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Joseph C. Goffreda

The stony hard gene in peach is a recessive gene which increases fruit firmness and shelf-life. Five progenies segregating for the stony hard trait were scored for several ripening-related characteristics. Fruit from stony hard segregants produced little or no ethylene, had lower respiration rates, and tended to ripen later than `normal' fruit. Stony hard fruit also had a lower percentage red overcolor in three of the five progenies. Stony hard fruit, harvested when firm-ripe, maintained their firmness after five days storage at 20°C. Firmness of stony hard fruit decreased significantly if the fruit were sprayed with ethephon (2-chloroethylphosphonic acid) at 250 ppm prior to storage. Fruit firmness of `normal' freestone or clingstone varieties was not significantly affected by the application of ethephon. The conversion of ethylene precursors to ethylene in stony hard fruit will also be discussed.

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Joseph C. Goffreda and Anita Scopel

Immature embryos or cotyledons were cultured at three stages of development (PF1=3, 30-60, or 100) from two unrelated apricot genotypes. Explants were cultured on MS medium supplemented with 2.4-D (0 or 1 μM) and either BA or TDZ (0, 0.5. 5.0 or 20 μM). Stage 1 embryos cultured on MS media without hormones tended to form embryoid-like structures. Regeneration was highest with stage 2 cotyledons on media containing between 5-20 μM TDZ and 1.0 μM 2.4-D; shoot morphology was abnormal at the highest level of TDZ. In another factorial experiment, stage 2 cotyledons were cultured on media containing TDZ (six levels, 0 to 20 μM) in combination with either 2.4-D (0 or 1 μM) or IBA (0, 1, or 5 μM), Regeneration of normal shoots was highest on the medium containing 5 μM IBA and no TDZ. Regenerated shoots were transferred to woody plant medium (WP) containing 3% sucrose and supplemented with 6 μM 2iP and 2.2 μM BA to promote stem elongation. Shoots were transferred to WP media supplemented with NAA or IBA to induce rooting. Culture on media containing 10 μM IBA in total darkness induced rooting in less than two weeks.

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Edward F. Durner and Joseph C. Goffreda

Three peach [Prunus persica (L.) Batsch] rootstock plantings were monitored for date and rate of bloom during Spring 1989 and 1990 to determine if the time of scion bloom on different rootstocks is determined by the date of initiation of bud growth in the spring or by the duration of a particular bud stage. Included were a 1984 planting of `Redhaven' on eight rootstocks, a 1984 planting of `Rio-Oso-Gem' and `Loring', each on 11 rootstocks, and a 1986 planting of `Encore' on 18 rootstocks. The effect of rootstock on bud phenology was consistent within scion cultivar over two extremely different spring temperature profiles. In `Redhaven' and `Rio-Oso-Gem', rootstocks affected the dates but not the rates of bud development. Rootstocks affected both the dates and rates of `Loring' and `Encore' bud development. No consistent effect of rootstock on yield could be associated with delayed bud development in `Rio-Oso-Gem', `Redhaven', or `Loring'; however, delayed bud development of `Encore' on `Okinawa' x `Cardinal' and 62325 resulted in enhanced yield following spring frosts.

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Thomas J. Molnar, Joseph C. Goffreda, and C. Reed Funk

Anisogramma anomala (Peck) E. Müller is the causal agent of the disease eastern filbert blight (EFB) of hazelnuts (Corylus spp.). Little is known of its genetic diversity and pathogenic variation. Most sources of host resistance have been identified in the Pacific Northwest, a region outside the native range of A. anomala believed to have limited diversity of the fungus due to a long history of quarantine and its relatively recent inadvertent introduction. In an attempt to investigate the pathogenic variation of A. anomala, 12 hazelnut genotypes that showed complete resistance in Oregon were inoculated with 12 isolates collected from across its native range. At the conclusion of the study, ‘Grand Traverse,’ ‘Ratoli’, OSU 541.147, OSU 495.072, and OSU 526.041 remained free of disease. ‘Closca Molla’, OSU 759.007, and OSU 587.044 were infected by most isolates. ‘Gasaway’ was infected by the Michigan isolate, which was also the only one to infect its offspring ‘Zimmerman’, although the lesion lacked sporulating stromata. Interestingly, ‘VR20–11’, another offspring of ‘Gasaway’, was infected by isolates from New Jersey, Minnesota, and Michigan. The Michigan isolate also caused the only signs of infection on OSU 408.040.

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Joseph C. Goffreda, Anna Voordeckers, and Shawn A. Mehlenbacher

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Niels O. Maness, Donna Chrz, and Joseph C. Goffreda

The peach mutation `Stony Hard' confers a slow softening attribute to the fruit and also confers a highly reproducible predisposal of fruit to soften abnormally to a mealy texture. Induction of mealiness required continuous 48-hour 100-ppm ethylene exposure. `Stony Hard' fruit exposed to low ethylene concentrations (l ppm) or discontinuous 100 ppm ethylene softened more rapidly than fruit exposed to ethylene-free air but to a normal texture. Ethylene treatment failed to induce mealiness in selections without the `Stony Hard' gene. As quantitative methods for assessment of mealiness, mesocarp-extractable juice decreased, and buffer soluble solids and soluble polysaccharide galacturonic acid content increased for mealy fruit. `Stony Hard' peach fruit represent the only known system in which the concentration and duration of exposure to ethylene can be used to manipulate softening and textural properties of the fruit. Supported by U.S. Dept. of Agriculture grant 93-34150-8409 and the Oklahoma Agricultural Experiment Station.

