Molecular Identification and In Vitro Plant Growth-Promoting Activities of Culturable Potato ( Solanum tuberosum L.) Rhi
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Molecular Identification and In Vitro Plant Growth-Promoting Activities of Culturable Potato (Solanum tuberosum L.) Rhizobacteria in Tanzania B. N. Aloo 1,2 R. Daniel 4
& E.
R. Mbega 1,3 & B. A. Makumba 3 & R. Hertel 4 &
Received: 1 October 2019 / Accepted: 12 June 2020/ # European Association for Potato Research 2020
Abstract 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.
* B. N. Aloo [email protected]; aloob@nm–aist.ac.tz Extended author information available on the last page of the article
Potato Research
Keywords Plant growth-promoting rhizobacteria . Plant growth promotion . Potato .
Solanum tuberosum . Tanzania
Introduction The potato (Solanum tuberosum L.) is one of the most cultivated crops worldwide that feeds more than a billion people daily with developing countries contributing more than half of its global harvest. Tanzania is one of the major potato producers in Sub-Saharan Africa (SSA) (Mende et al. 2015). According to recent reports by Senkoro et al. (2017), over 80% of Tanzania’s population in the potato-growing rural areas depends on the cultivation of the crop among other crops such as maize, sorghum, banana and wheat. However, potato is a high fertilizer input-demanding crop (Wu et al. 2013), requiring approximately 250 kg ha−1 of n
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