H. S. Gupta

Cold tolerance and plant growth promotion potential of Serratia marcescens strain SRM (MTCC 8708) isolated from flowers of summer squash (Cucurbita pepo).

Aim:  To determine the cold tolerance and plant growth promotion potential of Serratia marcescens strain SRM (MTCC 8708).

Characterisation of a psychrotolerant plant growth promotingPseudomonas sp. strain PGERs17 (MTCC 9000) isolated from North Western Indian Himalayas

A psychrotolerant, Gram negative, rod shaped, plant growth promoting bacterium (PGPB) was isolated from high altitude of North Western Indian Himalayas. The identity of the bacterium was confirmed by morphological, biochemical and sequencing of the 16S rRNA gene. The sequence analysis revealed maximum similarity withPseudomonas vancouverensis. It exhibited tolerance to a wide pH range (5–12; optimum 7.0) and salt concentrations up to 5% (w/v). The isolate produced 8.33 and 1.38 μg/ml of IAA at 15°C and 4°C respectively, on the third day after incubation. It solubilised 42.3, 66.3 and 74.1 μg/ml of tricalcium phosphate at 4, 15 and 28°C respectively after seven days of incubation. The strain also possessed HCN and siderophore production abilities at 4°C. It exhibited inhibitory activity against several phytopathogenic fungi in three different bioassays. The maximum relative growth inhibition was recorded againstSclerotium rolfsii andRhizoctonia solani (100%), followed byPythium sp. (73.1%) andFusarium oxysporum (19.7%), in volatile compound assays. Seed bacterization with the isolate enhanced the germination of wheat seedlings grown at 18±1°C by 20.3%. Bacterized seeds also recorded 30.2 and 27.5% higher root and shoot length respectively, compared to uninoculated controls.

Isolation, molecular characterization and growth-promotion activities of a cold tolerant bacterium Pseudomonas sp. NARs9 (MTCC9002) from the Indian Himalayas

A bacterium that grows and expresses plant growth promotion traits at 4 degrees C was isolated from the rhizospheric soil of Amaranth, cultivated at a high altitude location in the North Western Indian Himalayas. The isolate was Gram negative and the cells appeared as rods (2.91 x 0.71 microm in size). It grew at temperatures ranging from 4 to 30 degrees C, with a growth optimum at 28 degrees C. It exhibited tolerance to a wide pH range (5-10; optimum 8.0) and salt concentrations up to 6% (wt/vol). Although it was sensitive to Rifampicin (R 20 microg mi-1), Gentamicin (G 3 microg mi-1), and Streptomycin (S 5 microg mi-1), it showed resistance to higher concentrations of Ampicillin (A 500 microg mi-1), Penicillin (P 300 microg mi-1), Polymixin B sulphate (Pb 100 microg mi-1) and Chloramphenicol (C 200 microg mi-1). The 16S rRNA sequence analysis revealed maximum identity with Pseudomonas lurida. The bacterium produced indole Acetic Acid (IAA) and solubilizes phosphate at 4, 15 and 28 degrees C. It also retained its ability to produce rhamnolipids and siderophores at 15 degrees C. Seed bacterization with the isolate enhanced the germination, shoot and root lengths of thirty-day-old wheat seedlings by 19.2, 30.0 & 22.9% respectively, as compared to the un-inoculated controls.

Growth promotion of wheat seedlings by Exiguobacterium acetylicum 1P (MTCC 8707) a cold tolerant bacterial strain from the Uttarakhand Himalayas.

Exiguobacterium acetylicum strain 1P (MTCC 8707) is a gram-positive, rod-shaped, yellow pigmented bacterium isolated from soil on nutrient agar plates at 4°C. The identity of the bacterium was arrived on the basis of the biochemical characterization, BIOLOG sugar utilization pattern and sequencing of the 16S rRNA gene. It grew at temperatures ranging from 4 to 42°C, with temperature optima at 30°C. It expressed multiple plant growth promotion attributes such as phosphate solubilization, indole acetic acid (IAA), siderophore and hydrogen cyanide (HCN) production, differentially at suboptimal growth temperatures (15 and 4°C). At 15°C it solubilized phosphate (21.1 μg of P ml−1 day−1), and produced IAA (14.9 μg ml−1 day−1) in tryptophan amended media. Qualitative detection of siderophore production and HCN were possible at 15°C. At 4°C it retained all the plant growth promotion attributes. Seed bacterization with the isolate, positively influenced the growth and nutrient uptake parameters of wheat seedlings in glass house studies at suboptimal cold growing temperatures.

