Distribución, incidencia y alteraciones histológicas de una nueva enfermedad en betabel (beta vulgaris l.) causada por el falso agallador nacobbus aberrans, en el valle de tepeaca, Puebla, Mexico

We determined the distribution and incidence of the disease known as "Grain of red beet" and described the histological changes caused by the false root-knot nematode Nacobbus aberrans when it forms galls on the taproot and when it produces grain-like lesions on the head of the root of this vegetable. The results showed that the disease is distributed in several locations in the municipalities of Los Reyes Juarez, Quecholac and Palmar de Bravo, 50% of the sample plots, had an incidence ranging between 0-100%. Histological examination showed that in the galls of the main root, the nematode induced the formation of feeding sites "syncytia" located in the vascular cylinder. The cytoplasm of the affected cells was dense and granular, with one or two nuclei, nuclei and nucleoli were hypertrophied, there was thickening and dissolution of cell walls and hyperplasia around the lesion. In lesions such as "grain" of the nematode juvenile stages were found in cavities surrounded by lignified cells. When females invaded the reserve parenchyma, they induced a circumscribed lesion, which appeared to be a syncytium, but did not reveal the fundamental characteristics of this. Both in the galls of the main root and in the grain-like lesions found mature females with egg masses.