Screening,identification and biological characteristics of high IAA-producing strains of Paphiopedilum micranthum
[Objective]This study aims to screen and identify the high IAA-producing strains from the roots and leaves of Paphiopedilum micranthum and investigate the biological characteristics of the strains.[Method]The endophytic fungus was isolated from roots and leaves by using the tissue isolation method and identified based on their morphology and rDNA-ITS molecular biology.Moreover,the Salkowski colourimetric method was employed to screen the isolated strains with high IAA(indole-3-acetic aci)yield.Simultaneously,a single-factor experimental method was conducted to explore the optimal growth conditions for strain YD-16(Nemania cyclobalanopsina).[Result]The results indicated that thirty-three isolated strains were ultimately identified as 12 species belonging to 8 genera and they all differed in indole-3-acetic acid(IAA)production capability.The highest IAA yield was found in YD-16 strain.It could reach IAA level of(59.29±0.46)μg/mL and(17.36±0.09)μg/mL respectively when YD-16 strain was cultured in media with or without L-tryptophan.An optimal condition for the growth of YD-16 strain was in the neutral media with additives of protein peptone as nitrogen source,sucrose as carbon source under constant temperature of 25℃and dark condition.[Conclusion]Twelve species belonging to eight genera of endophytic fungus were identified from 33 strains obtained from leaves and roots of P.micranthum.Genus Biscogniauxia,Diaporthe,Hypoxylon,Nigrospora,and Xylaria were first reported to be isolated from P.micranthum.YD-16 strain had a high IAA production capacity.The nitrogen source preference was peptone,and the carbon source preference was sucrose and starch.The results lay a foundation for further study on nutrient physiological characteristics of YD-16 strain,its utilization and the conservation of P.micranthum.
Paphiopedilum micranthumendophytic fungiIAA secretion abilityoptimal conditions for growth
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