Abstract
Soil samples from various agro climatic zones of Andhra Pradesh, India were collected and screened for the isolation of effective microbes during 2009-10. Based on the efficacy and in vitro compatibility, nine microbial strains (Bacillus spp, Streptomyces spp, Azotobaacter spp and Frauteria spp) were identified and christened (VBT 01 to VBT 09). Each strain was evaluated for its plant growth promoting efficacy (PGP) in black gram (Vigna mungo (L.) Hepper) and its antagonistic activities against select pathogens. Pot culture studies recorded high percentage of seed germination (94.7%) when the black gram seeds were coated with VBT 09 as compared to untreated control (83.2%). Maximum radical length of 8.0 cm was recorded in VBT 09 as compared to control (0.53cm). PGP traits of all the strains such as Hydrogen cyanide (HCN), ammonia production and hydrolytic enzymes like cellulase, pectinase, protease and amylase were recorded at various levels. The positive production of HCN was recorded in VBT 05. Antagonistic activity was recorded against Macrophomina phaseolina (VBT 03), Sclerotium rolfsii (VBT 07), Fusarium oxysporum (VBT 05) and Rhizoctonia solani (VBT 04). Mycoparasitic activity of VBT 02 strain was significantly high (53.8% inhibition over control) against sclerotial bodies of Sclerotium rolfsii. However, none of the strains exhibited sclerotial parasitism against Rhizoctonia solani. Pot culture assay to study the consortia effect at different proportions recorded significant increase in shoot length (11.2cm) as compared to chemical fertilizer (9.77cm) and control (8.51cm).The root volume and shoot dry mass was 0.5cm3 and 0.15cm3 as compared to control 0.17cm3 and 0.09cm3 respectively. The total dry mass was higher in consortia treated pots (0.23g) than the pots treated with chemical fertilizer (0.2g). The consortium is named as Omega. An on-farm trial is being carried out to evaluate its efficacy as soil conditioner, plant growth promoter and disease resistance capabilities in paddy and sugarcane.
Highlights
Plant growth promoting microorganisms (PGPM) are heterogeneous in nature comprising bacteria, fungi and actinomycetes that survive in and around the root rhizosphere
Values superscripted by same alphabet are not significantly different according to Fisher’s Least Significance Difference test (P
Omega with nine effective microbes proved to be beneficial to black gram as efficient PGPR with good soil conditioning capabilities
Summary
Plant growth promoting microorganisms (PGPM) are heterogeneous in nature comprising bacteria, fungi and actinomycetes that survive in and around the root rhizosphere. PGPM enhance the plant growth and yield either directly or indirectly [1]. The direct plant growth promotion involves in the solubilization or mobilization of important nutrients (phosphorous, potash, zinc, sulphur, and iron) or fixing atmospheric nitrogen for the uptake of plants. They are known to produce various plant growth promoting hormones like indole acetic acid, gibberlic acid, cytokinins and ethylene [2]. In addition to these traits, an effective PGPM should be a rhizosperic competent, able to cope with the biotic and abiotic stresses and colonize in the rhizospere [8]
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