马铃薯连作地健康株与病株根区土壤微生态特性比较

Comparison of Microecological Characterization in Rhizosphere Soil between Healthy and Diseased Plants in Continuous Cropping Potato Fields

为探索甘肃省连作马铃薯健康生长的微生态机制,采用常规养分分析法测定了健康株与病株根区土壤中速效氮磷钾含量,稀释平皿涂抹法测定土壤放线菌数量,琼脂块法筛选拮抗放线菌;16S rRNA序列分析法鉴定优势放线菌,发酵液抑菌试验检测优势放线菌灭癌素链霉菌(S.gancidicus)对马铃薯病原真菌的抑菌作用。结果表明,在连作4年的田中:马铃薯病株根区土壤的速效P、K含量分别较健株低29.9%、12.5%,铵态氮含量较健株高24.1%。在高氏1号培养基上,病株根区土壤中放线菌总数、小单孢菌及未鉴定放线菌数量较健株分别减少51.1%、83.0%及53.9%;腐植酸琼脂培养基上,病株根区土壤中放线菌总数、链霉菌数量较健株分别减少46.0%、46.7%。在病、健株根区土壤中,对4株靶标真菌的拮抗潜势SAAP值病株均小于健株。健株根区土壤中的优势放线菌为灭癌素链霉菌(S.gancidicus),该菌对4株马铃薯常见土传病原真菌立枯丝核菌(R.solani)、茄病镰刀菌(F.solani)、硫色镰刀菌(F.sulphureum)和大丽轮枝菌(V.dahliae)均有抑制作用;病株根区土壤中的优势放线菌为加利利链霉菌(S.galilaeus),该菌为马铃薯疮痂病致病菌。由此可知,保持连作马铃薯健康生长的根区土壤微生态特征是,高量磷钾及低量氮的速效养分组合,较多放线菌且拮抗放线菌的拮抗潜势较大,优势放线菌为有益菌。

To explore the microecological mechanism of healthy plant growth in continuous potato fields in Gansu Province, China, we measured contents of available soil nitrogen （NHa＋-N）, phosphorus （P）, and potassium （K） using conventional soil nu- trient analytic methods, abtmdance of soil actinomycetes using serial dilution and plating techniques, and screened antagonistic actinomycetes from obtained actinomycete isolates using the agar block method. The selected dominant actinomycetes were iden- tified by 16S rRNA sequence analysis, and the inhibitory effect of one dominant actinomycete, Streptomyces gancidicus, was tested using culture filtrate. Results showed that in the four-year continuous potato field, available soil P and K contents in the rhizosphere of diseased plants were respectively 29.9% and 12.5% lower than those of healthy plants, whereas soil NH4＋-N con- tent in the rhizosphere of diseased plant was 24.1% higher than that of healthy plant. Compared with those from the rhizosphere of healthy plants, the number of soil actinomycetes, Micromonospora, and unidentified actinomycetes from the rhizosphere of dis- eased plants cultured with the Gausel medium decreased by 51.1%, 83.0%, and 53.9%, respectively, whereas the number of soil actinomycetes and Streptomyces from the rhizosphere of diseased plants cul^red with the Humic Acid medium decreased by 46.0% and 46.7%, respectively. The soil actinomycetes antagonistic potentiality （SAAP） of actinomycetes with antagonistic ef- fects on the four pathogenic fungi of potato were lower in the rhizosphere of diseased plants than in the rhizosphere of healthy plants. S. gancidicus and S. galilaeus were found dominant in the rhizosphere of healthy and diseased plants, respectively. In con-clusion, the microecology of rhizosphere soil that supports healthy plant growth in the continuous potato field is mainly charac- terized by： available nutrient combination of abundant P and K with relatively poor N contents; and a larger number of soil ac- tinomycetes than those of diseased plants, with the numerically dominant actinomycetes showing beneficial antagonistic effect on several common soil-borne pathogenic fungi.