Ascorbic Acid Induces the Increase of Secondary Metabolites, Antioxidant Activity, Growth, and Productivity of the Common Bean under Water Stress Conditions

One of the most vital environmental factors that restricts plant production in arid and semi-arid environments is the lack of fresh water and drought stress. Common bean (Phaseolus vulgaris L.) productivity is severely limited by abiotic stress, especially climate-related constraints. Therefore, a field experiment in split-plot design was carried out to examine the potential function of ascorbic acid (AsA) in mitigating the adverse effects of water stress on common bean. The experiment included two irrigation regimes (100% or 50% of crop evapotranspiration) and three AsA doses (0, 200, or 400 mg L−1 AsA). The results revealed that water stress reduced common bean photosynthetic pigments (chlorophyll and carotenoids), carbonic anhydrase activity, antioxidant activities (2,2-diphenyl-1-picrylhydrazyl free radical activity scavenging activity and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation assay), growth and seed yield, while increased enzymatic antioxidants (peroxidase), secondary metabolites (phenolic, flavonoids, and tannins), malondialdehyde (MDA), and crop water productivity. In contrast, the AsA foliar spray enhanced all studied traits and the enhancement was gradual with the increasing AsA dose. The linear regression model predicted that when the AsA dose increase by 1.0 mg L−1, the seed yield is expected to increase by 0.06 g m−2. Enhanced water stress tolerance through adequate ascorbic acid application is a promising strategy to increase the tolerance and productivity of common bean under water stress. Moreover, the response of common bean to water deficit appears to be dependent on AsA dose

Impact of the foliar application of nanoparticles, sulfate and iron chelate on the growth, yield and nitrogen assimilation in green beans

Nano-fertilizers (Nfs) have the potential to revolutionize agricultural systems through nanostructures ranging from 1 to 100 nm that address environmental responses and a more targeted biological demand. The purpose of this work was to study the impact of the foliar application of nanoparticles (NPs), sulfate and iron chelate on the growth, yield and assimilation of nitrogen in green beans. The iron was applied foliar in three different ways: Iron oxide nanoparticles (Fe2O3), ferric sulfate (Fe2(SO4)3) and iron chelate (Fe-EDDHA) in doses of 0, 25, 50, 100 and 200 ppm. The treatments that produced a higher total biomass increase were NPs and Fe-EDDHA at 50 ppm, with increases of 37% and 47% respectively compared to the control (with no application of Fe). Regarding the in vivo nitrate reductase activity, significant differences were obtained, particularly in the NPs and Fe-EDDHA treatment, with increases of 71% and 72% respectively. NPs at low doses favored maximum fruit production with increases of 88% in comparison to the control. Finally, it is concluded that the optimal doses that enhanced total biomass, production and assimilation of nitrogen were Fe2(SO4)3 at 25 ppm, Fe-EDDHA at 100 ppm and Fe2O3 at 25 ppm. The efficiency of foliar absorption of iron was found in treatments with Fe2O3 at 50 and 100 ppm. The foliar absorption efficiency of NPs offers sustainable alternatives to increase the productivity of the green bean

Osmoregulators proline and glycine betaine counteract salinity stress in canola

Salt inundation leads to increased salinization of arable land in many arid and semi-arid regions. Until genetic solutions are found farmers and growers must either abandon salt-affected fields or use agronomic treatments that alleviate salt stress symptoms. Here, field experiments were carried out to study the effect of the osmoregulators proline at 200 mg L-1 and glycine betaine at 400 mg L-1 in counteracting the harmful effect of soil salinity stress on canola plants grown in Egypt. We assessed growth characteristics, yield and biochemical constituents. Results show first that all growth characters decreased with increasing salinity stress but applied osmoregulators alleviated these negative effects. Second, salinity stress decreased photosynthetic pigments, K and P contents, whilst increasing proline, soluble sugars, ascorbic acid, Na and Cl contents. Third, application of osmoregulators without salt stress increased photosynthetic pigments, proline, soluble sugars, N, K and P contents whilst decreasing Na and Cl contents. It is concluded that the exogenously applied osmoregulators glycine betaine and proline can fully or partially counteract the harmful effect of salinity stress on growth and yield of canola.© INRA and Springer-Verlag, France 2012

Improving Snap Bean (Phaseolus vulgaris L.) Production under Reduced Input Systems

