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  • Author or Editor: Jose 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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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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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.

Free access

`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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Prunus phylogeny has been extensively studied using chloroplast DNA (cpDNA) sequences. Chloroplast DNA has a slow rate of evolution, which is beneficial to determine species relationships at a deeper level. The chloroplast-based phylogenies have a limitation due to the transfer of this organelle by interspecific hybridization. This creates difficulties when studying species relationships. Interspecific hybrids in Prunus occur naturally and have been reported, which creates a problem when using cpDNA-based phylogenies to determine species relationships. The main goal of this project was to identify nuclear gene regions that could provide an improved phylogenetic signal at the species level in Prunus. A total of 11 species in Prunus and within section Prunocerasus were used. Two peach (Prunus persica) haploids were used to test the reliability of the molecular markers developed in this project to amplify single-copy genes. A total of 33 major genes associated with vernalization response, 16 with tree architecture, and 3 with isozymes, were tested. Similarly, 41 simple sequence repeat (SSR) markers, seven cpDNA regions, and the internal transcribed spacer (ITS) region, were used. Multiple gene regions were identified and provided the greatest number of characters, greatest variability, and improved phylogenetic signal at the species level in Prunus section Prunocerasus. Out of those, trnH-psbA, PGI, MAX4, AXR1, LFY, PHYE, and VRN1 are recommended for a phylogenetic analysis with a larger number of taxa. The use of potentially informative characters (PICS) as a measure of how informative a region will be for phylogenetic analyses has been previously reported beneficial in cpDNA regions and it clearly was important in this research. This will allow selecting the region(s), which can be used in phylogenetic studies with higher number of taxa.

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Abstract

Embryos from five seedless Vitis vinifera L. clones were cultured in ovulo 6 weeks after pollination with V. rotundifolia Michx. A total of 19 hybrid seedlings from about 16,000 pollinations were identified using leaf morphology and starch-gel electrophoresis. Efforts to obtain more V. vinifera/V. rotundifolia hybrids carrying the seedless gene(s) using embryo rescue should be increased and these plants could act as breeding stock to introduce the seedless gene(s) from V. vinifera into V. rotundifolia.

Open Access

Trees without excessive branching are desirable for the reduction of pruning costs. Genetic diversity for less twiggy genotypes exists in peach and a branching index was developed for evaluation and selection of genotypes with reduced branching. The index is based on the number of total first-order branches and the number of second-order, third-order, and fourth-order branches measured on three randomly selected first-order branches. Index values were highly correlated (r 2 ≈0.7) with the total number of branches over two growing seasons and served as a good predictor of branching patterns observed in the third growing season. Thus, the developed branching index is a useful tool in peach breeding, allowing for the early selection of trees with more desirable tree architecture.

Free access