Three New Cultivars of Clementine: Clemenverd, Nero and Neufina

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1 Three New Cultivars of Clementine: Clemenverd, Nero and Neufina Antonio López-García, Javier Terol, Francisco R. Tadeo, Amparo Herrero-Ortega, Victoria Ibañez and Manuel Talón * Centro de Genómica, Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Valencia, Spain *Corresponding author: talon_man@gva.es Abstract In recent years we have generated various collections of citrus mutants. One objective of these collections is the selection of genotypes of commercial interest. In the present communication we describe 3 lines derived from clementine (Citrus clementina) through physical mutagenesis, named Clemenverd, Nero and Neufina. These lines that show enhanced agronomic traits as related to the parental genotype have been registered. Clemenverd shows delayed external maturation. Nero is an early cultivar of seedless clementine that maintains the excellence of clementine quality. On the other hand, Neufina holds well into February the commercial organoleptic qualities of the parental cultivar. Neufina also has excellent perdurability in the tree, making it an ideal option to extend the supply of clementines during winter. Keywords: acidity, Brix, color, fruit quality INTRODUCTION The importance of the Citrus Industry in Spanish agriculture is beyond doubt. Citrus cultivation occupies more than 300,000 hectares. In 2010, we produced 5.5 million tons of citrus fruits, of which approximately 57 and 32% were oranges and mandarins, respectively. Spain is the 6 th largest producer of oranges in the world and the 2 nd in mandarins. The contingent of citrus represents quantitatively the most important crop in the Valencian Community, with a production of about 3 million tons. In fact, it accounts for 60% of plant production and about a 50% of its total value. More than half of the irrigated acreage of the region, 176 thousand hectares, is occupied mainly with citrus on the coastal strip, characterizing its traditional historical landscape. The Spanish citrus production is export oriented and Spain is the first exporter of fresh citrus worldwide. Germany is the main destination, followed by France, United Kingdom, Ireland and Poland. These European countries consume fresh fruit and are therefore demanding products of high quality, which is generally determined by a number of intrinsic properties of the fruit such as seedlessness, easy pealing, attractive appearance, nutraceutical value and excellent taste. Clemenules is a cultivar that fully meets the expectations of European consumers: its fruit is of appropriate size and easy to peel, the rind color is attractive and the pulp is tender with melting flesh. Clementines present generally excellent organoleptic and nutritional quality, and are for these properties a world reference. Its main harvesting period generally covers the months of November and December. However, excessive production causes a decrease in its price that may go below even the real value as a consumer product, reducing producer profits and even causing losses. The traditional cultivars cultivated in our Community have been selected mainly by farmers as sport mutations and frequently present overlapping harvesting periods, favoring market supply, but also offer concentration. The answer to this problem requires a re-organization of the varietal structure. In this context, technology innovation altering the genetic characteristics becomes a major necessity in order to obtain new cultivars to extend the offer period and the optimal harvest of fruit. This article describes the characteristics of Clemenverd, Nero and Neufina, three new commercial cultivars derived by irradiation from Clemenules. Proc. XII th Intl. Citrus Congress Eds.: B. Sabater-Muñoz et al. Acta Hort. 1065, ISHS

2 These cultivars have high organoleptic quality, similar to that of Clemenules but differ from it mainly in the harvest period. Ionizing radiation is a breeding technique used worldwide that involves exposing propagation material sources to gamma rays, X-rays (both used frequently in the field of medicine) or particles such as neutrons, protons or accelerated electrons. Irradiation causes mutations in the DNA, which are usually stable and transmitted by grafting, emulating mutations that occur naturally in citrus. As a result of the treatment the genetic variability increases, and new lines are generated that differ generally in a few characters of the original cultivar while maintaining most characteristics of the varietal group. MATERIALS AND METHODS We have used irradiations for improving Clemenules. The objective of this improvement was double: to reduce the ability of these mandarins to produce seeds and to delay natural senescence. Senescence and related disorders in clementines are associated with the rapid loss of fruit quality, a phenomenon highly influenced by weather conditions. These disorders are manifested by the appearance of typical symptoms such as those of puffing and water spot. In order to improve these characteristics in the range of clementines, we started a project in 2002 that has generated thousands of irradiated plants derived from this line. These were multiplied in plots and in controlled conditions at IVIA for further evaluation. After extensive testing, since 2006 three cultivars, named Clemenverd, Nero and Neufina, have been recently registered and replicated for commercialization. RESULTS AND DISCUSSION Clemenverd was originated from irradiation of Clemenules buds (Iglesias et al., 2006). The tree is dense, with open and vigorous growth habit and without thorns. Wood is light colored and smooth, and does not shows knots and galls in the graft insertion. The junction zone of the secondary branches to the major ones is strong and stable so that no tearing occurs after years of production. The lanceolate leaves are large and dark green. Clemenverd may show certain tendency to alternate bearing. The fruits are large with oblate shape; the skin is thin and easily peeling. The first years of production Clemenverd shows coarse and low quality fruits, but these characteristics improved with increasing plant age. Clemenverd is self-incompatible, although some seeds can be developed if there is cross-pollination with compatible cultivars. The flesh is very tender and the juice of pleasant flavor. Its main feature is related to the fact that fruit color change takes place a month later than in Clemenules (Fig. 1), although the evolution of internal maturity is rather similar. Clemenverd fruits can be harvested during January, although higher color intensity is acquired in February when its external appearance is optimum (Table 1). Clemenverd, while green, shows resistance to ripening disorders such as water spot, puffing and others. Table 1. Harvesting periods and fruit characteristics of Clemenverd, Nero and Neufina, three new selections from Clemenules. Cultivar Fruit Juice Seeds Harvest Color Sugars Acidity diameter (%) and periods IC ºBrix (g/l) (mm) (w/w) pollen Yield Clemenverd January 21±3 64± ±1 6.7±0.1 Self-incomp. Alternate Nero Mid-Oct 20±3 62 ± ±1 8.6±0.1 Sterile High Neufina Jan-Febr 18±3 60± ±1 7.3±0.1 Self-incomp. High 240

