Plant Biostimulants Enhance Tomato Resilience to Salinity Stress: Insights from Two Greek Landraces.

Salinity, one of the major abiotic stresses in plants, significantly hampers germination, photosynthesis, biomass production, nutrient balance, and yield of staple crops. To mitigate the impact of such stress without compromising yield and quality, sustainable agronomic practices are required. Among these practices, seaweed extracts (SWEs) and microbial biostimulants (PGRBs) have emerged as important categories of plant biostimulants (PBs). This research aimed at elucidating the effects on growth, yield, quality, and nutrient status of two Greek tomato landraces ('Tomataki' and 'Thessaloniki') following treatments with the Ascophyllum nodosum seaweed extract 'Algastar' and the PGPB 'Nitrostim' formulation. Plants were subjected to bi-weekly applications of biostimulants and supplied with two nutrient solutions: 0.5 mM (control) and 30 mM NaCl. The results revealed that the different mode(s) of action of the two PBs impacted the tolerance of the different landraces, since 'Tomataki' was benefited only from the SWE application while 'Thessaloniki' showed significant increase in fruit numbers and average fruit weight with the application of both PBs at 0.5 and 30 mM NaCl in the root zone. In conclusion, the stress induced by salinity can be mitigated by increasing tomato tolerance through the application of PBs, a sustainable tool for productivity enhancement, which aligns well with the strategy of the European Green Deal.

Assessment of Growth, Yield, and Nutrient Uptake of Mediterranean Tomato Landraces in Response to Salinity Stress.

Salinity is a major stress factor that compromises vegetable production in semi-arid climates such as the Mediterranean. The accumulation of salts in the soil can be attributed to limited water availability, which can be exacerbated by changes in rainfall patterns and rising temperatures. These factors can alter soil moisture levels and evaporation rates, ultimately leading to an increase in soil salinity, and, concomitantly, the extent to which crop yield is affected by salinity stress is considered cultivar-dependent. In contrast to tomato hybrids, tomato landraces often exhibit greater genetic diversity and resilience to environmental stresses, constituting valuable resources for breeding programs seeking to introduce new tolerance mechanisms. Therefore, in the present study, we investigated the effects of mild salinity stress on the growth, yield, and nutritional status of sixteen Mediterranean tomato landraces of all size types that had been pre-selected as salinity tolerant in previous screening trials. The experiment was carried out in the greenhouse facilities of the Laboratory of Vegetable Production at the Agricultural University of Athens. To induce salinity stress, plants were grown hydroponically and irrigated with a nutrient solution containing NaCl at a concentration that could maintain the NaCl level in the root zone at 30 mM, while the non-salt-treated plants were irrigated with a nutrient solution containing 0.5 mM NaCl. Various plant growth parameters, including dry matter content and fruit yield (measured by the number and weight of fruits per plant), were evaluated to assess the impact of salinity stress. In addition, the nutritional status of the plants was assessed by determining the concentrations of macro- and micronutrients in the leaves, roots, and fruit of the plants. The key results of this study reveal that cherry-type tomato landraces exhibit the highest tolerance to salinity stress, as the landraces 'Cherry-INRAE (1)', 'Cherry-INRAE (3)', and 'Cherry-INRAE (4)' did not experience a decrease in yield when exposed to salinity stress. However, larger landraces such as 'de Ramellet' also exhibit mechanisms conferring tolerance to salinity, as their yield was not compromised by the stress applied. The identified tolerant and resistant varieties could potentially be used in breeding programs to develop new varieties and hybrids that are better adapted to salinity-affected environments. The identification and utilization of tomato varieties that are adapted to salinity stress is an important strategy for promoting agriculture sustainability, particularly in semi-arid regions where salinity stress is a major challenge.

Comparing the Nutritional Needs of Two Solanaceae and One Cucurbitaceae Species Grown Hydroponically under the Same Cropping Conditions.

