Trifoliata hybrids rootstocks for 'Lane Late' navel orange in Spain

Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.] and Cleopatra mandarin (C. reshni Hort. ex Tan.) are the most important rootstocks used in Spain, but they are problematic and it is necessary to search for new rootstocks with better all-round performance. The performance of 'Lane Late' navel orange [Citrus sinensis (L.) Osb] on ten rootstocks was determined in the South of the province of Alicante (Spain). They are Carrizo citrange, Cleopatra mandarin and eight new hybrids obtained at the Instituto Valenciano de Investigaciones Agrarias in Valencia (Spain): 020324 [Troyer citrange (C. sinensis × P. trifoliata) × Cleopatra mandarin], Forner-Alcaide 418 (F&A 418) [Troyer citrange × common mandarin (C. deliciosa Ten.)], Forner-Alcaide 13 (F&A 13), 030118, 030127 and 030131 (Cleopatra mandarin × P. trifoliata) and 030212 and 030230 (Cleopatra mandarin × Troyer citrange). Soil is clay loam, with pH 8.5 and electric conductivity in the saturation extract at 25ºC of 5.79 mS cm-1. Yield was weighed during the first nine harvests, fruit quality was determined in the last three. Pre-harvest fruit-drop was controlled for the 4th until 9th harvests. The trees of 'Lane Late' navel budded on Cleopatra mandarin were the tallest (2.5 m) and F&A 418 (1.6 m) the shortest of all rootstocks tested. Trees on 030131 hybrid and Carrizo citrange rootstocks had the highest mean yield (81.2 and 80.3 kg per tree per year respectively), while trees on F&A 418 produced the lowest mean yield (22.3 kg per tree per year). Trees on 030131, 020324 and 030212 had the highest yield efficiency as total cumulative yield per cubic meter of canopy volume (62.1, 58.7 and 55.9 kg m-3 respectively) whereas trees on 030127, F&A 418 and Cleopatra mandarin had lower yield efficiencies (45.0, 44.4 and 38.6 kg m-3, respectively). Pre-harvest fruit-drop was lower in trees grafted on Cleopatra mandarin (24.62 %) and on 030212 (26.61 %), and was also low on F&A 418 (27.76 %), 020324 (28.14 %) and 030230 (29.18 %) rootstocks. Trees on Carrizo citrange and 030127 experienced important fruit-drop (40.24 % and 38.27 % respectively). Trees on F&A 418 had the highest fruit weight and fruit size whereas trees on 030118 induced the lowest ones. The ripeness index was the highest on F&A 13 (18.3) and lowest on F&A 418 (15.3), 030212 (15.3)

Plant growth, yield and fruit quality of 'Lane Late' navel orange on four citrus rootstocks

This study analyses the influence of four citrus rootstocks, Citrus macrophylla Wester, Gou Tou Chen (Citrus hybrid), C. volkameriana Ten. & Pasq. and Cleopatra mandarin (C. reshni Hort. ex Tan.), on growth, yield and fruit quality on Lane Late navel orange. Trees were grown in a plot in Alicante (Spain), where the soil is clay loam, with pH 8.5 and electric conductivity in the 1/5 extract: 0.643 mmhos cm–1. Yield was weighed during four harvests, fruit quality was determined in 2007 and 2009. Cleopatra mandarin and Gou Tou Chen were found to be the most invigorating rootstocks for ‘Lane Late’ in heavy and calcareous soil. Trees on C. macrophylla rootstock produced the highest cumulative yield (328.81 kg tree–1), without significant differences compared to trees on Cleopatra mandarin (292.41 kg tree–1). Rootstock significantly affected fruit quality variables. C. macrophylla and C. volkameriana would appear to induce the highest fruit weight and ripening index

El panorama varietal y los nuevos patrones. Análisis de la situación actual

La utilización de patrones es preceptiva en los cítricos que se producen en España, ya que todas las variedades cultivadas, ya sean naranjas, mandarinas, limones o pomelos, son muy sensibles a hongos del género Phytophthora, que se encuentran presentes en casi todos los suelos. Durante muchas décadas, el patrón naranjo amargo (Citrus aurantium L.) fue el estándar utilizado en todas las plantaciones de cítricos de los países mediterráneos. Sin embargo, a partir de 1957, la aparición del virus de la tristeza de los cítricos (CTV) obligó a la reconversión de la totalidad de nuestra citricultura sobre patrones tolerantes a la enfermedad. Los principales problemas que se presentan en la citricultura española, además del virus de la tristeza, son: la clorosis férrica inducida en suelos calizos, la salinidad, la asfixia radical provocada por inundaciones o por una capa freática alta, la escasez de agua, los decaimientos y muerte de árboles ocasionados por hongos, principalmente del género Phytophthora, y los daños en las replantaciones producidos por el nematodo de los cítricos

Rootstock Effects on Leaf Photosynthesis in 'Navelina' Trees Grown in Calcareous Soil

