采用西瓜汁蔗糖琼脂培养基有效筛选西瓜枯萎病菌拮抗细菌

 在从摩洛哥引进的脐血橙田间植株的新梢嫩叶上观察到褪绿环斑和污斑,褪绿斑驳,叶背有边缘凹刻的圆形或近圆形环,以及脉明和叶脉环阻等症状。通过向Madam Vinous甜橙、邓肯葡萄柚等柑桔类指示植物的嫁接接种;用钝刀醮取汁液切割指示植物墨西哥来檬和埃特洛香的茎部进行机械传播;以及汁液磨擦接种草本指示植物昆诺藜等方法,鉴定到柑桔环斑病毒(citrus ringspot virus,CRSV)。嫁接接种的柑桔类指示植物上的症状包括新梢休克、新叶脱落,新叶表现褪绿环斑和污斑以及斑驳,脉明和叶脉环阻等;机械接种的柑桔类指示植物表现新叶的褪绿环斑症状;昆诺藜在接种后4~6d于接种叶上产生褪绿至坏死的局部枯斑,但无系统感染的症状出现。取表现症状的柑桔类指示植物和昆诺藜的叶片作接种源,汁液磨擦接种回接至昆诺藜,再现了同样的症状。

EFFECTIVE SCREENING OF ANTAGONISTIC BACTERIA TO FUSARIUM OXYSPORUM F.SP.NIVEUM BY WSA MEDIUM

Eleven media , such as CMA , TSA , PDA , PSA , NA , KMB , WSA , WA , OMA . VDYA and DPYA . were tested to determine their abilities to screen for antagonistic bacteria to Fusarium oxysporum f. sp. niveum (FON ) incubated on Petri dish plates at 28 .C . The result showed WSA medium composed of the extract of watermelon rind , sugar , bromothymol blue and agar was capable of distinguishing antagonis- tic bacteria clearly after 4 days. TSA medium used extensively to isolate antagonistic bacteria from rhizo- sphere, and rhizoplane of crop plant to root plant pathogenic fungi was of lower level to detect the inhibitory zone formed by antagonistic bacteria to FON compared with WSA medium , because FON and bacterium colonies grew more slowly and less obviously than on WSA medium. On CMA and WA medium plates , bacteria and FON grew showly , and some kinds of bacteria could not develop on WA medium plates. On PDA , PSA and OMA medium plates , FON colonies expanded too fast to detect the inhibitory zones . but bactrium colonies formed largely to cross over the colonies of FON on NA , PDA and KMB medium plates on which the inhibitory zones could not present. On VDYA and DPYA . FON and some bacteria grew with comparatively slower speed.