Abstract
Five strains of Streptomyces (CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90) were earlier reported by us as biological control agents against Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceri (FOC). In the present study, the Streptomyces were characterized for enzymatic activities, physiological traits and further evaluated in greenhouse and field for their plant growth promotion (PGP) of sorghum and rice. All the Streptomyces produced lipase, β-1-3-glucanase and chitinase (except CAI-121 and CAI-127), grew in NaCl concentrations of up to 6%, at pH values between 5 and 13 and temperatures between 20 and 40°C and were highly sensitive to Thiram, Benlate, Captan, Benomyl and Radonil at field application level. When the Streptomyces were evaluated in the greenhouse on sorghum all the isolates significantly enhanced all the agronomic traits over the control. In the field, on rice, the Streptomyces significantly enhanced stover yield (up to 25%; except CAI-24), grain yield (up to 10%), total dry matter (up to 18%; except CAI-24) and root length, volume and dry weight (up to 15%, 36% and 55%, respectively, except CAI-24) over the control. In the rhizosphere soil, the Streptomyces significantly enhanced microbial biomass carbon (except CAI-24), nitrogen, dehydrogenase (except CAI-24), total N, available P and organic carbon (up to 41%, 52%, 75%, 122%, 53% and 13%, respectively) over the control. This study demonstrates that the selected Streptomyces which were antagonistic to FOC also have PGP properties.
Highlights
Plant growth-promoting (PGP) microbes are rhizosphere associated organisms that colonize the rhizosphere and rhizoplane and improve plant growth when artificially inoculated onto the seeds or into soil
PGP traits of actinomycetes have been reported on pea (Tokala et al 2002), bean (Nassar et al 2003), tomato (El-Tarabily 2008), wheat (Sadeghi et al 2012) and rice (Gopalakrishnan et al 2012a)
Evaluation of Streptomyces strains for their enzymatic activities Chitinase, lipase and β-1,3-glucanase production Chitinase and lipase production was conducted for all five strains (CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90) of Streptomyces as described by Hirano and Nagao (1988) and Bhattacharya et al (2009), respectively
Summary
Plant growth-promoting (PGP) microbes are rhizosphere associated organisms that colonize the rhizosphere and rhizoplane and improve plant growth when artificially inoculated onto the seeds or into soil. PGP microbes may promote plant growth either by direct stimulation such as iron chelation, phosphate solubilization, nitrogen fixation and phytohormone production or by indirect stimulation such as suppression of plant pathogens and induction of resistance in host plants against pathogens (Basak and Biswas 2009; Hao et al 2011; Panhwar et al 2012). PGP and biological control of plant pathogens has been addressed using actinomycete, bacterial and fungal antagonists. PGP traits of actinomycetes have been reported on pea (Tokala et al 2002), bean (Nassar et al 2003), tomato (El-Tarabily 2008), wheat (Sadeghi et al 2012) and rice (Gopalakrishnan et al 2012a)
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