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David H. Byrne and Unaroj Boonprakob

December is 62 °F (16.7 °C) and of January is 59 °F (15 °C)]. The peach selections are adapted in areas where ‘EarliGrande’ ( Bowen, 1980 ) and ‘TropicBeauty’ can be grown commercially. These low-chill regions normally receive less than 200 chilling units

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David H. Byrne and Natalie Anderson

‘TexFirst’ is being released by Texas A&M University to provide a low-chilling commercially acceptable peach that ripens ≈1 week before ‘Flordaking’. This attractive, yellow-flesh peach ripens in late April to mid-May in the low and medium chill

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Todd W. Wert, Jeffrey G. Williamson, José X. Chaparro, E. Paul Miller and Robert E. Rouse

°24′36″W). The chilling hours (hours below 7.2 °C) accumulated at the three sites during the winter of 2004 to 2005 were 402 (north-central Florida), 162 (central Florida) and 125 (southwest Florida). Four low-chill peach cultivars [Flordaglo (150 cu

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Todd W. Wert, Jeffrey G. Williamson, Jose X. Chaparro, E. Paul Miller and Robert E. Rouse

The production of temperate zone fruit crops in subtropical environments has increased significantly in the last 30 years. Low-chill cultivars of apple, blueberries, plum, and peach have been developed by several breeding programs and are in

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Todd W. Wert, Jeffrey G. Williamson, Jose X. Chaparro, E. Paul Miller and Robert E. Rouse

failure, blind nodes appear to be incited by high temperatures during bud development ( Boonprakob and Byrne, 1990 ). The objective of this study was to evaluate the performance of four low-chill peach cultivars at three locations in Florida with respect

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David H. Byrne and Terry A. Bacon

A computer program was developed to calculate the percent contribution of the founding parents for any given peach or nectarine (Prunus persica) cultivar. The founding parents used most frequently for three low-chill (0 to 500 chill units) peach and nectarine breeding programs (Florida and Pelotas and Campinas, Brazil) were determined. The Florida program used several low-chill honey type peaches (`Hawaiian', `Okinawa') as a source of low chilling and then did extensive crossing with higher quality cultivars developed mainly in the northeastern United States. About 50% of the background of the Brazilian peach releases consists of local selections that were originally brought by the Portuguese explorers. Although each of the Brazilian programs used local peach materials, the local peaches used by each program are different. In addition, the program at Pelotas used germplasm from the Georgia–Florida and New Jersey breeding programs and the Campinas program used `Jewel' (honey peach) and several Florida nectarines (`Sunlite', `Sunred') in their development work. The founding parents among these three programs, although there is some common parentage, are different, and the intercrossing of materials from the various programs would be a useful approach to create more diversity in this germplasm.

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Peter Allan, Alan George and Robert Nissen

Low chill `Flordaprince' peach trees were grown in subtropical Australia, either following paclobutrazol application to dwarf the trees, or extra nitrogen to invigorate them. Fruits were thinned uniformly. Paclobutrazol significantly reduced the competing spring shoot growth and gave earlier maturity of larger, better quality fruits. It reduced the spring, but increased the autumn root flush. Stage 2 of fruit growth was slightly longer in vigorous trees, resulting in delayed seed growth and greater dry mass of the embryos. Starch reserves were greatest in the roots, followed by the trunk, shoots and leaves. The reserves were lowest during the second half of fruit development, but rose again after the end of shoot extension growth. Leaf N, P, and K levels decreased through the season while Ca and Mg increased. There were significantly lower K and higher Ca and Mg levels in dwarfed trees.

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Jaime Javier Martínez-Téllez

Almond production is restricted to areas with at least 300 chill units. Selection of plants with lower chilling requirements is a priority in our area. The progenies of two low chilling cvs. `Rané' and `Constantini' and one of medium chilling cv. `Cavaliera' were chosen for this study. The selected trees were open pollinated and 100 seeds of each variety were planted on individual pots after three week stratification. Three groups were formed according to the speed of germination and transplanted to the nursery. The date of blooming of each individual was recorded. A positive correlation was found between time of blooming of the progenitor and that of the progeny regardless of the origin. On the descendence of `Cavaliera', a positive correlation between speed of germination and bloom date was observed. However on `Constantini' and `Rané' progenies, the same correlation had no significance. `Cavaliera' produced a 45% of low chilling requirement descendants, `Rané' had 67% and `Constantini' had the higher ability to transmit the low chilling character with a 78% of the progeny with that trait.

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Paul M. Lyrene

Breeding to adapt temperate-zone fruit to subtropical production areas has been a formidable objective because so many different characteristics have to be changed, most of which are controlled by many genes. Recurrent selection is the only breeding method that can accomplish the required wholesale reorganization of the physiology of the plant. The principles of recurrent selection, developed and tested using short-generation organisms like fruit flies, rats, and maize, have been applied to the development of low-chill highbush blueberry (V. corymbosum L.) and peach [Prunus persica (L.) Batsch.] cultivars for northern and central Florida. These principles include using many parents per generation of crosses, minimizing the time between cycles of selection, and selecting simultaneously for all heritable traits that are important in the final product, with traits of highest economic importance and highest heritability being given the highest weight in selecting parents. Many characteristics changed during the breeding of low-latitude peach and highbush blueberry cultivars, including chill requirement, photoperiod response, resistance to various disease and insect pests, fruit chemistry, and growth patterns during a long growing season.

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Raúl Leonel Grijalva-Contreras, Arturo López-Carbajal, Adán Fimbres-Fontes, Cristobal Navarro-Ainza, Rogelio Juárez-González and Fabián Robles-Contreras

Apricot production in México is limited; actually, the area devoted to this crop is ≈880 ha, from which 230 ha are established in Sonora State. The main cultivar is `Canino'. The fruit yield ranges from 15 top 20 t·ha-1. The present study tested 20 low-chilling (300-400 chill hours) requirements of apricot selections; `Nemaguard' was the rootstock used. On the fourth production year, from the 20 apricot selections tested, 7-23, 1-81, and 15-1 yielded 31.8, 20.2, and 15.5 t·ha-1, respectively. all of these selections showed higher yields than `Canino' (14.6 t·ha-1). The fruit of these apricot selections ripened by mid-May, exhibiting a similar fruit quality (size, flavor, color, and °Brix) in all the tested selections. We have not recorded any important insect pests or diseases during this trial.