Iron (Fe) is abundant in soil, but its bioavailability can be limited by environmental factors, negatively impacting plant growth and productivity. While root mechanisms for enhancing Fe uptake are well-studied in some model plants, the responses of tolerant and susceptible grapevine rootstocks to low Fe availability remain poorly understood. This study examined the responses of two grapevine rootstocks, Fercal (tolerant) and 3309C (susceptible), to three Fe conditions: direct Fe deficiency (-Fe), induced Fe deficiency through the addition of bicarbonate (+Fe+BIC), and control (+Fe). Our main findings include: 1) more severe leaf symptoms in 3309C than in Fercal independent of the type of stress, 2) overall growth reduction due to direct Fe deficiency (-Fe), while under induced Fe deficiency (+Fe+BIC) Fercal strongly increased root biomass. This observation is supported by the increased expression of root-development related genes VviSAUR66 and VviZAT6, 3) enhanced organic acid contents under induced Fe deficiency (+Fe+BIC) and different organic acids profiles depending on applied stress and genotype, and 4) stronger modulation of gene expression in Fercal root tips, including enhanced expression of Fe mobilization and transport genes (VviOPT3, VviIREG3, VviZIF1). Overall, bicarbonate-induced Fe deficiency (+Fe+BIC) had greater negative effects than direct Fe deficiency (-Fe), with Fercal showing a higher adaptive capability to maintain Fe homeostasis.

Iron (Fe) deficiency is one of the important nutritional disorders for grapevine growing in alkaline and calcareous soils. Although Fe is an abundant element in soil, several factors limiting its availability, particularly the high levels of calcium carbonate or bicarbonate in soil, leading to a remarkable reduction in grapevine growth and productivity. The use of Fe chlorosis-tolerant rootstocks seems to be a cost-effective and efficient way to maintain Fe balance. Morphological and physiological changes occur in plants to cope with low Fe availability, including enhancement of ferric chelate reductase activity and altering root system by increasing lateral roots and root hairs. However, the mechanisms underlying these responses grapevine rootstocks are still unclear. Our study aimed to decipher the physiological and molecular mechanisms to prevent iron deficiency chlorosis under high lime conditions of different tolerant rootstocks. Our results confirmed different responses related to rootstock genotype (Fercal, 3309C) in root biomass, ferric chelate reductase activity and organic acid contents depending on direct (-Fe) or indirect (+Fe+BiC) Fe deficiency. Currently expression studies are performed to conclude on Fe uptake, transport and relocation, including their regulation signals e.g. transcription factors and phytohormones. Findings of this study will contribute to our knowledge on rootstock traits and optimize our strategy for vine nutrition.

Background In viticulture, iron (Fe) chlorosis is a common abiotic stress that impairs plant development and leads to yield and quality losses. Under low availability of the metal, the applied N form (nitrate and ammonium) can play a role in promoting or mitigating Fe deficiency stresses. However, the processes involved are not clear in grapevine. Therefore, the aim of this study was to investigate the response of two grapevine rootstocks to the interaction between N forms and Fe uptake. This process was evaluated in a hydroponic experiment using two ungrafted grapevine rootstocks Fercal (Vitis berlandieri x V. vinifera ) tolerant to deficiency induced Fe chlorosis and Couderc 3309 ( V. riparia x V. rupestris ) susceptible to deficiency induced Fe chlorosis. Results The results could differentiate Fe deficiency effects, N-forms effects, and rootstock effects. Interveinal chlorosis of young leaves appeared earlier on 3309 C from the second week of treatment with NO 3 − /NH 4 + (1:0)/-Fe, while Fercal leaves showed less severe symptoms after four weeks of treatment, corresponding to decreased chlorophyll concentrations lowered by 75% in 3309 C and 57% in Fercal. Ferric chelate reductase (FCR) activity was by trend enhanced under Fe deficiency in Fercal with both N combinations, whereas 3309 C showed an increase in FCR activity under Fe deficiency only with NO 3 − /NH 4 + (1:1) treatment. With the transcriptome analysis, Gene Ontology (GO) revealed multiple biological processes and molecular functions that were significantly regulated in grapevine rootstocks under Fe-deficient conditions, with more genes regulated in Fercal responses, especially when both forms of N were supplied. Furthermore, the expression of genes involved in the auxin and abscisic acid metabolic pathways was markedly increased by the equal supply of both forms of N under Fe deficiency conditions. In addition, changes in the expression of genes related to Fe uptake, regulation, and transport reflected the different responses of the two grapevine rootstocks to different N forms. Conclusions Results show a clear contribution of N forms to the response of the two grapevine rootstocks under Fe deficiency, highlighting the importance of providing both N forms (nitrate and ammonium) in an appropriate ratio in order to ease the rootstock responses to Fe deficiency.

Viticulture is a perennial cropping system that provides large inter-row space as a non-crop habitat for a range of different taxa. Extensive vegetation management has been shown to increase biodiversity and ecosystem service provision in vineyards. Important soil ecosystem services are decomposition, nutrient cycling, and pest regulation provided by the mesofauna (e.g., Acari and Collembola). However, studies investigating the effects of inter-row management on soil mesofauna are scarce. We studied the effect of inter-row management intensity (complete vegetation cover, alternating vegetation cover, and bare ground) and local pedoclimatic conditions on Acari and Collembola in nine Austrian vineyards. Our results showed that the clay content of the soil was the most important factor and increased the abundances of both analyzed taxa. Complete and alternating vegetation cover increased their abundance in comparison to bare ground management. Higher soil respiration slightly contributed to higher abundances of those two taxa in both years. In conclusion, besides the positive effects of the clay content in the soil, complete and alternating vegetation cover are feasible management practices for increasing soil mesofauna in vineyards.

In vineyards, the under-vine area is managed to control vegetation growth and to reduce the competing effect of growing plants on vines and fruit development. Applied under-vine management methods are the application of herbicides, soil tillage or the growth of spontaneous vegetation or cover crops. These methods affect pedo-climatic conditions differentially as well as the soil biota and have, therefore, consequences on soil functions and ecosystem services. In the presented case study, the effects of five under-vine management methods on the activity of soil hydrolytic enzymes, the soil water content, vine photosynthetic activity, shoot pruning weight, grape yield and quality are investigated in a vineyard in Lower Austria over three consecutive seasons. Thereby, we hypothesise that a permanent under-vine vegetation cover, either mowed or without mowing, supports the soil microbial communities and soil functions in a way to enhance water and nutrients availability for vines which partly compensates for the competition of the growing vegetation. Our results confirm effects on the soil water balance, more specifically, a reduced soil water content in 11-20 cm soil depths induced by a permanent vegetation cover as compared to herbicide application or soil tillage. Further consequences of permanent vegetation below vines were lower shoot pruning weights and lower berry weights, while total soluble solids and titratable acidity were not affected. The vine's photosynthetic activity, as well as the soil water content, were partly affected by treatments dependent on the precipitation ahead of the measurement. In parallel, the soil microbial activity was significantly enhanced by a permanent vegetation cover below the vines as compared to herbicide application, a trend which increased with the years of the project. In conclusion, permanent under-vine vegetation strongly promoted soil microbial activity without strong effects on shoot pruning weight, grape yield and quality. In the next step, a functional proof is necessary to characterise the interaction between soil microbial activity, soil water balance and vine nutrition and water status by using sensors for continuous measurements.