Plant growth-promoting traits ofStreptomyceswith biocontrol potential isolated from herbal vermicompost

Abstract

Tel.: +91 40 3071 3610; Fax: +91 40 3071 3074Three strains of Streptomyces were earlier reported by us as having potential for biocontrol of charcoal rot of sorghum, caused by Macrophomina phaseolina (Tassi) Goid., and plant growth promotion (PGP) of the plant. In the present investigation, the three Streptomyces were characterized for their physiological traits (tolerance of salinity, temperature, pH and resistance to 2 antibiotics) and further evaluated in the field for their PGP of rice, grown by a system of rice intensification (SRI) methods. All three Streptomyces were able to grow in NaCl concentrations of up to 12% (except MMA-32), at pH values between 5 and 13 and temperatures between 20 and 40 o C.They were highly resistant to ampicillin and trimethoprim (>800 ppm), sensitive to chloramphenicol, kanamycin and nalidixic acid (50−100 ppm) and highly sensitive to streptomycin and tetracycline (5−25 ppm). When evaluated for their PGP activity on seedlings of rice, % germination and shoot and root lengths were significantly enhanced over the control. In the field, the Streptomyces strains significantly enhanced the panicle length, filled grain numbers and weight, panicle weight, 1000 seed weight, tiller numbers, total dry matter, root length (39−65%), root volume (13−30%), root dry weight (16−24%), grain yield (9−11%) and stover yield (11−22%) over the control. In the rhizosphere soil (0−15cm from root) at harvest, the population of actinomycetes was significantly enhanced as was microbial biomass carbon (27−83%) and nitrogen (24−43%), dehydrogenase activity (34−152%), available P (13−34%) and N (30−53%) and % organic carbon (26−28%). This study further confirms that the selected Streptomyces have plant growth promoting properties.

Biocontrol and growth promotive potential of <i>Streptomyces</i> spp. in black pepper (<i>Piper nigrum</i> L.)

“…An increased availability of growth regulators produced by the organism was the reason attributed for the improvement in tomato growth (El-Abyad et al, 1993). Gopalakrishnan et al, 2012 investigated the PGP activities of the Streptomyces strains (CAI-21, CAI-26 and MMA-32) in rice grown under aerobic soil conditions by the SRI method and they reported that the Streptomyces strains significantly enhanced all the morphological parameters like plant height, tillering, panicle length and dry weight, filled grain number and weight, seed weight, stover and grain yield. This is also in accordance with our study.…”

Evaluation ofStreptomycesspp. for their plant-growth-promotion traits in rice

“…The ability of Streptomyces to tolerate abiotic stresses including salinity, pH, and temperature and antibiotics and fungicide tolerance are widely reported (Waksman 1959, Gopalakrishnan et al 2012aSadeghi et al 2012). Consequently, it can be stated that these strains have the capability to survive in harsh environments and can be used in the integrated disease management programs.…”

“…A total of six antibiotics namely ampicillin, chloramphenicol, kanamycin, nalidixic acid, streptomycin and tetracycline were studied for their resistance pattern against the five Streptomyces as per the standardized protocols of Gopalakrishnan et al (2012a). The five strains of Streptomyces were also evaluated for their tolerance to fungicides at field application level.…”

“…The field experiment was conducted as described previously (Gopalakrishnan et al 2012a). In brief, the 12-day-old single seedlings were uprooted from the nursery, their roots dipped in the respective Streptomyces spp.…”

“…The first three of the eight Streptomyces strains (CAI-21, CAI-26 and MMA-32) were also reported to have potential for PGP in rice (Gopalakrishnan et al 2012a). The objective of this study was to further characterize the remaining five Streptomyces strains (CAI-17, CAI-68, CAI-78, KAI-26 and KAI-27) for their enzymatic activities (cellulase, lipase and β-1, 3-glucanase), physiological traits (salinity, temperature, pH and resistance to antibiotics and fungicides) and evaluate, under field conditions, their PGP traits in rice grown using the system of rice intensification (SRI; Uphoff 2001; Kumar et al 2010) method.…”