Biological control of citrus blast disease using some yeast strains isolated from citrus orchards in the northern provinces of Iran

Citrus blast caused by Pseudomonas spp. is one of the most important diseases in the northern citrus growing provinces of Iran which causes considerable losses to citrus orchards in conducive climatic conditions. In this study, we tried to isolate and introduce some yeast strains from citrus orchards with acceptable biological control potential against the disease. The evaluations were performed under green house conditions on sour orange seedlings. Yeast cell suspensions were sprayed three times with two-days intervals on seedlings before pathogen inoculation. Statistical analysis of the results was carried out using Randomized Complete Block experimental design and comparison of disease severity means was performed by Duncan's Multiple Range Test. For the identification of the effective yeast strains, ITS regions of their rRNA operon were amplified using universal primers (ITS1 and ITS4) by PCR and the amplified fragments were sequenced. Based on the above procedures and comparison of the sequences with those deposited in the GenBank, the effective yeasts were identified as Sporobolomyces ruberrimus, Cryptococcus albidus, C. magnus and Rhodotorula sp.According to the results, S. ruberrimus, was the most effective yeast and controlled the disease more efficiently than other species.