Bacterial diversity and bio-chemical properties in the rhizosphere soils of Cumin and Coriander

Abstract

India is a major producer and consumer of seed spices. There are numbers of studies have been done on soil and crop parameters of these but there is lacuna on the study of soil bacterial community analysis in the seed spices. Soil microorganisms are known to play critical role in soil biochemical processes, nutrient cycling, soil fertility, and also influences plant performances. With the objectives to know microbial community composition and soil chemical and biological properties in rhizosphere of two seed spices plants- cumin and coriander we collected five soil samples from rhizosphere of cumin (NRCSS-SL-1 and NRCSS-SL-3) and coriander (NRCSS-SL-2, NRCSS-SL-4 and NRCSS-SL-5) grown in arid and semi-arid regions of India. Electrical conductivity (0.32–0.53 ds/m), organic carbon (0.03–0.64%), total nitrogen (223–258 kg/ha), total phosphorous (30–47.3 kg/ha) and total potash (206–388 kg/ha) were varied in samples. In biological properties bacterial and fungal populations were varied between 98.33 and 210 c.f.u. × 104 g−1 soil and 32–69.33 c.f.u. × 103 g−1 soil, respectively. Different soil enzyme activities dehydrogenase (37.96–57.68 µg TPF g−1 soil 24 h−1), acid phosphatase (14.66–24.72 µg p-NP g−1 soil h−1), and alkaline phosphatase (27.08–37.58 µg p-NP g−1 soil h−1) were varied in samples. Soil chemical and biological activities were found highest in NRCSS-SL-2 followed by NRCSS-SL-5 and lowest in NRCSS-SL-1. Amplicon sequencing of 16S rRNA gene was done in the collected samples to identify and quantify the bacterial community structure. A total 37 phyla were observed with varying abundances in different samples. Next generation sequencing shows that three phyla were present in order of Firmicutes (26–43%) > Proteobacteria (23–29%) > Actinobacteria (11–22%) and they were dominating in all the soil samples. Relative abundance of order Bacillales was highest (26–35%), followed by Rhizobiales (8–10%) and Actinomycetales (7–11%) in samples. There were many orders which found in very low abundance and moreover some were not present in all soil samples but these may play significant role in the soil ecosystem. The study concludes that rhizosphere soil of seed spices harbors wide range of unculturable microbes and climatic conditions have impact on their community structure. Microbial activities in terms of microbial colony count and enzyme activity are also influenced by soil chemical properties.