Switching over to closed-loop soilless culture systems, thus preventing pollution of water resources by nitrates and saving water and fertilizers, requires accurate estimations of the mean nutrient-to-water uptake ratios. To contribute to this objective, three fruit vegetable species (tomato, eggplant, cucumber) were grown hydroponically in a floating system under identical cropping conditions to quantify species differences in nutrient uptake. The composition of the nutrient solution used to feed the crops was identical for all species. The total water consumption and the concentrations of most nutrients (K, Ca, Mg, N, P, Fe, Mn, Zn, Cu, B) in the nutrient solution and the plant tissues were measured at crop establishment and at two different crop developmental stages. The obtained data were used to determine the uptake concentrations (UCs) using two mass balance models, one based on nutrient removal from the nutrient solution and a second based on nutrient recovery in the plant tissues. The experiment was conducted in the spring-summer season. The results revealed that the nutrient uptake concentrations were substantially different between species for all nutrients except for N, while there were also significant interactions between the two methods used for their estimation of some nutrients. Thus, the UCs of N, P, Ca, and some micronutrients were significantly higher when its estimation was based on the removal of nutrients from the nutrient solution compared to recovery from plant tissues, presumably because with the first method, losses due to denitrification or precipitation could not be separated from those of plant uptake. The comparison of the three greenhouse vegetables revealed a similar UC for nitrogen, while cucumber generally showed significantly lower UCs for P and for the micronutrients Fe, Zn, and Cu at both cropping stages compared to the two Solanaceae species. The obtained results can be used to precisely adjust the nutrient supply in closed-loop soilless cultivations to the plant uptake thus avoiding both depletion and accumulation of nutrients in the root environment.

Effects of NaCl and CaCl2 as Eustress Factors on Growth, Yield, and Mineral Composition of Hydroponically Grown Valerianella locusta.

Corn salad (Valerianella locusta) is a popular winter salad, cultivated as an ingredient for ready-to-eat salads. The application of mild salinity stress (eustress) can increase the flavor and reduce the nitrate content of certain crops but, at the same time, a wrong choice of the eustress type and dose can negatively affect the overall productivity. In this research, the effects of different isosmotic salt solutions, corresponding to two different electrical conductivity (EC) levels, were investigated on the yield and mineral composition of hydroponically grown Valerianella locusta "Elixir". Five nutrient solutions (NS) were compared, including a basic NS used as the control, and four saline NS were obtained by adding to the basic NS either NaCl or CaCl2 at two rates each, corresponding to two isosmotic salt levels at a low and high EC level. Corn salad proved moderately susceptible to long-term salinity stress, suffering growth losses at both low and high EC levels of saline solution, except from the low NaCl treatment. Hence, it appears that mild salinity stress induced by NaCl could be employed as an eustress solution and corn salad could be cultivated with low-quality irrigation water (20 mM NaCl) in hydroponic systems.

Hydroponic Common-Bean Performance under Reduced N-Supply Level and Rhizobia Application.

This study aims to explore the possibility of a reduced application of inorganic nitrogen (N) fertiliser on the yield, yield qualities, and biological nitrogen fixation (BNF) of the hydroponic common bean (Phaseolus vulgaris L.), without compromising plant performance, by utilizing the inherent ability of this plant to symbiotically fix N2. Until the flowering stage, plants were supplied with a nutrient solution containing N-concentrations of either a, 100%, conventional standard-practice, 13.8 mM; b, 75% of the standard, 10.35 mM; or c, 50% of the standard, 6.9 mM. During the subsequent reproductive stage, inorganic-N treatments b and c were decreased to 25% of the standard, and the standard (100% level) N-application was not altered. The three different inorganic-N supply treatments were combined with two different rhizobia strains, and a control (no-inoculation) treatment, in a two-factorial experiment. The rhizobia strains applied were either the indigenous strain Rhizobium sophoriradicis PVTN21 or the commercially supplied Rhizobium tropici CIAT 899. Results showed that the 50-25% mineral-N application regime led to significant increases in nodulation, BNF, and fresh-pod yield, compared to the other treatment, with a reduced inorganic-N supply. On the other hand, the 75-25% mineral-N regime applied during the vegetative stage restricted nodulation and BNF, thus incurring significant yield losses. Both rhizobia strains stimulated nodulation and BNF. However, the BNF capacity they facilitated was suppressed as the inorganic-N input increased. In addition, strain PVTN21 was superior to CIAT 899-as 50-25% N-treated plants inoculated with the former showed a yield loss of 11%, compared to the 100%-N-treated plants. In conclusion, N-use efficiency optimises BNF, reduces mineral-N-input dependency, and therefore may reduce any consequential negative environmental consequences of mineral-N over-application.

Fresh Pod Yield, Physical and Nutritional Quality Attributes of Common Bean as Influenced by Conventional or Organic Farming Practices.

