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  • Open access
  • 94 Reads
Analysis of Fusarium graminearum Antifungal Protein and Latrodectin-I effect over growth and toxigenesis of Aspergillus fungi with agrofood impact

Crops colonization by toxigenic fungi causes important economic losses, being presumed to increase with global change. Mycotoxins presence in crops affect food security by reducing the edible yield, nutritional values, and making cereal consumption unsafe. An efficient method to reduce mycotoxin content is to avoid fungi appearance or toxigenesis. This has been traditionally achieved with antifungal chemicals that negatively affect soil and ecosystem health. Current research aims for methods less harmful for the environment, as natural proteins or biocontrol.

We tested crop-associated fungi against two possible growth-inhibiting proteins: Fusarium graminearum Antifungal Protein (Fg-AFP) and Latrodectin-I (Ltd-I). The first is produced by Fusarium graminearum to compete with other fungi, and the latter is found in Latrodectus hesperus venom, and has just recently been correctly purified.

In a first assay, we exposed 4 Aspergillus strains against cellulose discs with four Fg-AFP and Ltd-I concentrations (7µg/µL, 3.5µg/µL, 1.4µg/µL and 0.7µg/µL). Results show that Fg-AFP inhibited 3 of the strains development, while Ltd-I just affected secondary metabolism.

We subsequently selected Aspergillus niger and A. flavus strains, based on their importance in maize crops and sensitivity to the proteins, for a second assay in which we included the protein on surface. Results show that Fg-AFP reduced A. niger and A. flavus growth by 46.3% and 24.3%, respectively, extending fungal latent period by 68.4% and 52.6%, respectively. Ltd-I had no effect over A. flavus, but increased A. niger growth by 18.4%, prolonging latent period by 67.5%. Regarding toxigenesis, ochratoxin A production by A. niger did not vary when exposed to the proteins, but aflatoxin B1 synthesis by A. flavus increased with both treatments.

Though this proteins have growth-limiting potential, they must be evaluated under wider concentration ranges to asses their effect over toxigenesis and usage as an alternative to harmful chemicals.

  • Open access
  • 50 Reads
Published: 01 May 2021 by MDPI in The 1st International Electronic Conference on Agronomy session Posters

Phosphorus (P) deficiency is one of the major limiting factor of wheat production at worldwide. Although silicon (Si) is known to improve plant growth under low phosphorus (P) conditions, the impact of Si supply on nutritional quality of wheat grains at field conditions remains unclear. This study is aimed to investigate the impact of Si fertilization on healthy attributes and yield of grains of wheat plants grown under P deficiency. A field experiment on an Andisol was conducted by using two wheat cultivars with contrasting tolerance to P deficiency (cv. Púrpura, sensitive to P-deficiency; and cv. Fritz, tolerant to P-deficiency) during two growing seasons. Three P fertilization doses (0, 200, 400 mg P kg-1 soil) were applied in combination with three Si levels (0, 250, 500 mg Si kg-1 soil). At mature grain stage, Si and P concentration, total phenols, phenolics acids, radical scavenging activity and yield components were evaluated. At both growing seasons, Si supply enhanced grain P concentration of cv. Púrpura grown in absence of P, whereas grain Si concentration increased in both cultivars along the gradient of P supply. Interestingly, increasing Si doses augmented phenol concentration and antioxidant capacity in grains of cv. Púrpura grown without P at both growing seasons. In contrast, Si decreased grain phenol concentration of cv. Fritz under P deficiency. A slight increment of phenolic acids induced by 250 mg kg-1 Si was also detected in grains of both wheat cultivars grown without P. A positive effect of Si fertilization on yield components and grain yield of both wheat cultivars grown either without or with P fertilization at both growing seasons was also found. Acknowledgments. FONDECYT Regular Project N°1201257.

  • Open access
  • 52 Reads
Regolith as baseline to a future space farm
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Heavy pay attention and investment of resources attended to space colonization were shown in the last decade. Indeed many space agencies, first upon all NASA which have set programs to create a stable settlement on Moon (in the next years) looking at the future with a first manned mission to Mars.

