The purpose of this investigation was to assess the influence of effective microorganisms on the growth and nutrient content of tomato transplants. There were two treatments: 1. with effective microorganism’s (EM) treatment; 2. without effective microorganism’s treatment – control. The height of tomato transplants was higher in control treatment compared to EM treatment. The stem diameter of tomato transplants was larger in EM treatment compared to control variant. The nutrient content of tomato leaves was very good. The contents of nitrates, N, P, K, Ca and Mg were higher in EM treatment compared to control treatment.

Micronutrients play a critical role in plant growth and development, and their deficiency can cause adverse effects on plant performance. Also, these elements can influence plant physiological processes as they incorporate in the molecular structure of enzymes as cofactors. In this study, the impacts of micronutrients solution containing manganese (125 ppm), iron (200 ppm), zinc (60 ppm), and copper (20 ppm) were investigated on growth parameters, yield, and antioxidant enzymes activity of tomato (Solanum lycopersicum) plants. Greenhouse tomatoes (cultivar Jet Star F1) were irrigated with the mentioned concentrations of elements in a completely randomized design with five independent biological replicates. The micronutrient treatment increased the specific activities of superoxide dismutase, ascorbate peroxidase, glutathione reductase, guaiacol peroxidase, catalase, phenylalanine ammonia-lyase, as well as phenols and salicylic acid contents in tomato leaves. However, malondialdehyde level and electrolyte leakage index were unaffected. Analysis of plant growth parameters revealed that micronutrients increased the stem diameter, root length, the number of leaves, stem height, and fruit’s fresh weight in the treated plants. Overall, our results indicated that micronutrients positively affected the growth and development of tomato plants without adverse effects on the health indices. Moreover, the application of micronutrients can magnify the antioxidant capacity of tomato plants through increasing enzymes activity as well as phenols and salicylic acid levels. These changes would benefit the plants under abiotic/biotic stress conditions where elevated levels of antioxidant activities are crucial.

Amaranthus palmeri is a weed that causes major crop losses every year. Farmers spend significant amounts of money on traditional herbicides to stop their growth. In this case study, we investigate the responses of Glyphosate-Susceptible and Glyphosate-Resistant Amaranthus palmeri to an organic 10% acetic acid herbicide solution instead of a 20 % acetic acid solution. Traditional herbicides are glyphosate-based. Overuse of these herbicides has led to glyphosate resistance in some plants. Amaranthus palmeri is one of them. Because of the overuse of the traditional glyphosate-based herbicides, two forms of the species have been documented. One is Susceptible to traditional herbicides Glyphosate Susceptible Amaranthus palmeri, and the other is resistant to traditional herbicides, Glyphosate Resistant Amaranthus palmeri. Hence, there is a need to find other products to control growth, thereby lessening our impact on the environment and spending less money. The lesser 10% acetic acid herbicide solution serves as a viable alternative.

Hypothesis: We hypothesized that although both forms respond differently to glyphosate-based herbicides, both will respond the same way to organic-based herbicides that include acetic acid. In this study, a 10% acetic acid solution was used versus the standard 20% acetic acid solution found in the organic agricultural vinegar herbicide. Previous studies suggest that at a very young age the 10% solution is strong enough to control growth. This is important because using a lesser concentration may be better for the environment since there will be less buildup over time. Using less is also less costly to the farmers' pocket.

Method: In the greenhouse, Amaranthus palmeri was grown in 24 pots using Carolina^® Seed Starter mix. The seeds were loosely placed in the soil about an inch from the top. Once 2 to 8 leaves per plant were apparent, the young Glyphosate-Susceptible and Glyphosate-Resistant Amaranthus palmeri leaves were sprayed with a 10% acetic acid solution. These plants are C4 plants and thus have stomata on their adaxial and abaxial leaf surfaces. Most leaves have stomata only on their abaxial surfaces.

Results: Using the JEOL Scanning Electron Microscope (SEM) we noted that stomata start responding to stress within two hours. The leaf surfaces of both plants respond the same way. Death starts to occur within 24 hours for both plant forms. The SEM micrographs show that stomata are open on the adaxial surfaces of both plant forms before they are treated. After treatment, the plants become stressed and the stomata close. However, there is a difference in the death rate. Eighty-five percent (85%) of the Glyphosate Susceptible plants died within 24 hours, while 100% of the Glyphosate-Resistant plants died within 24 hours.

Conclusion: Using a 10% solution of acetic acid as a growth control agent is successful and impacts the environment less.

Future studies will assess genomic data at different spraying times.

