Browsing by Author "Yarzabal Rodríguez, Luis Andrés"

Now showing 1 - 4 of 4

Antarctic pseudomonas spp. promote wheat germination and growth at low temperatures
(2018) Yarzabal Rodríguez, Luis Andrés; Chica Martínez, Eduardo José
The development of cold-active biofertilizers and biopesticides could help improve sustainable agriculture in mountainous regions. With this aim, both psychrophilic and psychrotolerant microorganisms have been prospected in cold regions around the world and tested for their plant-growth promoting (PGP) effects. Interestingly, very little is known about the PGP effects of polar microorganisms in commercial crops. This study aimed at isolating cold-active plant-growth promoting Pseudomonas spp. from Antarctic soils and testing their PGP effects, both in vitro and on wheat (Triticum aestivum). Twenty-five Pseudomonas spp. strains isolated from Antarctic soils at Greenwich Island (South Shetland Islands, Antarctic Peninsula) were tested. The isolates grew well at temperatures ranging from 4 to 30 °C and were therefore considered as eury-psychrophiles. The isolates solubilized tri-calcium phosphate at 8 and 16 °C in the presence of different sugars as sole carbon sources. Besides producing indole-acetic acid, siderophores and hydrogen cyanide, several isolates inhibited growth of three plant pathogenic fungi (Fusarium oxysporum, Pythium ultimum and Phytophtora infestans) by means of both soluble- and volatile-secondary metabolites. Bacterization of T. aestivum seeds with selected isolates significantly enhanced root elongation. Moreover, when grown in sterile soil and in a temperature-controlled growth chamber at 14 ± 1 °C, inoculated T. aestivum seedlings showed a significant increase in their root- and shoot-lengths compared to untreated controls. Overall, the results suggest that some of these Antarctic Pseudomonas spp. isolates could act as cold-active biofertilizers.
Microbial-based technologies for improving smallholder agriculture in the Ecuadorian Andes: current situation, challenges, and prospects
(2021) Yarzabal Rodríguez, Luis Andrés; Chica Martínez, Eduardo José
As in other Andean countries, smallholder agriculture is the base that supports food and nutrient security in Ecuador. Ironically, in spite of their importance, the development of context-appropriate technologies for these farming systems remains still at its infancy. Today, most smallholders in the Ecuadorian Andes practice a type of hybrid agriculture that merges traditional local practices and modern technologies. This mixture of traditional and “modern” conventional technologies does not always result in resource-efficient sustainable practices. Although they represent only part of a global solution, microbial-based technologies offer a great potential to improve the functioning of smallholder farms in the Ecuadorian Andes. From nutrient cycling to biocontrol and plant growth promotion, microbial technology applications match existing needs for technology development in these systems; however, as in many cases, knowledge gaps and context-adapted implementation are some of the challenges that slow down the spreading and efficient use of these technologies. Here we offer a review of the efforts made as of today to characterize, develop and test microbial-based technologies that could boost smallholder Andean agriculture with a particular focus in the Ecuadorian context. We also propose potential lines of action to increase or accelerate the impact of these technologies.
Role of rhizobacterial secondary metabolites in crop protection against agricultural pests and diseases
(Elsevier, 2019) Yarzabal Rodríguez, Luis Andrés; Chica Martínez, Eduardo José
Bacteria colonizing the rhizosphere of plants (=rhizobacteria) play different ecological roles in their natural environment. Some are deleterious to plant growth and health, while many others are beneficial and act as both promoters of plant growth (biofertilizers and phytostimulators) and/or controllers of plant pathogens (biocontrollers). The main mechanisms beneath the biocontrol abilities of the latter depend on the production and excretion of secondary metabolites. These metabolites are numerous and diverse and include, among others, antibiotics, siderophores, semiochemical quenchers, and/or elicitors of a plant’s induced systemic resistance (ISR). Owing to their production, other inhabitants of the rhizosphere are killed, inhibited, diminished, or deceived. Since this antagonistic activity affects crop pests and pathogens, plant growth is promoted in an indirect way. Therefore this natural ability of many rhizobacteria has been exploited successfully in the agricultural field to develop efficient biopesticides. These bioproducts, already marketed worldwide, often contain living microorganisms; however, the possibility of making profit from the microbial pure metabolites by developing such products is still in its infancy. Here we review some of the recent advances concerning the mode of action of some microbial secondary metabolites produced by rhizospheric bacteria, emphasizing their potential to develop ecofriendly biopesticides.
Root endophytic fungi promote in vitro seed germination in Pleurothallis coriacardia (Orchidaceae)
(2020) Maldonado Cedeño, Gabriela Patricia; Cevallos Cevallos, Juan Manuel; Yarzabal Rodríguez, Luis Andrés; Peña Tapia, Denisse Fabiola; Chica Martínez, Eduardo José
Seeds of many orchids rely on the presence of fungi to trigger the germination process and even to initiate the full development of protocorms. While attention has been directed towards the study of mycorrhizal fungi, the diversity and functions of endophytic fungi from orchid roots remain underexplored, and few studies have verified their ecological role. This is the case of Pleurothallis coriacardia, an endemic green Neotropical orchid with both epiphytic and lithophytic habits growing in High-Andean montane forests. In the present study, we screened the cultivable fraction of the endophytic fungi colonizing the roots of mature plants of P. coriacardia using ITS rDNA markers. We also tested the potential of these endophytic fungi to improve embryo development and seed germination. Most of the isolated endophytes were classified within Psathyrellaceae. Some isolates, identified as members of the Ilyonectria and Coprinellus genera, significantly promoted embryo development in vitro in P. coriacardia seeds, a result that highlights the ecological roles these endophytic fungi may play in nature.