Endophytic Fungal Pre-treatments of Seeds Alleviates Salinity Stress ffects in Soybean Plants
Ramalingam Radhakrishnan1, Abdul Latif Khan1,2, and In-Jung Lee1*
1School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Republic of Korea, 2Department of Biological Sciences and Chemistry, University of Nizwa, Nizwa, Oman
Journal of Microbiology, 51(6),850–857, 2013,
antioxidants, endophytic fungi, phytohormones, soybean
In the present study, four endophytic fungi (GM-1, GM-2,
GM-3, and GM-4) were tested for their ability to improve
soybean plant growth under salinity stress conditions. The
seed germination and plant growth were higher in seeds pretreated
with endophytic fungal cultures than their controls.
The positive influence of fungi on plant growth was supported
by gibberellins analysis of culture filtrate (CF), which
showed wide diversity and various concentrations of GAs.
Specifically, GA4, GA7, GA8, GA9, GA12, and GA20 were
found in fungal CFs. Under salinity stress conditions, GM-1
significantly enhanced the length and fresh weight of soybean
plants relative to other fungal treatments. GM-1 effectively
mitigated the adverse effects of salinity by limiting
lipid peroxidation and accumulating protein content. GM-2,
GM-3, and GM-4 also counteracted the salinity induced
oxidative stress in soybean plants through reduction of lipid
peroxidation and enhancement of protein content, maintaining
the length and fresh weight of shoots. The activities
of the antioxidant enzymes catalase, superoxide dismutase
and peroxidase were inhibited in salinity exposed plants,
while GM-1 significantly enhanced these antioxidant enzyme
activities in plants under salt stress. GM-1 treatment also
showed lower levels of abscisic acid and elevated levels of
salicylic acid in plants under salinity stress. Hence, GM-1 was
identified as Fusarium verticillioides (teleomorph Gibberella
moniliformis) isolate RK01 based on its DNA sequence homology.
These results suggest that endophytic fungal (F.
verticillioides) pre-treatment of soybean seeds would be an
effective method to promote soybean plant growth under
salinity stress conditions.