Relación entre "bactericera cockerelli" y presencia de "candidatus "liberibacter psyllaurous" en lotes comerciales de papa

The abnormal sprouting of tubers (without sprouts or with threadlike sprouts) and the internal browning of the potatoes are symptoms of a disease which is affecting the potato production in Mexico, in southwestern United States and Central America. This disease has been associated with the psyllid of the potato Bactericera cockerelli Sulc. With the purpose of clarifying the causes of this disease, samples were taken in 11 commercial batches of potato in an altitudinal transect between 2 600 and 3 500 m the potato producing area of Toluca in 2007. The population of B. cockerelli was determined using weekly samples of the adult insects caught in sticky yellow traps. At the end of the crop's growth period, the tubers produced in each batch were sampled and stored for six months. After this time, the percentage of tubers with abnormal sprouts was established and analyses were carried out with PCR to determine the presence of Candidatus Liberibacter psyllaurous and of phytoplasm in the tubers. The results indicate that the population of B. cockerelli and of the symptoms of the potato purpletip decreased with height. In heights above 3 200 masl,no significant problems related to the disease showed up. Of the potatoes with fine sprouts, 36% displayed internal browning and 58% of the tubers without sprouts displayed the same symptom, 54% of tubers with abnormal sprouting were positive for Candidatus Liberibacter psyllaurous and only 3.5% presented phytoplasm. These results indicate that Candidatus Liberibacter psyllaurousis related to the potato purple-tip symptoms in the Toluca area. La brotación anormal de los tubérculos (sin brotes o brotes ahilados) y el pardeamiento interno de los tubérculos, son síntomas de una enfermedad que está afectando la producción de papa en México, en el suroeste de Estados Unidos y América central. Esta enfermedad ha sido asociada con el psilido de la papa Bactericera cockerelli Sulc. Con el objetivo de dilucidar las causas de esta enfermedad, en 2007 se llevó a cabo un muestreo en 11 lotes comerciales de papa localizados en un transecto altitudinal entre 2 600 y 3 500 m en la región productora de papa de Toluca. La población de B. cockerelli fue determinada mediante muestreos semanales de los insectos adultos atrapados en trampas amarillas pegajosas. Al final del periodo de crecimiento del cultivo, los tubérculos producidos en cada lote fueron muestreados y almacenados por 6 meses. Después de este tiempo, se determinó el porcentaje