Scientia Agropecuaria

Long-Term impact of rice cultivation on soil quality indicators in Northern Amazonia Savanna

Valdinar Ferreira Melo — 2025-02-18

Changes in soil attributes following changes in management strategies in rice cultivation can alter soil quality, either positively or negatively. The aim of this study was to evaluate soil quality indicators, based on physical, chemical and microbiological soil attributes in Amazonian savanna under rice cultivation with different ages. The research was conducted in five areas under continuous rice cultivation during 1, 3, 8, 13, and 25 years, compared with local reference native vegetation. Soil samples were collected at 0-10 cm depth and evaluated for physical attributes such as texture and bulk density, chemical properties such as soil organic carbon, total nitrogen, exchangeable cations, available P, pH, CEC and C/N ratio; and microbiological attributes like microbial biomass carbon, soil microbial respiration, metabolic ratio and microbial coefficient. Acid phosphatase and urease activity were evaluated. With longer periods of time of rice cultivation, soil quality was enhanced with increasing soil fertility, increased soil organic carbon content and enzyme activity. The paddy soil indicators were sensitive to changes in rice cultivation and its duration. Acid phosphatase activity and available phosphorus increased with longer time of rice cultivation, indicating a possible conversion of inorganic into organic phosphorus forms, corroborated by increasing phosphatase activity. Microbiological (SMB-C, SBR, qMIC and qCO₂) and biochemical (urease and acid phosphatase) indicators, as well as soil organic carbon and total nitrogen were highly sensitive to land use changes. Chemical and microbiological indicators are suitable for estimating paddy soil quality in lowland of Amazonian savanna.

Hongos fitopatógenos foliares asociados al cultivo de Prunus persica L.: Identificación morfológica y molecular, y control biológico con Trichoderma asperelloides

Ángel Ceballos-Chávez — 2025-02-18

La presencia de hongos fitopatógenos foliares ocasiona severos daños en hojas y frutos de durazno (Prunus persica L.), en zonas productoras del sur de Chihuahua, México, lo que ha ocasionado una disminución en su producción en un 30%. El objetivo de este trabajo fue identificar morfológica y molecularmente los hongos fitopatógenos foliares asociados al cultivo del duraznero evaluando la patogenicidad en plantas de un año contra Trichoderma asperelloides. Se recolectaron hojas con lesiones color café y marrón en frutos momificados en planta de 19 huertos comerciales de durazno distribuidos en tres municipios de producción regional y nacional en el Estado de Chihuahua México. La identificación de hongos de cuatro aislamientos representativos se realizó utilizando métodos morfológicos. caracterización y análisis filogenético basado en la región espaciadora transcrita interna (ITS1 e ITS4) de ADN ribosomal, parte del factor de elongación de traducción 1-alfa (TEF) un segundo cebador secundario por cada uno de los géneros para, Collectotrichum ACT-512F y ACT-583R, Fusarium con EF1. Para las confrontaciones en planta se inoculo una concentración de 1x10⁶ conidios. mL^-1 de patógenos como de T. asperelloides, evaluando el diámetro y longitud de hoja, altura, severidad e incidencia. Se logró identificar la presencia de Fusarium sambucinum, Collectotrichum gleosporoides y Monilinia frutícola, además la cepa B-F-M1-A2-ACCH-3 de F. Sambucinum obtuvo los valores más altos en la inhibición de las variables de respuesta y en severidad Monilinia frutícola presentó 61,23% como el valor más alto. Se recomienda usar la cepa 3 como control biológico de fitopatógenos foliares.

Multilocus identification and pathogenetic characterization of Colletotrichum endophyte and pathogen species isolated from cocoa leaves and pods (Theobroma cacao) in Ecuador

Fernando Espinoza-Lozano — 2025-02-18

Cacao cultivation is one of the main agricultural products of Ecuador, known internationally for its quality and aroma. However, it is affected by fungal diseases including Moniliophthora roreri, Moniliophthora perniciosa, Phytophthora spp., and Colletotrichum spp. The genus Colletotrichum spp. is known for its characteristics that complicate traditional taxonomic identification. In cacao cultivation, it is one of the most frequently found species as an endophyte of leaves and fruits, yet it is also reported to cause the disease known as anthracnose on leaves and fruits. The objective of this work was to identify at the species level 16 Colletotrichum isolates, 13 from healthy leaf endophytes and 3 from pods with symptoms, through multilocus analysis of the ITS1, 5.8S, and ITS2 region, and partial sequences of the TUB2 and GAPDH genes. Subsequently, their pathogenicity was evaluated by inoculating healthy cacao pods and measuring the damage caused. The 16 isolates were identified as follows: from the gloeosporioides complex, C. siamense 6, C. chrysophilum 6, C. theobromicola 2 and from the boninense complex, C. karstii 2. The most frequently found species were those that caused symptoms, especially C. siamense, to which the strains were isolated from symptomatic pods belonged. This work provides relevant and accurate information about the diversity of Colletotrichum species that colonize cocoa plantations and identifies which species might cause the disease known as anthracnose. Additionally, it allows for a more precise diagnosis and consequently better treatment.