Phytohormone biosynthetic potential of different Rhizobium species
Haroon Shahzad, Atif Idrees, Iqtidar Hussain, Muhammad Arshad Khan, Bibi Sadia, Sami Ullah, Imran Qazi, Wajia Noor, Iqra Qayyum, Najeeb Ullah, Imtiaz Khan, Muhammad Jamil
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ABSTRACT
Plants may not have optimum growth hormone production
potential under suboptimal growth and environmental conditions. The exogenous
application of microbes is a potential and economical source of plant hormones.
A laboratory trial was performed to evaluate the hormone biosynthesis potential
of several soil microbes. Rhizobium sp. (Rhizobium trifolii, Rhizobium etli,
Rhizobium meliloti, Rhizobium ciceri, Azorhizobium caulinodans, Bradyrhizobium
japonicum, Rhizobium vulgaris, and Rhizobium phaseoli) were isolated from root
nodules of various legumes and were biochemically characterized. Absorption
spectroscopy (535, 254 and 665 nm λ) was used to quantify indole acetic acid
(IAA), gibberellin and cytokinin production of different Rhizobium species. B3
isolate of Rhizobium trifolii had yielded (14.54 and 21.37 µg mL-1)
IAA equivalents without and with L-tryptophan (L-TRP) supplement, that was
statistically at par with same species while significantly greater than other
Rhizobium isolates. Gibberellin production was found statistically
non-significant in all isolates. Rhizobium phaseoli (Vp1)
yielded 1.68 µg mL-1 cytokinin that was at par with the same species
isolates and with Rhizobium trifolii but was critically greater in amount than
other species. It was concluded that Rhizobium plays a vital role in plant
growth and development can produce auxin and gibberellins, but some could
produce cytokinin.
Keywords: Phytohormone, Biosynthesis, IAA, PGPR, Auxin, Gibberellins,
Cytokinin
ABSTRACT
Plants may not have optimum growth hormone production
potential under suboptimal growth and environmental conditions. The exogenous
application of microbes is a potential and economical source of plant hormones.
A laboratory trial was performed to evaluate the hormone biosynthesis potential
of several soil microbes. Rhizobium sp. (Rhizobium trifolii, Rhizobium etli,
Rhizobium meliloti, Rhizobium ciceri, Azorhizobium caulinodans, Bradyrhizobium
japonicum, Rhizobium vulgaris, and Rhizobium phaseoli) were isolated from root
nodules of various legumes and were biochemically characterized. Absorption
spectroscopy (535, 254 and 665 nm λ) was used to quantify indole acetic acid
(IAA), gibberellin and cytokinin production of different Rhizobium species. B3
isolate of Rhizobium trifolii had yielded (14.54 and 21.37 µg mL-1)
IAA equivalents without and with L-tryptophan (L-TRP) supplement, that was
statistically at par with same species while significantly greater than other
Rhizobium isolates. Gibberellin production was found statistically
non-significant in all isolates. Rhizobium phaseoli (Vp1)
yielded 1.68 µg mL-1 cytokinin that was at par with the same species
isolates and with Rhizobium trifolii but was critically greater in amount than
other species. It was concluded that Rhizobium plays a vital role in plant
growth and development can produce auxin and gibberellins, but some could
produce cytokinin.
Keywords: Phytohormone, Biosynthesis, IAA, PGPR, Auxin, Gibberellins, Cytokinin