Breeding for Early Bearing in Olive Used As a Control Are Reported
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HORTSCIENCE 42(3):499–502. 2007. efficiency of a comparative field trial includ- ing 15 selections, from the previously cited seedling progenies, and their three genitors Breeding for Early Bearing in Olive used as a control are reported. Comparison Lorenzo Leo´n1 and Rau´l de la Rosa with the previous results of the corresponding ´ seedling plants is also presented to define IFAPA Centro Alameda del Obispo, CICE, Junta de Andalucıa, Avda. criteria for early selection. Mene´ndez Pidal, s/n, Apdo. 3092, E-14080, Co´rdoba, Spain Diego Barranco and Luis Rallo Material and Methods Departamento de Agronomı´a, Universidad de Co´rdoba, Campus de Plant material. The selections evaluated Rabanales, Edificio Celestino Mutis, Carretera Madrid-Ca´diz, km 396, in this work come from the crosses and E-14014, Co´rdoba, Spain selfings, in the nine possible combinations of ‘Arbequina’, ‘Frantoio’, and ‘Picual’ olive Additional index words. cross-breeding, Olea europaea, vigor, yield efficiency cultivars carried out in 1992 and 1993. Seed- Abstract. The initial results of a comparative field trial of the first 15 selections of the olive lings obtained were subjected to a forcing (Olea europaea L.) breeding program of Cordoba, Spain, are presented. These selections growth protocol including germination of came from crosses among ‘Arbequina’, ‘Frantoio’, and ‘Picual’ that were also included seeds, and greenhouse and field growth as in the trial as controls. The trial was planted in July 2001 in a randomized block design described by Santos-Antunes et al. (2005). with 16 replications and was systematically evaluated for earliness of bearing, vigor, After three harvest seasons, 15 genotypes crop, and yield efficiency from 2001 to 2005. Significant differences among selections were selected from the initial population were found for all characters measured. A greater proportion of early-bearing genotypes mainly on the basis of their early crop (short than in previous cultivar collections were found, whereas mean accumulated yield was juvenile period) and high oil content, some of similar to former evaluations. Therefore, the shorter unproductive period obtained in them also presenting outstanding values for this work seems to indicate that the selection of seedlings for a short juvenile period has other agronomic traits of interest (Leo´n et al., provided a shorter unproductive period of the subsequent new cultivars. No correlation 2005). Vegetative propagation of those 15 between vigor at the seedling stage and vigor in the corresponding adult vegetative selected genotypes and the three genitors, propagated selection was found. If the data presented here are confirmed further, some used as a control, was carried out by semi- early-bearing cultivars could be suggested as new olive cultivars, the first obtained by hardwood stem cuttings in Spring 2000. cross-breeding in Spain. Additionally, some of them also show a low vigor and could be Propagated trees were planted in an open adapted to high-density hedgerow orchards. field in July 2001 at 6 · 5-m spacing in a randomized block design with 16 replications and one tree per elementary plot. However, the design was unbalanced after the second Olive plant material cultivated in all the olive-producing countries based in intraspe- year because of losses resulting from rodent Mediterranean areas, including Spain, is cific cross-breeding between cultivars of damage (Table 1). Trees were trained as characterized by the abundance of very old known merit aiming at combining the good single-trunk vase, with three to four main cultivars restricted to specific areas where qualities of the genitors in some of the geno- branches, and minimal pruning was carried they originally appeared (Barranco and Rallo, types of the progenies. Classic breeding pro- out to allow early bearing. Standard cultural 2000). The origin of olive domestication and gramsbycrossingandselectioninthe practices were followed, including irrigation growing has been explained by empirical progenies are reported in Turkey (Arsel and supply by in-line drips to avoid water stress selection of individuals for greater fruit size Cirik, 1994), Tunisia (Trigui, 1996), Greece of plants. and oil yield content within wild olive pop- (Pritsa et al., 2003), Israel (Lavee et al., 1999, Traits evaluated. In the initial seedling ulations and subsequent vegetative propa- 2003), and Italy (Bellini et al., 2002a; Fonta- population, genotypes producing flowers gation, about 2800 BC intheMiddleEast nazza et al., 1998). An attempt to select for and, consequently, fruit were identified as (Baldoni et al., 2006). This procedure, quality oil production in feral olive populations reaching