Examinando por Autor "Corazon Guivin, Mike"

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Determinación de la DL50 de Metanosulfonato de Etilo (EMS) para la inducción de cambios morfológicos y fisiológicos en plántulas de Plukenetia volubilis
(Universidad Nacional de San Martín, 2022-01-20) Corazon Guivin, Mike; Arévalo Rojas, Manuel; Acosta Córdoba, Ronny; Valverde Iparraguirre, Jorge; Ruiz Sánchez, María; Cerna Mendoza, Agustín; Guerrero Abad, Juan Carlos
El uso de mutágenos químicos es una herramienta muy utilizada para la generación de nuevas variantes genéticas en diversos cultivos agrícolas. Se evaluó el uso Ethyl Methanesulphonate (EMS) en semillas de Plukenetia volubilis L. para determinar la concentración óptima de EMS que redujera la germinación y/o emergencia de las semillas hasta un 50.0%, y evaluar las alteraciones morfológicas y fisiológicas en plántulas de P. volubilis durante la primera generación. Se empleó un DCA simple con diferentes dosis (0.0%, 0.5%, 1.0%, 1.5%, 2.0% y 3.0%) de EMS en un solo tiempo de exposición (30 hrs.), más un control absoluto (semillas sin tratamiento), para evaluar la sensibilidad mutagénica de P. volubilis L.., considerando parámetros como porcentaje de emergencia, altura de planta, pérdida de dominancia apical, clorosis y deformación de las hojas. Los resultados mostraron que la dosis de 3.0% de EMS con 30 hrs. de exposición, redujo hasta un 50.0% la emergencia de plántulas, valor considerado como la dosis letal media (DL50) para P. volubilis. Así mismo, se evidenciaron alteraciones fenotípicas como deformación de hojas, clorosis, disminución de la altura y pérdida de dominancia apical con el incremento de dosis de EMS. Estos resultados demuestran el potencial del EMS para ser utilizados en semillas de sacha inchi con el objetivo de generar nuevas variantes genética de esta especie.
Genetic diversity and population structure of Myrciaria dubia from the Peruvian Amazon: implications for germplasm conservation and crop improvement
(Springer Nature, 2026-03-27) Mejía de Loayza, Eduardo; Estivals, Guillain; Castro Ruiz, Diana; Chota Macuyama, Werner; Angulo Chávez, Carlos; Corazon Guivin, Mike; Rodríguez del Castillo, Ángel Martín; Alvarado Reategui, Jhon; Angulo Villacorta, Carlos; Mejía, Kember; Del Castillo Torres, Dennis; García Dávila, Carmen
Myrciaria dubia (camu-camu) is a shrubby fruit tree native to the continental Amazon whose fruits have been intensively harvested from wild stands, potentially reducing effective population sizes. We quantified genetic diversity and population structure across seven wild Peruvian Amazon populations and delineated river-basin genetic units to guide provenance-aware germplasm conservation and breeding. We genotyped 254 individuals from the Napo, Ucayali, Nanay, Tahuayo, Putumayo, Tigre, and Curaray basins using six polymorphic microsatellite loci. Overall, 48 alleles were detected. Observed heterozygosity (0.149–0.483) was generally lower than expected heterozygosity (0.220–0.531), and population-level inbreeding coefficients (FIS=−0.038– 0.560) indicated significant heterozygote deficits in Napo, Curaray, and Tahuayo. The Putumayo population harbored nine private alleles, representing a unique genetic reservoir. Pairwise differentiation was substantial (FST=0.093–0.660; Nei’s distance=0.068–1.734), with the strongest divergence between Tigre and Ucayali. Neighbor-joining, Bayesian assignment, and Discriminant Analysis of Principal Components (DAPC) initially supported three major genetic units and highlighted Putumayo as genetically isolated; additionally, hierarchical STRU CTURE analyses resolved eight clusters, and DAPC distinguished seven population-specific groups. Analysis of molecular variance attributed 56.5% of the variation within individuals and 34.7% among populations. Mantel tests supported isolation by distance based on straight-line geographic distances (r=0.53– 0.56; p≤0.017), whereas river-network distances were not significant. Overall, the data indicate a geographically structured genetic architecture shaped by dispersal limitation and basin-scale differentiation, supporting three provenance units for germplasm banking and breeding: (i) Napo–Ucayali–Nanay– Tahuayo, (ii) Tigre–Curaray, and (iii) Putumayo.
Native entomopathogenic nematodes from Peru control Spodoptera frugiperda, a major pest of Zea mays in the Peruvian Amazon
(MDPI, 2026-03-09) Fachin Ruiz, Grecia; Córdova Sinarahua, Deyvis; Romero Chávez, Lorena Estefani; Alvarado Ramírez, Jaime; Quesquen Lopez, Cesar; Flores García, Eybis; Koch Duarte, Christian; Cerna Mendoza , Agustín; Vásquez Bardales, Joel; Corazon Guivin, Mike
This study evaluated entomopathogenic nematodes (EPNs) isolated from a cacao agroforestry system in the Peruvian Amazon, focusing on their molecular characterization and efficacy against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae. Thirteen EPN isolates were obtained from 50 soil samples using the Galleria mellonella baiting technique. Mortality assays revealed significant differences among isolates at 24, 48, and 72 h, with isolates 11N-A4 and 8N-B1 being the most virulent, achieving maximum mortalities of 100% and 96.3% at 72 h, respectively. Median lethal time (LT50) values indicated rapid action of these isolates on G. mellonella larvae, with 33.3 h for 11N-A4 and 32.4 h for 8N-B1. Molecular identification using ITS, D2-D3 (LSU), and COI markers confirmed the isolates as Heterorhabditis sp. (11N-A4) and Heterorhabditis amazonensis (8N-B1). In bioassays with S. frugiperda larvae, both EPNs exhibited dose- and time-dependent mortality. H. amazonensis showed rapid action, reaching 100% mortality at the highest dose (60 IJs/larvae) within 48 h, whereas Heterorhabditis sp. displayed a gradual, sustained increase, attaining 91% mortality at 72 h. Median lethal dose (LD50) and LT50 values reflected the efficiency of both isolates, with Heterorhabditis sp. achieving lower LD50 at later stages and shorter LT50 at low-to-intermediate doses. These findings highlight the potential of Heterorhabditis sp. and H. amazonensis as effective biocontrol agents adapted to local conditions and represent the first report of H. amazonensis in Peru. Further studies under field conditions are required to confirm their suitability for incorporation into integrated pest management strategies in the Peruvian Amazon.