Isolation, characterization, and evaluation of bacterial root and nodule endophytes from chickpea cultivated in Northern India.

Endophytic bacteria from roots (12 isolates) and nodules (76 isolates) of chickpea legume grown under CCS Haryana Agricultural University farm were isolated. Among the endophytic bacteria, 50% from roots and 93.4% from nodules were Gram positive spore formers. Large number of endophytes from roots and nodules solubilized phosphate and produced ammonia. Isolate CRE3, and CNE215, were most efficient P solubilizers and. CRE12 and CNE76 being most efficient ammonia producer. Interestingly, few endophytic bacteria produced organic acid. Further selected 62 isolates were used to determine molecular diversity by RFLP of PCR amplified 16S rDNA. Endophytes from roots formed five separate clusters and nodule endophytes formed 13 clusters. Isolate CNE215 from nodules and CRE1 from roots possessed multiple beneficial traits and belonged two different clusters. These two isolates were identified after amplification and sequencing of 16S rRNA gene. Isolate CNE215 showed more than 98% similarity with partial sequence of 16S rRNA gene of Bacillus subtilis, whereas CRE1 showed more than 98% similarity with Bacillus licheniformis. Efficacy of these two strains was evaluated under field conditions and an increase up to 22.5% in grain yield over uninoculated control was observed with B. subtilis strain CNE215, whereas all the recommended biofertilizers were able to record an increase upto 14.4%.

Studies on salinization in Haryana soils on free-living nitrogen-fixing bacterial populations and their activity.

A total of 26 soil samples from saline soils of Haryana were collected. Based on their electrical conductivity (EC) values, which varied from 1.04 to 21.00 dS m(-1), the soils were categorized into non-saline soils (EC 0-2 dS m(-1)), weakly saline soils (EC 2-4 dS m(-1)), saline soils (EC 4-8 dS m(-1)), strongly saline soils (EC 8-16 dS m(-1)), and very strongly saline soils (EC >16 dS m(-1)). The pH values of these soil samples ranged from 6.03 to 8.62, while organic C, total N, and available P were in the range of 0.06-0.94%, 0.07-0.15%, and 0.11-0.29 µg g(-1) soil, respectively. As a measure of the impact of salinity on free-living N(2) fixers and their activity, the total bacterial populations on four media (Jensen's nitrogen-free medium, malate medium, Burk's medium, and soil extract agar medium) decreased from 6.12 to 3.70 log CFU g(-1) soil with increasing salinity level. PCR amplification of the nifH region of the DNA from 234 selected morphotypes from all the media showed the presence of nifH in 71 isolates. Out of these, 37% of the isolates were obtained using Jensen's medium; 35, 28, and 21% of the isolates were obtained using soil extract medium, Burk's medium, and malate medium, respectively. The majority of the free-living N(2) fixers (67%) were Gram negative. Apart from the acetylene reduction assay (ARA) activity in these isolates, other beneficial traits like ammonia excretion and indole acetic acid (IAA) production were also present. A decreasing trend in the activities was observed with increasing salinity levels. Isolates JN6, BP8, and MJ4 showed the highest ARA activity, ammonia excretion, and IAA production. The performance of isolates like BNC2 with good ARA activity, ammonia excretion, and IAA production and isolated from a very strongly saline soil should be further evaluated under high-saline conditions.

Establishment of Azotobacter on plant roots: chemotactic response, development and analysis of root exudates of cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.).

Biofertilizers contribute in N(2) fixation, P solubilization, phytohormone production and thus enhance plant growth. Beneficial plant-microbe interactions and the stability and effectiveness of biofertilizer depend upon the establishment of bacterial strains in the rhizosphere of the plant. This interaction depends upon many factors, one of them being plant exudates. Root exudates are composed of small organic molecules like carbonic acids, amino acids or sugars etc., which are released into the soil and bacteria can be attracted towards these exudates due to chemotaxis. The chemotactic behaviour of Azotobacter strains was studied using cotton (Desi HD 123 and American H 1098) and wheat (WH 711) seedlings and the root exudates of these two plants were chemically characterized. Analysis of the root exudates revealed the presence of sugars and simple polysaccharides (glucose), amino acids (glutamate, lysine) and organic acids (citric acid, succinic acid, maleic acid, malonic acid). Differences between cotton cultivars in root exudates were observed which influenced chemotactic response in Azotobacter. These results indicate colonization with rhizobacteria which implies that optimal symbionts, on the sides of both plant cultivar and bioinoculant bacteria can lead to better plant growth under cultivation conditions.