Future food situation will be strongly dominated by the changes in the population structures, developing economies, changes in diet and associated demand for food.1 It is assumed that the growth scenario of the population is predicated to increase by a further 700 million people in the Indogangetic Plains of India (IGP) (about equal to the current population of Europe) in the next 30 years. This will result in a greater demand for food, and it is estimated that the food grain requirement by 2020 in the region will be almost 50% more than at present.2 The IGP is now called as the ‘bread basket’ for South Asia, which is known to be the most extensive fluvial plains of the world. Rice and wheat are the two major cereal crops of this region, and this region produces about 50% of the total foodgrains to feed 40% of country’s population.3 IGP crops were consistently infested with endemic diseases such as sheath, rots, and wilt diseases caused by phytopathogenic fungi, that is, Rhizoctonia, Macrophomina and Fusarium were difficult to control because of their soil-borne pathogenic nature. They affect countries economy (US$36 million losses in India), as well as crop yields in tropical and subtropical regions.4, 5 Pesticides were reported to cause adverse effects on soil ecosystem and also induce resistance in pathogens.6 Nowadays biological pesticides are used as a potential tool to replace or augment conventional plant disease management that makes use of synthetic pesticides.7, 8, 9, 10 Rhizobacteria are beneficial to crops yields via nutrient acquisition,11 biocontrol,12, 13 plant hormone-like production14 and induction of systemic resistance.15 Bacillus is cosmopolitan in nature contributing 92% soil microbial library and effective biocontrol agent for various pests such as Macrophomina phaseolina,16, 17 Rhizoctonia solani18, 19 and Fusarium udum.20, 21 Various Bacillus species have been reported for their capacities to protect plants from pathogens and stimulate plant growth since long time.16, 17, 18, 19 They are used as a suitable biocontrol agent because of their ability to grow rapidly in vivo as well as in vitro condition, colonize and multiply in the rhizosphere, and compete aggressively with other microorganisms.22 The estimation of microbial diversity along with study of its ecological habitat is required for understanding its biogeography, community assembly and ecological processes.23 Ribosomal genes (16S rRNA gene) sequencing provides sufficient genetic information for bacterial identification, and it has been widely applied to the identification of different Bacillus species.24, 25 Amplified rDNA restriction analysis (ARDRA) has been useful for the identification and de-duplication of the microbes within a genus as well as at species level.26 In the present work, we discussed the population frequency and diversity analysis of Bacillus showing antagonisms against endemic tropical and subtemperate soil-borne phytopathogens (M. phaseolina, R. solani and F. udum), from different regions of IGP, India, as well as analysis of soil macronutrient composition (OC, N, P and K) and molecular characterization of Bacillus isolates through ARDRA analysis followed by identification by 16S rRNA gene sequencing of antagonistic Bacillus from IGP regions of India (see Supplementary Information).

A total of three hundred thirty-four Bacillus isolates were isolated from different ecoregions of IGP. The population frequencies of Bacillus isolates were fluctuated (3–72 × 104 g soil−1) such as Punjab belt soils harboured maximum Bacillus population while, Uttrakhand region had least population counts (Table 1). The fluctuation of Bacillus distribution may be due to difference in the physiochemical properties of soil and non uniform distribution of nutrients also.28

Table 1 Geographical location, soil physiochemical properties and enumeration of Bacillus isolates from Indogangetic Plains of India
Full size table

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