Snap bean (Phaseolus vulgaris L.) production by large scale commercial producers in Ethiopia is under intensive production and relies on high rates of nitrogen (N) fertilizer and irrigation during the dry season. Despite increasing interest to produce this crop, small scale farmers cannot afford the high cost of N fertilizer. Field and greenhouse experiments were conducted to test snap bean production under a low input production system better suited to small scale resource limited farmers. Field experiments were conducted in 2011 and 2012 under rain fed conditions, and in 2012 under irrigation, at three locations (Debre Zeit, Hawassa, Ziway) representing different climate zones in Ethiopia. This experiment used three N treatments: 0 and 100 kg N ha-1, and inoculation with Rhizobium etli [HB 429], and eight cultivars: Andante, Boston Contender Blue, Lomami, Melkassa 1, Melkassa 3, Paulista and Volta. The general objective of the field experiment was to determine the potential of snap bean production under a low input production system using rhizobium inoculation as the nitrogen source, and use rain fed conditions. Results obtained indicated that rhizobial inoculation and applied inorganic N increased on average the marketable pod yield of snap bean under rain fed conditions by 18 % and 43%, respectively. Nodulation and subsequent N2 fixation was not effective in improving yield or other traits of snap bean pod under irrigation, although applied N increased marketable yield by 33%. Melkassa 1 was the most suitable cultivar for a reduced input production system due to its successful nodulation characteristics, greatest N2 fixation levels and consistently good performance across locations under rain fed conditions. Commercial cultivars possessed the best pod quality characteristics and they yielded better under irrigation. Cultivars interacted with locations to affect pod traits including total soluble solids and concentrations of protein, calcium, and potassium under rain fed conditions. Snap bean cultivrs produced at Debre Zeit and Hawassa were similar in marketable yield and several other traits particularly under rain fed conditions. Zinc (Zn) concentration in pods was greatest at Hawassa both under rain fed and irrigated conditions. Conditions at Debre Zeit were the most conducive for supporting biological N2 fixation for snap bean production. The eight cultivars were also used for a greenhouse study that was evaluated treatments of drought stress of 50% field capacity (50% FC) during the vegetative (V4.4), flowering (R6) and pod formation (R7) developmental stages. Our result showed that drought stresses during reproductive stages (R6 and R7) were the most sensitive stages in deteriorating the quality of snap bean pods. Drought stress increased protein, phosphorus and Zn concentrations but it reduced iron concentration in snap bean pods. All cultivars had a similar response to drought stress. A second greenhouse experiment was conducted to test foliar application of growth regulators: the control, 10-5 M and 10-4 M concentrations of each of abscisic acid (ABA), kinetin and salicylic acid (SA); and two concentrations of yeast extract (4 g l-1 and 8 g l-1), under drought (50% FC) stressed and unstressed conditions. Foliar application of SA on snap bean under greenhouse conditions reduced the impact of drought stress, particularly the pod quality parameters: marketable yield, pod curving, texture and appearance of snap bean pods. However, application of ABA, kinetin and SA reduced pod quality of snap bean under unstressed conditions. In conclusion, pod yield improvement could be achieved by a N2 fixation system under rain fed conditions, which is more sustainable than N fertilizer inputs. Pod quality was also adequate for commercial export production. Rhizobium inoculant can therefore be used as an alternative N source, particularly under low input production system for resource-limited small-scale snap bean producers

Managing the Product Quality of Vegetable Crops under Abiotic Stress

Vegetables are an important part of the human diet due to their nutrient density and, at the same time, low calorie content. Producers of vegetable crops mainly aim at achieving high yields with good external quality. However, there is an increasing demand of consumers for vegetables that provide good sensory properties and are rich in secondary compounds that can be valuable for human health. Sub- or supra-optimal abiotic conditions, like high temperatures, drought, excess light, salinity or nutrient deficiency, may alter the composition of vegetable crops and at the same time, result in yield loss. Thus, producers need to adapt their horticultural practices such as through the choice of variety, irrigation regime, light management, fruit thinning, or fertilizer application to improve the yield and quality of the vegetable product. In the future, altered climate conditions such as elevated atmospheric CO2 concentrations, rising temperatures, or altered precipitation patterns may become additional challenges for producers of vegetable crops, especially those that cultivate in the open field. This raises the need for optimized horticultural practices in order to minimize abiotic stresses. As well, specific storage conditions can have large impacts on the quality of vegetables. This Special Issue compiles research that deals with the optimization of vegetable product quality (e.g. sensory aspects, composition) under sub- or supra-optimal abiotic conditions

