AUTHOR=Naqqash Tahir , Hameed Sohail , Imran Asma , Hanif Muhammad Kashif , Majeed Afshan , van Elsas Jan Dirk 

TITLE=Differential Response of Potato Toward Inoculation with Taxonomically Diverse Plant Growth Promoting Rhizobacteria

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00144

DOI=10.3389/fpls.2016.00144

ISSN=1664-462X

ABSTRACT=<p>Rhizosphere engineering with beneficial plant growth promoting bacteria offers great promise for sustainable crop yield. Potato is an important food commodity that needs large inputs of nitrogen and phosphorus fertilizers. To overcome high fertilizer demand (especially nitrogen), five bacteria, i.e., <italic>Azospirillum</italic> sp. TN10, <italic>Agrobacterium</italic> sp. TN14, <italic>Pseudomonas</italic> sp. TN36, <italic>Enterobacter</italic> sp. TN38 and <italic>Rhizobium</italic> sp. TN42 were isolated from the potato rhizosphere on nitrogen-free malate medium and identified based on their 16S <italic>rRNA</italic> gene sequences. Three strains, i.e., TN10, TN38, and TN42 showed nitrogen fixation (92.67–134.54 nmol h<sup>-1</sup>mg<sup>-1</sup> protein), while all showed the production of indole-3-acetic acid (IAA), which was significantly increased by the addition of <sc>L</sc>-tryptophan. <italic>Azospirillum</italic> sp. TN10 produced the highest amount of IAA, as measured by spectrophotometry (312.14 μg mL<sup>-1</sup>) and HPLC (18.3 μg mL<sup>-1</sup>). Inoculation with these bacteria under axenic conditions resulted in differential growth responses of potato. <italic>Azospirillum</italic> sp. TN10 incited the highest increase in potato fresh and dry weight over control plants, along with increased N contents of shoot and roots. All strains were able to colonize and maintain their population densities in the potato rhizosphere for up to 60 days, with <italic>Azospirillum</italic> sp. and <italic>Rhizobium</italic> sp. showing the highest survival. Plant root colonization potential was analyzed by transmission electron microscopy of root sections inoculated with <italic>Azospirillum</italic> sp. TN10. Of the five test strains, <italic>Azospirillum</italic> sp. TN10 has the greatest potential to increase the growth and nitrogen uptake of potato. Hence, it is suggested as a good candidate for the production of potato biofertilizer for integrated nutrient management.</p>