Resumen

MONTILLA, J. O.  y  RODRIGUEZ, D. Response of cultivars of Eucalyptus urophylla S. T. Blake to leaf necrosis caused by Harknessia sp. Rev. Fac. Agron. [online]. 2003, vol.20, n.1, pp.34-42. ISSN 0378-7818.

Commercial production of Eucalyptus in Venezuela began two decades ago. Clonally propagated material is used regularly for planting. Leaf necrosis, caused by Harknessia sp. was detected in 1999, which might become a threat to Eucalypt plantations. To evaluate resistance to the disease in the germplasm, a test was performed on five six-month old elite cultivars, grown in polyethylene bags. Plants were inoculated with a spore suspension, incubated at 26 ± 3ºC and 100% RH for 4 days, and then transferred to a shaded place. Incidence of leaf necrosis and defoliation were evaluated at 45 days. Disease severity was registered at 15, 30, 45, 60, and 75 days after inoculation. Significant difference (P<0,01) between cultivars was found for the three variables. No correlation was observed between disease incidence or severity and defoliation. Cultivars SMVEN-213, SMVEN-241, and SMVEN-256 showed less incidence and severity than SMVEN-191 and SMVEN-341. Although resistance to leaf necrosis was detected, all cultivars should be considered in a systematic planting to prevent a severe epidemic.

Palabras clave : Eucalyptus; fungus; phenotypic variability.