Pectin methylesterases (PMEs) are enzymes, encoded by multigene families, that catalyze the demethylesterification of cell wall homogalacturonans. The removal of methyl groups, if performed block-wise in large series of methylesters, leads to the production of homogalacturonans that can be cross-linked with calcium bridges. This fine modulation of the methylesterification status of the pectin network alters the mechanical properties of the cell wall and has been proven crucial for stomatal complex ontogenesis and function. Considering this significant role of PMEs, as well as their involvement in numerous plant development processes, we investigated the phenotypic implications of two Arabidopsis thaliana PME compromised mutants (pme2 and pme3) and the corresponding double mutant (pme2 pme3) in stomatal development and morphology. The cotyledons of the double mutant were larger and wider, while the ratio of length/width was smaller compared to that of WT plants. The stomatal patterning was also affected since the pme2 pme3 mutant displayed a higher number of mature stomata as well as a higher percentage of stomatal clustering. Furthermore, the guard cells of the double mutant displayed a lower ratio of cell length to width, indicating alterations in the morphology of mature stomata. As far as the cell wall matrix composition is concerned, callose and pectins’ epitope distribution displayed significant differences in pme single and double mutants compared to WT plants. Taken together, our results underline the indispensable role of PME2 and PME3 in stomatal development, since their functional disruption affects not only stomatal patterning but also the morphology and function of the guard cells.

Southern Portugal has a high natural variability of Cynara cardunculus L. at a biochemical and morphological levels, conducting to the necessity of genetic diversity studies, for further plant breeding within certain desired agronomic traits [1]. Cardoon as a multipurpose crop represents a natural source of sesquiterpene lactones, namely cynaropicrin [2].

Previously, 175 individuals (generation F0) of wild cardoon from different geographical locations in the Alentejo region were identified, collected and chemically and genetically characterized [1]. To improve the biotechnological cardoon impact, based on sesquiterpene lactones chemical profile, a transcriptomic analysis is ongoing in order to select the best genotypes for cynaropicrin production. Thus, 49 cardoon plants were collected from F1 populations, along 4 months (March, April, May and June), and fresh cardoon leaves were chemical analysed, in terms of Cc leaves-lipophilic extracts cynaropicrin content (mg/g DW). Results show a great variability in terms of cynaropicrin content, concerning the genotype and collection period. For transcriptome analysis, total RNA was extracted from biological samples wigh high and low level of cynaropicrin content. RNA concentration and integrity was assessed by Agilant BioAnalyzer. cDNA libraries will be prepared, and stranded paired-end sequencing will be performed on Illumina Sequencers. The next step will be the bioinformatics analysis of the transcriptome data.

This research is a necessary step for a better conservation of the wild cardoon gene pool and for a more efficient use for future breeding programs of C.cardunculus.

This work is supported by Program Alentejo 2020, through the European Fund for Regional Development (FEDER) under the scope of MedCynaraBioTec – Selection of Cynara cardunculus genotypes for new biotechnological applications: the value chain improvement of cardoon, a well-adapted Mediterranean crop (ALT20-03-0145-FEDER-039495). Authors also acknowledge FCT for Contrato – Programa to L. Marum (CEECINST/00131/2018), PhD grant to A. Paulino (SFRH/BD/145383/2019) and D. Rosa (SFRH/BD/143845/2019), and Project UIDB/05183/2020 to Mediterranean Institute for Agriculture, Environment and Development (MED).

References

[1] Castro M. M. et al. PLoS ONE, 2021, 16(6): e0252792

[2] Ramos, P. A. et al. J. Agric. Food Chem., 2013, 61(35), 8420-8429

Non-structural carbohydrates (NSC) are key components of plant tissue being involved in several metabolic and physiological processes, greatly affecting the growth and adaptation of plants. The total NSC content varies with species, organs, seasons, and environmental conditions. In this study, we compare the seasonal dynamics of NSC, including total soluble sugars (SS) and starch (St), present in leaves of Pinus pinaster, a tree native to the Western Mediterranean basin, and the invasive Hakea sericea, particularly problematic in areas with Mediterranean-type of climate. With no exception, SS, St, and NSC contents changed throughout the growing season in both species but with distinct patterns. In the native species, the highest SS and NSC contents occurred in winter, while St content was higher in spring. In turn, Hakea sericea had higher SS content in summer, and higher St and NSC contents in winter. Our results also showed that St was the dominant form of NSC. Comparing both species, Hakea sericea accumulated significantly higher amounts of St and NSC than Pinus pinaster, especially in winter. By contrast, the SS content did not vary significantly between species. The observed differences in NSC accumulation seemed to be related to the phenological cycle of both species but also suggest the superior performance of Hakea sericea over Pinus pinaster, even under unfavorable environmental conditions, which may explain its invasion success in the Mediterranean.