Enhanced soybean (Glycine max L.) plant growth and nodulation by Bradyrhizobium japonicum-SB1 in presence of Bacillus thuringiensis-KR1

Abstract Nodulation and subsequent nitrogen fixation are important factors that determine the productivity of soybean (Glycine max L.). The beneficial effects of nodulation can be enhanced when rhizobial inoculation is combined with plant-growth-promoting bacteria (PGPB). The PGPB strain Bacillus thuringiensis-KR1, originally isolated from the nodules of Kudzu vine (Pueraria thunbergiana), was found to promote growth of soybean plants (variety VL Soya 2) under Jensens tube and growth pouch conditions, when co-inoculated with Bradyrhizobium japonicum-SB1. Co-inoculation with Bacillus thuringiensis-KR1 (at a cell density of 10 cfu) provided the highest and most consistent increase in nodule number, shoot weight, root weight, root volume, and total biomass, over rhizobial inoculation and control, under both conditions. The results demonstrate the potential benefits of using nonrhizobial nodule occupants of wild legumes for the co-inoculation of soybean, with Bradyrhizobium japonicum-SB1, in order to achieve plant-growth promotion and increased nodulation.

COINOCULATION OF RHIZOBIUM LEGUMINOSARUM-PR1 WITH A COLD TOLERANT PSEUDOMONAS SP. IMPROVES IRON ACQUISITION, NUTRIENT UPTAKE AND GROWTH OF FIELD PEA (PISUM SATIVUM L.)

The effect of a cold tolerant Pseudomonas sp. Strain, PGERs17, on nodulation, iron acquisition and nutrient uptake of field pea (Pisum sativum L. variety VL Matar 42) seedling was determined on the basis of iron acquisition and growth promotion, chlorophyll content, physiologically available iron, Leghaemoglobin from nodules, nitrogen (N) uptake, phosphorus (P) uptake, potassium (K) uptake, iron (Fe), and zinc (Zn) uptake of shoots. Coinoculation of PGERs17 with Rhizobium leguminosarum-PR1 significantly (P > 0.05) increased nodulation (156.2%) and 57.1% higher plant biomass. Coinoculation enhanced total chlorophyll content (31.5%), physiologically available iron (106.7%), total iron (95.9%) and 17.5-fold higher leghaemoglobin concentration in root nodules over uninoculated control plants. Coinoculation also enhance N uptake (66.3%), P uptake (23.3%), K uptake (47.1%), and 2.75-fold higher Zn uptake of shoots compare with uninoculated control. Hence, cold tolerant Pseudomonas sp. strain PGERs17 can be employed as a bioinoculant along with Rhizobium leguminosarum-PR1 to enhance plant growth, iron acquisition and nutrient uptake of field pea enhance plant growth, iron acquisition and nutrient uptake of field pea seedlings at cold temperature conditions.

Isolation and toxicity evaluation of bacterial entomopathogens against phytophagous white grubs (Coleoptera: Scarabaeidae) in Indian Himalayan hills

The north-western Indian Himalayan hill region contains around 40 phytophagous species of white grub (Coleoptera: Scarabaeidae). Anomala dimidiata and Holotrichia seticollis are the predominant species. Under natural conditions, up to one-fifth of the population of the grubs was found to exhibit symptoms of bacterial infection. Therefore, we attempted to isolate and characterize the most potent bacterium for the management of white grubs. Of 27 bacterial isolates tested against A. dimidiata, WGPSB-2 was found to be highly toxic. Based on morphology, physiology, biochemistry and sequencing of the 16S rRNA gene, the isolate WGPSB-2 was identified as Bacillus cereus. A dose determination bioassay indicated that first instar grubs of A. dimidiata and H. seticollis were more susceptible than second instars. Although the LT90 values for second instar grubs exceeded 8 weeks, the grubs stopped feeding after ingestion of spores, mostly after the third week. In outdoor microplots, a dose of 1.7 × 1010 spores/m2 applied to the root zone was found to be potentially satisfactory for control of the pests. Bacillus cereus isolate WGPSB-2 appears to be a potentially effective bacterial pathogen for the management of white grubs.

