No abstract

Bacteria-mediated plant growth promotion is a well-established and complex phenomenon that is often achieved by the activities of more than one plant growthpromoting (PGP) trait, which may not always be present in a single organism. Biofilms developed using a combination of two organisms with useful plant growth-promoting rhizobacteria (PGPR) traits may provide a definite advantage. In this context, in vitro studies were conducted evaluating the PGP traits of novel biofilms developed using Trichoderma as matrix and agriculturally important bacteria (Azotobacter chroococcum, Pseudomonas fluorescens and Bacillus subtilis) as partners. Such biofilms exhibited higher values for various biochemical attributes as compared to the individual organisms and dual cultures. Trichoderma-Bacillus and Trichoderma-Pseudomonas biofilms exhibited enhanced antifungal activity, ammonia, indole acetic acid (IAA) and siderophore production, as compared to the other treatments. Trichoderma-Azotobacter biofilm recorded the highest nitrogenase activity and 1-aminocyclopropane-1carboxylic (ACC) deaminase activity. The synergism in terms of the PGP traits in the biofilms revealed their promise as superior PGP inoculants.

Greenhouse and laboratory studies were undertaken to evaluate the suitability of extractants for determining the boron (B) status of arid soils of Rajasthan (India) using mustard (Brassica juncea L.) as a test crop. Mustard is an important oilseed crop of northern India, which is widely grown in Rajasthan. This crop is sensitive to B deficiency. For predicting response of mustard to B application, several extractants have been tried with variable results. Seven extractants, commonly used for estimating the availability of B, were evaluated and B in soil extract and in plant tissue were assayed using the azomethine-H colorimetric method. The suitability of seven extractants for ORDER REPRINTS determining available soil B was assessed by correlating the amount of extractable B in untreated soils with Bray's percent yield, plant tissue B concentration and B uptake by mustard. The results indicate that hot 0.01 M CaCl 2 and hot water extracted comparatively more B than other extractants. The amount of B extracted by these extractants was found to be in the following order: hot 0.01 M CaCl 2 > hot water > 1.0 M NH 4 OAc (pH 4.8) > sorbitol þ NH 4 OAc þ TEA ¼ mannitol þ NH 4 OAc þ TEA > mannitol þ CaCl 2 > salicylic acid þ NH 4 OAc þ TEA. Simple correlation coefficients of the amount of B extracted by different extractants and soil characteristics were calculated. Based on present studies, the suitability of extractants for mustard crop in arid soils of Rajasthan may be arranged as follows: hot 0.01 M CaCl 2 > hot water > sorbitol þ NH 4 OAc þ TEA ¼ mannitol þ NH 4 OAc þ TEA > 1.0 M NH 4 OAc (pH 4.8) > salicylic acid þ NH 4 OAc þ TEA> mannitol þ CaCl 2 soluble B. The critical values in respect to sufficiency of extractable B for mustard plants were: 0.52 for hot 0.01 M CaCl 2 , 0.33 for hot water, 0.31 for mannitol þ CaCl 2 , 0.34 for 1.0 M NH 4 OAc (pH 4.8), 0.19 for sorbitol þ NH 4 OAc þ TEA, 0.24 for mannitol þ NH 4 OAc þTEA and 0.19 mg kg À1 for salicylic acid þ NH 4 OAc þ TEA. The critical B concentration in mustard plants was 28.05 mg kg À1 on dry weight basis.

No abstract

No abstract

No abstract

No abstract

No abstract