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Open Access Highly Accessed Research article

Plant growth promotion and Penicillium citrinum

Sumera Afzal Khan17, Muhammad Hamayun2, Hyeokjun Yoon1, Ho-Youn Kim6, Seok-Jong Suh1, Seon-Kap Hwang1, Jong-Myeong Kim1, In-Jung Lee2, Yeon-Sik Choo3, Ung-Han Yoon3, Won-Sik Kong5, Byung-Moo Lee4 and Jong-Guk Kim1*

Author Affiliations

1 Department of Life Science and Biotechnology, Kyungpook National University, South Korea

2 Department of Agronomy, Kyungpook National University, South Korea

3 Department of Biology, Kyungpook National University, South Korea

4 Department of Agricultural Bio-resource, National Academy of Agricultural Science, RDA, South Korea

5 Department of Herbal Crop Research, National Institute of Horiticultural & Herbal Science, RDA, South Korea

6 Department of Horticulture, University of California-Davis, USA

7 Center of Biotechnology, University of Peshawar, Pakistan

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BMC Microbiology 2008, 8:231  doi:10.1186/1471-2180-8-231

Published: 22 December 2008

Abstract

Background

Endophytic fungi are known plant symbionts. They produce a variety of beneficial metabolites for plant growth and survival, as well as defend their hosts from attack of certain pathogens. Coastal dunes are nutrient deficient and offer harsh, saline environment for the existing flora and fauna. Endophytic fungi may play an important role in plant survival by enhancing nutrient uptake and producing growth-promoting metabolites such as gibberellins and auxins. We screened roots of Ixeris repenes (L.) A. Gray, a common dune plant, for the isolation of gibberellin secreting endophytic fungi.

Results

We isolated 15 endophytic fungi from the roots of Ixeris repenes and screened them for growth promoting secondary metabolites. The fungal isolate IR-3-3 gave maximum plant growth when applied to waito-c rice and Atriplex gemelinii seedlings. Analysis of the culture filtrate of IR-3-3 showed the presence of physiologically active gibberellins, GA1, GA3, GA4 and GA7 (1.95 ng/ml, 3.83 ng/ml, 6.03 ng/ml and 2.35 ng/ml, respectively) along with other physiologically inactive GA5, GA9, GA12, GA15, GA19, GA20 and, GA24. The plant growth promotion and gibberellin producing capacity of IR-3-3 was much higher than the wild type Gibberella fujikuroi, which was taken as control during present study. GA5, a precursor of bioactive GA3 was reported for the first time in fungi. The fungal isolate IR-3-3 was identified as a new strain of Penicillium citrinum (named as P. citrinum KACC43900) through phylogenetic analysis of 18S rDNA sequence.

Conclusion

Isolation of new strain of Penicillium citrinum from the sand dune flora is interesting as information on the presence of Pencillium species in coastal sand dunes is limited. The plant growth promoting ability of this fungal strain may help in conservation and revegetation of the rapidly eroding sand dune flora. Penicillium citrinum is already known for producing mycotoxin citrinin and cellulose digesting enzymes like cellulase and endoglucanase, as well as xylulase. Gibberellins producing ability of this fungus and the discovery about the presence of GA5 will open new aspects of research and investigations.