Effects of Temperature, Relative Humidity, and Leaf Wetness Period on the Development of Rice Leaf Blast

잎도열병(稻熱病) 발생(發生)에 미치는 온도(溫度), 상대습도(相對濕度) 및 잎표면상(表面上)의 수분존재시간(水分存在時間)의 영향(影響)

  • Choi, W.J. (Dept. of Agric. Biology, Seoul National University) ;
  • Park, E.W. (Dept. of Agric. Biology, Seoul National University) ;
  • Lee, E.J. (Dept. of Plant Pathology, Agricultural Sciences Institute)
  • 최우정 (서울대학교 농생물학과) ;
  • 박은우 (서울대학교 농생물학과) ;
  • 이은종 (농촌진흥청 농업기술연구소 병리과)
  • Published : 1987.12.30

Abstract

The optimum temperature range for conidial germination of Pyriculacia oryzae on a slide glass was $26{\sim}30^{\circ}C$, at which at least four hours of leaf wetness period was required to germinate. Conidial germination was significantly reduced under dry conditions (relative humidity<85%) at $34^{\circ}C$ but not at lower temperature (18, 22, 26, $30^{\circ}C$). Number of lesions developed were greater at $26^{\circ}C$ than at other temperature tested. The average leaf wetness period required for production of a lesion per plant was 22 hours at $18^{\circ}C$, 16 hours at $22^{\circ}C$, 10 hours at $26^{\circ}C$, and 8 hours at $30^{\circ}C$. Less than one lesion per plant occurred at $34^{\circ}C$ even under 24 hours of leaf wetness period. The time period between inoculation and lesion appearance was $7{\sim}8$ days at $18^{\circ}C$, $4{\sim}5$ days at $22^{\circ}C$ and $26^{\circ}C$, and $3{\sim}4$ days at $30^{\circ}C$. The time period required for lesion appearance after inoculation was not affected by leaf wetness period and relative humidity. Lesion length increased most rapidly at $30^{\circ}C$ during the first four days after lesion appearance. Thereater, the rate of increase in lesion length was geratest at $26^{\circ}C$. The average increment of lesion length per day when relative humidity was greater than 90% was 0.7mm at $18^{\circ}C\;and\;22^{\circ}C$, 1mm at $26^{\circ}C$, and 0.8mm at $30^{\circ}C$. When relative humidity was less than 85%, the increments of lesion length per day were approximately $50{\sim}60%$ of those under humid conditions (relative humidity>90%) at all temperature regimes except $30^{\circ}C$. Relative humidity did not significantly affected lesion length at $30^{\circ}C$.

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