Drought-Tolerant Pseudomonas spp. Improve the Growth Performance of Finger Millet (Eleusine coracana (L.) Gaertn.) Under Non-Stressed and Drought-Stressed Conditions

Application of plant growth-promoting bacteria(PGPB)is an environmentally sustainable option to reduce the effects of abiotic and biotic stresses on plant growth and productivity.Three 1-aminocyclopropane-1-carboxylic acid(ACC)deaminase-producing drought-tolerant bacteria were isolated from a rain-fed agriculture field in the Central Himalaya of Kumaun region,Uttarakhand,India and evaluated for their efficiency in improving finger millet(Eleusine coracana(L.)Gaertn.)plant growth under non-stressed and drought-stressed conditions.These bacteria withstood a substrate metric potential of -1.0 MPa(30% polyethylene glycol 8000)and therefore were considered drought-tolerant.These strains were identified as Pseudomonas spp.by fatty acid methyl ester analysis and 16S rRNA gene sequencing.The ACC deaminase activity of these strains was characterized at the biochemical level,and the presence of acd S gene,the structural gene for ACC deaminase,was confirmed by the polymerase chain reaction.Two sets of pot trials in glass house were set up,one for normal(non-stressed)and the other for drought-stressed conditions.After 5 weeks,one set of plants was subjected to drought stress for 5 d,while the other set continued to be watered.The same growth parameters were recorded for both sets of plants after 40 d of plant growth.The results of pot trials showed that treatments inoculated with ACC deaminase-producing bacterial strains significantly improved the growth performance of finger millet plants and foliar nutrient content as compared to uninoculated treatments under both non-stressed and drought-stressed conditions.In addition,a significant increase in antioxidant activity was observed,wherein bacterial stain inoculation improved plant fitness by protecting it from oxidative damage induced by drought.     

Use of specific phospholipid fatty acids for identifying and quantifying the external hyphae of the arbuscular mycorrhizal fungus Gigaspora rosea

The external hypha of arbuscular mycorrhizal (AM) fungi, extending from roots out into soil, is an important structure in the uptake of phosphate from the depletion zone around each root. In this paper, we analysed some phospholipid fatty acids (PLFAs) derived from external hyphae of four AM fungi (Glomus etunicatum, Glomus clarum, Gigaspora margarita and Gigaspora rosea) to find fatty acids which may be useful as specific markers for identifying and quantify the external hyphae of Gigaspora species. Leek (Allium porrum L.) seedlings inoculated with each AM fungus were grown in river sand. Sand samples were collected and four PLFAs (16:1ω5, 18:1ω9, 20:1ω9 and 20:4) in the sand were analysed. In addition, the hyphal biomass in the sand was determined by the direct microscopic method. PLFAs 18:1ω9 and 20:4 were found in all the AM-inoculated and non-inoculated sand samples. PLFA 16:1ω5 was detected in the sand inoculated with G. etunicatum, G. clarum and Gi. rosea. PLFA 20:1ω9 was detected only in the sand inoculated with Gi. rosea. PLFAs 16:1ω5 and 20:1ω9 were not found in the sand inoculated with Gi. margarita. The amount of PLFA 20:1ω9 was closely correlated with the amount of biomass of external hyphae of Gi. rosea (r=0.937, P<0.001), whereas no correlation was observed for PLFA 16:1ω5. The 20:1ω9 content of Gi. rosea was approximately 6.56 nmol mg⁻¹ hyphal biomass. We suggest that PLFA 20:1ω9 can be used as a specific marker for identifying and quantifying the external hyphae of Gi. rosea, at least in controlled experimental systems.