ABSTRACT
The aim of the experimental work was to optimize the previously used Phillips and Hayman (1970) method of staining roots for microscopic assessment of mycorrhizal frequency in the root material. The materials used in the experiment were the roots of strawberry plants of the cultivar “Elsanta” obtained in a greenhouse experiment in May 2012. Morphological features of the roots were assessed using a root scanner, and then attempts were made to stain the roots in four types of dyes: 0.01% methylene blue, 0.01% acridine orange, 0.01% malachite green, and 0.01% carbol fuchsin. A comparative microscopic assessment was made of the effects of staining with the four types of dyes the structures of mycorrhizal fungi formed in strawberry roots. Mycorrhizal frequency (F%) in the stained root samples was also compared. Next, the usefulness of these dyes for staining the roots of other fruit plant species, such as apple, sweet cherry, blackcurrant and sour cherry, was evaluated. It was concluded that the staining of roots at a temperature of up to 65°C did not cause tissue breakdown, and that the clearing time used—20 to 30 minutes, and the use of carbol fuchsin were found to be the most effective combinations in achieving good quality microscopic images. During microscopic examinations, a satisfactory contrast was noted between root tissues and the structures of mycorrhizal fungi. The use of carbol fuchsin for staining roots also helped to expose a greater number of fungal structures and obtain higher values of mycorrhizal frequency in the roots of strawberries, blackcurrants, sour cherries, sweet cherries and apples, in comparison with other dyes tested. The newly developed method of staining roots with carbol fuchsin, compared with the method used previously (Phillips and Hayman, 1970), is both less time consuming and less labour intensive.