Are Traditional Lima Bean (Phaseolus lunatus L.) Landraces Valuable to Cope with Climate Change? Effects of Drought on Growth and Biochemical Stress Markers

[EN] Agrobiodiversity and adaptability to environmental changes derived from global warming are challenges for the future of agriculture. In this sense, landraces often have high levels of genetic variation, tightly connected with the changing environmental conditions of a territory. The genus Phaseolus, with five domesticated species, is one of the most important sources of proteins, carbohydrates and micronutrients in various countries. This study aimed to compare the adaptation capacity to drought, in the vegetative growth phase, of a commercial cultivar and two landraces traditionally cultivated in the Mediterranean basin of Phaseolus lunatus (Lima bean). Growth and biochemical responses of the analysed genotypes to different water¿deficit treatments were evaluated and compared. In addition, the effectiveness of the voltammetric method for evaluating stress levels in cultivated plants was tested. The studied parameters revealed that P. lunatus is a drought tolerant species, showing similar results for the three cultivars. However, contrary to what was expected from the germination phase results, the commercial variety Peru showed some better responses under water stress conditions. Finally, the voltammetric method proved to be a good and fast tool for assessing oxidative stress in cultivated plants, showing results in agreement with total phenolic compounds and total flavonoid fluctuations.Martínez-Nieto, MI.; González-Orenga, S.; Soriano, P.; Prieto-Mossi, J.; Larrea, E.; Doménech-Carbó, A.; Tofei, AM.... (2022). Are Traditional Lima Bean (Phaseolus lunatus L.) Landraces Valuable to Cope with Climate Change? Effects of Drought on Growth and Biochemical Stress Markers. Agronomy. 12(7):1-20. https://doi.org/10.3390/agronomy1207171512012

The role of volatile organic compounds in plant response to environmental stresses

I composti organici volatili biogenici, anche chiamati BVOC, sono metaboliti secondari prodotti e rilasciati nell\u2019ecosistema dagli organismi viventi, incluse le piante. Essi posseggono caratteristiche peculiari, tra le quali il basso peso molecolare, la lipofilia e l\u2019elevata pressione di vapore a temperatura ambiente. Ad oggi, 1700 specie di VOC differenti sono state isolate e caratterizzate. Nelle piante, i VOC rappresentano l\u20191% di tutti i metaboliti secondari conosciuti. Il gruppo pi\uf9 vasto dei VOC comprende i terpenoidi, seguito da fenilpropanoidi e benzenoidi, i derivati di acidi grassi, che includono i cosiddetti \u201cGreen Leaf Volatiles\u201d, e i derivati dalla via di biosintesi degli amminoacidi. I VOC sono emessi non solo dalle foglie, ma anche da fiori e frutti in diverse qualit\ue0 e quantit\ue0. Tuttavia, mentre i VOC emessi dai tessuti riproduttivi hanno lo scopo di aumentare produttivit\ue0 e fitness della pianta, quelli emessi da tessiti vegetativi servono principalmente come strategia di difesa. Il coinvolgimento dei VOC nella protezione delle piante \ue8 stato ampiamente studiato e dimostrato contro vari fattori, tra cui stress sia abiotici (temperatura, siccit\ue0) che biotici (erbivori, agenti patogeni). Difatti, l'interesse per lo sviluppo di strategie agricole sostenibili basate sui VOC \ue8 in aumento. Tuttavia, le conoscenze sui meccanismi molecolari che coinvolgono i VOC in risposta a uno stress specifico presentano diverse lacune. In dettaglio, questa tesi si propone di approfondire (1) il ruolo dell'isoprene, il pi\uf9 abbondante terpene in atmosfera, nella resistenza alla siccit\ue0 (2) i meccanismi difensivi, tra cui l'emissione di VOC e i riarrangiamenti del proteoma, innescati dal fungo Colletotrichum lindemuthianum in Phaseolus vulgaris. Concentrandosi sulla proteomica abbinata all'analisi di VOC e metaboliti, questo lavoro fornisce nuove prove a sostegno dell'importanza dei VOC nella difesa delle piante e fornisce nuovi possibili oggetti per ulteriori studi.Biogenic Volatile Organic Compounds (BVOCs) are secondary metabolites produced by living organisms, especially by plants, and released in the ecosystem. They are characterized by having low molecular weight, lyophilic properties and high vapor pressure at ambient conditions. So far, more than 1700 species of different plant VOCs have been isolated and characterized according to their chemical structure. They represent the 1% of the total secondary metabolites known in plants. The larger group of VOCs are terpenoids (mono-, di-, homo-, hemi- and sesquiterpenes), followed by phenylpropanoids, benzenoids, fatty acid derivates (including Green Leaf Volatiles or GLVs), and derivates from branched-amino acid biosynthesis. VOCs are not only released from leaves, but also from non-green tissues as roots, flowers, and fruits in different quantity and quality. While the VOCs emitted from reproductive organs primarily promote plant productivity, those released by leaves serve mainly for defence. The role of VOCs in plant protection has been widely investigated and proved against various stressors, including abiotic (temperature, drought) and biotic (herbivores, pathogens) sources. In fact, the interest in developing sustainable agricultural strategies based on VOCs is rising. However, the knowledge about molecular mechanisms involving VOCs in response to a specific stress is still missing at some extents. In detail, this thesis aims to deeper investigate (1) the role of the hemiterpene isoprene in drought resistance (2) defensive mechanisms, including VOCs emission and proteome rearrangements, triggered by the fungus Colletotrichum lindemuthianum in Phaseolus vulgaris. By focusing on proteomics coupled with metabolomics and VOCs analysis, this work provides new evidence supporting the importance of VOCs in plant defence and furnish new possible targets for further studies