In this perspective, a key role going to be played by Bioregenerative Life-Support Systems (BLSS), because providing all consumables for the crew members life-support from Earth becomes un-realistic (high cost and planning time to keep). An alternative solution to reduce the payloads and the support delivery can be given by the implementation of BLSS through the in situ resource utilization (ISRU). Specifically, improving the use of moon' and martian's regolith (the “soil” of a planet or a satellite) and promoting the re-use of waste materials produced either during the journey than to live in the future colony such as human excreta and food residues.

Nowadays few works have investigated the feasibility of use of these resources for crop productions and the effects on crop yield and nutritional quality. Our work aims to fill this gap, by using regolith simulants mixed at different rates with an amendment as plant growth substrates, to evaluate afterwards their effects on crop (lettuce) growth and quality. Furthermore, the physicochemical properties of each substrate, as affected by root exudation, are monitored over time.

Our first surveys on lettuce showed significant differences in term of physiological parameters, mineral composition, and polyphenolic compound content; accordingly, the bioavailability of the main nutrients was quite dissimilar in the diverse substrates, in particular in the highly-dynamic rhizosphere.

  • Open access
  • 51 Reads
One plant-based biostimulant stimulates good performances of tomato plants grown in open field

Most agricultural practices have evolved towards biological and sustainable systems. The purpose of modern agriculture is to reduce inputs without reducing yield and quality. This objective can be achieved through breeding programs and the identification of organic molecules capable of activating plant metabolism. Biostimulants contain a wide range of mostly still unknown bioactive compounds. These products are generally able to improve the plant's nutrient utilization efficiency and increase tolerance to biotic and abiotic stresses. The aim of this study was to determine biometric measurements and metabolic profiling of two tomato genotypes grown in open field and treated or not with a plant-derived biostimulant named CycoFlow (Agriges). The application of the biostimulant stimulated growth (plants up to 55.06% higher) and yield per plant (up to 111.66%). In plants treated with the biostimulant, antioxidants and pigments contents in fruit were higher compared to non-treated plants. In particular, the content of β-carotene increased after treatments with CycoFlow. The present study proves that the application of plant-derived biostimulant can increase tomato performance in the field.

  • Open access
  • 63 Reads
Evaluation of biofungicide activity of endophytic bacteria isolated from blackberry bush (Rubus ulmifolius Schott) against two phytopathogenic fungi

Agriculture is one of the main human activities, supplying food for a human population which is continuously growing. Crop diseases are responsible for huge economic losses and they are caused for different types of organisms such as fungi. Botrytis cinerea and Fusarium sp. are two of the most dangerous due to their ability to expand and colonize different crops. Pesticides have been used to control them, but the overuse has resulted in the development of resistances. Thus, biopesticides have risen as a potential alternative against these phytopathogens since their use decrease the negative effects and increase the positive responses by the plants.

The main objective of this work is the isolation of endophytic bacteria from blackberry bush and the evaluation of their activity against both B. cinerea and Fusarium sp.

Firstly, we evaluated different mechanisms in vitro. The production of enzymes with hydrolytic activities against fungal cell wall components and the production of diffusible and volatile organic compounds (VOCs) with antifungal activity. Results showed 54% of isolates produced diffusible molecules against B. cinerea and 51% against Fusarium sp. While 19% produced VOCs against B. cinerea and 16% against Fusarium sp.

Secondly, genomes of selected strains were sequencing and studied to find those molecules which are responsible for the activities seen in vitro. Operons involved in biosynthesis of molecules such as PKS (polyketide synthases), NRPS (NonRibosomal Peptide Synthetase) and phenolic compounds, known for their antifungal activity, were found their genomes.

In conclusion, selected strains isolated from blackberry bush may represent a strong ally against some of the worst pathogens that agriculture faces, such as Botrytis cinerea and Fusarium sp.

Authors thank the Ministerio de Ciencia e Innovación for financing the project “Análisis de la biodiversidad funcional con aplicación para la mejora en la producción de arándano y mora”. Ref.: PID2019-109960RB-100.

  • Open access
  • 70 Reads
Evaluation of the potential of a Rhizobium sp. strain to improve the productivity of Lactuca sativa L. under salinity

Currently, there is a scientific consensus which indicates that the human production model and energetic consumption are involved in the rising of climate change. The impact that this global climatic alteration causes is translated into various adverse environmental conditions, which affect crop production and yield, such as soil salinity. In this sense, one of the alternatives with great potential to ensure productivity and sustainability within the agriculture is the use of biofertilizers, based on plant growth promoting rhizobacteria (PGPR). The application of microorganisms as fertilizers has been shown as an interesting practice to improve the development and nutritional content of crops, even in stressful situations.