Citrus crops in the Mediterranean region are often grown in high pH calcareous soils, which promote nutrient imbalances, especially iron deficiency. 'Navelina' trees grafted on eight different citrus rootstocks were assessed in terms of their relative tolerance to these soils. To do so, leaf gas exchange and chlorophyll a fluorescence parameters were measured for 2 consecutive years in leaves without visible injury symptoms. Trees were grown on the rootstocks Carrizo citrange, hybrids of Cleopatra mandarin x Poncirus trifoliata no. 5 (F-A 5),13 (F-A 13), and 16 (030116), Troyer citrange x common mandarin no. 18 (F-A 418), King mandarin x P. trifoliata no. 7 (F-A 517), 020324 (Troyer citrange x Cleopatra mandarin), and Volkamer lemon x P. trifoliata no. 64 (230164). gs and transpiration rate were clearly lower in leaves of shoots grafted on Carrizo citrange than in those on the other rootstocks assayed, but net photosynthetic flux did not differ. However, leaves of shoots on Carrizo citrange displayed a decline in their maximum quantum yield of PSII photochemistry [variable fluorescence/maximum fluorescence (F(v)/F(m)) ratio] and other chlorophyll parameters in the steady state such as photochemical quenching (qp) and the quantum efficiency of PSII photochemistry as well as an increase in nonphotochemical quenching (q(N)). Other rootstocks such as 030116, F-A 517 and, especially, F-A 5 showed the highest Phi(PSU) and F(v)/F(m) values, whereas F-A 5 had the lowest qN in the steady state. The photosynthetic characteristics observed in leaves on Carrizo citrange showed them to be the least tolerant to these calcareous conditions, whereas photosynthesis of 'Navelina' trees budded on F-A 5 were the most tolerant

Screening of ‘King’ Mandarin Hybrids as Tolerant Citrus Rootstocks to Flooding Stress

This work compares the tolerance to long-term anoxia conditions (35 days) of five new citrus ‘King’ mandarin (Citrus nobilis L. Lour) Poncirus trifoliata ((L.) Raf.) hybrids (named 0501XX) and Carrizo citrange (CC, Citrus sinensis (L.) Osb. Poncirus trifoliata (L.) Raf.), the widely used citrus rootstock in Spain. Growth parameters, chlorophyll concentration, gas exchange and fluorescence parameters, water relations in leaves, abscisic acid (ABA) concentration, and PIP1 and PIP2 gene expressions were assessed. With a waterlogging treatment, the root system biomass of most hybrids went down, and the chlorophyll a and b concentrations substantially dropped. The net CO2 assimilation rates (An) and stomatal conductance (gs) lowered significantly due to flooding, and the transpiration rate (E) closely paralleled the changes in gs. The leaf water and osmotic potentials significantly increased in most 0501 hybrids. As a trend, flooding stress lowered the ABA concentration in roots from most hybrids, but increased in the leaves of CC, 05019 and 050110. Under the control treatment (Ct) conditions, most 0501 hybrids showed higher PIP1 and PIP2 expressions than the control rootstock CC, but were impaired due to the flooding conditions in 05019 and 050110. From this study, we conclude that 0501 genotypes develop some adaptive responses in plants against flooding stress such as (1) stomata closure to prevent water loss likely mediated by ABA levels, and (2) enhanced water and osmotic potentials and the downregulation of those genes regulating aquaporin channels to maintain water relations in plants. Although these traits seemed especially relevant in hybrids 050110 and 050125, further experiments must be done to determine their behavior under field conditions, particularly their influence on commercial varieties and their suitability as flooding-tolerant hybrids for replacing CC, one of the main genotypes that is widely used as a citrus rootstock in Spain, under these condition

Gene Expression under Short-Term Low Temperatures: Preliminary Screening Method to Obtain Tolerant Citrus Rootstocks

Climate change and global warming are leading to a change in weather patterns toward hot and cold waves. Citrus fruits are a tropical or subtropical crop whose growth is altered by changes in weather patterns. Thus, in the present work, two experiments are evaluated to obtain a screening method to select citrus rootstocks that help us to select new low-temperature-tolerant plant materials. One cold experiment was carried out with the Poncirus trifoliata and Citrus macrophylla rootstocks at 4 °C for 4, 8, 24 and 56 h. A second experiment was performed at 4 °C for 5 days with subsequent acclimatization lasting 0, 5, 10 and 24 h. The expression of the cold response genes CAMTA1, CAMTA3, CAMTA5, CBF1, ICE1 and COR413 IM1 was quantified. The results showed that the best rootstock selection strategy was the second experiment, as a higher expression of the genes CAMTA3, CAMTA5, CBF1 and COR413 IM1 was seen in the tolerant genotype P. trifoliata. We quantified the gene expression of proline biosynthesis P5CS1, dOAT and the proline transporters PROT1 and PROT2; the concentration of the amino acid proline in leaves was also quantified. These results once again showed that the best experiment to differentiate between tolerant and sensitive rootstocks was the second experiment with acclimation time