Estratégias inovadoras para otimizar o uso do ferro em culturas hortícolas.

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Silencing of FRO1 gene affects iron homeostasis and nutrient balance in tomato plants

Publication . Gama, Florinda; Saavedra, Teresa; Dandlen, Susana; García‐Caparrós, Pedro; de Varennes, Amarilis; Nolasco, Gustavo; Correia, Pedro José; Pestana, Maribela

BackgroundIron chlorosis is an abiotic stress of worldwide importance affecting several agronomic crops. It is important to understand how plants maintain nutrient homeostasis under Fe deficiency and recovery. AimsWe used the virus-induced gene silencing (VIGS) method to elucidate the role of the FRO1 gene in tomato plants and identify the impact on regulation of the root ferric-chelate reductase (FCR) activity and nutritional homeostasis. MethodsTomato plantlets cv. "Cherry" were transferred into half-strength Hoagland's nutrient solution containing 0.5 & mu;M of Fe (Fe0.5). In phase I, two treatments were established: control (Fe0.5) plants and VIGS-0.5 plants corresponding to plants with the FRO1 gene silenced. In phase II, plants from Fe0.5 and VIGS-0.5 were transferred to new nutrient solution and then grown for a further 14 days under 0 and 10 & mu;M of Fe (as 0.5 & mu;M would not be enough for the larger plants during phase II). Therefore, four treatments were imposed: Fe0, Fe10, VIGS-0, and VIGS-10. ResultsVIGS-0.5 plants had significantly lower chlorophyll (Chl) and root FCR activity compared to the respective non-silenced plants and retained more Cu and Zn in the roots at the expense of stems (Cu) or young leaves (Zn). Iron concentration in roots and stems decreased in FRO1 gene-silenced plants, compared to control plants, but the allocation to different organs was similar in both treatments. ConclusionsThere was a partial recovery of leaf Chl in the VIGS-10 plants and a higher concentration of Fe in all organs. In contrast, the allocation of Cu to roots decreased in the VIGS-10 plants.

2023Journal article

Open Access

Nutritional performance of Five Citrus rootstocks under different Fe levels

Publication . Pestana, Maribela; García-Caparrós, Pedro; Saavedra, Teresa; Gama, Florinda; Abadía, Javier; Varennes, Amarilis de; Correia, Pedro José

Iron is an essential micronutrient for citrus, playing an important role in photosynthesis and yield. The aim of this paper was to evaluate the tolerance to Fe deficiency of five citrus rootstocks: sour orange (S), Carrizo citrange (C), Citrus macrophylla (M), Troyer citrange (T), and Volkamer lemon (V). Plants were grown for 5 weeks in nutrient solution that contained the following Fe concentrations (in µM): 0, 5, 10, 15, and 20. At the end of the experiment, biomass (dry weight— DW), leaf area, total leaf chlorophyll (CHL), and the activity of root chelate reductase (FCR) were recorded. Additionally, the mineral composition of roots (R) and shoots (S) was evaluated. Principal component analysis was used to study the relationships between all parameters and, subsequently, the relations between rootstocks. In the first component, N-S, P-S, Ca-S, Cu-S, Zn-S, Mn-S, Zn-R, and Mn-R concentrations were related to leaf CHL and FCR. Increases in leaf CHL, Mg-R, and DW (shoots and roots) were inversely related to Cu-R, which was shown in the second component. The values obtained were consistent for V10, C15, and C20, but in contrast for S0 and S5. In conclusion, micronutrient homeostasis in roots and shoots of all rootstocks were affected by Fe stress conditions. The Fe/Cu ratio was significantly related to CHL, which may be used to assist rootstock performance.

2023-09-13Journal article

Open Access

Effects of foliar application of organic acids on strawberry plants

Publication . Saavedra, Teresa; Gama, Florinda; Rodrigues, Maria Joao; Abadía, Javier; de Varennes, Amarilis; Pestana, Maribela; Da Silva, José Paulo; Correia, Pedro José

The large economic costs and environmental impacts of iron-chelate treatments has led to the search for alter-native methods and compounds to control iron (Fe) deficiency chlorosis. Strawberry plants (Fragaria x ananassa) were grown in Hoagland's nutrient solution in a greenhouse with two levels of Fe: 0 and 10 mu M Fe(III)-EDDHA. After 20 days, plants growing without Fe showed typical symptoms of Fe deficiency chlorosis in young leaves. Then, the adaxial and abaxial sides of one mature or one young leaf in each plant were brushed with 10 mM malic (MA), citric (CA) or succinic (SA) acids. Eight applications were done over a two-week period. At the end of the experiment, the newly emerged (therefore untreated), young and mature leaves were sampled for nutritional and metabolomic analysis, to assess the effectiveness of treatments. Leaf regreening was monitored using a SPAD-502 apparatus, and the activity of the ferric chelate-reductase activity (FCR) was measured using root tips. Iron deficiency negatively affected biomass and leaf chlorophyll but did not increase FCR activity. Application of succinic acid alleviated the decrease in chlorophyll observed in other treatments, and the overall nutritional balance in the plant was also changed. The concentrations of two quinic acid derivatives increased under Fe deficiency and decreased in plants treated with succinic acid, and thus they are proposed as Fe stress markers. Data suggest that foliage treatments with carboxylates may be, in some cases, environmentally friendly alter-natives to Fe(III)-chelates. The importance of Fe mobilization pathways in the formulation of new fertilizers is also discussed.

2022Journal article

Open Access