Hugo Magdaleno Ramírez Tobías

Assessing agricultural water quality is fundamental to minimizing and mitigating irrigation's environmental impacts. Leachate dynamics and physicochemical parameters as environmental stress indicators were evaluated. For tomato (Solanum lycopersicum L.) seedling production, we used soilless substrates. The study evaluated four treatments: T1 (100% coconut fiber), T2 (75% coconut fiber + 25% perlite), T3 (100% peat moss), and T4 (75% peat moss + 25% perlite). A controlled irrigation regime lasted 16 days, including fertilizer and fungicide applications. We collected and analyzed 192 leachate samples for eight parameters. Measured parameters included pH, electrical conductivity (EC), total dissolved solids (TDS), Na⁺, NO₃⁻, K⁺, and Ca²⁺. T3 showed the highest average volume retained (AVR). T2 exhibited the highest average leachate volume (AVL). Nitrate concentrations were higher in T4 and lower in T1, exceeding regulatory limits. Concentrations of Na⁺, K⁺, and NO₃⁻ posed contamination risks. These findings highlight the need for improved monitoring to enable safe agricultural reuse.

Los hongos micorrizógenos arbusculares (HMA) son organismos esenciales y de suma importancia para las plantas terrestres. Se seleccionaron distintas comunidades vegetales de México en los estados de Coahuila, Guanajuato, San Luis Potosí, Tamaulipas y Veracruz, en donde se recolectó suelo rizosférico con el objetivo de aislar esporas de HMA. La identificación taxonómica se llevó a cabo mediante el análisis de las características morfológicas de las esporas, comparándolas con los artículos originales de cada especie descrita. Se identificaron 4 especies de HMA pertenecientes al género Septoglomus (S. altomontanum, S. fuscum, S. furcatum y S. turnauae), que constituyen su primer registro en México. Con estas 4 especies, la riqueza total de HMA en México se eleva a 171, lo cual evidencia una diversidad significativa de HMA en las comunidades vegetales del país.

Climate change poses an increasing challenge to tropical agriculture, particularly for heat-sensitive crops such as local varieties of beans (Phaseolus vulgaris L.). This study evaluated the effects of induced passive heat on the root architecture and symbiotic interactions of two local genotypes, Tayní and Bruncas, using Open Top Chambers under field conditions. Both varieties were included in the analysis and exhibited consistent qualitative responses to warming, with no contrasting cultivar-specific trends detected. Both varieties developed more roots and greater root area compared to the control, while mycorrhizal colonization increased up to 80% under warming. Soil temperature emerged as the main environmental factor influencing root expansion. These findings highlight the adaptive plasticity of local bean varieties under induced passive heat.

Climate change is a major constraint for common bean (Phaseolus vulgaris L.) cultivation in tropical regions, where elevated temperatures drastically affect reproductive efficiency and yield. This study aimed to evaluate the response of two local varieties, Matambú and Tayní, under passive induced heat using Open Top Chambers (OTC) in the humid tropics of Costa Rica. A factorial randomized block design with two genotypes and two environments (control and OTC) was applied to assess morphological, physiological, and yield-related traits. OTC increased daily maximum, minimum, and mean air temperatures by +2.29, +0.93, and +2.80 °C, respectively, and raised cumulative growing degree days by 325 °C·day⁻¹ compared with the control. Heat stress reduced grain yield by more than 80% (from 0.15 to 0.03 t·ha⁻¹) and significantly lowered the harvest index, confirming strong reproductive vulnerability. However, Matambú maintained higher nodulation and above-ground biomass under heat, whereas Tayní showed marked declines in pod set and nodule number. Correlation analyses revealed that pod number and harvest index were the strongest predictors of yield across environments. These results provide the first field evidence of local varietal responses to induced passive heat in Costa Rican common bean varieties and highlight Matambú as a valuable genetic resource for breeding climate resilient cultivars.

Weeds growing in Mesoamerican traditional maizefields, or milpas , represent a reserve of genetic resources and knowledge. To explore tendencies on the influence of natural and cultural attributes on milpa weeds and their knowledge, we studied species richness, perception, and use of adventitious plants in milpas across an agroclimatic and cultural gradient in Altiplano , Rioverde , and Huasteca milpas in the state of San Luis Potosi, México. The study involved semi-structured interviews and recording weed presence in milpas. Farmers from Huasteca , who often used herbicides and fertilizers in milpas, had a negative perception of weeds and their milpas registered a lower species richness. By contrast, farmers from Altiplano, who mostly managed milpas without industrial inputs, perceived weeds in an ambivalent manner (neither positive nor negative) and their milpas registered the highest species richness. Thus, an association between weed richness and management practices was identified. Farmers collectively recognized 67% of the species present in milpas, and from the total number of species registered, interviewees mentioned specific medicinal uses of nine species that have not been scientifically studied although those species have other scientifically known uses. Forage was the most common use of weeds in milpas from Altiplano and Rioverde , food in Rioverde , and agronomic as soil fertilizer in Huasteca . Milpa farmers collectively still preserve knowledge about weeds that showed differences depending on the uses and region. Promoting milpa agroecosystem ethnobiological knowledge is important to maintain sustainable practices and biodiversity.