Exploring the fertiliser potential of biosolids from algae integrated wastewater treatment systems

High rate algae oxidation ponds (HRAOP) for domestic wastewater treatment generate biosolids that are predominantly microalgae. Consequently, HRAOP biosolids are enriched with minerals, amino acids, nutrients and possibly contain plant growth regulator (PGR)-like substances, which makes HRAOP biosolids attractive as fertiliser or PGR. This study investigated HRAOP biosolids as a starting material for a natural, cost-effective and readily-available eco-friendly organic fertiliser and/or PGRs. Various HRAOP extract formulations were prepared and their effect on plant growth and development was evaluated using selected bioassays. Initial screening included assessing the effect on change in specific leaf area, radish cotyledon expansion as an indicator of PGR-like activity, and seed germination index (GI). More detailed studies on fertiliser efficacy and PGR-like activity utilised bean (Phaseolus vulgaris) and tomato (Solanum lycopersicum) plants. Combined effects of sonicated (S) and 40% v/v methanol (M) extract (5:1 SM) had impressive plant responses, comparable to Hoagland solution (HS). Other potentially fertiliser formulations included 0.5% M, 1% M, 2.5% S and 5% S formulations. The 5:1 SM and 5% S showed greater PGR-like activity, promoting cotyledon expansion by 459 ± 0.02% and 362 ± 0.01%, respectively. GI data showed that none of the formulations negatively impacted germination. Further investigation showed that the 5% S formulation increased leaf length, width and area by 6.69 ± 0.24, 6.21 ± 0.2 mm and 41.55 ± 0.2 mm². All formulated fertiliser extracts had no adverse effect on chlorophyll content and plant nutrient balance as indicated by C:N (8-10:1) ratio. In addition, plants appeared to actively mobilise nutrients to regions where needed as evidenced by a shift in shoot: root ratio depending on C, N and water availability. Furthermore, 5% S caused a 75% increase in tomato productivity and had no effect on bean productivity. Whereas, 5:1 SM and 1% M formulation improved bean pod production by 33.3% and 11%, respectively but did not affect tomato production. Harvest index (HI) however indicated a 3% reduction in tomato productivity with 5:1 SM and little or no enhancement in bean productivity with both 5:1 SM and 5% S treatments. Bean plants treated with 5:1 SM and 5% S produced larger fruits, which could be an indication of the presence of a PGR effect. Overall, HRAOP biosolids extracts prepared and investigated in this study demonstrated both fertiliser characteristics and PGR-like activity with performances comparable and in some cases exceeding that of commercial products. However additional research is needed to confirm presence of PGR-like activities and fertiliser efficacy

Exploring the fertiliser potential of biosolids from algae integrated wastewater treatment systems

