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Effect of Temperature on Lesion Enlargement and Sporulation of Pyricularia oryzae in Rice Leaves. Hajime Kato, National Institute of Agricultural Sciences, Nishigahara, Kita-ku, Tokyo, Japan; Takuji Kozaka, National Institute of Agricultural Sciences, Nishigahara, Kita-ku, Tokyo-Japan, Present address: Tokyo University of Agriculture and Technology, Fuchu-shi, Tokyo. Phytopathology 64:828-830. Accepted for publication 9 January 1974. DOI: 10.1094/Phyto-64-828.

Blast lesions on rice leaves expanded faster but reached a smaller final size at high temp regimes of 32 C continuously, 32/25 C day/night, or 32/20 C day/night in a 12-h thermoperiod than at 25 C or 25/16 C day/night. At 16 C, or 20/16 C day/night, the enlargement rate was slow and constant during the 25 days of observation. The potential for conidium formation reached a peak value earlier at higher temp than at median and lower temp. The maximum potential occurred at the median temp. Sporulation proceeded for more than 20 days at each thermal treatment.

Additional keywords: Oryza sativa, epidemiology.