Gmelina arborea is the second most planted tree species in Costa Rica, and one of the most important in several Latin American countries. In recent years, a disease caused by Ceratocystis fimbriata, has spread throughout Latin America, leading to the complete root of the tree in a few months. This study was conducted to evaluate the incidence, severity and genetic tolerance control of the Ceratocystis wilt in G. arborea. Data is based on a 2.4-year-old clonal trial, with 34 elite genotypes, at Río Jiménez, Guácimo in the Costa Rican Caribbean region. The variables diameter at breast height (DBH), total height, disease incidence and disease severity were evaluated. A pathogenicity index was proposed as a new selection criterion. SELEGEN (EMBRAPA) software was used for the evaluation of the genetic control in all traits investigated. Overall incidence rate was 39 % and severity was 13 %. Mean clonal heritability for severity was h2mc= 0.59 and for incidence h2mc= 0.47, these values were high evidencing that both traits are under a strong genetic control. The pathogenicity index becomes a useful discrimination criterion for ranking genotypes by their disease tolerance. An infection pattern inversely proportional to the DBH was observed. Although none of the 34 genotypes evaluated recorded total resistance to C. fimbriata, eight of these genotypes show strong genetic tolerance to the disease, and high productivity. Their use can be encouraging and will contribute to the reduction of Ceratocystis wilt impact in the country, as well as in the tropical Latin America region.
