Validación del tamaño muestral en lotes comerciales para la evaluación de la incidencia de Leifsonia xyli subsp xyli, agente causal del raquitismo de la caña soca

BERTANI RP; HENRIQUEZ D; JOYA CM; FUNES C; DÍAZ EF; MORANDINI M; GONZÁLEZ V; DIGONZELLI P; PLOPER LD

Otro; XVIV Reunión Técnica Nacional de la Caña de Azúcar; 2014

Abstract Sugarcane represents the main sugar crop in the world. It is affected by a number of diseases, including ratoon stunting disease (RSD), caused by Leifsonia xyli subsp. xyli, which can decrease production yields. Since seedcane health is one of the most important aspects to be considered in crop management, Estación Experimental Agroindustrial Obispo Colombres (EEAOC) began in 2000/2001 the Vitroplants Project to produce high quality seedcane. Because this pathology does not show visible symptoms in the field, it is important to have a correct diagnosis in the laboratory. To obtain reliable RSD incidence levels, an adequate sample must include a representative number of stalks. However, practical and economical considerations require that these samples be no larger than necessary to provide reliable results. In the 2012/2013 growing season, 400 stalks were randomly taken of a 5 ha commercial field. These samples were analyzed with serologic techniques (tissue-blot immunoenzymatic assay or TBIA), and then randomly and repeatedly divided into 50 samples of 80, 60, 40, 30, 20 and 10 stalks each. Incidence percentages of the disease were estimated by determining the number of infected stalks out of the total number of analyzed stalks. Coefficients of variation were calculated for each sample size. The data suggest that RSD incidence levels were more reliable as samples were larger; but taking into account practical and economic considerations, a sample size of 20 stalks should be acceptable in estimating the RSD incidence levels in a commercial field no bigger than 5 ha. Leifsonia xyli subsp. xyli, which can decrease production yields. Since seedcane health is one of the most important aspects to be considered in crop management, Estación Experimental Agroindustrial Obispo Colombres (EEAOC) began in 2000/2001 the Vitroplants Project to produce high quality seedcane. Because this pathology does not show visible symptoms in the field, it is important to have a correct diagnosis in the laboratory. To obtain reliable RSD incidence levels, an adequate sample must include a representative number of stalks. However, practical and economical considerations require that these samples be no larger than necessary to provide reliable results. In the 2012/2013 growing season, 400 stalks were randomly taken of a 5 ha commercial field. These samples were analyzed with serologic techniques (tissue-blot immunoenzymatic assay or TBIA), and then randomly and repeatedly divided into 50 samples of 80, 60, 40, 30, 20 and 10 stalks each. Incidence percentages of the disease were estimated by determining the number of infected stalks out of the total number of analyzed stalks. Coefficients of variation were calculated for each sample size. The data suggest that RSD incidence levels were more reliable as samples were larger; but taking into account practical and economic considerations, a sample size of 20 stalks should be acceptable in estimating the RSD incidence levels in a commercial field no bigger than 5 ha.