the Symposium on Wheats for More Tropical Environments - cimmyt

174Recent Advances inResearch on Wheat Scab in Chinaz.z. Llu, Plant Protection institute, ShaDghal Academy ofAgricultural ScleDcles, Shanghai, People'. RepubUc of ChiDaA_tractWheat scab (head. blight) caused by Gibberella zeae (Schw.) Petch is one of <strong>the</strong>most serious wheat diseases in South China. especially in <strong>the</strong> middle and lowerreaches of <strong>the</strong> Yangtze River. where <strong>the</strong>re is a hfghfrequency of incidencecausing considerable loss in yield. Scab is estimated to occur on 6.7 millionhectares in China and. in years ofsevere epidemics. losses rangefrom 10 to40~. Comprehensive research has been carried out on causal organisms.resistance of wheat varieties and testsfor resistance. including inoculationmethods. epidemiology and integrated control measures.Wheat scab (head blight). caused byGibberella zeae (SChw.) Petch. occursin almost all of <strong>the</strong> humid and semihumidregions of <strong>the</strong> tropics. <strong>the</strong>subtropics and in certain temperatezones of <strong>the</strong> world. It is one of <strong>the</strong> mostserious wheat diseases in South China.especially in <strong>the</strong> middle and lowerreaches of <strong>the</strong> Yangtse River. where <strong>the</strong>disease has a high incidence andfrequently causes severe losses. During<strong>the</strong> 28 years from 1957 to 1984. <strong>the</strong>rewere four years of severe epidemics and15 years of moderate epidemics in thisregion: <strong>the</strong> average frequency ofepidemics was about 68%. In years ofsevere epidemics. <strong>the</strong> rate of infectedspikes reached more than 50%. andyield loss ranged from 10 to 40%.: inyears with moderate spread. <strong>the</strong> ratesof infected spikes and yield loss were 20to 50% and 5 to 15%. respectively. It isestimated that wheat scab occurs in anarea that covers more than 6.7 mUlionhectares in China (7.8). Besides <strong>the</strong>direct losses caused by <strong>the</strong> disease. <strong>the</strong>pathogen also produces mycotoxins.which can cause mycotoxicoses inhumans and domestic animals (19.20).Therefore. <strong>the</strong>re is a great need to studyand control wheat scab.In 1974. a cooperative research teaminvolving scientists from 12 provincesand cities was organized by <strong>the</strong> ChineseMinistry of Agriculture. Comprehensiveresearch has been carried out on causalorganisms. resistance of wheat varietiesto scab. epidemiology and integratedcontrol measures: signiftcant advanceshave been achieved.Scab-Producing OrganismsFusarium .pp.In 1955. Yu Da-Fu (25) reported that<strong>the</strong> wheat scab-causing species ofFusarium along <strong>the</strong> Yangtse River wereF. graminearum. F. montliforme.F. culmorum and F. avenaceum. From1976 to 1980. <strong>the</strong> cooperative researchteam (1.22.28) collected 2.450 samplesof diseased wheat heads from 21provinces and cities. Eighteen speciesand varieties ofFusarium wereisolated. identlfted and classifted as tohigh. moderate or low levels ofvirulence on wheats.The species and varieties with highvirulence were:• F. graminearum Schwabe• F. camptoceras Wr. and Rg.• F. equtseti (Corda) Sacc. var.compactum (Wr. Joffe)• F. sulphureum SChlecht.• F. culmorum (W.G. Smith) Sacc.