Isolation of novel plant-beneficial soil bacteria to enhance legume crop productivity

Non-Peer ReviewedPlant roots support the growth of a variety of soil microorganisms that have beneficial or detrimental effects on plant growth. As producers move to earlier seeding into cool wet soils, problems with pea and lentil seedling decay (damping off) and root rot are increasing. Attempts to control Pythium and Fusarium spp. with seed coatings containing the fungicides Captan or Thiram are being used however, the activity of these compounds is limited to approximately 2-3 weeks after planting. The objective of this project is to isolate microorganisms with the ability to be competitive in the rhizosphere of plants and biologically control root diseases of legumes. Over six hundred isolates were obtained from the rhizosphere of chickpea, lentil and pea from commercial farms in Rosetown and North Battleford, Saskatchewan. Preliminary characterization of the isolates indicates that the collection consists of 16 actinomycetes, 4 yeasts and over 580 bacteria. Eighty percent of the isolates produced siderophores and the ability to inhibit the growth of Rhizoctonia and Pythium was observed in 11.6% and 7.5% of the isolates, respectively. Additional characterization of the isolates to be studied will be plant growth promotion, root colonization, growth at low temperature and identification

Improved inoculants for lentil

Non-Peer Reviewe

A growth chamber study on the effects of metribuzin on the rhizobium-lentil symbiosis

Non-Peer Reviewe

Biocontrol of damping-off and root-rot causing pathogens by novel Rhizobacteria isolated in Saskatchewan

Non-Peer ReviewedIn Saskatchewan, land area used to grow pulse crops is increasing, and maintenance of plant health is imperative to produce an economically viable resource. The objective of this study is to characterize novel rhizobacteria for plant growth promoting properties: enhancing the root and shoot growth of pea and lentil, and suppressing the growth and disease severity caused by fungal pathogens. From in vitro assays, isolates 5-6, 4-31, and 2-9 suppressed the growth of fungal pathogens. Mechanisms which suppress the growth of fungal pathogens may include the production of enzymes which degrade the cell wall of the fungi, and antifungal metabolites. In studies where rhizobacteria were inoculated in combination with commercial Rhizobium inoculants onto pea and lentil seeds, isolate 2-9 significantly increased the root dry weight of pea, and isolate 4-31 and 5-6 increased the ability of Rhizobium to fix nitrogen in pea and lentil, respectively. Fungicide compatibility studies using two commonly-used products (Apron®-FL, Crown®) showed that isolate 5-6 was compatible with both fungicides, whereas isolates 4-31 and 2-9 were compatible only with Apron®-FL. The three bacterial isolates (5-6, 4-31, and 2-9) chosen for possible development of a commercial inoculant show promise to be effective biological control agents against fungal pathogens

Enhancement of pulse crops: influence of novel rhizobacteria on the interaction of pea, lentil, and pathogenic fungi

Non-Peer ReviewedIn Saskatchewan, land area used to grow pulse crops (pea, lentil, bean, and chickpea) is increasing every year; between 2000 and 2001, an increase of 20% was recorded. Maintenance of plant health is imperative to produce an economically viable resource. The objective of this study is to characterize novel rhizobacteria for plant growth promoting properties: enhancing the development of pea and lentil plants, and suppressing the growth and disease severity caused by phytopathogenic fungi. Rhizobacterial isolates were selected from a preliminary group of 580 based on the ability to suppress Pythium, Rhizoctonia, and Fusarium spp. In in vitro assays, no one isolate, except for isolate 5-6, had shown the ability to strongly suppress all three pathogenic fungi. Additionally, the presence of pea or lentil seeds affected the ability of the strains to suppress the fungi. Bacterial cellfree filtrate suppressed the growth of Pythium and Rhizoctonia spp., thus fungal suppression is mediated by antifungal metabolites. Furthermore, suppression of Rhizoctonia sp. is correlated to the production of proteolytic enzymes by the rhizobacteria. Plant growth promoting rhizobacteria (PGPR) are important in food production by increasing crop productivity, and reducing crop losses caused by soil-borne phytopathogens

