Occurrence of Yeasts in Cultivated Soils in El-Minia City, Egypt

Abstract

Two-hundred two yeast strains were isolated from rhizosphere (87 strains) and nonrhizosphere (115 strains) areas of potato, maize, vegetable marrow, and cabbage plants. On the basis of 26 morphological and physiological properties, the isolated yeast strains were assigned to 9 genera and 15 species. Trichosporon beigelii, Kluyveromyces marxianus and Torulaspora del- brueckii were the dominant species. Cryptococcus humicolus and Candida tropicalis were represented by considerable numbers of strains. Of low occurrence were Saccharomyces cerevisiae and Candida blankii. Other yeast species were represented by single or two strains. Total counts of yeast cells per gram dry soil ranged from 1.1×10³ to 6.6×10³ in soil samples of rhizosphere areas and from 6.5×10² to 5.6×10³ in soil samples of nonrhizosphere areas. Types of the tested plants affected not only the total counts of yeast cells but also spectra of yeast species. Relationships of age of potato plant, moisture contents of soil samples, and its pH values and total counts of yeast cells were discussed.

Key Words:

• Rhizosphere
• Trichosporon beiglii
• Yeasts