The aim of this work was the search of new bacterial strains with potential to improve plant development under saline stress conditions. Firstly, a Rhizobium sp. strain was isolated from white clover nodules. Its ability to solubilize phosphates and produce siderophores and indoleacetic acid (IAA) was showed in vitro. Then, fluorescence microscopy assays exhibited that this isolated was able to colonize lettuce root system. Finally, through seedlings and greenhouse experiments, it was possible to verify its ability to improve plant growth. Furthermore, the greenhouse trail, developed under a salinity concentration of 100 mM NaCl, showed that this strain helped mitigate this abiotic stress in lettuce, and even to enhance the content in bioactive compounds, such as phenolic acids and flavonoids, of this horticultural crop.

This research was funded by the grants AGL2015-70510-R from MINECO (Spanish Ministry of Economy, Industry and Competitiveness) and VA2I/463AC06 from Salamanca Provincial Government and Strategic Research Programs for Units of Excellence from Junta de Castilla y León (CLU-2018-04).

  • Open access
  • 44 Reads
Published: 01 May 2021 by MDPI in The 1st International Electronic Conference on Agronomy session Posters

Although both silicon (Si) and lignin accumulate on plant cell walls and confer resistance to multiple biotic and abiotic stresses, the impact of Si on lignin production in plants grown under phosphorus (P) stress still remains unknown. We evaluated the effect of Si on the lignin accumulation pattern and the expression of lignin biosynthesis-related genes in wheat grown at different P levels. Two wheat cultivars differing in tolerance to P deficiency (Púrpura-sensitive and Fritz-tolerant) were hydroponically grown with P (0, 0.01 or 0.1 mM) in combination with Si (0, 1 or 2 mM) during 21 days. At harvest, lignin concentration, lignin distribution pattern and the gene expression of phenylalanine ammonia lyase (TaPAL) and cinnamyl alcohol dehydrogenase (TaCAD) were analyzed in shoots. Lignin concentration of both wheat cultivars did not vary at different P doses; nevertheless, 2 mM Si increased lignin accumulation at either 0 mM P (cv. Púrpura) or 0.01 mM P (cv. Fritz), with a more noticeable effect in Púrpura than in Fritz. In fact, confocal microscopy analyses showed stronger Safranine O staining after Si was added to both cultivars grown under P-limitation. Interestingly, Si also induced the expression of lignin biosynthesis-related genes. Up-regulation of TaPAL was detected in cv. Púrpura grown at low P levels, with a further increase in plants treated with Si. Likewise, Si addition to P-stressed plants of cv. Fritz increased the transcript level of TaPAL by 1.5-fold. Similarly, the expression level of TaCAD augmented by 1.7- fold as a result of Si supply to both cultivars grown at low P. Overall our results shows that Si induced the biosynthesis of lignin in shoots of wheat plants grown under P stress. Acknowledgments. FONDECYT Regular Project N° 1201257 and FONDECYT Postdoctoral Project N° 3200901.

  • Open access
  • 49 Reads
Published: 01 May 2021 by MDPI in The 1st International Electronic Conference on Agronomy session Posters

Current evidence shows that silicon (Si) can alleviate multiple plant stresses by inducing the antioxidant defense and phenolic metabolism of plants. Nevertheless, the mechanisms underlying these responses remains unclear. We investigated the Si effect on the phenolic metabolism of two barley cultivars differing in their tolerance to phosphorus (P) deficiency (cv. Sebastian, P-deficiency tolerant and cv. Traveler, P-deficiency sensitive). Plants were hydroponically grown with P (0, 0.01 or 0.1 mM P; applied as Na2HPO4) in combination with Si (0, 1 or 2 mM Si; applied as Na2SiO3). At harvest, total phenols, antioxidant capacity, individual phenolics and the gene expression of enzymes involved in the synthesis of soluble phenolic compounds including phenylalanine ammonia lyase (HvPAL) and chalcone synthase (HvCHS) were analyzed in shoots. In cv. Sebastian grown without P, Si reduced both total phenols and antioxidant capacity to levels comparable to plants supplied with an optimal P dose. In contrast, increasing Si doses triggered an enhancement of total phenols and antioxidant ability in cv. Traveler cultivated in absence of P. Seven flavonoids were identified, being the most relevant the derivatives of apigenin and lutonarin. Although we did not observe clear effect of Si on the content of individual phenolics in cv. Sebastian exposed to P stress, an increment in the concentration of apigenin-pentoxide-hexoside was detected in cv. Traveler as a consequence of Si application to P-deficient plants. Differential expression of genes associated with the synthesis of phenolics was also induced by Si under P-stress. The transcript level of HvPAL diminished in cv. Sebastian and augmented in cv. Traveler due to Si supply under P limitation. Likewise, Si decreased HvCHS expression in cv. Sebastian grown without P, whereas an up-regulation of HvCHS was observed when Si was applied to cv. Traveler grown with low P. Acknowledgments. FONDECYT Regular Project N°1201257.

