Incidencia de potyvirus y caracterización molecular de PVY en regiones productoras de papa (Solanum tuberosum L) de Colombia / Incidence of potyvirus and molecular characterization of PVY in potato (Solanum tuberosum L) growing regions of Colombia

Los problemas virales reducen los rendimientos y la calidad del tubérculo semilla en cultivos de papa de todo el mundo. Esta investigación se planteó con el fin de evaluar los niveles de incidencia de potyvirus en diez de las principales regiones cultivadoras de papa de los departamentos de Antioquia, Boyacá, Cundinamarca y Nariño (Colombia), y las características genotípicas del virus Y de la papa (Potato virus Y, PVY), seleccionado por ser el potyvirus más limitante de este cultivo. Para la evaluación de la incidencia se utilizaron pruebas de Elisa con anticuerpos que reconocen epítopes comunes a los potyvirus, mientras que las pruebas moleculares incluyeron el análisis filogenético de secuencias parciales del gen de la cápside viral de 33 aislamientos, así como la secuenciación de una porción de los extremos 5´ y 3´del genoma de dos cepas colombianas de este virus. Los resultados confirmaron la presencia de potyvirus en los cultivos de los cuatro departamentos evaluados, con una incidencia promedio del 72%, siendo este nivel superior al 56% en todas las zonas evaluadas. Los análisis moleculares del PVY, permitieron asociar las cepas colombianas estudiadas con las razas PVYN y la variante PVYNTN, esta última responsable de la enfermedad conocida en el mundo como PTNRD (Potato tuber necrotic ringspot disease).

Potato viruses are responsible for significant reductions in seed quality and crop yields around the world. In this study, we evaluate the levels of incidence of potyvirus in ten potato growing regions of Colombia from the provinces of Antioquia, Boyacá, Cundinamarca and Nariño. As PVY is the most limiting potyvirus in potato farming, a molecular characterization of Colombian PVY strains was also performed. Incidence was evaluated by ELISA using general potyvirus antibodies. Phylogenetic analysis were made on the partial sequence of the capsid gene from 33 isolates. A portion of the 5´ and 3' genome ends was obtained from two Colombian strains. Results confirmed the presence of potyvirus in the four provinces with an average incidence of 72%. The lowest incidence value was 56%. Molecular analysis clustered all Colombian isolates with strains PVYN and PVYNTN, the latter responsible for the disease known as PTNRD (Potato tuber necrotic ringspot disease).

Carbohydrate content of some potato virus Y-diseased solanaceous plants

Different carbohydrate components, viz. total soluble reducing and non reducing sugars and starch were compared in leaves of four solanaceous plants namely Lycopersicon esculentum cv. Money maker [susceptible tomato]; Lycopersicon pimpinellifolium L. [resistant tomato]; Capsicum annuum cv. "California Wonder" [pepper] and Solanum nigrum var. judaicum [Enab El-Deeb] at different intervals after inoculation with an isolate belonging to Y° group of the common strain of potato virus Y [PVY] studies indicate that: i - In susceptible tomato: virus infection lowered significantly the total carbohydrate content and starch content and decreased also the monosaccharide content but increased sucrose concentration. ii- In resistant tomato: virus infection decreased significantly all carbohydrate fractions except only the monosaccharides. iii- In pepper: virus infection lowered the total carbohydrate content as a result of decreased monosaccharides, sucrose and starch components .iv- In Enab El-Deeb: virus infection also decreased the total carbohydrate as well as the starch and total soluble sugars