Evaluation of Spray and Point Inoculation Methods for the Phenotyping of Puccinia striiformis on Wheat

The fungus Puccinia striiformis causes yellow (stripe) rust on wheat worldwide. In the present article, new methods utilizing an engineered fluid (Novec 7100) as a carrier of urediniospores were compared with commonly used inoculation methods. In general, Novec 7100 facilitated a faster and more flexible application procedure for spray inoculation and it gave highly reproducible results for virulence phenotyping. Six point inoculation methods were compared to find the most suitable for assessment of pathogen aggressiveness. The use of Novec 7100 and dry dilution with Lycopodium spores gave an inoculation success rate of 100% in two independent trials, which was significantly higher and more consistent than for spore suspension in Soltrol 170, water, water + Tween 20, and Noble agar + Tween 20. Both Soltrol 170 and Novec 7100 allowed precise quantification of inoculum, which is important for the assessment of quantitative epidemiological parameters. New protocols for spray and point inoculation of P. striiformis on wheat are presented, along with the prospect for applying these in rust research and resistance breeding activities.

Tomato Anther Callus Production: Solidifing Agent and Concentration Influence Induction of Callus

Anthers from. three tomato cultivars, `L-680A', `Ailsa Craig', and `Licato', were plated on DBM1 medium solidified with one of four solidifying agents, Bacto-agar, Gelrite, Noble agar, or Phytagar, to evaluate their ability to promote initiation and growth of tomato anther callus. The optimum concentration of each solidifying agent was compared with a liquid control. Optimum levels of the various solidifying agents were (in g·liter-1) Phytagar, 5; Gelrite, 3; Noble agar, 6 and Bacto-agar, 8. Both the number and diameter of calluses were affected by type of solidifying agent and anther genotype. Significant interactions were also found between tomato cultivars and solidifying agent. Noble agar produced good results with `L-680A' and `Ailsa Craig', but not with `Licato'. Bacto-agar reduced the number and size of callus by 38% when compared with the liquid treatment and by 42% when compared with the best agar treatment (Noble agar).

Electron microscopy of nocardial cell division

Nocardia polychromogenes is an aerobic, gram (+), non-motile, partially acid-fast actinomycete with primary mycelia that fragment into bacillary and coccoid elements.For scanning electron microscopy, N. polychromogenes culture strain Waksman 3409-A was grown on Potato Dextrose Agar at 25 C for 12-72 h. Five mm2 sections of the colonies, including portions of the interior and perimeter were fixed by exposure to osmium fumes for 16-24 h and air dried for 2 h. Specimens, mounted on stubs and sputter coated with gold, were viewed in a Cambridge Stereoscan Mark II scanning electron microscope. For transmission electron microscopy, the organism was grown on Potato Dextrose Agar at 25 C for 12-32 h. Whole colonies, 1-2 mm in diameter, were fixed by exposure to osmium fumes for 24 h. After suspension in noble agar, cells taken from the periphery of the fixed colonies were stained with 0. 5% uranyl acetate made in acetate-veranol buffer.

Counterimmunoelectrophoresis of staphylococcal antibody

Modifications of the staphylococcal counterimmunoelectrophoresis technique were evaluated to determine how variations in the procedure affected results. Neither a buffer pH range of 7.8 to 9.0 nor buffer molarity of 0.015 or 0.025 when tested in combinations caused appreciable differences. However, use of different agar preparations or delay in addition of antigen to the test slide altered the location of the precipitin band. Agarose was found to be more sensitive in determining the serum precipitin titer and provided a better photographic record than either Ionagar or Noble agar.