Iron nutrition of fruit tree crops

Although iron (Fe) needs by fruit trees are relatively low, Fe deficiency represents the main constraint for successful cultivation of fruit tree crops in calcareous and alkaline soils. Kiwifruit, peach and pear, several Citrus and Vaccinium spp. are very susceptible to Fe chlorosis, cherry and grape are relatively susceptible and apple is relatively tolerant. The typical Fe deficiency symptoms, the interveinal leaf yellowing starting from apical leaves which may progress and turn into necrosis, exhibit a temporal and spatial variability, requiring an efficient diagnosis systems. Iron deficiency reduces yields and fruit quality and forces growers to adopt measures for controlling and preventing the development of Fe chlorosis. The most widely adopted Fe fertilizers are the synthetic chelates, that do not represent a sustainable management approach, due to the cost and their potential pollution of the soil and water environments. The genetic approach to prevent chlorosis is based on the choice of tolerant rootstocks, which are known to activate mechanisms for improving Fe uptake under condition of low Fe availability. Unfortunately, for several fruit crops iron tolerant rootstocks have some adverse agronomic characteristics (e.g. excessive vigor) which make their adoption unlikely in modern fruit industry. Alternatives to Fe chelates have been identified and need to be tested and adapted to different conditions: they should aim at the improvement of soil environment for root growth and activity and/or to the enhancement of Fe availability in the soil and in the tree

Arbuscular mycorrhiza symbiosis in viticulture: a review

International audienceAbstractViticulture is a major worldwide economic sector with a vine area of 7.52 million ha, wine production of 288 Mhl, and wine exports of 26 billion euros. Nevertheless, viticulture has to adapt to new challenges of pest management, such as pesticide reduction, and climate change, such as increasing droughts. Viticulture adaptation can benefit from arbuscular mycorrhiza, a plant–fungus symbiosis. Here, we review the ecosystemic services of arbuscular mycorrhiza for grapevine production. The major points are the following: (1) arbuscular mycorrhiza fungi increase grapevine growth and nutrition by a better access to soil nutrients and by activating the regulation of plant transport proteins for phosphorus (P), nitrogen (N), and other elements. (2) Arbuscular mycorrhiza fungi increase the tolerance to abiotic stresses such as water stress, soil salinity, iron chlorosis, and heavy metal toxicity. (3) Arbuscular mycorrhiza fungi protect against biotic stresses such as root diseases. (4) Arbuscular mycorrhiza fungi produce glycoproteins and a dense hyphal network that increases soil stability and save soil nutrients up to 14 % of the grape production income. (5) P fertilisation reduces mycorhization. (6) Using herbaceous plants as cover crops favors arbuscular mycorrhiza fungi