Endophytic fungal association via gibberellins and indole acetic acid can improve plant growth under abiotic stress: an example of <it>Paecilomyces formosus </it>LHL10

• Main Authors: Khan Abdul, Hamayun Muhammad, Kang Sang-Mo, Kim Yoon-Ha, Jung Hee-Young, Lee Joong-Hwan, Lee In-Jung
• Format: Article
• Language: English
• Published: BMC 2012-01-01
• Series: BMC Microbiology
• Subjects: <it>Paecilomyces formosus </it>LHL10; Salinity; Cucumber plant growth; Gibberellins and indole acetic acid; Endogenous plant hormones
• Online Access: http://www.biomedcentral.com/1471-2180/12/3

<p>Abstract</p> <p>Background</p> <p>Endophytic fungi are little known for exogenous secretion of phytohormones and mitigation of salinity stress, which is a major limiting factor for agriculture production worldwide. Current study was designed to isolate phytohormone producing endophytic fungus from the roots of cucumber plant and identify its role in plant growth and stress tolerance under saline conditions.</p> <p>Results</p> <p>We isolated nine endophytic fungi from the roots of cucumber plant and screened their culture filtrates (CF) on gibberellins (GAs) deficient mutant rice cultivar <it>Waito-C </it>and normal GAs biosynthesis rice cultivar Dongjin-byeo. The CF of a fungal isolate CSH-6H significantly increased the growth of <it>Waito-C </it>and Dongjin-byeo seedlings as compared to control. Analysis of the CF showed presence of GAs (GA₁, GA₃, GA₄, GA₈, GA₉, GA₁₂, GA₂₀and GA₂₄) and indole acetic acid. The endophyte CSH-6H was identified as a strain of <it>Paecilomyces formosus </it>LHL10 on the basis of phylogenetic analysis of ITS sequence similarity. Under salinity stress, <it>P. formosus </it>inoculation significantly enhanced cucumber shoot length and allied growth characteristics as compared to non-inoculated control plants. The hypha of <it>P. formosus </it>was also observed in the cortical and pericycle regions of the host-plant roots and was successfully re-isolated using PCR techniques. <it>P. formosus </it>association counteracted the adverse effects of salinity by accumulating proline and antioxidants and maintaining plant water potential. Thus the electrolytic leakage and membrane damage to the cucumber plants was reduced in the association of endophyte. Reduced content of stress responsive abscisic acid suggest lesser stress convened to endophyte-associated plants. On contrary, elevated endogenous GAs (GA₃, GA₄, GA₁₂and GA₂₀) contents in endophyte-associated cucumber plants evidenced salinity stress modulation.</p> <p>Conclusion</p> <p>The results reveal that mutualistic interactions of phytohormones secreting endophytic fungi can ameliorate host plant growth and alleviate adverse effects of salt stress. Such fungal strain could be used for further field trials to improve agricultural productivity under saline conditions.</p>