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. cereus , B. subtilis , Azotobacter ), brinjal
(Azospirillum , Azotobacter ) 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.