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Two F1 hybrid Prunus rootstocks, K62-68 and P101-41, developed from a cross of `Lovell' [susceptible to both Meloidogyne incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood] and `Nemared' (resistant to both root-knot nematode species), were selfed to produce two F2 seedling populations. Vegetative propagation by herbaceous stem cuttings was used to produce four or eight self-rooted plants of each F2 seedling for treatment replications. Eggs of M. incognita and M. javanica were inoculated into the potted media where plants were transplanted, and plants were harvested and roots examined for signs and symptoms associated with root-knot nematode infection ≈120 days later. Segregation ratios in both F2 families suggested that resistance to M. incognita in `Nemared' is controlled by two dominant genes (Mi and Mij) and that to M. javanica by a single dominant gene (Mij). Thus, Mij conveys resistance to both M. incognita and M. javanica.

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Fruit trees grown in soils contaminated with lead arsenate (PbHAsO4) pesticide residues are subject to arsenic (As) phytotoxicity, a condition that may be exacerbated by use of phosphate fertilizers. A potted soil experiment was conducted to examine the influence of phosphate fertilizer on accumulation of As and lead (Pb) in apricot (Prunus armeniaca) seedlings grown in a lead arsenate-contaminated Burch loam coil. Treatments were fertilizer source (mono-ammonium phosphate [MAP], ammonium hydrogen sulfate [AHS]) and rate (0, 8.7, 17.4, and 26.1 -mmol/liter), and presence/absence of lead, arsenate contamination (231 -mg/kg coil). Plant biomass accumulation was reduced by lead arsenate presence and by high fertilizer rates, the latter due to soil salinization. Phytoaccumulation of As was enhanced by lead arsenate presence and by increasing MAP rate but was not influenced by AHS rate, salinity, or acidity of soil. Phytoaccumulation of Pb was enhanced by lead arsenate presence but was not influenced by fertilizer treatment.

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Abstract

Deep supercooling in Prunus flower buds was related to vascular development. The continuity of the xylem was monitored by following the movement of a water-soluble dye. Dye was translocated into the primordia of 3 Prunus species which do not supercool, but it was not observed to move into the primordia of 11 species which avoid freezing injury by deep supercooling. Dye uptake may provide a simple and inexpensive technique to screen for bud supercooling.

Open Access

The influence of the species in spring frost sensibility was determined for the Prunus species peach (P. persica (L.) Batsch), sweet cherry (P. avium L.), almond (P. dulcis (Mill.) Webb/P. amygdalus Batsch), japanese plum (P. salicina Lindl.), and blackthorn (P. spinosa L.). The confidence intervals for lethal temperatures of 10% (LT10) and 90% (LT90) bud injury were also determined. In 2000 and 2001, seven frost treatments were made for each one of the phenological stages comprised between B (first swell) and I (jacket split) in two cultivars per each species. The relationships between frost temperature and the proportion of frost damaged buds for each cultivar, year, and phenological stage were adjusted to linear regression models. The 95% confidence intervals were also calculated. The spring frost hardiness order of the species, from the least to most hardy, was as follows: sweet cherry, almond, peach, japanese plum, and blackthorn. Despite the highly homogeneous nature of the frost and bud characteristics, the temperature range for a given injury degree was quite broad, since the confidence interval's breadth for LT10 was as high as about 3 °C and as high as about 6 °C for LT90. Consequently, when critical temperatures are used in making decisions as to when to begin active frost protection, a prudent measure would be to take the temperature references from the upper limits in the confidence intervals.

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Evergreen genotypes of peach [Prunus persica (L.) Batsch] have been identified in Mexico, where terminal growth on evergreen trees is continuous under favorable environmental conditions. This evergreen trait in peach is controlled by one single gene (evg), and this evergreen condition is homozygous recessive. Four dominant AFLP markers, EAT/MCAC, ETT/MCCA2, EAT/MCTA, and ETT/MACC, were found to be tightly linked to the evg locus at 1 cM, 4.6 cM, 5.8 cM, and 11 cM, respectively. All four markers were sequenced and identified. A peach BAC library was constructed by using the pBeloBAC11 vector for building the physical map for the evg gene. This library represents four times the coverage of the peach genome with the average insert size of 50 to 70 kb. The EAT/MCAC AFLP marker fragment was used for screening the peach BAC library. A single BAC clone, 18F12, was confirmed to contain this fragment. The final BAC contig for this evg gene region and the potential homology between peach and Arabidopsis thaliana will be presented and discussed.

