rather than promotion. Meanwhile, Trichoderma showed great indole-3-acetic acid (IAA) production leading to the optimum IAA values of 45.38 and 52.30 µg/ml at 11 and 13 days after inoculation, respectively. The results of this study indicated that marine fungi are promising agents having antagonistic mechanisms involving antibiosis production and plant growth promotion and may be developed as novel biocontrol agents for rice disease management.
Highlights
Marine invertebrates are multicellular animals such as sponges, corals and sea fans
Ten marine-derived fungi crude extracts, namely Emericella stellatus KUFA0208, Eupenicillium parvum KUFA0237, Neosartorya siamensis KUFA0514, N. spinosa KUFA 0528, Talaromyces flavus KUFA 0119, T. macrosporus KUFA 0135, T. trachyspermus KUFA0304, Trichoderma asperellum KUFA 0559, T. asperellum KUFA 0559 and T. harzianum KUFA 0631 were determined for their fungicidal activity against five rice pathogens in vitro
The results showed that the extracts of E. stellatus KUFA0208 and N. siamensis KUFA0514 exhibited the best antifungal activity, causing complete cessation of the mycelial growth of Alternaria padwickii, Bipalaris oryzae, Fusarium semitectum, Pyricularia oryzae and Rhizoctonia solani at 10 g/L
Summary
Marine invertebrates are multicellular animals such as sponges, corals and sea fans. Some marine invertebrates can produce a diversity of bioactive compounds that are used in the pharmaceutical and agrochemical industries.[1,2,3,4] Especially, marine sponges are considered as an important source of natural products for cytotoxic, antibiotic and anti-cancer compounds.[5,6,7] In addition, marine sponges are the host of various symbiotic microorganisms such as archaic, bacteria, cyanobacteria, fungi and microalgae which are sources of various natural products.[8,9,10] Marine-derived fungi can be found in the marine ecosystem growing together with marine invertebrates. Talaromyces tratensis KUFA 0091, which was isolated from the marine sponge, Mycale sp., possessed high potential biological activity in controlling rice pathogens, namely, Alternaria padwickii, Curvularia lunata, Fusarium moniliforme, and Bipolaris oryzae.[21,24] The ethyl acetate crude extract of T. tratensis displayed mycelial inhibition of B. oryzae at concentrations increasing from 100 ppm to 10,000 ppm, with values ranging from 52.36% - 100% inhibition in vitro.[21] Under field conditions, the application of the spore suspension and its crude extract effected reduction of disease incidence of up to 60%.21,24 This marine fungus proved to be a potent agent in controlling post-harvest disease stem end rot on mango fruit caused by Lasiodiplodia theobromae.[25] many crude extracts isolated from marine fungi isolated from Thai waters showed potent antifungal activity on plant pathogens at 1 g/ L using dilution plate assays.[26] In addition, these marine fungi were found able to tolerate salinity at NaCl concentrations of up to 10% by increasing osmotic pressure.[22,27]
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