Prediction of Rice Leaf Blast. I. Meteorological Variables and the Development of the Number of Lesions

Abstract

利用逐步迥歸法分析氣象變數與水稻臺南五號及臺農六十七號葉稻熱病之關係，建立十三個預測方程式，以預測葉稻熱病S型病斑數目之進展。當不同年度之氣象變數及發病資料綜合分析時所得之預測方程式，其預測值與實測值比各年度之個別資料分析時所得之預測方程式更為接近。 綜合分析由第一組氣象變數所得之預測方程式所包含之變數有最低氣溫、平均氣溫、氣溫在21~24℃之小時數，最高相對濕度、相對濕度90%以上之小時數及雨量等六個變數，而由第二組氣象變數所得之預測方程式所包含之變數有氣溫在18.1~21℃之小時數，24.1~27.0℃之小時數，相對濕度75.1～85.0%之小時數，90.1~95.0%之小時數及降雨量等五個變數。個別分析第一組氣象變數所得之預測方程式所包含之變數有最低氣溫、氣溫在21~24℃之小時數及最高相對濕度等三個變數，而由第二組氣象變數所得之預測方程式所包含之變數有氣溫15.1~18.0℃之小時數，相對濕度75.1~85.0％之小時數，相對濕度85.1~90.0%之小時數及露水時間等四個變歡，不同之預測方程式包．含3~4個不同之氣象變數。 預測方程式之R2（決定係數）均達極顯著，同時其平均變異值除有二個方程式在預測1977及1978年時高於10％以外，其餘變異值均在10%以下，故所得之預測方程式具有準確性。 A stepwise regression was used to analysis the relationships between meteorological variables and blast incidence of rice cultivars, Tainan 5 and Tainung 67. Thirteen predicting cquations were obtained for predictir.g the development of the number of “S” lesions. When data from various years were combined for analysis, the equations obtained were more agreeable between measured and estimated values than equations derived from those of individual years. The most important independent variables included in the predicting equations derived from the first group of meteorological variables combined together for analysis, were minimum temperature, average temperature, hours of temperature 21-24℃, maximum RI-I, hours of RH over 90%, and quar.tity of rainfall. The independent variables in the equations derived from the second group of meteorological variables, were hours of temperature 18.1-21.0℃ and 24.1-27.0℃, hours of RH 75.1-85.0% and 90.1-95.0%, and quantity of rainfall. When the meteorological variables were analyzed separately, the independent variables included in the equations from the first group of meteorological variables, were minimum temperature, hours of temperature 21-24℃, and maximum RH. The independent variables from the second group of meteorological variables, were hours of temperature 15.1-18.0℃, hours of RH 75.1-85.0% and 85.1-90.0%, and dew period. Each predicting equations contained 3 to 4 various meteorological variables. Coefficients of determination (R2) in the predicting equations were significant at 1% level, and the average variations of all the equations, were under 10% except two of them showing higher than 10% in 1977 and 1978. Therefore, it was thought that the equations were reliable for predicting the development of “S” lesions of rice leaf blast