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Antonio L. García, Jesús Gallego, Vicenta Fuentes, Nuria Nicolás, and Ramón Madrid

The effects of different levels of phosphorus fertilization and water provision on the mineral nutrition of two clonal rootstocks of Prunus were studied. Two-year-old Prunus seedlings, Hybrid GF677 (Prunus persica × Prunus amygdalus) (PH) and Pollizo Puebla de Soto 101 (Prunus insititia) (PI) were planted in an uncultivated calcareous soil (a Xeric torriorthent derived from marl) under greenhouse conditions. They were drip irrigated with subterranean water of slightly alkaline pH (7.63), EC 0.88 dS·m–1, with a low chloride and high sulphate content. The experiment lasted two annual cycles. In October of the second year the leaf nutrient concentration and dry weight of the total leaf weight were determined in four trees of each combination of rootstock × irrigation level × fertilization treatment. The nutritive state of these trees was analyzed by vector analysis. The results point to a highly significant influence of the rootstock nature on the leaf concentrations of most nutrients. Very low Zn and Cu concentrations were recorded on both rootstocks, for both irrigation levels and several fertilizing treatments. Vector analysis confirmed the Cu deficiency resulting from several of the fertilizing treatments and both irrigation levels in PH rootstocks.

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Carlos H. Crisosto, F. Gordon Mitchell, and Zhiguo Ju

The susceptibility to chilling injury (CI) or internal breakdown (IB) was evaluated in the most currently planted yellow- and white-flesh peach [Prunus persica (L.) Batsch] and nectarine [Prunus persica var. nectarine (L.) Batsch] and plum [Prunus salicina Lindel] cultivars from different breeding sources and fruit types. Cultivars were segregated into three categories (Cat. A, B, and C) according to their susceptibility to CI or IB symptoms (mealiness and flesh browning) when exposed to 0 °C or 5 °C storage temperatures. Cultivars in Cat. A did not develop any symptoms of CI after 5 weeks of storage at either temperature. Cultivars in Cat. B developed symptoms only when stored at 5 °C within 5 weeks of storage. Cultivars were classified in Cat. C when fruit developed CI symptoms at both storage temperatures within 5 weeks of storage. Most of the yellow- and white-flesh peach cultivars developed IB symptoms when stored at both storage temperatures (Cat. C). Most of the new nectarine cultivar introductions did not develop CI symptoms when stored at 0 °C or 5 °C after 5 weeks (Cat. A). Three out of six plum cultivars tested had CI symptoms within 5 weeks storage at 0 °C. However, all of the plum cultivars tested developed CI symptoms when stored at 5 °C (Cat. B). The importance of proper temperature management during postharvest handling was demonstrated.

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Dongyan Hu, Zuoshuang Zhang, Donglin Zhang, Qixiang Zhang, and Jianhua Li

Ornamental peach (Prunus persica (L.) Batsch) is a popular plant for urban landscapes and gardens. However, the genetic relationship among ornamental peach cultivars is unclear. In this report, a group of 51 ornamental peach taxa, originated from P. persica and P. davidiana (Carr.) Franch., has been studied using AFLPs. The samples were collected from China, Japan, and US. A total of 275 useful markers ranging in size from 75 to 500 base pairs were generated using six EcoRI/MseI AFLP primer pairs. Among them, 265 bands were polymorphic. Total markers for each taxon ranged from 90 to 140 with an average of 120. Two clades were apparent on the PAUP–UPGMA tree with P. davidiana forming an outgroup to P. persica, indicates that P. davidiana contributed less to the ornamental peach gene pools. Within P. persica clade, 18 out of 20 upright ornamental peach cultivars formed a clade, which indicated that cultivars with upright growth habit had close genetic relationship. Five dwarf cultivars were grouped to one clade, supported by 81% bootstrap value, indicating that they probably derived from a common gene pool. These results demonstrated that AFLP markers are powerful for determining genetic relationships in ornamental peach. The genetic relationships among ornamental cultivars established in this study could be useful in ornamental peach identification, conservation, and breeding.

