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

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

Colonization of the alfalfa rhizosphere by plant growth promoting rhizobacteria

Non-Peer ReviewedPlant growth promoting rhizobacteria (PGPR) were evaluated for their ability to colonize the alfalfa rhizosphere and increase dry matter yield of alfalfa. Field trials at Beaverlodge, AB., Sun Prairie, WI. and Outlook, SK. demonstrated that PGPR's Pseudomonas 31-12 (Ps.) and Serratia 2-68 co-inoculated with Rhizobium meliloti increased the dry matter yield by 11, 9 and 7%, respectively. In the first year of a three year field study planted in May 1993 at Outlook, the effect of formulation carriers on colonization of the alfalfa rhizosphere by spontaneous rifampicin resistant mutants (rif+) of PGPR's Ps. 31-12 and Serratia 2-68 was measured. No rif+ microorganisms were detected in the rhizosphere of uninoculated alfalfa. plants. Ps. 31-12 was the better colonizer of the rhizobacteria examined with populations exceeding 1 o6 cells per root 169 days after planting. The population of Ps. 31-12 was 10 times greater 35 and 169 days after planting in the peat formulation than in the clay formulation. Similarly, the population of Serratia 2-68 in the alfalfa rhizosphere was 1000 times greater in the peat formation than in the clay formulation. The populations of these microorganisms will be measured over the next two growing seasons

Increased dry matter yield of alfalfa following inoculation with plant growth promoting rhizobacteria

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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

Influence of Alternaria spp. on susceptibility of canola and mustard to Pythium spp., Fusarium spp., and Rhizoctonia solani

Non-Peer ReviewedSeed exudates have been shown to inhibit the growth of some fungi responsible for seed rot and seedling blight in canola and mustard. Alternaria brassicae, A. alternata and A. raphani can all be found on seed of canola and mustard. Previous work indicates deep infections of Alternaria brassicae and A. raphani significantly reduce seed germination while A. alternata had no direct effect on germination. The objective of this study is to determine the effect of seed exudates on seed rot and seedling blight caused by Rhizoctonia solani, Fusarium spp. and Pythium spp. and determine if seed borne Alternaria is synergistic to these pathogens by breaking down defensive compounds in the seed exudates. Seed will be inoculated with Alternaria alternata. to create superficial surface infection. Susceptibility to Pythium, Fusarium and Rhizoctonia of artificially infected seed lots and naturally infected seed lots will be tested on water agar, blotter test and pot test. Seed exudates will also be obtained from seed lots after surface sterilization and bioassays of the ability of these exudates to support growth of pathogenic fungi and beneficial bacteria will be assessed

Liquid rhizobial inoculants for lentil and field pea

Non-Peer ReviewedThe traditional peat legume inoculants are viewed by western Canadian farmers as being difficult to apply. Accordingly, more "user-friendly" inoculants are being developed to ensure more wide-spread inoculation of legumes. A liquid inoculant developed by LiphaTech was evaluated as a carrier for Rhizobium leguminosarum strains 99A1 for lentil and 128C56G for pea. These two strains survived at titres exceeding log 8.0 per mL for ten months at 5°C and there was no loss of viability during shipping and handling. The Prairie Agricultural Machine Institute (PAMI) determined that the liquid inoculant gave a very flowable and uniform coverage of the seeds when applied through a grain auger and various types of seeding equipment. Liquid inoculant for pea and lentil resulted in yields equal or better than those observed for the traditional peat-based inoculant

Influence of growth factors on the plant pathogens by select suppression of Pseudomonads

Non-Peer ReviewedRhizobacteria were evaluated for their ability to inhibit the growth of damping-off pathogens such as Pythium ultimum, Rhizoctonia solani and common root rot pathogen, Cochliobolus sativus. The level of antagonism by Pseudomonads 63-28, U-14 and Ral-3 was examined on solid growth media under varying conditions of temperature, pH, and sources of C, N, and amino acids. In vitro antibiosis of the pathogens was greatly influenced by environmental and nutritional conditions. Generally, antagonism was greatest at 25-300C and decreased at 400 C. The influence of pH appears to be rhizobacteria and pathogen dependent. For example, optimum inhibition of P. ultimum growth by 63-28 was between pH 4.6-6.0, whereas, optimum inhibition of R. solani growth by U-14 was at 7.6-9.1. Growth inhibition of C. sativus by Ral-3 was pH independent. Mannitol or trehalose strongly enhanced the antifungal activity of 63-28, whereas lactose had a negative effect. Antagonism of 63-28, U-14 and Ral-3 was enhanced by nitrogen sources tested except NaNO2 on U-14. The influence of the amino acids did not effect Ral-3, but, antibiosis by 63-28 was increased by amino acids phenylalanine, arginine, or histidine. U-14's activity was increased with the addition of proline, serine, or arginine. The results from this study clearly show that growth factors have a significant impact on microbial antagonism

Formulation development and delivery of biopesticides

Non-Peer ReviewedBiopesticide formulation development is integral for end product development and risk reduction associated with commercialization and acceptance by the end user. Development of robust formulations for biopesticides is a key step towards advancing this technology into integrated pest management systems. A granular formulation protocol using extrusion-spheronization-fluidized bed drying for biopesticidal bacteria and fungal hypha and spores is described. Establishing low granule water activity (aw, 0.2-0.3) is a key factor in extending the shelf-life of the product. Starch type and amount provided controlled release attributes to the biopesticide granules. Microencapsulation of bioherbicide, Colletotrichum truncatum 00-003B1 (Ct), conidia and bioinsecticide nucleopolyhedrovirus (NPV), by complex coacervation is described for foliar application of biocontrol agents

Use of cultivar resistance and crop rotation with Bacillus subtilis for clubroot control in canola

Non-Peer ReviewedThis study was conducted to assess additional strategies potentially complimentary to cultivar resistance or biocontrol in control of clubroot. New granular Bacillus subtilis formulations and a seed dressing method were developed to facilitate biofungicide delivery in field trials. The granular formulations were applied in furrow during seeding at 50 kg/ha to a clubroot resistant (CR) and susceptible (CS) canola cultivar, respectively, in three field trials. The seed dressing applied approximately 1×105 to 5×106 cfu/seed doses of the biocontrol agent, and was evaluated on the CS cultivar seeded to different crop-rotation scenarios where the plots had a 1-year, 3-year, or 11-year break from last canola crop. Clubroot disease pressure was high at all trial sites with disease severity indexes (DSI) ranging from 69% to 98% on the CS cultivar. None of the granular formulations reduced clubroot substantially, whereas the CR cultivar showed a high effect, reducing DSI to below 15% and doubling the yield over that of CS cultivar. Plots of varying rotation showed a pattern of clubroot pathogen pressure, with those of 1-year break from canola being the highest. The DSI for all rotational scenarios was high, reaching 100% in short-rotation plots. Biofungicide seed dressing did not reduce DSI, but longer crop rotation often reduced gall size slightly, showed much milder above-ground damage, and increased the yield significantly relative to short rotation in two separate trials. Even a 3-year break from canola was highly beneficial, with the yield doubled as opposed to that with only 1-year break from canola