Improvement in seed performance, management of finger millet [Eleusine coracana (L.) Gaertn.] through bio-prospecting fluorescent Pseudomonas spp. with respect to their plant growth prom
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Date
2016-06
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College of Forestry, Ranichauri campus, V.C.S.G Uttarakhand University of Horticulture and Forestry
Abstract
Due to increasing incidence of climate change, the time is opportune for identifying such crops that are able to tolerate adverse environmental conditions, without having a significant effect on their growth and development. Finger millet (Eleusine coracana L.) is one of them, being a hardy crop it is relatively easy to grow under stressful regimes, without hampering the net productivity. The crop finger millet is being cultivated in the Himalayan region by the traditional hill farmers as life support plant species from time immemorial. Finger millet characteristically adapt to unfavourable ecological conditions including biotic and abiotic stresses. Diseases and insects pests’problems have been negligible in such hardy crops. However, with changing climate, it is now known to be affected by several diseases and their lives are exposed to numerous abiotic stresses viz., drought, uncertainty in rains, flood etc. In view of this, a repository of 42 fluorescent Pseudomonas isolates was established with a particular reference for improving seed performance, management of diseases and delay in drought response of finger millet. All the isolates were morphologically and biochemically characterized. Many fluorescent pseudomonads from the repository were identified as good HCN producers, siderophore producers and P-solubilizers. In vitro dual culture assay revealed that out of 42 bacterial isolates, 27 isolates were antagonistic to Sclerotium rolfsi (ranged from 22.5 % to 83.5 %), 30 to Rhizoctonia solani (ranged from 21.2 % to 85.0 %), 26 to Pyricularia grisea (18.46 % to 80.0 %) and 25 isolates were antagonistic to Helminthosporium nodulosum (ranged from 36.2 % to 78.5 %), the four major pathogens causing foot rot, sheath/banded blight, blast and leaf spot diseases in finger millet respectively.
In present study, fluorescent pseudomonads viz., UUHF Psf-4, 11, 12, 15 and 41when applied through seed bio-priming performed best in enhancing seed quality parameters viz., first count, standard germination, root length, shoot length, plant height, seedling fresh weight, seedling dry weight and vigour index-I and II of finger millet plants when compared to untreated control under both in vitro and in vivo conditions. Among all the tested isolates UUHF Psf-4 was found to have maximum potential with respect to biocontrol and plant growth promotion activities. The present study also investigated the role of Pseudomonas inoculation through seed bio-priming method in alleviating deleterious effects of drought stress in finger millet. Green house study was conducted with an aim to explore the mechanism underlying plant water stress resilience in response to Pseudomonas inoculation. One factor was six treatments (five best isolates of Pseudomonas viz., UUHF Psf-4, 11, 12, 15 and 41 , selected on the basis of conducted different preliminary screenings and one untreated control) and other factor was five levels of drought stress viz., no stress, 6 DDS, 9 DDS, 12 DDS and 15 DDS. Measurements on membrane stability index, proline content, malondialdehyde (MDA) and phenolics content were carried out. With or without exposure to drought, seed bio-priming with Pseudomonas isolates promoted seedling growth, the most consistent effect being an increase in shoot and root growth. The primary direct effect of colonization was promotion of root growth, regardless of water status, and an increase in water content, which it is proposed, caused a delay in many aspects of the drought response of finger millet. Drought stress from 6 to 15 days of withholding water induced an increase in the concentration of many stress induced metabolites in finger millet leaves. Pseudomonas colonization caused a decrease in malondialdehyde content and an increase in phenolics concentration, proline and membrane stability index. Whereas maximum accumulation of malondialdehyde content was noticed in untreated control. Evidences presented in this research indicate that drought stress resistance in finger millet was alleviated through osmoregulation, amelioration of damage caused by ROS and accumulation of phenolics compounds along with increased root and shoot growth. It is concluded that seed bio-priming with selected fluorescent Pseudomonas isolates reduced the severity of the effects of drought stress though the amelioration was better in UUHF Psf-4 for most of the parameters studied under present materials and conditions. This research merits attention as it additionally opens the avenues for the use of application through seed bio-priming in finger millet plants for enhanced biotic and abiotic stress tolerance.