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W.V. Welker and D.M. Glenn

Peach (Prunus persica L. Batsch) trees were grown for five growing seasons in uniform-sized vegetation-free areas arranged in three patterns within a tall fescue (Festuca arundinacea Schreb.) sod. Trees grown in a vegetation-free area arranged in a strip pattern grew better than trees grown either in the center or edge of a square. The distribution pattern of the vegetation-free area influenced growth during the first 4 years; however, at the end of 5 years, differences in canopy width and trunk cross-sectional area were minimal. Thus, there is much latitude in distributing the available vegetation-free area as orchard floor management practices dictate.

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Daniela Giovannini, D. Michael Glenn, Ralph Scorza, and W.V. Welker

Our objective was to evaluate the dry-matter partitioning between the roots and shoots of two genetically size-controlled peach [Prunus persica (L.) Batsch] types, dwarf and pillar, compared to a full-sized standard peach type. Compared to the pillar and standard types, the dwarf type had a reduced leaf: root ratio, less allocation of dry matter to woody tissue and more to leaf tissue. Genetically size-controlled peach trees have a smaller root system, but a lower leaf: root ratio and may require modified soil and water management techniques to ensure high productivity.

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T.G. Beckman, W.R. Okie, and A.P. Nyczepir

Clonally replicated peach seedlings [Prunus persica (L.) Batsch] of Lovell, Nemaguard, and four F1 selections of Lovell × Nemared were tested for field survival on a peach tree short life site. Rootstock families differed in growth, survival, and longevity. Genetic variation was similar to environmental variation for most families. Based on seedling within rootstock family, estimated broad-sense heritabilities for survival and longevity were high. The use of clonally replicated seedlings allowed the selection of apparently superior individuals from both Lovell and the other more short-lived rootstock families in a single screening.

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Osamu Arakawa and Joe M. Ogawa

The skin of `Elegant Lady' peach [Prunus persica (L.) Batsch.] fruit turned black when exposed to 100 ppm ferrous sulfate solution. This color change appeared on the red and the yellow portions of the fruit. Microscopy of the skin showed blue-black pigment distribution in epidermal and hypodermal tissues. Some epidermal and hypodermal cells discolored immediately when exposed to ferrous solutions, but many cells turned black later. Some cells with anthocyanin pigments did not discolor. Chromic acid showed that tannic substances were distributed in the epidermal and hypodermal cells, and they likely are the main factor in black discoloration of peach fruit exposed to solutions containing Fe.

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W.R. Okie, G.L. Reighard, T.G. Beckman, A.P. Nyczepir, C.C. Reilly, E.I. Zehr, W.C. Newall Jr., and D.W. Cain

Long-term field trials of a wide range of peach [Prunus persica (L.) Batsch] germplasm on two peach tree short-life (PTSL) sites revealed marked differences in survival among lines. Generally, cuttings and seedlings of a given line performed similarly, as did ungrafted seedlings and their counterparts grafted to a commercial cultivar. No apparent relationship existed between a line's chilling requirement and survival. B594520-9 survived best in Georgia and South Carolina, providing significantly greater longevity than Lovell, the standard rootstock for use on PTSL sites. B594520-9 is derived from root-knot-nematode-resistant parentage, and progeny of surviving seedlings have demonstrated root-knot resistance similar to Nemaguard seedlings.

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J.E. Epperson, M.C. Chien, and W.O. Mizelle Jr.

An analysis was conducted using time-series data to identify possible structural change in the farm-gate demand for South Atlantic fresh peaches [Prunus persica (L.) Batsch.]. Structural change was not found in the price-quantity relationship. However, a failing per capita consumption of South Atlantic fresh peaches was found to be associated with an increase in the per capita consumption of fresh fruits in general. Thus, measures such as promotion and advertising, uniform quality control, and cultivar development may increase the demand for South Atlantic fresh peaches.

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E.W. PAVEL and T.M. DEJONG

The fruit growth of three peach (Prunus persica (L.) Batsch cvs. `Spring Lady', `Flamecrest', `Cal Red') and two apple cultivars (Malus domestica Borkh. cvs. `Cox Orange', `Golden Delicious') was measured weekly during the 1988 growing period. Seasonal patterns of fruit relative growth rate calculated on a dry weight basis were very similar for both species. Changes in nonstructural carbohydrate composition of peach mesocarp and apple pericarp were correlated with the two physiological phases of sink-activity of the relative growth rates Changes in sucrose concentrations seemed to coincide with increasing dry matter accumulation for both species, even though fructose was a dominant sugar in apples.