SOME ASPECTS ON THE BIOLOGY OF HETEROSPORIUM ECHINULATUM (BERK) COOKE.
Heterosporium echinulatum was confirmed to be the causal agent of carnation ringspot. Morphological changes in affected carnation leaves were examined, as well as the proliferation of the fungal reproductive structures through the stomates. An "in vitro" follow-up of the biological cycle was performed, determining a 40-hour cycle for this fungus under laboratory conditions. PDA (potato, dextrose, agar) -based culture media prepared with twice the concentration of dextrose (PD2A) and enriched with petal and leaf extracts of four varieties of carnation with different degrees of susceptibility to the action of the pathogen, were used to evaluate mycelial growth and conidia production, obtaining differential responses. The effect of nutrient content, pH, temperature and light conditions on the medium was evaluated. It was found that the optimum medium for "in vitro" growth of the fungus was that enriched with petal extract from the variety Candy clemaxi (Z-PD2A), and that nitrogen in the NH4 form, increased acidity and a temperature of 22 °C favors mycelial growth and conidia production. Four carnation varieties were inoculated with a suspension of 50,000 conidia/ml, determining an incubation period of six to nine days for the pathogen under greenhouse conditions.
Novoa, C., Casallas, J., Briceño, G., Orozco de A, M. and de Granada, E.G. (1992). SOME ASPECTS ON THE BIOLOGY OF HETEROSPORIUM ECHINULATUM (BERK) COOKE.. Acta Hortic. 307, 233-240