Inoculation Technique for Fungus Cultures

A plastic straw and wood applicator stick serve as a simple, inexpensive, and disposable inoculation unit for fungal studies. The method gives a uniform and intact inoculum. The technique is especially useful because a large number of agar plates can be inoculated rapidly.     

Phase-Locked Loop Technique to Record Resonance Frequency of Plant Tissue

An apparatus based on the phase-locked loop technique has been developed in order to record automatically the resonance frequency of a mechanically vibrating plant specimen. Hereby changes in the elasticity of the plant material can be continuously recorded. In order to demonstrate the use of the apparatus, elasticity changes of Avena coleoptiles due to exchange of the root medium were continuously recorded.     

Effects of Plant Contact, Inoculation Pattern, Leaf Wetness Regime, and Nitrogen Supply on Inoculum Efficiency in Rice Sheath Blight

An experimental design was developed which allowed the measurement of inoculum efficiency (IE) represented by lesions of a leaf-borne disease such as rice sheath blight. In this design. IE is measured as the ratio of newly established lesions on trap plants relative to the inoculum present in a canopy, i.e. lesions artificially established on source plants, IE of the rice sheath blight pathogen, Rhizoctonia solani , was studied under semi-controlled conditions in which the effects of the following factors were measured; contact frequency among host tissues, amount and location of inoculum in the canopy, leaf wetness regime, and nitrogen content of the host plant. The conduciveness of these factors to sheath blight infection was measured in terms of IE which was expressed as the ratio of the density of daughter lesions on trap rice hills to the density of mother lesions on the inoculated quadrat hills. IE generally declined with the three successive batches of trap hills used in the experiments. It was significantly higher at closer plant spacings and under interrupted leaf wetness regimes. IE was not affected by the amount, nor by the location, of inoculum (mother lesions) in the canopy, but was significantly lower in hills with high total nitrogen content.     

Pathogenicity of Meloidogyne hapla to Lettuce as Affected by Inoculum Level, Plant Age at Inoculation and Temperature

Pathogenicity of Meloidogyne hapla to lettuce was influenced by inoculum level, age of plant at inoculation and temperature. Top weight of ''Minetto'' lettuce was reduced 32% when 2-week-old lettuce plants were each inoculated with five egg masses. Higher inoculum levels did not further decrease top weight significantly. Inoculation at seeding reduced top growth more than inoculation of 1-, 2- or 3-week-old seedlings. M. hapla reduced growth more at the intermediate (21.1 C night and 26.7 C day), than at the low (15.5 C night and 21.1 C day) or high (26.7 C night and 32.2 C day), temperature regimes.     

Plant Reactions to Inoculation of Roots with Fungi and Bacteria

The potential of 120 isolates of fungi and bacteria from plant rhizospheres to interfere with plant development and growth was studied in greenhouse experiments. The pure cultured isolates were obtained from plant roots in the field and applied as suspensions to the roots of eight test plant species. 10–20% of the isolates caused distinct symptoms on shoots, growth retardations without other symptoms or growth promotions. Responses of treated plants ranged from death of plants soon after treatment to up to about 40% higher shoot fresh weight than in control plants. Two bacterial isolates induced strong reactions in most of the plant species tested while other isolates showed a more or less pronounced specificity by giving reactions in only some of the plant species tested.     

Plant Tissue 2

A new five-element electrical model was proposed recently (Zhang,Stout, and Willison, 1990; Zhang and Willison, 1991) to representplant tissues. In previous studies on the relationship betweenelectrical impedance and cold-hardiness, one of us had analyseddata in relation to a simpler three-element electrical model.Here, we have re-analysed these data in relation to the morecomplex model. F-tests showed that the new model always fittedmeasured impedance spectra significantly better (P<0·005)than the earlier model. The previously reported increase inintracellular resistance during cold acclimation was found tobe related to increased resistance of both the cytoplasm andvacuole In the species trial of birdsfood trefoil and alfalfa, coldacclimation was accompanied by an increase in extracellularresistance and a decrease in capacitances of both the plasmamembrane and tonoplast. In the cultivar trial of birdsfoot trefoil,cold acclimation did not affect plasma membrane capacitancein Viking and extracellular resistance in both Leo and Viking.In the species and growth time trial, cold acclimation was accompaniedby a decrease in plasma membrane capacitance in alfalfa butnot in birdsfoot trefoil Key words: Electrical impedance, cold acclimation, equivalent electrical circuit     

Direct Delivery of Inoculum to Shoot Tissue Interferes with Genotypic Resistance to Ralstonia solanacearum in Tomato Seedlings

Employing known susceptible and resistant genotypes and pure bacterial inoculum (0.1 OD; 10⁸ CFU/ml^?1), five different inoculation methods were tried to assess the response of tomato genotypes to Ralstonia solanacearum. This included seed‐soaking inoculation, seed‐sowing followed by inoculum drenching, or at 2‐week stage through petiole‐excision inoculation, soaking of planting medium with inoculum either directly or after imparting seedling root‐injury. Seed‐based inoculations or mere inoculum drenching at 2 weeks did not induce much disease in seedlings. Petiole inoculation induced 90–100% mortality in susceptible checks but also 50–60% mortality in normally resistant genotypes within 7–10 days. Root‐injury inoculation at 2‐week seedling stage appeared the best for early and clearer distinction between resistant and susceptible lines. The observations suggest a role played by the root system in governing genotypic resistance to the pathogen. Direct shoot inoculation is to be adopted only for selecting highly resistant lines or to thin down segregating populations during resistance breeding.     

The Adaptation of the Immunofluorescence Technique for Use in Bacteriological Investigations of Plant Tissue

Summary: The preparation of plant tissue for examination by the fluorescent antibody technique is described. The procedures suggested are intended to overcome some of the major obstacles encountered and the efficacy of the method for plant investigations is upheld by its successful application in a simple test system.     

Intra- and Interspecific Variation in Plant Response to Inoculation with Deleterious Rhizosphere Pseudomonads

Accessions of wheat, spinach, lettuce and different Brassica species were tested in greenhouse experiments for reaction to inoculation with two isolates of growth-inhibitory rhizosphere bacteria. Seedlings grown in non-sterile soil were inoculated with bacterial suspension and shoot dry weight was measured after five weeks. Large differences were found between the plant species tested in their average sensitivity to each bacterial isolate, and in the majority of plant species, significant differences were also found between accessions in the response to one or both isolates. These findings suggest that, in addition to the variation between plant species, intraspecific variation in the reaction to deleterious bacteria is a common feature in plants. This supports the hypothesis that plant reaction to rhizosphere bacteria is under genetic control. The results further indicate specificity in the interactions between plants and bacterial isolates, both at the plant species level and at the accession level.     

Enzyme Formation in Higher Plant Tissue:1

Discs cut from Jerusalem artichoke tubers stored at 20 °Cproduced considerably less invertase than discs cut from tubersstored at 4 °C. Gibberellic acid stimulated synthesis ofinvertase in tissue previously stored at 20 °C, restoringit to the level of cold-stored tubers.     

Miniature Tissue Culture Technique with a Modified Plastic Microplate

Plastic microplates were modified to accommodate four glass microscope slides as surfaces for cell cultivation. Tissue cultures grown on these slides can be utilized for fluorescent-antibody and other cytological staining techniques.