Lipids are biomolecules of great scientific and biotechnological interest due to their extensive applications. Microalgae are potential biological systems used in the synthesis of lipids, particularly Chlorella sp., which is characterized by its high lipid content and for having the right profile for the obtainment of biofuel. Lipid production in microalgae is influenced by several physical and chemical factors. Any modification thereof can cause a stress response represented by changes in synthesized lipid composition, varying from one species to another. This paper evaluates the effect of different light wavelengths, photoperiods and calcium carbonate (CaCO3) supply in lipid synthesis in Chlorella sp. In order to do so, the microalgae was grown in Bold's Basal Medium (BBM) at 20ºC with constant aeration and subject to low blue (470 nm) and red (700 nm) light wavelengths, 0,5 g.L-1 and 1,5 g.L-1 concentrations of CaCO3 and 6-hour light, 18-hour darkness (6:18) and 18-hour light, 6-hour darkness (18:6) photoperiods. The results indicate a higher growth rate for microalgae under red light, 0,5 g.L-1 of CaCO3 and a photoperiod of 6:18. On the other hand, lipid production is higher under blue light, 1,5 g.L-1 of CaCO3 and an18:6 photoperiod. Analysis by gas chromatography indicate that the fatty acids in the samples are oleic, linoleic and palmitoleic, which are of recognized importance in the biodiesel industry. This suggests that neutral lipid synthesis can be optimized in two stages: first, by promoting growth and subsequently, by inducing lipid production.

Vegetative propagation of sweet potato lead to the accumulation of diseases from generation to generation, which represents a threat to both productivity and conservation of genetic resources. In vitro techniques can help to overcome phytosanitary problems by applying plant material cleaning strategies. The objective of this study was to develop in vitro micropropagation strategies for the production of high-quality plant material of an orange-fleshed variety of sweet potato recently released in Colombia. Molecular identification of contaminating microorganisms was performed by sequencing the 16S rRNA gene for bacteria and ITS for fungi. Five disinfection protocols were evaluated, three of which were previously developed for sweet potato and included disinfection with 0.5, 1, and 2% sodium hypochlorite respectively, while two protocols are proposed in this work and included washing with povidone-iodine, disinfection with sodium hypochlorite 2%; one of these two new protocols also contains acetic acid and quaternary ammonium. For the evaluation of the viability of in vitro plants after disinfection, they were acclimatized in a greenhouse, reintroduced, and a molecular testing by PCR of 16S rRNA gene and ITS was carried out to verify the phytosanitary status of the material. The contaminating microorganisms found were filamentous fungi of the genera Fusarium, Sarocladium, Cladosporium and Aspergillus, yeasts of the genera Pseudozyma and Moesziomyces, and the actinobacterium Curtobacterium sp. The results indicated that washing with povidone-iodine and disinfection with 2% sodium hypochlorite, acetic acid and quaternary ammonium was the most efficient disinfection protocol, reducing the number of contaminated cultures by up to 10% and eradicating 70% of contaminants. The in vitro plants established in the greenhouse remained healthy and, after reintroduction, the molecular test for bacteria and fungi was negative. These results allowed the generation of an optimized protocol that can be incorporated into the in vitro micropropagation process to generate contamination-free sweet potato seeds.

Sweet potato is a crop with a wide capacity to adapt to adverse conditions. To study the tolerance of the sweet potato to a low-altitude environment, 34 genotypes comprising three groups from different altitude conditions ranging from 18–599, 924–1298, 1401–2555 meters above sea level were evaluated. These genotypes were evaluated through ecophysiological parameters: net photosintetic rate (Pn), stomatal conductance (G_S), transpiration (E), leaf internal CO₂ (ICO₂), vapor pressure deficit (VPD) and leaf internal temperate (LT). sSubsequently, water use efficiency (WUE) and carboxylation efficiency index (CEI) were estimated. Simultaneously, morpho-agronomic characterization of the genotypes was conducted including descriptors and morpho-colorimetric parameters. A wide ecophysiological variability was found among genotypes from high, intermediate and low altitudes, when those were evaluated under low altitude conditions. The genotypes that presented major soil coverage efficiency and leaf size showed greater Pn, WUE and CEI, and Low VPD and E, aspects that benefited the ability to form roots the under low-altitude environment. The altitudinal origin of the genotypes influenced the ecophysiological response under low altitude conditions. The capacity of certain sweet potato genotypes to tolerate low altitude conditions were due to to different mechanisms, such as certain morphoagronomic traits that allowed them to adjust their physiological processes, especially those related to photosynthesis.

Introduction. Dry rot is a disease that has acquired great importance in Colombia because it causes losses in yam (Dioscorea rotunda Poir.) tubers, both in the field and in postharvest, affecting the economic income and productivity of smallholders. Information on the causal agents of this disease is scarce, so the strategies for managing this problem are unclear. Objective. To identify and characterize fungi associated with the dry rot disease of yam tubers. Materials and methods. This research was carried out between March and October 2019, in the coastal zone of the Córdoba department in the Colombian Caribbean. Yam tubers were collected in storage, due to the fact that farmers keep them as seeds for future harvests. In the laboratory, the associated fungi was isolated from the lesions, characterized, and then identified through the amplification of the ITS (Internal Transcribed Spacer) region of the ribosomal DNA. Results. Twenty-eight fungal growths associated with dry rot of yam tubers were isolated and grouped into eleven morphotypes of which ten species were identified, belonging to nine fungal genera. Conclusion. Six fungi could be associated with the dry rot of yam tubers in the coastal zone of Colombia. These would be: Lasiodiplodia theobromae, Fusarium solani, Rhizopus oryzae, Neocosmospora rubicola, Neoscytalidium dimidiatum, and Curvularia aeria.

Esta investigación tuvo como objetivo el aislamiento y caracterización de bacterias con potencial para promover el crecimiento del pasto Pennisetum clandestinum en suelos salinos simulados. De muestras de suelo rizosférico de P. clandestinum se aislaron 92 bacterias Gram positivas, diez aislados crecieron en agar nutritivo suplementado con NaCl (2,578 M). Los aislados se evaluaron bajo condiciones de invernadero; las cepas identificadas como KISA 34 y KISA 71 fueron seleccionadas como las mejores con base a la prueba estadística de Dunnet (p≤ 0,05) y fueron identificadas molecularmente como Bacillus amyloliquefaciens KISA 34 y Bacillus subtilis KISA 71. Estas cepas tienen la capacidad de producir; amonio, exopolisacáridos y celulosa, y tanto en presencia como ausencia de NaCl, produjeron índoles totales y solubilización de fósforo. La evaluación de las cepas en invernadero evidenció que el T6 - KISA 34 + KISA 71+ 25 % (Roca Fosfórica RF) con respecto al T2- testigo químico completo incrementaron de manera significativa la biomasa y el desarrollo de la planta (p≤ 0.05). Los resultados de esta investigación demostraron que las cepas aisladas tienen la capacidad de crecer en suelos salinos conservando sus características como promotoras de crecimiento vegetal con efectos positivos sobre P. clandestinum.