Examinando por Autor "Rivas, Johan"

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Endophytic Trichoderma and Bacillus isolates suppress Lasiodiplodia theobromae-associated dieback in blueberry under arid coastal conditions
(Nature Portfolio / Springer Nature, 2026-03-31) Villanueva Olivera, William; Valladolid Suyón, Esteban; Palomino Arias, Mickel; Paredes Jacinto, Juan Carlos; Rivas, Johan; Solórzano Acosta, Richard Andi; Jaramillo Carrión, María
Blueberry (Vaccinium corymbosum L.) production represents one of the main pillars of Peruvian agro-exports; however, its sustainability is increasingly threatened by wood-infecting fungal diseases such as dieback. This study was conducted in the Nuevo Proyecto–Olmos area (Lambayeque, Peru), covering a total cultivated area of 176 ha. The objectives were to molecularly identify the fungal pathogens associated with blueberry dieback to perform a preliminary evaluation of the antagonistic potential of endophytic microorganisms. Pathogens were isolated and characterized using morphological and molecular approaches, followed by pathogenicity tests and in vitro efficacy assays of beneficial microorganisms. Disease incidence was dominated by Lasiodiplodia spp., followed by Neopestalotiopsis, Fusarium, and Diaporthe. Lasiodiplodia theobromae was the most prevalent and aggressive species, confirming its association with the observed disease symptoms. For the genus Lasiodiplodia, temperatures between 25 and 30 °C favored mycelial growth, whereas 20 °C and 35 °C limited development. Endophytic isolates of Trichoderma spp. and Bacillus spp. inhibited pathogen mycelial growth by more than 60% under in vitro conditions. These findings highlight the potential of beneficial microorganisms as preliminary candidates for the biological control of wood-infecting fungi in blueberry production systems.
Native halotolerant consortia modulate soil–plant interactions under moderate salinity
(Taylor & Francis Group, 2026-03-02) Palomino Arias, Mickel; Salazar Coronel, Wilian; Paredes Jacinto, Juan Carlos; Rivas, Johan; Muñoz Leiva, Yulissa Marisol; Aldava Pardave, Uriel; Jaramillo Carrión, María; Valladolid Suyón, Esteban; Solórzano Acosta, Richard Andi
Soil salinity is a major limitation for rice production in arid regions, reducing plant growth, yield, and grain quality. This study assessed the effect of halotolerant strains of Bacillus subtilis and Pseudomonas putida on the growth, productivity, and soil chemical properties of Oryza sativa L. INIA 515 'Capoteña' under initial soil salinity of 4.75 dS m⁻¹. Eight treatments were evaluated, including bacterial consortia, and non-inoculated control. The selected strains exhibited high salt tolerance, with B. subtilis BacF and P. putida P4 growing at up to 10% NaCl. Although most physiological and agronomic variables did not differ significantly among treatments, treatment T5 (BacF + P4) showed a moderate tendency towards better values, particularly in panicle number, aerial biomass, total biomass, grain yield, and SPAD across the growth cycle. At the edaphic level, T5 significantly increased soil pH and promoted a slightly synergistic mobilisation of K, Mg, and Na. Structural equation modelling indicated that magnesium strongly enhanced total plant biomass, while organic matter positively influenced grain yield. These findings indicate that native halotolerant consortia may influence soil–plant interactions under controlled conditions, but agronomic benefits remain limited and require field validation.