Environmental and Experimental Botany 71 (2011) 280–286 Contents lists available at ScienceDirect Environmental and Experimental Botany journal homepage: www.elsevier.com/locate/envexpbot Effects of moderate and severe iron deficiency chlorosis on fruit yield, appearance and composition in pear (Pyrus communis L.) and peach (Prunus persica (L.) Batsch) Ana Álvarez-Fernández, Juan Carlos Melgar 1 , Javier Abadía ∗ , Anunciación Abadía Department of Plant Nutrition, Aula Dei Experimental Station, CSIC, P.O. Box 13034, E-50080 Zaragoza, Spain article info Article history: Received 27 April 2010 Received in revised form 14 December 2010 Accepted 19 December 2010 Keywords: Fruit appearance Fruit composition Fruit load Fruit maturity Iron chlorosis Iron deficiency abstract The effects of different levels of Fe-deficiency chlorosis on the fruit yield, appearance and composition of pear and peach trees grown in field orchards have been studied. The major effect of Fe deficiency in both species was a large yield reduction, even when chlorosis was moderate, associated to decreases in fruit tree load. Fruit size increased with moderate chlorosis in both species and decreased with severe chlorosis in peach. In peach, moderate or severe chlorosis affected uniformly all branches, leading to firmer fruits with higher acidity, total phenolics and carboxylates. This indicates a delayed maturity that can be attributed to a low C-availability for fruits. In Fe-deficient pear trees, the majority of fruits (98%) were on non-chlorotic or moderately chlorotic branches, and fruits were less green and firm with an increased sugars/acids ratio. This indicates an advanced fruit maturity that can be attributed to an increased C-availability for fruits. All chlorosis levels increased within-tree variation in fruit appearance. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Iron (Fe) deficiency is a major constraint for successful cultiva- tion of fruit tree crops in calcareous or alkaline soils around the world, which account for one-third of the earth’s surface (Hansen et al., 2006; Rombolà and Tagliavini, 2006). Fruit tree species dif- fer in their susceptibility to Fe deficiency, and it is widely accepted that pear and peach are among the most susceptible fruit crops (Rombolà and Tagliavini, 2006). In Spain, the second pear and peach producing country in Europe (FAOSTAT, 2008), Fe deficiency chlorosis is a major problem in the most important pear and peach production area, the Ebro valley basin (Sanz et al., 1992). Typical symptoms of Fe deficiency include the development of interveinal chlorosis, starting from the apical leaves (Abadía and Abadía, 1993); leaf chlorosis is the most visible symptom of Fe deficiency in many high value crops, including pear, peach and orange (Citrus sinensis (L.) Osbeck) (Rombolà and Tagliavini, 2006). In the case of pear, Fe chlorosis is atypical, since it often occurs in the whole leaf lamina, Abbreviations: Chl, chlorophyll; FW, fresh weight; PEPC, phosphoenolpyruvate carboxylase; TSS, total soluble solids. ∗ Corresponding author. Tel.: +34 976 716056; fax: +34 976 716145. E-mail address: jabadia@eead.csic.es (J. Abadía). 1 Current address: Citrus Center, Texas A&M University - Kingsville, 312 N Inter- national Boulevard, Weslaco, TX 78596, USA. including veins (Abadía et al., 1989); also, chlorosis often affects pear branches to different extents, with some remaining green and other exhibiting different degrees of chlorosis. Iron deficiency- induced leaf chlorosis leads to reduced photosynthetic efficiency and electron transport, with less C being fixed via photosynthe- sis (Abadía, 1992; Larbi et al., 2006). Iron chlorosis hinders shoot growth and causes fruit yield decreases, tree defoliation and a 5–6 year shortening of the tree productive lifetime (Rombolà and Tagliavini, 2006; Sanz et al., 1992). Fruit tree crops have relatively low Fe requirements, in the range 1–2 g of Fe per tree and year (Abadía et al., 2004; Rombolà and Tagliavini, 2006). However, in these crops fruits are impor- tant nutrient sinks and therefore resource limitations may threaten the next generation. Severe fruit yield losses have been reported to occur with Fe deficiency in peach, pear, Citrus, kiwifruit (Actinidia deliciosa), olive (Olea europaea L.) and plum (Prunus americana Marsh), generally associated to reductions in fruit load (number of fruits per tree; see Rombolà and Tagliavini, 2006; Álvarez-Fernández et al., 2006 for reviews). Yield losses are often accompanied with reductions in fruit size that decrease market value (Álvarez-Fernández et al., 2006). For instance, Fe deficiency results in marked reductions in peach fruit load, which are depen- dent on the leaf chlorophyll (Chl) concentration; losses higher than 80% were found at Chl concentrations below 5 nmol cm -2 (Álvarez- Fernández et al., 2006). However, fruit size was much less affected than fruit number (Álvarez-Fernández et al., 2006). In green fruits 0098-8472/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.envexpbot.2010.12.012