the adult phase during the first years repeated in the traditional areas of cultivation, is also ongoing in Australia (Sedgley, 2004). after planting (Santos-Antunes et al., 2005). determines the current distribution of cultivars. However, in contrast to other fruit trees, very Height and trunk diameter before the begin- This situation is changing in the last few few new breed cultivars have been reported in ning of each growing season, and fruit and years, however, because many cultivars are olive (Bellini et al., 2002b; Brooks and Olmo, oil yield of the individual seedlings in the unsuitable for a sustainable modern olive 1997; Fontanazza et al., 1998; Lavee, 1978; first three harvest seasons were recorded industry. As a consequence, some of the most Lavee et al., 1986, 1999, 2003, 2004). (Leo´n et al., 2004b). important cultivars have spread outside their In Spain, an olive breeding program was In the comparative field trial orchard original area, such as ‘Picual’ and ‘Arbequina’ initiated in 1992 in Cordoba aimed at super- containing the 15 selections and the three in Spain (Consejerı´a de Agricultura y Pesca, seding the main cultivars in use (Rallo, 1995). genitors, plants were systematically evalu- 2003) or ‘Leccino’ and ‘Frantoio’ in Italy Earliness of bearing and oil productivity were ated for earliness of bearing, vigor, crop, and (Cimato, 1998). Nevertheless, reports on com- two of the main objectives of this breeding yield efficiency in the 4 years after planting, parative field trials of olive cultivars from program. In olive, productivity has special from 2001 to 2005. Height and trunk diameter different origins are very scarce in all Medi- interest for breeding because most olive prior the beginning of each growing season terranean countries. At the same time, the need cultivars were selected for extensive or tradi- were recorded. In the last year (Feb. 2005), for more suitable cultivars prompted the devel- tional dry land systems of production. There- canopy height and width (measured east–west opment of olive breeding programs in the main fore, the exploitation of the genetic potential and north–south) were also recorded, and for productivity at intensive growing could be canopy surface and volume were calculated still very limited (Lavee, 1990). The forced from these measurements (Del Rı´o et al., Received for publication 4 Jan. 2007. Accepted for growth protocol to shorten the juvenile period 2005a). Trees were harvested as described publication 24 Feb. 2007. and the results of the agronomic evaluation of for the initial seedling population, and fruit This work has been supported in part by project RTA2005-00031-C02-01, National Institute of seedling progenies performed in this breeding and oil yield of individual trees were recorded Agricultural Research, Ministry of Education and program have already been reported (Leo´n in 2003–2004, 2004–2005, and 2005–2006. Culture, Spain. et al., 2004a, b; Santos–Antunes et al., 2005). Yield efficiency indexes were calculated as 1To whom reprint requests should be addressed; In this work, the results concerning earli- the ratios between cumulative yield (fruit e-mail [email protected] ness of bearing and initial crop and yield yield, oil yield) and vigor measurements HORTSCIENCE VOL. 42(3) JUNE 2007 499 recorded in the last year (trunk cross-sectional Table 1. Number of bearing trees by year and average unproductive period of the evaluated cultivars and area, canopy area, and canopy volume). selections. Data analysis. In the comparative field Planted Surviving Bearing trees Average trial, average unproductive period was cal- Genotype Origin trees (2001) trees 2003 2004 2005 unproductive period (y) culated by counting the number of bearing Arbequina (A) — 16 15 14 15 15 2.1 trees each year from 2003 to 2005 (2–4 years Frantoio (F) — 16 15 2 10 15 3.2 after planting). Agronomic data recorded Picual (P) — 16 15 12 15 15 2.2 (vigor, cumulated crop, and yield efficiency UC-I 1-19 F · P 16 15 — 6 15 3.6 indexes) were subjected to analysis of vari- UC-I 2-68 P · A 16 16 11 16 16 2.3 ance to test the effect of genotypes, and UC-I 4-62 F · P 16 13 6 13 13 2.5 separation of the means at P < 0.05 were UC-I 5-44 P · A 16 16 14 16 16 2.1 UC-I 6-9 A · P 16 14 9 14 14 2.4 computed. Correlations between vigor and UC-I 7-8 A · P 16 14 9 14 14 2.4 yield measurements obtained in the compar- UC-I 7-34 P · A 16 13 12 13 13 2.1 ative field trial orchard and the initial seed- UC-I 7-60 F · P 16 15 4 14 15 2.8 ling population were also calculated. UC-I 8-7 P · A 16 14 7 14 14 2.5 UC-I 8-20 P · A 16 13 9 13 13 2.3 Results and Discussion UC-I 9-67 A · P 16 16 14 16 16 2.1 UC-I 10-30 F · P 16 16 3 15 16 2.9 Earliness of bearing. The first significant UC-I 10-54 A · P 16 14 10 14 14 2.3 bearing occurred 2 years after planting.