Diversidad genética de aislados de Phytophthora infestans colectados en zonas productoras de papa y tomate de Guatemala / Genetic diversity of Phytophthora infestans isolates collected from tomato and potato producing areas in Guatemala

Phytophthora infestans (Mont) DeBary es el agente causal de la enfermedad conocida como tizón tardío, la cual ha sido catalogada como la enfermedad de plantas más devastadora reportada en la historia de la humanidad. Este patógeno afecta plantas de importancia económica de la familia solanaceae, como el tomate y la papa. P. infestans es un oomicete heterotálico y necesita de dos tipos de apareamiento, A1 y A2, para presentar reproducción sexual, la cual es la vía por la que este patógeno incrementa su grado de diversidad, a través de una recombinación de su material genético, que representa el mayor desafío para el manejo de la enfermedad. Este estudio determinó el nivel de variabilidad genética, a través del marcador molecular amplified fragment length polymorphism (AFLP), de 22 aislados de P. infestans colectados en diferentes zonas productoras de papa y tomate. Con el perfil de bandas generado por el marcador molecular, se realizó un análisis cluster y se elaboró un dendograma de tipo unweighted pair group method with arithmetic mean (UPGMA), con el índice de Dice, mediante una matriz de distancias genéticas. Los aislados fueron situados en tres grupos principales, los cuales responden al lugar de procedencia y al tipo de planta hospedera. Se encontró un valor de similitud de 0.49 entre los aislados analizados, por lo que se concluyó que la variabilidad genética de P. infestans en Guatemala es alta.

Phytophthora infestans (Mont) DeBary is the causal agent of late blight disease, which has been cataloged as the most devasting plant disease in the history of humankind. This pathogen is capable of affecting economically important plants of the solanaceae family, such as tomato and potato. P. infestans is a heterothallic oomycete for which it needs two types of mating known as A1 and A2 to present a sexual reproduction, which is the main way by this pathogen increases its degree of genetic diversity through a recombination of its genetic material; this condition represents the major defiance to control this disease. This study determined the level of genetic variability, through the molecular marker amplified fragment length polymorphism (AFLP), of 22 P. infestans isolates collected in different potato and tomato producing areas in Guatemala. With the band profile generated by the molecular marker AFLP, a cluster analysis was performed creating a UPGMA dendrogram with Dice´s index through a genetic distances matrix. The isolates were located in three main groups, which respond to the place of origin and the type of host plant. A similarity value of 0.49 was found among the analyzed isolates. It is concluded that genetic variability of the isolates analyzed is high.

Response of nitrogen components of tomato plants to potato virus- Y infection

Changes in nitrogen components of leaves of susceptible [Lycopersicon esculentum cv. Moneymaker] and resistant [Lycopersicon pimpinellifolium L.] tomato species, at various intervals post- inoculation with Yo group [common strain of potato virus Y [PVY]] were recorded. In susceptible tomato species, virus infection lowered the total nitrogen content as a result of decreased amino peptide, nitrate and total nitrogen components. The maximum decrease was recorded after 28 days post-inoculation. The remaining components were not affected by the infection, but the insoluble nitrogen increased, reaching maximum at 14 and 21 days post-inoculation. In resistant tomato species, virus infection stimulated total nitrogen accumulation as a result of increased peptide, nitrite and insoluble nitrogen contents. The effect was most pronounced at 14 days post- inoculation. The other components were less than in the control. The drop reached its maximum after 7, 21 and 28 days post-inoculation