Arbuscular mycorrhizal fungi (AMF) play a crucial role in the resilience of plants subjected to water deficit. The objective of this study was to evaluate the impact of AMF from a semi-arid and humid ecosystem, applied as inocula (two monospecific and two consortia), and three irrigation doses (100%, 85%, and 70%) on tomato plant growth. A factorial experiment in a completely randomized design was used. Colonization with monospecific inocula (EH and ES) showed contrasting differences at 85% and 100% irrigation rates. With gradually increasing irrigation rates, colonization decreased with the CH consortium, while the CS consortium showed similar colonization levels at all three irrigation rates. AMF from humid environments (monospecific or in a consortium) did not affect equatorial diameter when the irrigation rate was reduced by 15%, while polar diameter was similar at all three irrigation rates. Inocula from the semi-arid ecosystem promoted the greatest equatorial and polar diameters at the 100% irrigation dose. The monospecific inoculum of C. etunicatum (ES) showed great potential to promote plant growth and development at the 100% irrigation dose and could be a biotechnological tool to improve tomato yield under conditions similar to those of this study.

The objective of this study was to assess the effect of the association of Leucaena leucocephala, and its co-inoculation with a strain of the arbuscular mycorrhizal fungus (AMF) Claroideoglomus claroideum and a local isolate of rhizobium, on the performance of associated grasses (Bouteloua gracilis, Bouteloua curtipendula and Setaria macrostachya). The mycorrhizal structures and nodulation were also studied. Three independent experiments, one for each grass species, were grown in association with L. leucocephala co-inoculated and non-inoculated, or alone (control treatment). Grasses associated with co-inoculated L. leucocephala produced a greater number of stems than those associated with non- inoculated L. leucocephala. B. gracilis and B. curtipendula grown with co-inoculated L. leucocephala accumulated higher biomass. The concentration of chlorophylls a, b and total chlorophylls in S. macrostachya were favored by the association with L. leucocephala; whereas in B. gracilis such effect was only observed for chlorophyll b. Co-inoculation promoted the development of mycorrhizal structures in the rhizosphere and the number of nodules in roots of L. leucocephala, although the percentage of effective nodules did not reflect differences due to treatments. In conclusion, the association of grasses with L. leucocephala and its inoculation with AMF and local rhizobium isolates not only promotes the development of mycorrhizal structures and nodulation, but also increases growth and the content of photosynthetic pigments in the associated grasses. El objetivo de este trabajo fue evaluar el efecto de la asociación de Leucaena leucocephala, y su co-inoculación con una cepa del hongo micorrízico arbuscular (HMA) Claroideoglomus claroideum y un aislado local de rizobio, sobre el comportamiento de las gramíneas asociadas (Bouteloua gracilis, Bouteloua curtipendula y Setaria macrostachya). Se estudiaron las estructuras micorrízicas y la nodulación. Se realizaron tres experimentos independientes, uno por cada gramínea, en asociación con L. leucocephala co-inoculada y sin inocular, o sola (como testigo). Los pastos asociados con L. leucocephala co-inoculada produjeron mayor cantidad de tallos que aquellos asociados con L. leucocephala sin inocular. B. gracilis y B. curtipendula acumularon mayor biomasa cuando se asoció con L. leucocephala co-inoculada. Las concentraciones de clorofilas a, b y totales en S. macrostachya y la de clorofila b en B. gracilis se vieron favorecidas por la asociación con L. leucocephala. La co-inoculación promovió el desarrollo de estructuras micorrízicas en la rizósfera y el número de nódulos en raíces de L. leucocephala, aunque el porcentaje de nódulos efectivos no reflejó diferencias entre tratamientos. En conclusión, la asociación de gramíneas con L. leucocephala y su inoculación con HMA y aislados de rizobios locales no solo promueve el desarrollo de estructuras micorrízicas y la nodulación, sino también aumenta el crecimiento y el contenido de pigmentos fotosintéticos en las gramíneas asociadas