The citrus rootstocks Cleopatra mandarin, Poncirus trifoliata, forner-alcaide 5 and forner-alcaide 13 vary in susceptibility to iron deficiency chlorosis.

1 Instituto Valenciano de Investigaciones Agrarias, Centro de Citricultura y Produccion Vegetal, Carretera MoncadaNaquera Km. 4.5, 46113, Moncada, Valencia, Spain. Address correspondence to M. Angeles Forner-Giner: Tel: 34 96 3424000. Fax: 34 96 3424001. E-mail: forner_margin@gva.es Abstract We have studied the tolerance to iron chlorosis of four citrus seedling rootstocks: the two hybrids Forner-Alcaide 5 (F-A 5) and Forner-Alcaide 13 (F-A 13), as well as their parents [Cleopatra mandarin (Citrus reshni Hort. ex Tan.) and Poncirus trifoliata (L.) Raf.]. Six-month-old potted plants were grown in four different iron concentrations (0, 9, 18 and 36 μM) and leaf iron content, dry weight, total chlorophyll content, catalase activity and root ferric chelate reductase (FCR) activity were measured after 60 days. F-A 5 had the highest FCR activity, total chlorophyll content, total dry weight and iron content in roots. P. trifoliata, a genus susceptible to iron chlorosis, showed the lowest total chlorophyll content, FCR activity and total dry weight. F-A 5 is an iron-chlorosis-tolerant rootstock, which may be suitable for use in soils that cause this problem.