Influence of several surfactans, solvents, and fungicides on the activity of Pyricularia oryzae cavara and the rice blast severity.
1989
Kim B.S. | Chung Y.R. | Cho K.Y.
Influences of serveral surfactants and organic solvents on the activity of Pyricularia oryzae Cavara and the occurrence of rice blast were investigated to get information of establishment of a screening system for fungicides of newly synthesized chemicals. Relationship between in vitro tests and in vivo tests was also analyzed in the experiment using three effective fungicides for rice blast, such as Blasticidin-S, Isoprothiolane, and Tricyclazole. All organic solvents except acetone used in the tests induced phytotoxicity to the rice plants and reduced the severity of rice blast. Acetone, however, had no effect on disease severity and the growth of P. oryzae even at high concentration of 40 %. Among four tested surfactants, Tween-20 inhibited neither spore germination nor mycelial growth of P. oryzae at 1,000 ppm. But other three surfactants, NP-13.3, Triton, and LE-13.6 reduced spore germination and mycelial growth of the fungi at 100 ppm. Control values of Blasticidin-S and Isoprothiolane against rice blast in vitro tests were correlated very well with the efficacy of these fungicides in the inhibition of spore germination and mycelial growth of the pathogen. Tricyclazole, on the other hand, was not effective in the inhibition of mycelial growth or spore germination of P. oryzae in vitro tests, but this fungicide highly reduced the severity of rice blast in vivo tests. Based on these results, it seems that acetone and Tween-20 are proper organic solvent, and surfactant, respectively, in a fungicide screening system for rice blast. The bioassay using plants appears to be more effective as a fungicide screening system than an in vitro assay.
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