4. Discussion
Till now most studies have focussed on the PGPR on soil and plant performance (Berg and Zachow, 2011). As far as we know, there have been no such studies in the field of the chickpea seed endophytic bacterial interactive effects on the soil health as well as plant productivity. Our previous research studies showed the effect of chickpea seed bacterial endophytes on plant defence and plant growth in lab condition (Mukherjee et al., 2020b). The results of our present study revealed the effects of endophytes both on the plant growth and yield as well as in soil nutrients and health (Table. 2; Fig. 1 to 5). Among all the soil chemical property, soil pH did not show any significant change in our experiment both in pot and field condition, as the soil are slightly alkaline and didn’t show any significant effect on the yield. But other biochemical properties of soils like EC, OC and OM were significantly increased in all three treatments in consortia> E. cloacae BHUJPCS-21>E. hormaechei BHUJPCS-15> control order. This result indicates that the microbial consortia along with the microbe help to induce the soil quality through the change of EC, OC and OM, as these are important indicators of soil health and crop productivity. Where the electrical conductivity (EC) is an important physicochemical property directly linked with the concentration of soil ions, from the experimental data we can hypothesize that our microbial strains have the potential property to improve the EC of soil. OM is also an important factor for soil health and plant productivity and it helps to improve the soil water holding capacity, serve as raw source of soil and plant nutrients. Data also indicates that the seed endophytes application increase the nutrient availability (Available N, P and K) in experimental soil both in the pot and field condition. Soil nutrient is an essential property for the crop production. Thus N, P, K are also very crucial elements for several enzymes, proteins, hormones, amino acids and building block of genetic materials both in plants and microbes ( Maathuis 2009; Krouk et al., 2010, Mukherjee et al., 2019). During our experiment we observed that the consortia treatment showed highly significant response followed by E. cloacae BHUJPCS-21 and E. hormaechei BHUJPCS-15 under both pot and field conditions. Similar response was supported by Raklami et al., (2019) during soil analyses of microbial consortia treated experiment. We have observed a linear correlation with the increased plant dry weight and length, seeds production, pigments synthesis in microbial consortia treatments with increase in available soil N, P, K content. We have also observed increase in essential soil enzyme like alkaline phosphatase, urease, beta glycosidase and dehydrogenase (DHA) upon application of seed endophytic microbes and its consortia. The soil enzymes are known to be a function of microbial activity and our results clearly showed increase in soil enzyme that were directly linked that our microbial culture have some effect on the soil enzyme activity. Same result was observed by Guo et al., (2019) and showed that the application of microbes in soil enzymes in can increase the soil enzymes activity than the untreated soil. Increase in the plant health in terms of growth, dry weight, height and yield supported that the endophytic bacterial consortia helps to increase the crop health and productivity (Yadav et al., 2017). Increase in the crops’ productivity and soil health in the terms of essential enzymes and nutrients (Available N, P and K) was due to the fact that microbes are known to be functional as community in the soil ecology. It explains that high number of different property containing strains in microbial consortia led to the better alternative in terms of plant biomass, shoot length and crop productivity. To best of our knowledge this is the first-time report of chickpea seed endophytic microbial consortia for improving the soil health and increasing the crop productivity. Similar types of studies were done in tomato plant by the use of microbial consortia by Akintokun et al., (2016). Malik and Sindhu (2011) used another microbial consortium (Pseudomonas sp. and Mesorhizobium sp.) to increase the plant growth. Several different research works have been reported on the application of double microbial consortia in different plants to check the growth and yield of different plants such as potato (B. cereusB. subtilisAzotobacter ), brinjal (AzospirillumAzotobacter ) and Radish (B. subtilis  and P. fluorescens ) (Singh et al., 2013; Sood and Sharma2001; Patel et al., 2011; Mohamed and Gomaa 2012).
Increase in productivity is further supported by our finding of higher level of photosynthetic pigments such as chlorophyll a, b and total chlorophyll in the consortia treated test plants as compared with control. In the consortia treatments the chlorophyll contains in terms of chl a, chl b, total chlorophyll in chickpea both in pot trial and field trial significantly increased than the untreated control plants followed by other treatments. Eleiwa et al. (2012) showed similar results in wheat plant in field trial on the application of B. polymyx andA.brasilinseas which dramatically increase the amount of chlorophyll a, b and carotenoids in treated plants. The photosynthetic activity is directly proportional to the enhanced productivity (Mbarki et al., 2018), the pigments help to accumulate more energy and also helps in higher photosynthate assimilation in plants.
Some other previous reports have suggested the effect of PGPR using single-strain inoculations (Lucy et al., 2004), but the microbial consortia also showed more beneficial effects than single strain (Ryu et al., 2007). Seed endophytic microbial consortium possibly mimics the natural soil environmental conditions where the important soil microbial community can leave. Hence, in the present study enhanced soil nutrient, other physiochemical content and growth and yield of chickpea plant in the endophytic microbial consortium treatment could be an attribute to the natural and synergistic environmental effects of the two-chickpea seed endophytic bacteria.