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Jorge B. Retamales and Claudio Valdes

Bitter pit is the most important physiological disorders for apples in Chile. During the 1995–96 season, the predictive capacity of bitter pit through magnesium infiltration of the fruit in commercial orchards of three locations in South Central Chile: San Fernando (SF), Curico (CU), and San Javier (SJ) was established. Three orchards were chosen in each location and for each cultivar; fruit were collected 60, 40, and 20 days before commercial harvest. Fruit were infiltrated for 2 min with magnesium chloride at 0.05 M using vacuum levels of 500 or 100 mm Hg for `Granny Smith' and `Braeburn', respectively. The predictive capacity (correlation between predicted and effective bitter pit—after 90 days at 2°C + 10 days at 18°C) increased closer to harvest; with regards to location: SF > CU > SJ. Bitter pit-like symptoms, caused by Mg infiltration stabilized 16 days after infiltration. Bitter pit incidence was better predicted than severity. Bitter pit was better predicted for `Granny Smith' than for `Braeburn'.

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Eric J. Hanson and Jorge B. Retamales

`Bluecrop' highbush blueberries (Vaccinium corymbosum L.) received various N fertilizer treatments for 5 years. Treatments were evaluated by measuring berry yields and leaf N levels annually and bush size after 5 years. Nitrogen fertilizers increased yields and leaf N levels compared with nonfertilized controls. Split applications of urea (half applied at budbreak, half at petal fall) resulted in 10% higher yields than the same amount in a single application at budbreak. Urea and two controlled-release fertilizers (CRF) with different dissolution rates (3 to 4 months, 8 to 9 months) resulted in similar yields and leaf N levels when compared at the same rate of N. The dissolution rate of the CRF materials did not affect yields or leaf N levels.

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Jorge B. Retamales, Claudio Valdes, and Verónica Donoso

Bitter pit (BP) is the main physiological disorder of apples in Chile. Its incidence affects pre- and postharvest handling of the fruit and the profitability of this species. Since 1991, its control and prediction have been studied by this research team through field and laboratory trials. The BP incidence is linked to the fruit Ca concentration; however, fruit Ca analysis has not adequately predicted BP incidence in postharvest. Several authors have proposed Ca/Mg antagonism, which has been the basis to develop a predictive method through fruit Mg infiltration (IMG) 40 days before harvest. IMG has been massively used for two seasons in Chile, with 375 samples processed in 1997 and 1170 in 1998. The industry has been increasing its proportion of the samples processed, from 22% in 1997 to 71% in 1998. The most prominent varieties are `Granny Smith' (GS) > `Braeburn' (BR) > `Royal Gala' (RG) > `Red King Oregon' (RKO). The massive use of IMG has obtained predictive capacities (r 2 between BP predicted and BP after 3 months regular cold storage) of 0.8 for `Fuji'; 0.7 for GS, BR, and RG; and 0.58 for RKO. (This reduction in the predictive capacity with regards to the previous research under controlled conditions would, in part, be due to problems in obtaining fruit samples: non-uniform fruit size, inadequate sampling dates, diverse fruit numbers, etc.) Developments are underway to increase the geographical coverage of the service, the predictive capacity of the method for certain cultivars and productive areas and the number of samples processed.

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Jorge B. Retamales and James F. Hancock

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Jorge B. Retamales and Cerardo A. Accedondo

Calcium gradients were established in firm (`Bluecrop' and `Blueray') and soft (`Ivanhoe') highbush blueberry (Vaccinium corymbosum L.) fruits from a 7-year-old planting at La Union, southern Chile. Manual firmness measurements established that `Ivanhoe' fruit was softer than either `Bluecrop' or `Blueray'. In all varieties, Ca concentrations were: seed > pulp > epidermis; opposite trends were found for K+Mg/Ca ratios. Seed number and Ca concentration in the pulp were negatively correlated in `Bluecrop' and `Ivanhoe', but not in `Blueray'. In a related experiment, the response of `Bluecrop' to preharvest sprays of two calcium sources (chloride and nitrate) in four doses (0, 47.5, 35, or 190 g Ca/100 liters of water) was studied; dose and source interactions were not significant. Both calcium sources affected fruit Ca concentrations similarly;l calcium applications, either as nitrate or chloride, increased Ca significantly in epidermis and seed; the highest dose was required to raise significantly Ca concentrations in the pulp. K+Mg/Ca ratios in nitrate- or chloride-treated fruit were: pulp > seed > epidermis.

