Plant growth promotion and Penicillium citrinum.
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.


CONCLUSIONS
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.
Khan
Sumera Afzal
SA
Department of Life Science and Biotechnology, Kyungpook National University, South Korea. shumakhan@gmail.com
Hamayun
Muhammad
M
Yoon
Hyeokjun
H
Kim
Ho-Youn
HY
Suh
Seok-Jong
SJ
Hwang
Seon-Kap
SK
Kim
Jong-Myeong
JM
Lee
In-Jung
IJ
Choo
Yeon-Sik
YS
Yoon
Ung-Han
UH
Kong
Won-Sik
WS
Lee
Byung-Moo
BM
Kim
Jong-Guk
JG
D019659:Asteraceae / Q000382:microbiology; D027466:Atriplex / Q000187:drug effects / Q000254:growth & development*; D001681:Biological Assay; D004271:DNA, Fungal / Q000235:genetics; D005874:Gibberella / Q000378:metabolism; D005875:Gibberellins / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D012275:Oryza / Q000145:classification / Q000187:drug effects / Q000254:growth & development*; D010407:Penicillium / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology
D004271:DNA, Fungal; D005875:Gibberellins