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  • Author or Editor: José Chaparro x
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Abstract

Heterosis for embryo length was observed in interspecific crosses between the peach clones ‘Flordaking’ and FL 82–27, and ‘Nonpareil’ almond. No consistent differences in embryo length were observed in peach when selfing was compared to outcrossing to the unrelated peach selection FL 9-26C.

Open Access

Genetic interaction of the pillar (PI) and weeping (WE) growth habit genotypes was investigated in peach [Prunus persica (L.) Batsch]. Data from F2, BC1P1, and BC1P2 families showed that PI (brbr) was epistatic to the expression of WE (plpl). A unique growth habit not previously described in peach, and referred to as arching (AR), was recovered in the F2 family. Arching trees showed an upright phenotype similar to Brbr heterozygotes, but had a distinct curvature in the developing shoots. Progeny testing of AR trees revealed their genotype is Brbrplpl.

Free access

Citrus kinokuni ‘Mukaku kishu’ PI539530 and its progeny were studied to identify random amplified polymorphic DNA (RAPD) primers associated with seedlessness. Ninety-one F1 [(Robinson op) × C. kinokuni] individuals showed a 1:1 segregation ratio between seedless and seeded phenotypes with seedless as a single dominant gene. Bulked segregant analysis was used to identify markers associated with the seedless locus. Eighteen RAPD primers were mapped into a partial linkage group (≈55.8 cM length) with four RAPD primers flanking the seedless locus: OPAI11-0.8 at 8.7 cM, OPAJ19-1.0 at 8.4 cM, OPM06r-0.85 at 4.3 cM, and OPAJ04r-0.6 at 6.4 cM. The identification of molecular markers linked to C. kinokuni Fs seedless locus constitutes an important and major tool for citrus breeding and selection.

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The primary purpose of the three-way cooperative regional project involving the USDA, University of Georgia, and University of Florida, is to develop improved fresh-market peach cultivars for use in the moderate-chill areas of the southeastern United States. Since 1995, this project has concentrated on the development of non-melting flesh materials as an alternative to conventional melting-type cultivars. It is our belief that the slower softening, non-melting characteristic will allow growers to pick fruit several days later at a more mature stage, thus improving eating quality without sacrificing shipping ability. To date, this program has released three non-melting peach cultivars and is poised to release several more. Through our postharvest evaluations we have been able to demonstrate that these new releases and selections have equal, if not superior, firmness compared to current commercial melting-type cultivars, in combination with higher soluble solids and soluble solids/titratable acidity ratios. Compared to current commercial melting-type cultivars, the new non-melting releases and selections display superior red skin blush, fruit shape, and cropping ability. Moreover, they are of comparable size and have a significantly reduced incidence of split and shattered pits.

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`Gulfking' and `Gulfcrest' peaches are jointly released for grower trials by the U.S. Department of Agriculture, Agricultural Research Service, the Georgia Agricultural Experiment Station, and the Florida Agricultural Experiment Station. Trees of `Gulfking' and `Gulfcrest' produce an attractive, sweet-tasting, yellow and non-melting flesh fruit intended for the fresh fruit market. They are expected to produce fruit with tree-ripened aroma and taste while retaining firmness for longer shelf life than fruit from conventional melting-flesh cultivars. Trees of `Gulfking' reach full bloom most seasons in mid-February in lower southern Georgia and are estimated to require 350 chill units. We expect this new peach to be adapted in areas where `Flordaking' has been successfully grown. Fruit ripen 73 to 80 days from full bloom, typically in early May, usually with `Flordaking' in southern Georgia. The fruit are large, ranging from 105 to 130 grams. Commercially ripe fruit exhibit 80% to 90% red (with moderately fine darker red stripes) over a deep yellow to orange ground color. Fruit shape is round with a recessed tip. Pits are medium small and have little tendency to split even when crop loads are low. Trees of `Gulfcrest' are estimated to require 525 chill units. This is based on full bloom consistently occurring with `Sunfre' nectarine at Attapulgus, Ga. where full bloom occurs most seasons in early-March. Fruit ripen 62 to 75 days from full bloom, typically in early to mid-May, usually a few days after `Flordacrest' in southern Georgia. The fruit are medium-large, averaging about 105 g. Commercially ripe fruit exhibit 90% to 95% red over a deep yellow to orange ground color. Fruit shape is round with a recessed tip. Pits are medium small and have little tendency to split even when crop loads are low.

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Tree size and branching control has gained importance as labor and pruning costs have increased. In addition, the occurrence of blind nodes is a critical factor that affects peach tree architecture and productivity in subtropical climates. Seven backcross families segregating for branching and blind nodes were developed using ‘Flordaguard’ peach × P. kansuensis or ‘Tardy Nonpareil’ almond F1s backcrossed to ‘AP00-30WBS’, ‘UFSharp’, or ‘UF97-47’ peach selections and evaluated for branching index and blind node frequency during the winters of 2010 and 2011. P. kansuensis backcrosses presented increased branching and lower blind node incidence, whereas almond backcrosses presented less branching and higher blind node incidence, resembling the P. kansuensis and almond F1 parents, respectively. There was also broad variability for branching and blind nodes within the P. kansuensis and ‘Tardy Nonpareil’ almond backcross families influenced by the peach parents that were used to generate the backcross populations. The moderate heritability and year-to-year correlation for these traits indicate that they are affected by the environment, but selection for reduced branching and lower blind node incidence is feasible.

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Abstract

Thirty-six peach and nectarine [Prunus persica (L.) Batsch] cultivars were evaluated for flower bud number (flower buds/node) over 2 years. Cultivar, year, and year × cultivar effects were highly significant. Cultivars released from California breeding programs generally had fewer flower buds than those from eastern U.S. programs, suggesting that selection for cropping consistency in eastern breeding programs has resulted in release of cultivars with many flower buds. Variance component estimates from this study and from 2 years of sampling trees of ‘Redhaven’ indicates that sampling over years and increasing the number of shoots sampled per tree is warranted. Variability among trees within cultivar was low.

Open Access

Inheritance of the blood-flesh (red-violet mesocarp) trait in peach [Prunus persica (L.) Batsch.] was investigated in S1, S2, F1, F2, F3, BC1P1, and BC1P2 families derived from `Harrow Blood', a clone showing anthocyanin accumulation in fruit about 45-50 days after anthesis. This trait invariably was associated with the red midrib leaf phenotype in `Harrow Blood', an S1 family from `Harrow Blood', and in green leaf F2 progeny derived from `Harrow Blood' × `Rutgers Red Leaf 2n'. A segregation ratio of about 3 blood-flesh : 1 wild-type was observed in the S1 family, but F1 progeny produced only wild-type fruit. Examination of F2 progeny segregating for the blood-flesh and red leaf traits revealed no evidence of epistasis. Based on segregation ratios in F1, F2, F3, BC1P1, and BC1P2 families from this cross, the F1 family from `Contender × (`Harrow Blood' × `Rutgers Red Leaf 2n'), and six additional F1 families from crosses between `Harrow Blood' and green leaf clones with wild-type fruit, we propose that blood-flesh is controlled by one gene, designated bf (blood-flesh). The blood-flesh phenotype was associated with reduced tree height in S1 and F2 progeny derived from `Harrow Blood'. Segregation for leaf blade color deviated significantly (P = 0.05) from the expected 3 red : 1 green ratio in six of the F2 families derived from selfing seven F1 trees from `Harrow Blood' × `Rutgers Red Leaf 2n'.

Free access