3 Fig. 1. Color delay in Clemenverd (left) in comparison with Clemenules (right). Picture was taken early December, Nero is a seedless early cultivar of Clemenules (López-García et al., 2011). It was originated from irradiations performed on latent buds. The tree is basically similar to Clemenules, vigorous, of globose appearance and with open growth habit. In general, it does not present spines but some smaller ones may appear in the most vigorous vegetative shoots. Wood is light colored and smooth, without knots and galls in the graft insertion. The lanceolate leaves are small to medium and light green with smooth edges and no winged petiole. The fruits are large and show a flattened shape; the thin skin is orange and is very attached to the pulp, although peels very easily (Fig. 2). The flesh is tender and of crunchy texture; it has good flavor and juice content (Table 1). The harvesting period begins within 15 to 20 days before Clemenules. Nero fruits are very suitable for standard degreening process to increase precocity. This cultivar does not produce seeds in any condition because it shows male and female sterility. In fruits manually pollinated with Fortune pollen, Nero presented an average of 0.28 seeds per fruit, representing a reduction of 98% in comparison with the number of seeds obtained under identical culture conditions in Clemenules, that averaged 26 seeds per fruit (Table 2). On the other hand, the anthers of the flowers are variable in color from pale yellow to complete white and only produce small amounts of pollen grains with very low fertility. Nero does not induce the formation of seeds in other compatible cultivars. 241

4 Fig. 2. Fruit of Nero, an early seedless clementine. Table 2. Average seed number per fruit of Nero and Clemenules under open and hand pollination with Fortune pollen. Year Open pollination Hand pollination Nero Clemenules Nero Clemenules Average Neufina was originated by irradiation of Clemenules buds. In general, the agronomical behavior of Neufina is very similar to that of the typical clementine trees. Its yield during the studied years was similar to the yield of the parental, like vegetative development and bearing. This cultivar has no thorns and is resistant to Alternaria and other pests, just as Clemenules. Neufina has not showed signs of alternate bearing. One of the most significant improvements of this cultivar is its extraordinary ability to preserve the fruit in perfect condition from maturing in November well into February. The tree storage capacity of the fruit is a property that makes it particularly interesting in a season devoid of clementines. The fruits of this new cultivar are basically similar to the conventional fruits of clementine, except that its persistence in the tree makes them marketable until February (Fig. 3). In spite of this longer harvesting period, the fruits of this new clementine, have shown minor incidences of water spot, puffing, creasing, cracking or any other alteration of the ring. During maturation, little fruit abscission has been observed. Hand harvesting of Neufina fruits can be performed, in principle, from November to February, since these fruits have high adhesion to the stem and very persistent calyx. Peel color is orange and hand peeling is very easy, similar to Clemenules. The fruit has a marked firmness, and in general, its size is similar to that of 242

5 Clemenules. Organoleptically, this cultivar is alike its parental; its fruits are juicy, tender and melting, do not present residues and are very palatable. This new clementine shows ºBrix and acidity contents slightly higher than the range shown by Clemenules. During January, Neufina fruits increases soluble sugar content, but do not undergo a drastic reduction in acid content as typical in clementines (Table 1). Fig. 3. Fruit of Neufina (right) and Clemenules (left). Picture was taken March, 6 th, In conclusion, Clemenverd, Nero and Neufina meet the expectations of consumers due to their high organoleptic quality that is very similar to Clemenules. However, the three cultivars are distinguished primarily from their parental cultivar in the optimum harvest period. Nero is a seedless early cultivar, while Clemenverd and Neufina are late clementines. These cultivars, in principle, can help to reduce the high production of Clemenules during the months of November and December expanding the harvesting period while maintaining high quality standards in markets. ACKNOWLEDGEMENTS This work was funded by the Spanish Ministerio de Ciencia e Innovación PSE and IPT grants. We would like to thank Elena Blazquez, Angel Boix, Juan Vicente Muñoz, Matilde Sancho and Isabel Sanchis for his invaluable help in field and laboratory tasks. Literature Cited Iglesias, D.J., Lópea-García, A., Ibáñez, V. and Talón M Dos nuevos registros de Clementina (Citrus clementina Hort. ex Tan.): Clemenverd y Nero. Comunidad Agraria 8: López-García, A., Boix, A., Herreo-Ortega, A., Iglesias, D.J., Muñoz-Sanz, J.V., Navarro, P., Salvador, A. and Talón M Nero, una variedad temprana de Clementino sin semillas. Calidad de la fruta, cualidades organolépticas y características agronómicas. Levante Agrícola 404:

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