VIEW ARTICLE

Potential for Conidium Formation of Pyricularia oryzae in Lesions on Leaves and Panicles of Rice. Hajime Kato, Laboratory of Plant Pathology, The Tohoku National Agricultural Experiment Station, Omagari, Japan, Present address of senior author: The National Institute of Agricultural Sciences, Nishigahara, Kita-ku, Tokyo; Tsugio Sasaki(2), and Yukio Koshimizu(3). (2)(3)Laboratory of Plant Pathology, The Tohoku National Agricultural Experiment Station, Omagari, Japan. Phytopathology 60:608-612. Accepted for publication 20 October 1969. DOI: 10.1094/Phyto-60-608.

The potential for conidium formation by Pyricularia oryzae in lesions on rice leaves increased rapidly and decreased slowly with time. Conidium formation reached a peak from 3 to 8 days after appearance of lesions, when they developed a central grey zone with a dark purple-brown margin. Sporulation was heavier in lesions when expanding leaves were inoculated than when inoculations were made 3 or 4 days after they became fully expanded. Lesions on the upper five leaves of each culm could produce conidia at the initial heading stage of a population of rice plants. The peak of sporulation in lesions on the penultimate leaf inoculated during its expansion coincided with the initial stage of heading. In spikelets, the presporulation period was shorter than in the rachis and in the neck node. The peak of potential for sporulation of spikelets and of neck nodes inoculated at the time of their emergence occurred from the 4th to the 8th day, and from the 8th day after appearance of lesions, respectively. Spikelets and neck nodes inoculated 10 days after their emergence had much lower yield potential than ones inoculated just after emergence. Maximum conidium production on the infected rachises occurred from 10 to 20 days after lesions appeared. These diseased organs on the panicle could supply conidia to neighboring panicles.