The present study investigated the diversity of culturable rhizobacteria associated with potato (S. tuberosum L.) in Tanzania and assessed their in vitro plant growth-promoting (PGP) activities to deduce their potential as biofertilizers. Potato rhizosphere soil and tuber samples (54 samples in total) were collected from 9 villages in three different agro-ecological regions in Tanzania. A total of 145 rhizobacterial isolates were obtained, 52 of which were selected and identified by partial 16S rRNA gene sequences and screened for various PGP traits in vitro including qualitative and quantitative solubilization of phosphorus (P), zinc (Zn) and potassium (K), nitrogen (N₂) fixation and production of ammonia (NH₃) in nitrogen-free medium, and indole-3-acetic acid (IAA), gibberellic acids (GA) and siderophores production. The results showed that the isolates were all Gammaproteobacteria, belonging to 4 families (Enterobacteriaceae, Yersiniaceae, Pseudomonadaceae and Morganellaceae) and 9 genera (Enterobacter, Klebsiella, Serratia, Pseudomonas, Morganella, Buttiauxella, Pantoea and Cedecea). Significant differences (P < 0.05) were observed for all assessed PGP abilities of the external and endophytic rhizobacterial isolates except for quantitative siderophore production and qualitative P and K solubilization for the external rhizobacteria and production of IAA and GA for the endophytic rhizobacteria. Among the best PGP isolates which can be exploited for biofertilization of the potato were Klebsiella pneumoniae KIBS1, K. grimontii LUTS10, Serratia liquefaciens KIBT1, Enterobacter ludwigii KIBS10 and Citrobacter freundii MWALS6. Comparative evaluation of PGP abilities of these two groups of isolates revealed significant differences (P < 0.05) only for NH₃ and IAA production and qualitative K solubilization.

本研究调查了与坦桑尼亚马铃薯（S. tuberosum L.）相关的可培养根瘤菌的多样性，并评估了其体外植物促生长（PGP）活性，以推断其作为生物肥料的潜力。马铃薯根际土壤和块茎样品（总共54个样品）是从坦桑尼亚三个不同农业生态区的9个村庄收集的。总共获得了145种根瘤菌分离株，其中16种rRNA基因序列已被选择和鉴定，并在体外筛选了各种PGP特性，包括定性和定量溶解磷（P），锌（Zn）和钾（K） ，氮（N ₂）固定和氨（NH ₃）在无氮培养基中生产，并生产吲哚-3-乙酸（IAA），赤霉素（GA）和铁载体。结果表明，该菌株都γ-变形菌，属于4个科（肠杆菌科，Yersiniaceae，假单胞菌和Morganellaceae）和9属（肠杆菌属，克雷白杆菌，沙雷氏菌，假单胞菌，摩根，布丘氏，成团泛菌和Cedecea）。显着差异（P <0.05）观察到的所有评估的外部和内生根瘤菌分离物的PGP能力，除了定量的铁载体生成和定性的P和K增溶作用，以及内生根瘤菌的IAA和GA生成。可以用于马铃薯生物肥育的最佳PGP分离株包括肺炎克雷伯氏菌KIBS1，格里蒙克鲁斯氏菌LUTS10，液化沙雷氏菌KIBT1，路德维氏肠杆菌KIBS10和弗氏柠檬酸杆菌MWALS6。两组分离物的PGP能力比较评估显示， 仅对于NH _3有显着差异（P <0.05） 以及IAA生产和定性K增溶。