Relaciones entre los hongos filamentosos y solubilizadores de fosfatos con algunas variables edáficas y el manejo de cafetales
Raúl Hernando Posada, Marina Sánchez de Prager, Ewald Sieverding, Karla Aguilar Dorantes & Gabriela Patricia Heredia-Abarca
ABSTRACT
Filamentous and phosphate solubilizing fungi relationships with some edaphic parameters and coffee plantations management. Soil properties and the environment have multiple outcomes on fungal communities. Although, the interaction effects between management intensity, pH, available phosphorus, organic carbon, soil texture and different fractions of water stable macro-aggregates on the communities of microscopic filamentous fungi (MFF), iron phosphate solubilizing fungi (PSF-Fe), and iron and calcium phosphate solubilizing fungi (PSF-(Fe+Ca)), have been previously evaluated in field conditions, this has never been performed in terms of their combined effects, neither with phosphate solubilizing fungi. To assess this, we collected 40 composite soil samples from eight Mexican and Colombian coffee plantations, with different management intensities and physico-chemical edaphic parameters, during 2008-2009. We isolated different communities of MFF, PSFFe and PSF-(Fe+Ca), by wet sieving and soil particles culture in Potato-Dextrose-Agar from soil samples, and we classified isolates in terms of their phosphate solubilizing ability. Following the principal component analysis results, we decided to analyze fungal communities and abiotic factors interactions for each country separately. Structural Equation Models revealed that organic carbon was positively associated to MFF richness and number of isolates (λ>0.58), but its relationship with PSF-Fe and PSF-(Fe+Ca) were variable; while the available phosphorus, pH and water stable macro-aggregate fractions did not show a clear pattern. Management intensity was negatively related to PSF-Fe (λ≤-0.21) morphotype richness and the number of isolates in Colombian coffee plantations. We found that the relationships of clay and organic carbon content, and available phosphorus and soil pH, with the species richness and number of isolates of MFF, PSF-Fe and PSF-(Fe+Ca) were highly variable; this made impossible to generalize the responses between saprotrophic fungal groups and geographic zones. The management intensity was not related to species richness and number of isolates of MFF in any coffee areas, while for PSF the relationship could not be defined. The different water stable macro-aggregates fractions did not show a defined pattern in relation to the species richness and the number of isolates of saprophytic and phosphate solubilizing fungi (PSF). This study highlights the need to take into account edaphic and geographic context in order to reach a better understanding of the intensity management effects on MFF and PSF function in agroecosystems.
RESUMEN
El suelo y sus propiedades tienen múltiples relaciones con las comunidades fúngicas. El efecto conjunto de la intensidad de manejo y las variables edáficas, incluida la estabilidad de agregados sobre las comunidades de hongos microscópicos filamentosos (HMF), solubilizadores de fosfato de hierro (HSP-Fe) y solubilizadores tanto de fosfato de hierro como de calcio (HSP-(Fe+Ca)) no han sido evaluadas en campo. A partir de 40 muestras edáficas de ocho plantaciones de café de Colombia y México, con diferentes intensidades de manejo (IMPC) y con diferencias en sus variables edáficas, se aislaron y evaluaron las comunidades de HMF, HSP-Fe y HSP-(Fe+Ca) durante 2008-2009. Empleando modelos basados en ecuaciones estructurales se encontró que el carbono orgánico se relacionó positivamente con la riqueza y abundancia de HMF (λ>0.58) y fue variable en su relación con HSP-Fe y HSP- (Fe+Ca). Las relaciones del fósforo disponible, pH y las fracciones de macro-agregados fueron altamente variables. El IMPC se relacionó negativamente con HSP-Fe (λ≤-0.21) en cafetales colombianos. Se discuten las interacciones para cada conjunto de variables (químicas, estabilidad de macro-agregados y de manejo de plantación) y se explican las relaciones resultantes. Las relaciones de cada variable son inseparables del contexto edáfico y geográfico, los cuales imprimen marcadas diferencias.