Expression of Soil Chemical and Biological Behavior on Nutritional Quality of Aromatic Rice as Influenced by Organic and Mineral Fertilization

The aim of the study was to evaluate changes in the yield and nutritional characteristics of aromatic rice as influenced by organic versus mineral fertilization. Aromatic rice was grown on four levels of cattle manure (CM; 5, 10, 15, and 20 Mg ha−1). Other treatments were equivalent amounts of nitrogen (N), phosphorus (P), and potassium (K) in different levels of manure fertilizer and mineral fertilizer. After 6 years of cropping, organically managed plots were superior to mineral-fertilized plots in terms of grain yields of rice at 5, 10, and 15 Mg ha−1. Cattle manure at 20 Mg ha−1 and its equivalent NPK through mineral-fertilizer treatment provided 41.1% and 37.9% increases in average grain yield (5.2 and 5.1 Mg ha−1) over the unamended control. Protein content was greater in mineral-fertilized rice grains at all levels of CM. Soil dehydrogenase, β-glucosidae, urease, and acid phosphatase activities were greater in soil treated with CM than soil treated with the corresponding mineral fertilizer at all levels. There was buildup of soil-available N, K, and iron (Fe) in soils treated with CM. Grain hardness increased with increasing rates of nutrient application for both mineral-fertilized and organically grown rice; in contrast, amylose content was lower in treatments receiving more nutrients, irrespective of nutrient sources. In terms of functional property, phenol content in rice grain increased with increasing nutrient supply. Potassium and Fe contents were more in CM-treated rice than in mineral-fertilized treatments at greater rates of application. Results suggest that after building up the soil nutrient status, comparable yield and better nutritional and functional qualities of rice can be achieved in organically managed soils than in mineral-fertilized soils.

Yield potential of garden pea (Pisum sativum L.) varieties, and soil properties under organic and integrated nutrient management systems

The identification of suitable crop varieties that respond best to organic management is the key to achieving better crop yields. A field experiment was conducted during the winter season of 2005–2006 and 2006–2007 at Almora (Indian Himalayas) to evaluate the performance of five varieties of garden pea (Pisum sativum L.) and changes in the soil properties under organic and integrated nutrient management (INM) systems. The yield reduction under organic management was 14.4% in 2005–2006 and 10.1% in 2006–2007 compared with INM. Among the garden pea varieties ‘Vivek Matar 9’, ‘Vivek Matar 8’ and ‘Azad pea 1’ produced similar but significantly higher pod yield compared to other varieties. The soil pH, organic carbon, and microbial activities in terms of dehydrogenase and phosphatase (acid and alkaline) were higher in the plots under organic management compared to INM. The latter, however, had higher activity of urease, and N, P, and K contents in soil. We conclude that at least 15–20% price premium for organic garden pea may be required to offset the higher cost of cultivation and low yields under organic production system. Among the garden pea varieties, ‘Azad pea 1’, ‘Vivek Matar 8’ and ‘Vivek Matar 9’ were found suitable for organic cultivation.

Evaluation of mulching, stale seedbed, hand weeding and hoeing for weed control in organic garden pea (Pisum sativum sub sp. Hortens L.)

Weeds are often recognized as the principal biotic constraint to organic crop production. Development of suitable weed control measures is, therefore, a prerequisite for profitable organic farming. A field experiment was conducted during the winter season of 2003–2004 and 2004–2005 in the Indian Himalayas to evaluate the effect of mulching, stale seedbed, hand weeding and hoeing on weeds and yield of organic garden pea (Pisum sativum sub sp. Hortens L.). The weed population ranged from 249–477 m−2, and Polygonum plebejum L. (34%), Melilotus indica L. (31%) and Avena ludoviciana Dur. (17%) were the predominant weeds in the experimental field. Season long weed-crop competition reduced the green pod yield of garden pea by 74% in 2003–2004 and 93% in 2004–2005. All the weed control treatments significantly reduced the population and biomass of weeds resulting in significant increase in green pod yield of garden pea compared to unweeded control. The highest weed control efficiency (84% reduction in weed biomass) was achieved with hand weeding 30 and 60 days after sowing (DAS) closely followed by stale seedbed coupled with one hand weeding (77%). Both these treatments produced significantly higher green pod yield compared to other treatments in both the years. In 2003–2004, hand weeding (30 and 60 DAS) recorded the highest gross margin (Indian Rupees 115,400 ha−1) closely followed by stale seedbed coupled with one hand weeding (Indian Rupees 109,700 ha−1). In the second year, however, the latter treatment gave the highest gross margin (Indian Rupees 56,900 ha−1) compared to other treatments.