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Christopher D. Gussman, Joseph C. Goffreda, and Thomas J. Gianfagna

Ethylene production and fruit softening during postharvest storage of several apple (Malus domestica Borkh.) ripening variants were compared with two standard cultivars. PA14-238 and D101-110 produced only low levels of ethylene (<10 μl·kg–1·hour–1) at harvest and throughout most of 86 days of storage at 4C, whereas `Red Chief Delicious' and `Golden Delicious' fruit produced >100 μl ethylene/kg per hour during the same time period. PA14-238 and D101-110 flesh disks converted aminocyclopropane-1-carboxylic acid (ACC) but not methionine (MET) to ethylene. `Red Chief Delicious' readily converted both MET and ACC to ethylene at the end of cold storage. PA14-238 fruit were the firmest and did not soften during postharvest storage; however, D101-110 softened appreciably. NJ55 did not produce ethylene at harvest, but produced a significant amount of ethylene (90 μl·kg–1·hour–1) during storage. Despite its high capacity to produce ethylene, NJ55 remained nearly as firm as PA14-238 at the end of cold storage.

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Niels O. Maness, Donna Chrz, and Joseph C. Goffreda

The `Stony Hard' gene of peach conferred a unique ability to manipulate softening and textural properties of the fruit by controlling the concentration and duration of exposure to ethylene. Fruit ripened in ethylene-free air softened very slowly. Exposure of fruit to 1 ppm ethylene continuously for 48 h, or discontinuously at 100 ppm over the same time period, significantly accelerated softening—to a normal texture. Exposure of fruit to 100 ppm ethylene continuously for 48 h induced softening to the same level, but to a mealy texture. We have prepared cell walls and conducted sequential chemical extractions from fruit exposed to the ethylene treatments above. Galacturonic acid content of chelator soluble pectin fractions decreased for mealy fruit, compared to fruit with normal texture, indicating that selective pectin degradation was associated with mealiness. Other differences in polysaccharide sugar composition and apparent molecular size associated with slow, accelerated, and abnormal softening in peach fruit will be addressed.

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Thomas J. Molnar, Sara N. Baxer, and Joseph C. Goffreda

An eastern filbert blight resistance screening technique was developed that reduces the time required to identify susceptible Corylus avellana L. seedlings from the previously reported 14 to 16 months after inoculation to 6 to 7 months. To accomplish this, hazelnuts were harvested at maturity, treated with GA3, germinated, and grown for about 8 weeks at 24 °C day/18 °C night with 16-hour daylengths. Seedlings were then moved to a humidity chamber and inoculated with ascospores of Anisogramma anomala (Peck) E. Müller 3 times over 2 weeks by misting until run off with a solution of 1 × 106 ascospores/mL in sterile distilled water. Following inoculation, seedlings were returned to the original greenhouse for 8 weeks and then were moved to a 10 to 15 °C day/5 to 10 °C night greenhouse with natural daylengths for 4 weeks. They were then moved to a 4 °C cold room for 8 weeks to receive chilling. Afterwards, seedlings were returned to a greenhouse at 24 °C day/18 °C night where stromata development was visible in 4 to 6 weeks.

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Norman Lalancette, Daniel L. Ward, and Joseph C. Goffreda

A field study was conducted during the 2007 and 2008 growing seasons to determine and compare the susceptibility of 33 peach (Prunus persica L. Batsch) cultivars and advanced selections to rusty spot caused by Podosphaera leucotricha. During each season, the progression of peach rusty spot was monitored on three cultivars of varying susceptibility to determine when the epidemics had terminated. At that time, disease incidence and severity were estimated as percent infected fruit and number of lesions per fruit, respectively, for all cultivars in the study. Observations were recorded on fruit sampled from four replicate trees of each cultivar located in experimental plantings at the Rutgers Agricultural Research and Extension Center, Bridgeton, NJ. No fungicide sprays were applied to the trees during the study. Overall disease incidence values, estimated by averaging data from both years, varied widely across cultivars, ranging from 5% to 68% fruit infected. The three most susceptible cultivars were Autumnglo, Jerseyqueen, and Bounty, whereas the three least susceptible cultivars were Gloria, Harrow Beauty, and Sugar May. Results of Tukey-Kramer mean separation groupings and relative susceptibility rankings across both years were used to place cultivars into five disease susceptibility categories. The most susceptible cultivars were characterized as having yellow flesh with normal melting flesh texture and acidity, whereas less susceptible cultivars tended to have white-fleshed stony-hard subacid fruit. Among eight quantitative fruit characteristics examined for association with disease levels, ripening date, fruit weight at pit hardening, and fruit pubescence were found to be positively correlated with rusty spot development. Finally, the relationship between disease incidence and lesion density within the 0 to 0.5 incidence range, based on data from all cultivars in the study, agreed closely with former models derived from only a single cultivar.