Table_4_Methylobacterium sp. 2A Is a Plant Growth-Promoting Rhizobacteria That Has the Potential to Improve Potato Crop Yield Under Adverse Conditions.xlsx

A Gram-negative pink-pigmented bacillus (named 2A) was isolated from Solanum tuberosum L. cv. Desirée plants that were strikingly more developed, presented increased root hair density, and higher biomass than other potato lines of the same age. The 16S ribosomal DNA sequence, used for comparative gene sequence analysis, indicated that strain 2A belongs to the genus Methylobacterium. Nucleotide identity between Methylobacterium sp. 2A sequenced genome and the rest of the species that belong to the genus suggested that this species has not been described so far. In vitro, potato plants inoculated with Methylobacterium sp. 2A had a better performance when grown under 50 mM NaCl or when infected with Phytophthora infestans. We inoculated Methylobacterium sp. 2A in Arabidopsis thaliana roots and exposed these plants to salt stress (75 mM NaCl). Methylobacterium sp. 2A-inoculated plants, grown in control or salt stress conditions, displayed a higher density of lateral roots (p < 0.05) compared to noninoculated plants. Moreover, under salt stress, they presented a higher number of leaves and larger rosette diameter. In dual confrontation assays, Methylobacterium sp. 2A displayed biocontrol activity against P. infestans, Botrytis cinerea, and Fusarium graminearum, but not against Rhizoctonia solani, and Pythium dissotocum. In addition, we observed that Methylobacterium sp. 2A diminished the size of necrotic lesions and reduced chlorosis when greenhouse potato plants were infected with P. infestans. Methylobacterium sp. 2A produces indole acetic acid, solubilizes mineral phosphate and is able to grow in a N2 free medium. Whole-genome sequencing revealed metabolic pathways associated with its plant growth promoter capacity. Our results suggest that Methylobacterium sp. 2A is a plant growth-promoting rhizobacteria (PGPR) that can alleviate salt stress, and restricts P. infestans infection in potato plants, emerging as a potential strategy to improve crop management.

从栽培品种德西蕾（cv. Desirée）的马铃薯（Solanum tuberosum L.）植株中分离得到一株革兰氏阴性粉红色色素杆菌，命名为2A菌株；该菌株宿主的生长状态显著更优、根毛密度更高、生物量显著高于同龄其他马铃薯品系。通过用于序列比对分析的16S核糖体DNA（16S ribosomal DNA）序列分析表明，2A菌株隶属于甲基杆菌属（Methylobacterium）。对2A菌株全基因组序列与该属其他物种的核苷酸同源性比对后发现，该菌株所代表的物种目前尚未被正式报道过。体外实验体系中，接种甲基杆菌属（Methylobacterium）sp. 2A的马铃薯植株，在50 mM氯化钠（NaCl）胁迫环境下，或是被致病疫霉（Phytophthora infestans）侵染时，生长表现均更为优异。我们将甲基杆菌属sp. 2A接种至拟南芥（Arabidopsis thaliana）根部，并将植株置于75 mM氯化钠盐胁迫环境中。与未接种的对照组相比，无论在正常培养还是盐胁迫条件下，接种2A菌株的植株侧根密度均显著更高（p < 0.05）。此外，在盐胁迫环境下，接种菌株的植株叶片数量更多，莲座直径更大。在双重对峙培养实验中，甲基杆菌属sp. 2A对致病疫霉（Phytophthora infestans）、灰葡萄孢（Botrytis cinerea）以及禾谷镰孢（Fusarium graminearum）表现出生防活性，但对立枯丝核菌（Rhizoctonia solani）和德巴利腐霉（Pythium dissotocum）无此效果。此外，我们观察到，当温室栽培的马铃薯植株被致病疫霉侵染时，预先接种2A菌株可减小坏死病斑面积并减轻褪绿症状。甲基杆菌属sp. 2A可合成吲哚乙酸，能够溶解矿物磷酸盐，且可在无氮培养基中生长。全基因组测序分析揭示了与该菌株促植物生长能力相关的代谢通路。本研究结果表明，甲基杆菌属sp. 2A是一株可缓解盐胁迫的植物促生根际细菌（PGPR, Plant Growth-Promoting Rhizobacteria），能够抑制马铃薯植株受致病疫霉侵染，有望成为优化作物生产管理的潜在策略。