攀西地区玉米根际耐旱放线菌多样性及促生特性分析

Diversity and plant growth-promoting characteristics of drought-tolerant actinomycetes in rhizosphere of maize in Panxi Plateau, China

摘要:

【背景】 植物根际促生菌能加速根际土壤的营养元素循环，改善土壤微生物群落结构，提高土壤肥力。【目的】 认识攀西地区玉米根际耐旱放线菌的多样性，同时筛选促生耐旱放线菌。【方法】 以攀西地区烟草-玉米轮作田中玉米根际土为研究材料分离筛选耐旱放线菌，运用BOXA1R聚类分析和16S rRNA基因测序技术分析攀西地区耐旱放线菌多样性并鉴定明确其系统发育地位，测定其产1-氨基环丙烷-1-羧酸(1-amino-1-cyclopropanecarboxylic acid, ACC)脱氨酶、产铁载体、降解纤维素、溶磷能力，以及抑制病原菌的能力，筛选出高效促生耐旱菌株进行玉米幼苗干旱促生试验。【结果】 共分离筛选得到31株耐旱放线菌，BOXA1R聚类分析得到的31株耐旱放线菌分别属于链霉菌属(Streptomyces)、类诺卡氏菌属(Nocardioides)、冢村氏菌属(Tsukamurella)、戈登氏菌属(Gordonia)和拟无枝酸菌属(Amycolatopsis)，其中链霉菌属为优势属。31株促生耐旱放线菌中，25.80%具有产铁载体能力，32.25%具有溶磷能力，9.68%具有纤维素降解能力，74.19%具有产ACC脱氨酶能力。抑菌试验表明，菌株SICAU-37和SICAU-70对3种病原真菌稻瘟病菌(Magnaporthe oryzae)、烟草疫霉(Phytophthora nicotianae)和玉米尾孢菌(Cercospora zeina)均有抑制作用，抑菌直径/菌落直径(HD/CD)均在2以上。综上，菌株SICAU-37和SICAU-70促生、抑菌性能突出，筛选为进行干旱促生试验的菌株。经鉴定这2株菌分别为耐酪酸冢村菌(Tsukamurella tyrosinosolvens)和石斛拟无枝酸菌(Amycolatopsis dendrobii)。在干旱条件下，菌株SICAU-70能有效促进玉米幼苗的生长，可使株高和地上部鲜重提高9.44%和33.42%。【结论】 攀西地区烟草-玉米轮作田中玉米根际存在较为丰富多样的促生耐旱放线菌，具有潜在的应用价值。

关键词:植物根际促生菌;耐旱放线菌;多样性分析;干旱

Abstract:

[Background] Plant growth-promoting rhizobacteria can accelerate nutrient cycling in the soil and improve the structure of soil microbial communities to enhance soil fertility. [Objective] To reveal the diversity of drought-tolerant actinomycetes in the rhizosphere of maize in Panxi Plateau, China and screen out plant growth-promoting drought-tolerant actinomycetes. [Methods] Drought-tolerant actinomycetes were isolated and screened from the rhizosphere soil of maize in the field with tobacco-maize rotation in Panxi Plateau, China. BOXA1R cluster analysis was performed to assess the diversity of drought-tolerant actinomycetes, and 16S rRNA gene sequencing was employed to determine their phylogenetic positions. The abilities of the isolates to produce ACC deaminase and siderophores, degrade cellulose, solubilize phosphorus, and inhibit pathogens were evaluated. The drought-tolerant strains capable of efficiently promoting plant growth were selected for drought stress experiments on maize seedlings. [Results] A total of 31 strains of drought-tolerant actinomycetes were isolated and identified. BOXA1R cluster analysis revealed that these strains belonged to Streptomyces, Nocardioides, Tsukamurella, Gordonia, and Amycolatopsis, among which Streptomyces was the dominant genus. Among the 31 isolates, 25.80%, 32.25%, 9.68%, and 74.19% could produce siderophores, solubilize phosphorus, degrade cellulose, and produce ACC deaminase, respectively. Strains SICAU-37 and SICAU-70 exhibited inhibitory effects on the pathogenic fungi Magnaporthe oryzae, Phytophthora nicotianae, and Cercospora zeina, with the ratios of the inhibitory zone diameter to the colony diameter being greater than 2 against all the three fungal species. Notably, strains SICAU-37 and SICAU-70 with prominent plant growth-promoting and antifungal properties were selected for drought stress experiments. Upon identification, these two strains were determined to be Tsukamurella tyrosinosolvens and Amycolatopsis dendrobii, respectively. Under drought conditions, SICAU-70 effectively promoted the growth of maize seedlings, increasing the plant height and fresh shoot weight by 9.44% and 33.42%, respectively. [Conclusion] The fields with tobacco-maize rotation in Panxi Plateau harbor diverse and rich plant growth-promoting drought-tolerant actinomycetes, which have application potential.

Key words:plant growth-promoting rhizobacteria;drought-tolerant actinomycetes;diversity analysis;drought