Characterization of antagonistic rhizobacteria having plant growth promoting effects on mustard (Brassica juncea L.)
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Date
2015
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CCSHAU
Abstract
Indian mustard (Brassica juncea L.) is an important oilseed crop grown across the Northern Indian
plains. The major constraints in growing mustard are diseases, aphid pests, weeds and abiotic stresses which are
responsible for reduction in the growth, yield and oil production. Alternaria blight disease caused by Alternaria
brassicae is the important disease of Indian mustard, which causes 10-70% yield losses. Fungicides mancozeb and
iprodione are applied to control this disease. However, increasing awareness about environment pollution has
emphasized the need for use of biocontrol agents for substituting pesticides. In the present study, seventy-eight
bacterial isolates were obtained from the mustard rhizosphere at 50 and 75 days of plant growth and 305 isolates
were procured from the Department of Microbiology, CCS H.A.U., Hisar. Out of 383 isolates tested, 20.88%
isolates inhibited the growth of fungi Alternaria brassicae. Highest antagonistic activity (halo zone to growth
ratio) was shown by isolate HMR25 (5.03) followed by HMR33 (4.68) and HMR70 (4.12). On the basis of
variation in antagonistic activity, 46 isolates were further tested for production of indole-3-acetic acid (IAA), δ-
aminolevulinic acid (ALA) and potassium solubilization activity. Twelve isolates showed 5-15 μg/ml IAA
production and maximum IAA production was observed in isolate HMR57 (19.95 μg/ml) followed by HMR39
(17.99 μg/ml) and HMR2 (16.45 μg/ml). Maximum ALA production was observed in isolate WSA56 (15.62
μg/ml) followed by HMM21 (14.74 μg/ml) and HMM49 (14.45 μg/ml). Highest potassium solubilizing index (KSI)
was observed in isolate HMR56 (3.50) followed by HMR73 (3.46) and HMR29 (3.25). Five antagonistic
isolates HMR70, JMM16, HMR48, WHA64 and HMR25 were further selected for growth promotion and disease
control on mustard crop under pot house conditions. At 25 days after sowing (DAS), isolate HMR70 showed
77.5% increase in shoot dry weight followed by JMM16 (47.5%) whereas 100% disease control was observed with
HMR25, HMR48 and HMR70. At 50 DAS, JMM16 showed 161.1% increase in shoot dry weight followed by
HMR70 (136.1%) whereas 100, 80.0 and 80.0% disease control was observed with isolates HMR25, HMR48 and
WHA64, respectively. At 75 DAS, isolate HMR70 showed 114.6% increase in shoot dry weight followed by
HMR48 (77.5%) and JMM16 (55.0%) whereas 100, 83.33 and 83.33% disease control was observed in HMR25,
HMR48 and HMR70. Single inoculation of isolates HMR70 and JMM16 showed significant increase in shoot dry
weight as compared to control. Coinoculation of rhizobacterial isolates HMR70, HMR48 and HMR25 with A.
brassicae caused 83.33, 83.33 and 100.0% disease control, respectively at 75 days of plant growth. Rhizobacterial
isolates HMR70, JMM16 and HMR25 showed more stimulation of mustard growth and also suppressed the
disease. These three rhizobacterial isolates could further be assessed for their plant growth promotion and disease
control potential under field conditions for their subsequent use as efficient biofertilizer and biocontrol agents.
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Keywords
Bacteria, Planting, Diseases, Biological development, Fungi, Productivity, Biological control, Vegetative propagation, Pathogens, Biological phenomena