为探索地黄连作栽培中真菌病害的大规模爆发机制, 明确自毒物质所介导的土壤病原菌增多的根际生物学过程, 本研究利用PDA平板法, 经过显微鉴定和真菌ITS鉴定分析, 从地黄连作土壤和发病植株中分离到镰刀菌菌株31株, 并进行了致病性检测。结果表明, 串珠镰刀(菌株编号RPP009)、茄病镰刀(菌株编号CCS013)、禾谷镰刀(菌株编号CCS024)、雪霉叶枯病菌(菌株编号CCS038)和尖孢镰刀(菌株编号CCS043)在接种3 d后就表现出明显的致病能力, 严重影响地黄幼苗的株高(为对照的23.40%~30.20%)和植株鲜重(为对照的23.58%~38.94%), 并引起地黄植株变黄畸形, 根毛和须根减少, 在接种2周后致使全部植株枯萎死亡, 具有很强的致病性。专化型鉴定表明, 菌株Fusarium oxysporum (菌株编号CCS043)和Monographella nivale (菌株编号CCS038)只侵染地黄, 不侵染其他试验材料, 植株感病初期在中午时分下部叶片缺水萎蔫, 早晚又有所恢复, 如此反复, 至3~5 d, 叶片则不能恢复正常直立, 枯萎死亡。镜检发现, 感病植株茎部维管束变褐色至暗褐色, 后逐渐导致周围海绵组织破裂, 进而致使地下块根逐渐变黑腐烂, 初步判定两株菌株为地黄专化型病原菌。
Rehmannia glutinosa is an important medicinal plant in China that requires 8 10 years plastochrone for replanting, making it almost impossible for continuous cropping. Previous studies had shown that soil-borne diseases caused by microbial imbalance in rhizosphere microecology were the main obstacles to continuous cropping of R. glutinosa. However, little has been reported on the identification of formae speciales of R. glutinosa. Thus this study used the PDA-plate method after microscopic identification and analysis of ITS fungi identification to successfully screen 31 strains of Fusarium from soil under continuous cropping of R. glutinosa. Pathogenic detection results showed that strain Fusarium moniliforme (No. RPP009), F. solani (No. CCS013), F. graminearum (No. CCS024), Monographella nivalis (No. CCS038) and F. oxysporum (No. CCS043) were highly pathogenic. These strains severely decreased the height (by 23.40%~30.20% compared with CK) and fresh weight (by 23.58%~38.94% compared with CK) of R. glutinosa seedlings within 3 days after inoculation, subsequently causing organ deformation and death after 2 weeks. Further host biotype identification test results showed that F. oxysporum (No. CCS043) and M. nivalis (No. CCS038) strains only infected R. glutinosa and not other materials used in the experiment. The leaves of lower part of disease plants repeatedly turned hydropenic at noon and eventually withered followed by plant death after 3 5 days. Microscopic examination showed that stem vascular system in diseased plants turned brown or duck which led to the disagglomeration of spongy tissues. Underground root tubers then eventually ducked and decayed. The preliminary analysis suggested that the two identified strains were formae speciales of R. glutinosa.