INCIDENCE AND GEOGRAPHICAL DISTRIBUTION OF CALYX SPOT ON ROSELLE IN GUERRERO, MEXICO

Abstract

Background: Roselle calyx spot (MCJ) causes losses of 80% of the yield of this crop. Objective: To know the geographical distribution of the leaf and calyx disease of the roselle in the producing localities and municipalities of the state of Guerrero. Methodology: The recognition area included the Costa Chica region (Ayutla de los Libres, Tecoanapa, San Marcos and Acapulco de Juárez), Costa Grande (Atoyac de Álvarez and Coyuca de Benítez) and the North region (Copalillo). The delimitation of the commercial plots considered a distance> 10 km, for a sampling in five of golds, evaluating the incidence and severity of MCJ. The information was integrated into a database of geographic information systems and the spatial pattern was analyzed. The variables were analyzed in random blocks, with five repetitions, under the procedure with proc rank and an analysis of variance proc glm, the separation of means was used by the Tukey-Kramer procedure and Spearman's linear correlation coefficients were calculated. Results: The disease has a differential geographical distribution, the highest incidence (> 75%) in calyx occurred in the municipalities of Tecoanapa and Ayutla, however, its presence in the leaves can increase the incidence in calyx in Acapulco, San Marcos, Copalillo and Coyuca de Benítez. The highest severity index was presented in Tecoanapa with 2.87, showing differences with Ayutla, Acapulco and San Marcos with 2.24, 2.06 and 1.04 respectively (p <0.05). Atoyac and Copalillo only had leaf spots and Coyuca de Benítez the disease was not detected. The Tecoanapa and Coneja genotypes had leaf and calyx spotting values of 2.85 and 2.17 respectively, with significant differences with the Criollo, Jersey and Sudan genotypes with low values of 1.59, 0.75 and 0.31 respectively (p <0.05); Jersey and Sudan showed symptoms only on leaves. The plantations at altitudes of 19-100 m had severity values with 2.38, followed by> 100 m with 2.09 and 0-18 m with 0.93 (p <0.05). The severity of the MCJ was correlated with the altitude, genotypes and producing municipalities. Implications: The disease distribution maps made it possible to identify municipalities with higher risk, genotypes and altitudes with higher and lower incidence and severity of MCJ. Conclusions: The study shows that the MCJ in Guerrero is influenced by the genotypes and altitudes of the sowing areas, which causes a diverse incidence and severity of the disease among producing municipalities.