Occurrence and meteorological factors of corn rust disease and yield losses

Abstract

玉米銹病在本省有普通型（由Puccinia sorghi引起）及南方型（由P. polysora引起）兩種。然而，目前以南方型銹病發生較為普遍。銹病病勢進展一般呈開口向下之二次方曲線，但發病較重時則呈一次方直線。銹病的發生和氣象因子有關，春作玉米南方型誘病的發生和發病7天前之溫度24.1~28.0℃及28.1~32.0℃相關最大，秋作玉米則和8~14天前之溫度20.1~24.0℃、24.1~28.0℃及28.1~32.0℃相關最大。利用複迴歸分析鎊病病斑面積率及侵染速率和氣象因子之關係可得到迴歸方程式，將不同年代、不同期作之氣象因子代入方程式時可得到預測值，經比較預測值與實測值甚為接近，可做為預測之用。 在產量損失方面，本省尚缺有關研究報告。在國外，Russell 1965年報告，普通型銹病利用6個雜交組合經過兩年的結果，其產量損失在15.3~23.5％。Kim及Brew-baker 1976年報告普通型銹病對產量及農藝性狀之影響，在子實產量有35％之減產，在鮮草重有27％之損失，在穗長有11％之差異，在穗徑有10％之不同，在株高、穗位高及吐絲期有5%之差別。Randle等1984年利用兩個甜玉米品系Jubilee（中感）及StylePak（感）觀察其農藝性狀之差異，結果顯示在銹病發生區及無銹病區在吐絲期，穗長、穗徑及果穗含水率均有明顯的差異。Pataky1987年利用甜玉米品系Gold Cup（中抗）、Stylepak（感）及Florida Staysweet（感）來比較普通型銹病引起之產量損失，結果顯示收穫前一週調查時每10％銹病引起6%穗重及6.5％穗數之損失。在南方型銹病方面，Rodriguez-Ardon等1980年報告利用感病雜交品系在1976及1978從5月25日開始每隔兩週種植一次，共種三次，其予實產量減產4、23及45%，所以晚植者產量損失特別高。 Two kinds of corn rust, common rust (Puccmia sorghi) and southern rust (P. polysora) were found in Taiwan, However, southern rust is more wide-spread at present. Disease development of corn rust showed quadratic regression curve equations in general, but it showed linear equations when the disease was serious. By analyzing the single correlation of rust and meteerolgical factors, it indicated that the most important factors were temperature 24.1~28.0℃ and 28.1~32.0℃ seven days before disease occurrence during spring crop, and 20.1~24.0℃、24.1~28.0℃、28.1~32.0℃ 8~14 days before disease occurrence during fall crop. By analyzing the relationship between increasing infected leaf area percentage and meteorological factors, 8 equations were obtained, while 11 equations were obtained from the relationship between infection rate and meteorological factors Those equations were derived from fall crop of 1990 at Chia-yi area. The predicted values from those equations obtained were very close to the obsened values, therefore, it is suggested that those equations might be used for predicting rust disease of corn. For yield losses caused by rust disease, not much information was found in Taiwan. Russell in 1965 reported that the losses on grain yields caused by common rust were 15.3?3.5% after 2 years tests on 6 crosses. Kim and Brew- baker in 1976 indicated that the effects of common rust on grain yield was 35%, fresh plant weight with ear was 27%, ear length was 11%, 10% on ear diameter, and 5% difference on plant height, car height, and silking stage. Randle et a in 1984 by using two sweet corn lines Jubilee (moderate susceptible) and Stylepak (susceptible) to observe the differnces on agronomic characteristics, the results showed that the silking stage, ear length, ear diameter and ear water content were quite different on rusted and non-rusted plots. Pataky in 1987 estimated that yield reduction due to common rust on Gold Cup (moderate resistant), Stylepak (susceptible) and Florida Staysweet (susceptible) was 6% of the maximum total ear weight and 6.596 of the maximum total number of marketable ears for each 11)36 rust severity. Roe driguez-Ardon et al showed that on susceptible hybrids, in three biweekly plantings (beginning about 25 May) in 1976 and 1978, southern rust caused average yield reductions of 4、23 and 45% respectively