Biological evaluation of neopeptins isolated from a Streptomyces strain.
BACKGROUND
Microbial secondary metabolites are a rich source of antifungal agents and have merit as alternatives to synthetic fungicides. To develop disease control agents against powdery mildew, the lipopeptide antibiotic neopeptins were identified from the culture broth of a Streptomyces sp., and in vivo control efficacy of the compounds was evaluated on cucumber plants under glasshouse conditions.


RESULTS
The Streptomyces sp. KNF2047 antagonistic against powdery mildew development in cucumber plants was isolated from a soil sample. Antifungal compounds were purified from the culture broth and identified as neopeptin A and B. In vitro microtitre assays revealed the inhibitory activities of the compounds in the range 128-512 microg mL(-1) against the mycelial growth of Alternaria mali, Botrytis cinerea, Cladosporium cucumerinum, Colletotrichum lagenarium, Didimella bryoniae and Magnaporthe grisea. Although neither compound showed remarkable in vitro antifungal activity against other plant pathogenic fungi, a mixture of neopeptins (484 mg of neopeptin A and 290 mg of neopeptin B per gram of partially purified powder) showed potent protective and curative activity against cucumber powdery mildew in vivo. The disease control activity of the neopeptins at a concentration of 2.4 mg L(-1) was 92.1%, which was similar to that of the commercial fungicide fenarimol (89.3% at 63 mg L(-1)) and that of the commercial biocontrol agent Actinovate (67.4% at 2 x 10(7) cfu L(-1)).


CONCLUSIONS
Neopeptin mixtures isolated from Streptomyces sp. KNF2047 showed potent disease control activity against powdery mildew development on cucumber plants. .
Kim
Yun Sung
YS
Biopesticide Research Unit, Central Research Institute of Kyung Nong Corporation, Gyungju, Gyungbuk, Korea.
Kim
Hyeong Min
HM
Chang
Cheol
C
Hwang
In Cheon
IC
Oh
Hyuncheol
H
Ahn
Jong Seog
JS
Kim
Ki Deok
KD
Hwang
Byung Kook
BK
Kim
Beom Seok
BS
D001203:Ascomycota / Q000187:drug effects*; D018553:Cucumis sativus / Q000382:microbiology; D047630:Depsipeptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D005659:Fungicides, Industrial / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010935:Plant Diseases / Q000382:microbiology; D013302:Streptomyces / Q000737:chemistry*
D047630:Depsipeptides; D005659:Fungicides, Industrial; C526112:neopeptin A; C526113:neopeptin B