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During the past several years, we have been interested in genes and gene-products involved in various aspects of ripening and maturation in peach (Prunus persica) fruit. The ethylene biosynthetic and signal transduction pathways are of particular interest due to the role of this hormone in such processes. Recently, we isolated a cDNA encoding a homologue of the ethylene receptor ETR1 from a near fully ripe (20–60N) peach fruit cDNA library. This cDNA clone, PpETR1, is nearly 2300 bp in length, with a 5' untranslated region of 268 bp, a 3' untranslated region of 150 bp, and an ORF of 1881 bp, encoding a protein of 70 kDa. The cDNA is most closely related to an ETR1 homologue from apple (Malus domestica), i.e., 95% identity at the amino acid level, but shows considerable similarity to Arabidopsis thaliana ETR1, as well. A comparison of the similarity among cloned ETR1 genes from a range of plant species will be presented.

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Most sweet cherry (Prunus avium L.) cultivars grown commercially in the Pacific Northwest U.S. are susceptible to powdery mildew caused by the fungus Podosphaera clandestina (Wall.:Fr.) Lev. The disease is prevalent in the irrigated arid region east of the Cascade Mountains in Washington State. Little is known about genetic resistance to powdery mildew in sweet cherry, although a selection (`PMR-1') was identified at the Washington State Unive. Irrigated Agriculture Research and Extension Center that exhibits apparent foliar immunity to the disease. The objective of this research was to characterize the inheritance of powdery mildew resistance from `PMR-1'. Reciprocal crosses between `PMR-1' and three high-quality, widely-grown susceptible cultivars (`Bing', `Rainier', and ëVaní) were made to generate segregating progenies for determining the mode of inheritance of `PMR-1' resistance. Progenies were screened for susceptibility to powdery mildew colonization using a laboratory leaf disk assay. Assay results were verified by natural spread of powdery mildew among the progeny seedlings in a greenhouse and later by placement among infected trees in a cherry orchard. Progenies from these crosses were not significantly different (P > 0.05) when tested for a 1:1 resistant to susceptible segregation ratio, indicating that `PMR-1' resistance is conferred by a single gene, which we propose to designate as PMR-1.

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New Prunus rootstocks and selections were evaluated for their reaction to Meloidogyne arenaria (Neal) Chitwood, M. incognita (Kofoid & White Chitwood), or M. javanica (Treub) Chitwood. Most of the clones were peach-almond hybrids (P-AHs) [P. persica (L.) Batsch × P. dulcis (Mill.) D.A. Webb] or plums of Spanish and French origin. In a first experiment, the P-AH Hansen 2-168 and plums GF-31 (P. cerasifera Ehr.) and GF 8-1 (P. cerasifera × P. munsoniana Weigth et Hedr.) were highly resistant to the mixture of five isolates of M. javanica. The P-AHs Barrier and Titan × Nemared were resistant and moderately resistant, respectively; GF-677, MB 3-13, MB 2-2, and MB 2-6 were susceptible. In the second and third experiment, the plums P 1079, P 2175, the hybrids Afgano (P. dasycarpa Ehrh.), G × N No 22, and G × N No 15, both P-AHs, and Nemared peach were highly resistant to mixtures of five isolates of M. incognita or M. arenaria. The plums P 2980 (P. cerasifera) and GF 8-1 tested against either root-knot species were also highly resistant. Cachirulo × (G × N No 9), a P-AH, showed less resistance to M. arenaria than to M. incognita. Montclar (P. persica) and the P-AHs Torrents AC and GF-677 were susceptible to both species.

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Water potential at soil-root interface (WPs-r) appears to be a good indicator of soil water availability to the plants. However, it is not easy to measure it routinely. Plant water status is more convenient to manage from bulk soil water potential (WPsoil) determination if a good relationship between WPsoil and WPs-r can be established. In order to elucidate this relationship in different substrates, three soil mixes: Mix-1) composted bark, peat, sand; Mix-2) peat, bark, sand, compost; and Mix-3) peat, sawdust, sand, were used with Prunus × cistena. Two-year-old field grown plants were placed in a greenhouse. After soil water was depleted to different levels, WPsoi1, xylem water potential (WPxylem). transpir-ation as well as stomatal conductance were measured using a portable gas exchange system. WPs-r was calculated from these measured data. Plants grown in Mix-2 kept higher WPs-r until WPsoil decreased to -24 KPa, while WPs-r in the plants grown in Mix-1 began to decrease at -5 KPa of WPsoil. Mix-3 showed a medium critical WPsoil for WPs-r to decrease. Since there was a better availab-ilty of soil water to the plants, plants in Mix-2 also showed higher WPxylem. Dynamic analysis showed that plants in Mix-2 kept better plant water status mainly by avoiding water stress. Plants in Mix-3 also avoided water stress, but it was, at least in part, attributed to less leaf area

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The term “cherry” identifies a group of species belonging to the genus Prunus within the family Rosaceae that is native to Europe and Western Asia ( Stéger-Máté, 2012 ). Sweet cherry ( Prunus avium L.), the most cultivated species, is grown for

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