LIBRO-CONGRESO-CITRUS

selections (‘Caffin’ and ‘Spinoso VCR’), a medium (‘SRA 63’) and a late (‘Rubinio VCR’). The trial was
conducted in a sandy soil with pH 8.26 (Total lime 6%, active lime 1.6 %). The planting distance was 5x4 m
using a randomized complete-block design. The four selections of clementine on ‘Alemow’ showed over
the years 2006-2011 the highest cumulative yield, followed by ‘Carrizo’ and ‘Swingle’. Sour orange induced
a reduction of 50% on cumulative production than ‘Carrizo’. The most productive variety was clementine
‘SRA 63’ followed by ‘Spinoso’. In terms of qualitative characteristics, ‘Alemow’ induced a reduction of
total soluble solids concentration, and ‘Flying Dragon’ induced the highest content. Based on the induced
production characteristics and tolerance to tristeza, ‘Carrizo’ and ‘Swingle’ are confirmed as subjects able
to replace the sour orange. Even if clementine ‘SRA 63’ was the most productive variety, is problematic
the evaluation of a variety within the clementines, without taking into account the ripening period, for the
enormous influence of this factor on crop profitability.
S18P06
Is there a relationship between ferric-chelate reductase activity in roots of Poncirus trifoliata and
leaf chlorophyll contents?
Correia P.J., Lopes D., Duarte A., Gama F., Saavedra T. and Pestana M.
Institute of Mediterranean Agricultural and Environmental Sciences - University of Algarve (ICAAM/UAlg), Faculty of Sciences and
Technology, Portugal. aduarte@ualg.pt
Poncirus trifoliata is a citrus rootstock very sensitive to Fe deficiency which is very common in crops grown in
calcareous soils due to the detrimental effect of bicarbonate ion. Higher plants have distinct behaviors when
faced with bicarbonate-induced Fe chlorosis, and several mechanisms may be activated under Fe shortage.
The aim of this study was to investigate the activity of ferric-chelate reductase (FC-R), a key enzyme in Fe
uptake, and to establish relationships with leaf chlorophyll. Plants were grown in nutrient solutions without
Fe (0 µM Fe), with 1 µM Fe, with 120 µM Fe and with 120 µM Fe plus CaCO3 (1 g L-1). Total leaf chlorophyll
in young and mature leaves was determined using a calibration model based on a relationship between SPAD
readings and concentration of chlorophyll (r2=0.95; P