  • Open access
  • 102 Reads
Efficiency of potassium and phosphate solubilizing Actinobacteria in wheat plant growth promotion
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Soil fertility and plant nutrition require an adequate management of essential macronutrients such as Potassium (K) and phosphorus (P) which are mandatory for plant development. In this context, rock phosphate (RP) has been considered as a natural source for manufacturing P-based fertilizers. However, its poor bioavailability is the major drawback for its direct application in agriculture. Therefore, the exploitation of beneficial microbes as biofertilizers has become of paramount importance in agricultural sector due to their potential role in food safety, quality and sustainable production. In this study, we evaluated the ability of nine Phosphate solubilizing Actinobacteria (P13 - P14 - P15 - P16 - P17 - P18 - BC3 - BC10 and BC11) to release P and K from RP and rock potassic (RK) respectively in in vitro and greenhouse conditions. The most performant strains were P18, BC3, BC10 and BC11 since they had not only a broad spectrum of RP solubilization but also had the capacities to solubilize mica as an insoluble source of potassium. Moreover, all strains were able to produce IAA, siderophore, HCN and ammonia and improved significantly the germination rate and the vigor index of wheat. Furthermore, the four efficient strains (P18- BC3 – BC10 and BC11) significantly improved all the agronomic parameters of wheat under RP and RK fertilization in greenhouse conditions namely root length (1.75 – 23.84%), root volume (41.51 – 71.46%), root dry weight (46.89 – 162.41%), shoot length ( 8.92 – 23.56%) and shoot dry weight ( 2.56 – 65.68%) compared to the un-inoculated control. The 16 S rRNA gene sequencing and phylogenetic analysis identified these isolates belong to Streptomyces and Nocardiopsis genera. These findings showed that these strains are promising candidates for the implementation of efficient biofertilization strategies to improve soil fertility and plant yield under Rock P and RK fertilization.

  • Open access
  • 71 Reads
Analysis of the sensitivity of spring wheat and white mustard seedlings to the essential oil of parsley seeds
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Published: 01 May 2021 by MDPI in The 1st International Electronic Conference on Agronomy session Posters

Natural substances with great biological potential, i.e., herbicidal, are essential oils (EO). Their use may adversely affect not only weeds but also crop species. Therefore, the study aimed to assess the phytotoxic potential of the EO from the seeds of parsley (Oleum petroselini) against germination and the initial growth of seedlings of two crops: spring wheat (Triticum aestivum L.) and white mustard (Sinapis alba L). The EO was obtained by steam distillation, and its chemical composition was analysed using the GC/MS method. Two series of laboratory experiments were carried out. The oil in water (o/w) solutions with ethyl alcohol (2.0%) were used in five doses: 0.004; 0.007; 0.01; 0.02; 0.03 g liter-1 (w/w). The Petri dishes were lined with filter paper, soaked in the o/w solution. Next, 20 seeds of the tested species were laid out. The dishes were left in the dark at room temperature for seven days. Then the seedlings were counted, and the length of their roots and shoots [mm] were measured. In total, 20 chemical components (98%) were identified in the EO from the parsley seeds, among which α-pinene, β-pinene, and apiol dominated. It was found that spring wheat was more sensitive to the OE than white mustard. The o/w solutions, at the lowest dose already, significantly inhibited the growth of seedlings of both species while not significantly affecting the number of germinated seeds. In conclusion, the EO from parsley seeds has a phytotoxic potential against the tested crops, especially against wheat. Still, the physiological mechanisms of this phenomenon need to be recognized.