| Cyathula officinalis Dieback is a new and destructive disease of Cyathula officinalis in Sichuan in recent years.On this paper,the symptoms of the disease,the isolation and identification of the pathogen,biological characteristics and indoor fungicides screening was studied first and systematically.Also,the soluble protein,isoesterase patterns and acid phosphatase patterns of Phoma Cyathula were investigated.The main results are as follows.1.Symptoms of Cvathula officinalis Dieback and the pathogen identificationCyathula officinalis Dieback mainly damaged the stalks and wattles,sometimes also leaves.In the beginning,some small watery spots appeared,which would gradually developed into some approximate rounds or dark brown spots in size of 3～20mm and the expanding elliptical or Rectangular dark brown spots as the result.Numerous maculas(sporopycnidium) scattered out from the surface were observed which lead to the stalks broken and the whole plant wilt.The disease were usually betided at the branching spot.Based on morphological classification and with molecular biology technology, Cyathula officinalwas Dieback pathogen was a new Species of Phoma genus.It was named According to its host,Phoma Cyathula.The pathogen's sporopycnidium in diameter of 60～360μm with brown paries scattered or gathered under the host's epiderm and released conidia from the orifice.Conidia,colourless,sphericity or ellipsoid in shape,in size of 3～12.5μm×1.25～5μm,was monadic,elliptic,cylindric,spindly or pyriform and usually has a oil ball in the center.2.The biological characteristics of Phoma CyathulaTwo strains were used to determine the biological characteristics.The temperature range for mycelium growth and sporulation was 10～30℃.The optimum temperature for mycelium gorwth was 25℃and for sporulation 20℃.In the utilization of carbon source,it is better with glycose and disaccharides than polysaccharide,and the most suitable nitrogen sources was organic,pH value range for hypha's gowth and sporulation was 5～11,the optimum between 5～7.The pathogen could grow and sporulate better on PDA, oatmeal,10%+PDA,20%+agar than others.The quantity of sporulation was utmost on mannitol-agar medium.No remarkable effect on the hypha growth of 2 strains was observed with light treament.They all reached utmost quantity of sporulation in total darkness.Conidia were able to germinate in sterile deionized water but at a low percentage,sugar and host juice stimulated conidial germination of the pathogen.Conidia germinated at 10 to 30℃,with optimum temperature between 20 and 25℃.The lowest relative humidity of germination was 93%,Germination ratio rose with raising RH and and the maximum rate of conidia germination was in water.The optimum pH value for sporulating and germ tube extending was pH5～8.Conidia was sensitive to light.Germination ratio and germ tube all met their maximum in total darkness.The lethal temperature of hypha of strain 1 and 2 was 51℃and 49℃,respectively,and conidia was 57℃.3.Diversity of Phoma Cyathula and electrophoresis analysisSoluble protein,acid phosphatase and isoesterase patterns of Phoma Cyathula from the same location in ya'an were analyzed by polyacrymide gel vertical electronphoresis.Band spectrum had certain difference between strains with different culture Characters in the same region,which suggested the in-species heterogeneity existing.This consequentially complicated the categories by isoesterase,acid phosphatase and soluble protein electrophoresis pattern.We preliminarily consider these mutual enzyme bands as the sign bands of this species.4.Virulence determination of fungicides to Cyathula officinalis Dieback PathogenThe five fungicides were tested in laboratory to determine the effect on the hypha growth and germination of conidia.The results showed that carbendazim was The most effective one.Thiophanate-methyl and mancozeb were two good fungicides. Chlorothalonil was inferior to mancozeb,then Mancozeb almost had no effect.
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