Brown rot is one of the most important diseases of stone fruit worldwide. In most European countries, the main agents of Brown rot were considered to be Monilinia laxa and M. fructigena. However, during the last decade M. fructicola has been found in high frequencies in most countries around the Mediterranean basin, including Greece. Taking into account that M. fructicola is considered to be of higher risk for fungicide resistance development compared to M. laxa or M. fructigena, this study was initiated aiming to determine the fungicide sensitivity profile of isolates originating from peach orchards in Greece. In total, 230 M. fructicola isolates were collected and assessed for their sensitivity to the SDHI fungicides boscalid and fluopyram and the DMI fungicide tebuconazole. Sensitivity assays were based on the inhibition of germ tube or the mycelial growth for SDHIs and DMIs, respectively. The assays revealed that 53.9% of the isolates (n=124) were sensitive to all the three fungicides tested, while 46.1% (n=106) were characterized as resistant. In detail, 7.8% (n=18) and 8.7% (n=20) of the SDHI-resistant subpopulation had a resistance factor (RF) higher than 2 to fluopyram and boscalid, respectively. In addition, a high percentage (29.6%) of the isolates (n=68) were resistant to tebuconazole with a RF values ranging from 2 to 13. To the best of our knowledge, this is the first report of resistant strains of M. fructicola to SDHIs and DMIs in Greece. Ongoing studies will elucidate the molecular mechanisms of resistance in these isolates.

Funding

This research has been co-financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH–CREATE–INNOVATE (project code: T1EDK- 04591).

The objective of this research was to evaluate the sensitivity of leafy crops to ozone levels and the possible effects of this pollutant in the peri-urban crops.

Ground level ozone is widely recognized as the most damaging air pollutant to vegetation due to its phytotoxicity and prevalence at high concentrations over rural/agricultural regions. Also, 90% of the urban population is exposed to ozone exceeding the WHO guideline (EEA, 2017). Developing peri-urban agriculture is regarded as one of the key strategies to attend the high food demands, which helps to reduce the environmental impacts of the food system. However, the threat of the peri-urban agriculture is the air quality and the effects in the food security. Ozone causes a wide variety of damage in leafy crops including visible injury, reduction in photosynthesis, alterations to carbon allocation, and reduction in yield quantity and quality.

Ozone levels on the peri-urban farm of central Spain have exceeded the critical level for protection of vegetation during the summer months. Two studies were developed to evaluate the effects of ozone on a local variety of leafy crops. An open-top chamber experiment of ozone has been used to gain insights of response to this variety of ozone. Different physiological parameters were measured to identify traits related to the sensitivity/ tolerant to ozone. At the same time, to find out the extent of the problem, a bioindication vegetable garden was cultivated in this area, where the plants were followed-up meticulously.

The results of the fumigation study showed a moderate reduction in commercial production, changes in pigment concentrations, and alterations in nutritional quality of this variety. Also, the ozone reduces the gas exchange rate, with a higher reduction in stomatal conductance than photosynthesis. We didn't identify significant alteration of Swiss chard varieties in the bioindication vegetable garden. The different response to air pollution could be related to the environmental conditions.

Salt stress is one of the major threats to sustainable agriculture as it is considered as an external environmental constraint that limits growth and productivity of plants. It is more common in arid regions due to excessive evaporation which causes accumulation of inorganic salts that disrupts the plant metabolism. It also increases the negative influence of drought stress as plants being unable to absorb water due to osmotic effects. It disrupts the normal functioning of the plants and triggers secondary stresses resulting in oxidative burst. Thereby, plants adaptation to salt stress,a rely on signals and pathways that helps plant in establishing cellular ionic and osmotic homeostasis. Additionally, Stress-responsive transcription factors play crucial roles in salt stress responses and tolerance. The main transcription factors includes bZIP, AP2/ERF, WRKY, NAC, bHLH, and MYB families, for the mediation of stress response.

Plants growing in acidic soils frequently develop beneficial interactions with stress adapted microorganisms. In an acidic soil with Mn toxicity, the arbuscular mycorrhizal fungi (AMF) associated to Ornithopus compressus were found to benefit plant growth. In wheat, increased growth and lower shoot Mn levels were promoted by the presence of extraradical mycelium (ERM) developed by these AMF, but the levels of other metals are not yet evaluated. In the present study, Al, Fe and Zn levels were quantified, by inductively coupled plasma mass spectrometry (ICP-MS), in shoots of wheat grown in acidic soil without and with the previous development of AMF associated to O. compressus. Additionally, soil was disturbed to understand the influence of disrupting ERM structure. Shoots of wheat grown in undisturbed soil (intact ERM) more than doubled in dry weight. Toxic Mn levels reduced c.a. 4-fold while the concentrations of Al, Fe and Zn decreased 2.3, 1.5 and 2.3-fold, respectively. Disruption of ERM structure inhibited the decrease in metal levels in 55% and 28% for Mn and Zn, respectively, while for Al and Fe no substantial variations were observed. Under Mn toxicity, the colonization of wheat by intact ERM of AMF associated to O. compressus appears to manage the uptake of Al, Fe and Zn, and positively influence plant growth, in acidic soil. Further studies will focus on the subcellular distributions of these metals in wheat shoots to assess preferential sites of accumulation or action.