Nitrous oxide emissions from soil profiles seeded with pulse crops

Non-Peer ReviewedInoculation of legumes with Rhizobium spp. is a common worldwide agricultural practice that is used to increase crop yield and to improve soil fertility without adding nitrogen (N) fertilizers. There is concern that N2 fixation by legumes enhances emissions of nitrous oxide (N2O) – a powerful greenhouse gas (GHG). The objectives of this experiment were: 1) to measure N2O emissions from soil profiles under inoculated and non-inoculated pulse crops; 2) to investigate the relationship between N2O emissions and N2 fixation by pulse crops. The experiment was carried out in the Phytotron of the University of Saskatchewan with soil flats seeded with inoculated and non-inoculated lentils and peas and fertilized spring wheat. N2O emissions from soil profiles were measured using Profile Gas Samplers (PGS), and were analyzed with a GC. Results indicated that inoculated lentils and peas did not substantially increase N2O emissions, and N2O emissions may not be associated with N2 fixation under the conditions in this experiment

Submerged fermentation of Colletotrichum truncatum for biological control of scentless chamomile

Non-Peer ReviewedColletotrichum truncatum is being developed for biocontrol of scentless chamomile (Matricaria perforata). For potential mass production, a study was conducted to determine the possibility of submerged culturing. Fungal cultures were grown in V8-juice broth or a basal-salts liquid supplemented with carbon (C) and nitrogen (N) sources (C:N ratio at 10:1) in 500-ml flasks at 16 °C, 22 °C, or 28 °C in darkness to determine the impact of temperature. Sporulation was highest in the basal-salts medium at 16 °C, yielding about 1 x 106 sp/ml after two weeks. Further improvements were explored by examining the effects of various C and N sources, C concentrations, and C:N ratios. After comparison of nine C sources and eight organic and inorganic N sources, glucose and casamino acids were considered to be effective supplements to the basal-salts medium. Increasing glucose concentration from 5 to 40 g/L enhanced spore yields, but decreased biocontrol efficacy when glucose was 20 g/L or higher. In comparison to non-treated controls, spores produced at 5 g/L glucose reduced fresh weight of scentless chamomile by approximately 75% as opposed to only 39% by spores produced at 40 g/L glucose. Media amended with 10 g/L glucose supported high levels of sporulation without compromising the efficacy of spores. No significant difference in sporulation or efficacy was observed among C:N ratios ranging from 5:1 to 40:1

Effect of herbicides on growth and nitrogen fixation potential (ARA) of field pea and lentil

Non-Peer Reviewe

Growth and nitrogen fixation of field pea and lentil as influenced by herbicides: a three year field study

Non-Peer ReviewedA three-year field study was conducted in the Dark Brown and Black Soil Zones of Saskatchewan to assess the effects of trifluralin (Treflan ), metribuzin (Sencor), MCPB (Tropotox), and sethoxydim (Poast) on growth and symbiotic nitrogen fixation of field pea (Pisum sativum cv. Trapper) and lentil (Lens culinaris cv. Eston). Herbicides were applied at Saskatchewan recommended field rates and twice the recommended field rates. Treflan, Sencor, and Poast did not adversely affect plant growth or nitrogen fixation potential of field pea and lentil when applied at recommended field rates. Similarly, application of MCPB at the recommended rate did not adversely affect field pea under normal growing conditions. In some instances, herbicide application at the recommended rate was observed to have a stimulatory effect on growth and nitrogen fixation. In contrast, at application rates in excess of those currently recommended in Saskatchewan, or when plants were severely stressed by unfavorable growing conditions such as poor soil moisture, plant growth, yield, nodulation, and nitrogen fixation were adversely effected by herbicides. These effects were not consistent nor were they predictable. MCPB is not registered for use in lentil and, when applied in this crop, often resulted in reduced nitrogen fixation and seed yield. In all cases, data suggest that reductions in the nitrogen fixation potential were due to indirect effects of herbicide application on plant growth rather than to direct effects on nodulation and nitrogenase activity