A Study on Sexual Fertility and a Determination of Vegetative Compatibility Groups among Glomerella cingulata Isolates from Citrus Trees in Mazandaran Province, Iran

Glomerella cingulata is the causal agent of anthracnose disease on citrus that attacks weakened trees. The sexual stage is rare in nature but can be produced in laboratory under certain conditions. Sixty-seven single-spore isolates were selected from citrus in Mazandaran province to be used in this study. Isolates were cultured on YPSS for investigating heterothallism and homothallism. To understand homothallism of isolates, they were cultured on YPSS alone and then placed at 21?C with 12h dark and 12h light for 15-21 days. An 8.8% of isolates were homothallic, while others were paired in YPSS of the above conditions to be investigated for heterothallism. 25% of the isolates were found as heterothallic. Perithecia of smooth walls along with necks were produced. Asci were in groups with any ascus containing 8 one celled ascospores. For VCG determination, forty one isolates were employed. Isolates were cultured on 5% MMC for selecting nit mutants. Two isolates could not grow on MMC and were found as wild types. After selecting nit mutants, they were cultured in media of different nitrogen sources for detecting phenotypes of nit mutants. The maximum percentage of nit occurred in the case of nit 1 (66%). Nit 3 was 56% and nit M 53%. The inter-isolate combinations started in MM among different nits of any isolate with two HSI isolates being found. Other 37 isolates were crossed together with different nits on MM with all the cultures being placed at 25?C in the dark. Thirty five VCGs were identified. The isolates that produced perithecium were different from the ones producing heterokaryons. Sexual stage along with sexual fertility is one of the factors of diversity that ended up with many groups in vegetative compatibility.