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Chad E. Finn, Jorge B. Retamales, Gustavo A. Lobos, and James F. Hancock

The cultivated strawberry of South America, the octoploid Fragaria chiloensis, has a long and interesting history. Although the origin of the species in Chile has not been completely determined, it may have been introduced from North America by birds. After making landfall in Chile, the species spread from the coast into the mountains eventually developing four biotypes. At least two native peoples, the Mapuche, between Rio Bío-Bío and south–central Chile, and the Picunche, between Rio Itata and Rio Bío-Bío, began the domestication process. Although white- and red-fruited forms were domesticated, the white form (likely because of its fruit size) may have been preferred because the red-fruited types are not mentioned as frequently in the literature. At the time of the Spanish invasion of Chile, F. chiloensis was widely grown in small garden plots. Under the Spanish rule, larger plantings, first of 1 to 2 ha and later of many hectares, were grown. As the Spanish continued their exploration and conquest of South America, they carried F. chiloensis with them up the western coast to Perú and Ecuador. For many years these scattered plantings were the source of fresh fruit for the burgeoning human populations. The cultivated F. ×ananassa was introduced in Chile ≈1830 but F. chiloensis was still preferentially grown. In the early 1900s, a large canning industry emerged serving hundreds of acres of F. chiloensis. By the 1950s, F. ×ananassa began to predominate and the rise in importance of the University of California and European-developed cultivars displaced much of the traditional F. chiloensis production. An increased awareness of this vast native Chilean genetic resource arose in the 1980s and 1990s. Scientists at the Universidad de Talca, associated with USDA-ARS Plant Exploration Office-sponsored trips to Chile, and with El Instituto de Investigaciones Agropecuarias–Cauquenes in Chile have collected and characterized germplasm that represents not only tremendous diversity, but captures many of the land races that have been developed. This germplasm has been used in small commercial plantings (0.1 to 0.3 ha) and in breeding programs to further develop F. chiloensis commercial cultivars. A small but vibrant community of small growers, particularly in Chile and Ecuador, produce the land races for commercial sale in local markets. Approximately 30 to 40 ha of open-field plantings are cultivated in Chile with yields averaging ≈3 to 4 tons/ha. The selected F. chiloensis genotypes and collected clones from the wild have served as a valuable source of germplasm in modern breeding programs and the development of new cultivars with the white color and aromatic flavor typical of some of the traditional selections well underway.

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Jorge B. Retamales, Peter D.S. Caligari, Basilio Carrasco, and Guillermo Saud

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Takashi Nishizawa, Sayuri Nagasawa, Yuko Mori, Yuko Kondo, Yuka Sasaki, Jorge B. Retamales, and Arturo Lavin

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Basilio Carrasco, Marcelo Garcés, Pamela Rojas, Guillermo Saud, Raúl Herrera, Jorge B. Retamales, and Peter D.S. Caligari

The chilean strawberry displays high fruit quality and tolerance to abiotic and biotic factors. Additionally, this species has a rich cultural history going back for at least several thousand years in association with aboriginal people activities and continues at a reduced level today. After its introduction to Europe during the 18th century, it formed an interspecific hybrid to become the maternal species of the commercial strawberry, Fragaria ×ananassa Duch. The objectives of the current investigation were to determine the level and patterns of partitioning of intersimple sequence repeat (ISSR) diversity. ISSR markers were used to assess the genetic diversity in 216 accessions of F. chiloensis, which represented the two botanical forms present in Chile [F. chiloensis ssp. chiloensis f. chiloensis and F. chiloensis ssp. chiloensis f. patagonica (L.) Duch.]. Our results showed high genetic diversity at the species level [polymorphic ISSR loci (P) = 89.6%, gene diversity (h) = 0.24 ± 0.17, Shannon's index (S) = 0.37 ± 0.24] and a lower genetic diversity in f. chiloensis than f. patagonica. The analysis of molecular variance (AMOVA) showed a moderate genetic differentiation among accessions (φst = 14.9%). No geographic patterns for ISSR diversity were observed. AMOVA, structure, and discriminant analysis indicated that accessions tend to group by botanical form. The impact of domestication on the genetic structure of chilean strawberry and its application to breeding and conservation are discussed.