In vitro Antifungal Activities of Fungicides against Japanese Plum Fruit Anthracnose Fungi

BACKGROUND: In order to select a fungicide that can effectively control anthracnose disease in Japanese plum fruit, mycelial growth inhibition effect and spore germination inhibition effect of six fungicides were tested in vitro against six isolates of Colletotrichum acutatum and five isolates of C. gloeosporioides that were isolated from diseased Japanese plum fruit. METHODS AND RESULTS: Inhibitory effects of fungicides on mycelial growth were investigated after inoculating each isolate on potato dextrose agar amended with four discriminatory concentrations of each fungicide for 7 days at $25^{\circ}C$. For spore germination inhibitory effect, each isolate of the Colletotrichum spp. was cultured in potato dextrose agar for 7-14 days at $25^{\circ}C$. After adjusting the concentration of spores of each isolate to $1{\times}10^6mL^{-1}$ by diluting with 0.025% PDB, the spore suspension was mixed with each fungicide (1:4, v/v), and $60{\mu}L$ aliquots were dispensed to sterile hole slide glass. Hole slide glasses were placed in a humidified box and incubated for 15 hours at $25^{\circ}C$. Then, spore germination was observed under an optical microscope. At recommended concentration of fungicide prochloraz manganese showed the highest mycelial growth inhibitory effect and dithianon showed the lowest mycelial growth inhibition. The $EC_{50}$ values for the inhibition of spore germination by dithianon and pyraclostrobin were $0.069-0.126{\mu}g/mL$ and $0.37-1.59{\mu}g/mL$, respectively. Although benomyl, prochloraz manganese, azoxystrobin, and tebuconazole did not inhibit the spore germination, they appeared to restrain mycelial growth by abnormal growth of germ tube and mycelium after germination. CONCLUSION: Dithianon seemed to have preventive effect. Prochloraz manganese, azoxystrobin, and tebuconazole were likely to have control effect. Pyraclostrobin is considered to have both preventive and control effect against anthracnose disease of Japanese plum fruit.

자두 탄저병균에 대한 살균제의 활성

탄저병이 발생한 자두에서 분리된 C. acutatum 6개와 C. gloeosporioides 5개 균주에 대한 benoomyl, prochloraz manganese complex, azoxystrobin, pyraclostrobin, tebuconazole 및 dithianon의 균사생장억제효과와 포자발아억제효과를 in vitro에서 검정하였다. 포장 권장사용농도를 기준으로 비교하면, prochloraz manganese가 탄저병 균주의 균사생장을 가장 효과적으로 억제하였다. 포자발아억제에서는 dithianon과 pyraclostrobin의 효과가 가장 높았다. Benomyl, prochloraz manganese complex, azoxystrobin 및 tebuconazole은 포자의 발아를 억제하지는 않았으나, 발아 후 비정상적인 발아관의 신장을 유기하여 균사생장 억제하였다. 본 연구의 결과를 통해 자두 탄저병에 대하여 dithianon은 예방효과, prochloraz manganese, azoxystrobin, tebuconazole 등은 치료효과, pyraclostrobin은 예방 및 치료효과가 높은 약제로 판단되며, 포장 적용시험을 통해 자두의 탄저병을 효과적으로 방제할 수 있는 약제를 선발해야 할 것이다.