The aim of the current study wat to comparatively assess the impact of different nitrogen (N) fertilization schemes on fresh pod yield and yield quality in either organically or conventionally grown common beans (Phaseolus vulgaris L.). Prior to common bean crop establishment, the experimental field site was cultivated following either organic (a) or conventional (b) farming practices with a winter non-legume crop (Brassica oleracea var. italica) (BR), or (c) with field bean (Vicia faba sp.) destined to serve as a green manure (GM) crop. At the end of the winter cultivation period the broccoli crop residues (BR) and green manure biomass (GM) were incorporated into the soil and the plots that accommodated the treatments (a) and (c) were followed by an organically cultivated common bean crop, while the conventional broccoli crop was followed by a conventionally cropped common bean crop. Additional to the plant residues (BR), sheep manure (SM) at a rate of 40 kg N ha-1 was also applied to the organically treated common beans, while the plots with a conventionally cropped common bean received 75 kg N ha-1. Organic common bean treated with SM + BR produced smaller pods of higher dry matter and bioactive compound content, responses that are correlated with limited soil N availability. No significant variations were observed on yield components and N levels of pods cultivated under organic (SM + GM) and conventional cropping systems. Pod sugar and starch content was not influenced by the different fertilization practices. In conclusion, we have demonstrated that the combined application of SM + GM can be considered as an efficient N-fertilisation strategy for organic crops of common bean, benefiting their nutritional value without compromising yield.

Oral sucrosomial iron improves exercise capacity and quality of life in heart failure with reduced ejection fraction and iron deficiency: a non-randomized, open-label, proof-of-concept study.

AIMS: Oral sucrosomial iron (SI) combines enhanced bioavailability and tolerance compared to conventional oral iron along with similar efficacy compared to intravenous iron in several conditions associated with iron deficiency (ID). METHODS AND RESULTS: In this non-randomized, open-label study, we sought to evaluate prospectively the effects of SI on clinical parameters, exercise capacity and quality of life in 25 patients with heart failure (HF) with reduced ejection fraction (HFrEF) and ID, treated with SI 28 mg daily for 3 months, in comparison to 25 matched HFrEF controls. All patients were on optimal stable HF therapy. Patients were followed for 6 months for death or worsening HF episodes. There were no differences in baseline characteristics between groups. At 3 months, SI was associated with a significant increase in haemoglobin, serum iron and serum ferritin levels (all P ≤ 0.001) along with a significant improvement in 6-min walked distance and Kansas City Cardiomyopathy Questionnaire (all P < 0.01), even after adjustment for baseline parameters; these differences persisted at 6 months. Over the study period, there were no deaths, while 10 patients (20%) in total (four in the SI group and six in the control group), experienced worsening HF (odds ratio 0.51, 95% confidence interval 0.41-6.79, P = 0.482). Drug-associated diarrhoea was reported by one patient in the SI group and led to drug discontinuation; no other adverse events were reported. CONCLUSIONS: In this proof-of-concept study, SI was well tolerated and improved exercise capacity and quality of life in HFrEF patients with ID. Randomized studies are required to further investigate the effects of this therapy.

Safety and efficacy of salt substitution with a low sodium-potassium enriched dietary salt in patients with heart failure with reduced ejection fraction: A pilot study.

BACKGROUND AND AIMS: Increased sodium intake is associated with increased risk of decompensation in patients with heart failure. This non-randomized, open-label, controlled study aimed to examine the feasibility, preliminary safety and efficacy of a low sodium-potassium enriched salt substitute compared to regular table salt in patients with heart failure with reduced ejection fraction (HFREF). METHODS: Fifty patients (68% male, NYHA I/II/III 6%/68%/26%, mean age 70 ± 9 years, LVEF 31 ± 5%, median BNP 112 pg/ml) were included. Of these, 30 patients received the salt substitute (maximum consumption of 2 g daily), who were prospectively compared to a control group of 20 age/sex/NYHA class-matched HFREF patients who consumed regular salt (maximum consumption of 2 g daily). Consumption of regular salt was prohibited in the salt substitution group. All patients were followed for 12 weeks. RESULTS: Patient groups did not differ by sex, age, LVEF, NYHA class, 6MWD, and BNP at baseline. In primary safety analysis, no significant differences were detected between groups regarding SBP (p = 0.052), DBP (p = 0.159), HR (p = 0.246), serum potassium (p = 0.579), serum sodium (p = 0.125), and eGFR (p = 0.710) throughout the 12 weeks. Secondary efficacy analysis revealed a statistically significant difference in 6MWD at 12 weeks between the salt substitute and regular salt groups after adjustment for baseline 6MWD (mean difference±SEM, 4.7 ± 2.1 m, F = 4.92, p = 0.031). CONCLUSIONS: In this pilot study, a low sodium-potassium enriched salt substitute was found to be safe compared to regular salt in HFREF patients, while it resulted in a small albeit significant improvement in exercise capacity, possibly justifying further investigation with randomized clinical studies.