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Keywords: Applied Sciences
Agriculture & related technologies
Techniques, equipment & materials
Issue Date: 2010
Abstract: Several rhizobial strains were isolated from the root nodules of mung bean (Vigna radiate L.), chickpea (Cicer arietinum L.) and lentil (Lens culinaris M.) plants collected from different sites by using YMA medium. Colonies showing prolific growth were streaked on fresh medium and twenty fast growing pure cultures from each host were selected, coded and preserved in 20% glycerol at -20 °C. A series of jar experiments were carried out to screen three most efficient isolates from twenty selected isolates of each rhizobium species (i.e. Rhizobium phaseoli, Mesorhizobium ciceri and Rhizobium leguminosarum) on the basis of their growth promoting potential with maize and wheat seedlings under axenic conditions. Results of the jar experiments revealed that most of the isolates from all the three rhizobium species exhibited growth promoting activities in both the crops except the isolates of R. leguminosarum species in which most of the isolates remained deleterious for maize seedlings. Based upon the data regarding jar experiments, nine isolates (i.e. CRI 28 , CRI 34 , CRI 35 , LSI 21 , LSI 29 , LSI 32 , A 18 , S 6 and S 17 ) screened as the best for maize were found different from the nine best isolates (i.e. CRI 31 , CRI 37 , CRI 38 , LSI 19 , LSI 23 , LSI 30 , N 8 , N 16 and S 43 ) screened for wheat crop clearly indicating the strain-crop specificity. These isolates were used for subsequent pot and field studies. In case of pot experiments, increases up to 47.89% and 30.29% in grain yields of maize and wheat, respectively over un-inoculated control were recorded due to inoculation with the selected rhizobial isolates. Whereas, under field conditions, inoculation with the selected rhizobial isolates resulted in increased plant height (up to26.51%), shoot fresh and dry weight (up to 76.95 and 52.26%), air dried cob yield (up to 64.53%), grain yield (up to 63.37%), 1000-grain weight (up to 28.88%), %K in grains and straw (up to 29.49 and 29.08%), %N in grains and straw (up to 32.06 and 25.45%) and %P in grains and straw (up to 47.37 and 41.57%) of maize compared with un-inoculated control while, in wheat, the selected isolates improved plant height (up to 17.54%), tillers per plant (up to 39.29%), average spike length (up to 45.30%), straw yield (up to 35.15%), grain yield (up to 36.67%), 1000-grain weight (up to 28.52%), %K in grains and straw (up to 46.77 and 17.78%), %N in grains and straw (up to 16.49 and 34.55%) and %P in grains and straw (up to 25.30 and 66.66%) compared with un-inoculated control. Overall, each set of the nine selected isolates promoted the growth and yield of their respective test crop in pots and also proved as effective PGPR in field but their efficacy varied among the species. Characterization of the selected rhizobial isolates of maize and wheat revealed that all the isolates were having more than one mechanism of action. Hence the growth promotion caused by these selected isolates could be a function of multiple mechanisms. Conclusively, it is stated that selected rhizobial strains could be used as PGPR for non-legumes. Moreover, the use of general PGPR strains of Rhizobium spp. could be avoided to a significant extent without knowing the particular information about the compatibility potential of the strains toward specific crop variety, soil and environmental conditions for which it could be used. In other words, strains of Rhizobium spp. recognized for the growth and yield promotion of non- legumes could be used efficiently and effectively only against specific host under specific set of soil and environmental conditions for maximum benefits.
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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