High rate algae oxidation ponds (HRAOP) for domestic wastewater treatment generate biosolids that are predominantly microalgae. Consequently, HRAOP biosolids are enriched with minerals, amino acids, nutrients and possibly contain plant growth regulator (PGR)-like substances, which makes HRAOP biosolids attractive as fertiliser or PGR. This study investigated HRAOP biosolids as a starting material for a natural, cost-effective and readily-available eco-friendly organic fertiliser and/or PGRs. Various HRAOP extract formulations were prepared and their effect on plant growth and development was evaluated using selected bioassays. Initial screening included assessing the effect on change in specific leaf area, radish cotyledon expansion as an indicator of PGR-like activity, and seed germination index (GI). More detailed studies on fertiliser efficacy and PGR-like activity utilised bean (Phaseolus vulgaris) and tomato (Solanum lycopersicum) plants. Combined effects of sonicated (S) and 40% v/v methanol (M) extract (5:1 SM) had impressive plant responses, comparable to Hoagland solution (HS). Other potentially fertiliser formulations included 0.5% M, 1% M, 2.5% S and 5% S formulations. The 5:1 SM and 5% S showed greater PGR-like activity, promoting cotyledon expansion by 459 ± 0.02% and 362 ± 0.01%, respectively. GI data showed that none of the formulations negatively impacted germination. Further investigation showed that the 5% S formulation increased leaf length, width and area by 6.69 ± 0.24, 6.21 ± 0.2 mm and 41.55 ± 0.2 mm². All formulated fertiliser extracts had no adverse effect on chlorophyll content and plant nutrient balance as indicated by C:N (8-10:1) ratio. In addition, plants appeared to actively mobilise nutrients to regions where needed as evidenced by a shift in shoot: root ratio depending on C, N and water availability. Furthermore, 5% S caused a 75% increase in tomato productivity and had no effect on bean productivity. Whereas, 5:1 SM and 1% M formulation improved bean pod production by 33.3% and 11%, respectively but did not affect tomato production. Harvest index (HI) however indicated a 3% reduction in tomato productivity with 5:1 SM and little or no enhancement in bean productivity with both 5:1 SM and 5% S treatments. Bean plants treated with 5:1 SM and 5% S produced larger fruits, which could be an indication of the presence of a PGR effect. Overall, HRAOP biosolids extracts prepared and investigated in this study demonstrated both fertiliser characteristics and PGR-like activity with performances comparable and in some cases exceeding that of commercial products. However additional research is needed to confirm presence of PGR-like activities and fertiliser efficacy

Soil selenium (Se) biofortification changes the physiological, biochemical and epigenetic responses to water stress in Zea mays L. by inducing a higher drought tolerance

Requiring water and minerals to grow and to develop its organs, Maize (Zea mays L.) production and distribution is highly rainfall-dependent. Current global climatic changes reveal irregular rainfall patterns and this could represent for maize a stressing condition resulting in yield and productivity loss around the world. It is well known that low water availability leads the plant to adopt a number of metabolic alterations to overcome stress or reduce its effects. In this regard, selenium (Se), a trace element, can help reduce water damage caused by the overproduction of reactive oxygen species (ROS). Here we report the effects of exogenous Se supply on physiological and biochemical processes that may influence yield and quality of maize under drought stress conditions. Plants were grown in soil fertilized by adding 150 mg of Se (sodium selenite). We verified the effects of drought stress and Se treatment. Selenium biofortification proved more beneficial for maize plants when supplied at higher Se concentrations. The increase in proline, K concentrations and nitrogen metabolism in aerial parts of plants grown in Se-rich substrates, seems to prove that Se-biofortification increased plant resistance to water shortage conditions. Moreover, the increase of SeMeSeCys and SeCys2 forms in roots and aerial parts of Se-treated plants suggest resistance strategies to Se similar to those existing in Se-hyperaccumulator species. In addition, epigenetic changes in DNA methylation due to water stress and Se treatment were also investigated using methylation sensitive amplified polymorphism (MSAP). Results suggest that Se may be an activator of particular classes of genes that are involved in tolerance to abiotic stresses. In particular, PSY (phytoene synthase) gene, essential for maintaining leaf carotenoid contents, SDH (sorbitol dehydrogenase), whose activity regulates the level of important osmolytes during drought stress and ADH (alcohol dehydrogenase), whose activity plays a central role in biochemical adaptation to environmental stress. In conclusion, Se-biofortification could help maize plants to cope with drought stress conditions, by inducing a higher drought tolerance