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Christopher S. Walsh, Julia M. Harshman, Anna E. Wallis, Amy Barton Williams, Michael J. Newell, and George R. (G.R.) Welsh

pollination success, precocity, and productivity in ‘Magness’ pear plantings, we began testing asian pear trees for their effectiveness as pollinizers for ‘Magness’ ( Miller and Walsh, 1984 ). Not long after we began that initial study, we realized that asian

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Regina M. Prunty and Richard P. Marini

Asian pears bloom profusely and require early hand-thinning to produce large saleable fruit. In 1998, `Shinko' and `Hosui' trees were sprayed with Accel, Ethrel, NAA or carbaryl when average fruit diameter was ≈9 mm. Superior oil was added to all treatments at the rate of 2.5 mL/L. Fruit set was reduced 40 to 70% by Accel at 84 ppm and ethephon at 678 ppm, but NAA at 8 ppm and carbaryl were less effective. In 1999, Accel was applied at a range of 0 to 105 ppm and ethephon was applied at a range of 0 to 678 ppm. All treatments contained carbaryl and oil. Fruit set/100 flower clusters declined linearly with increasing ethephon concentration on `Shinko', but was not tested on `Hosui'. Fruit/100 blossom clusters declined linearly with increasing Accel concentration on `Shinko'. On `Hosui' Accel reduced fruit set by more than 40%, but treatments did not differ significantly (5% level) from the control. In both years `Shinko' was easier to thin than `Hosui'.

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Akihiro Itai and Naoko Fujita

temperate zones. The attributes that constitute good quality in one species may differ from that in another, as is the case with European and Asian pears. The attributes of European pears, for example, include its soft buttery texture, whereas those of Asian

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Yong Seo Park, Clara Pelayo, Betty Hess-Pierce, and Adel A. Kader

`Shinko' and `Shinsui' Asian pears were kept in air, 2 kPa O2, 2 kPa O2 + 2.5 kPa CO2, and 2 kPa O2 + 5 kPa CO2 (balance N2 in each treatment) at 0 °C or 5 °C for up to 24 weeks. The three CA treatments reduced respiration (O2 consumption) and ethylene production rates relative to air control pears; these rates were higher at 5 °C than at 0 °C and higher for `Shinsui' than for `Shinko' pears. While `Shinsui' pears had a climacteric pattern of respiration and ethylene production rates, `Shinko' pears produced very small quantities of ethylene and exhibited a non-climacteric respiratory pattern. `Shinko' pears had a much longer postharvest life than `Shinsui' pears (24 weeks vs. 12 weeks at 0 °C). CA treatments had a greater effect on delaying deterioration of `Shinsui' than `Shinko' pears, which were more sensitive to CO2 injury and associated accumulation of fermentative metabolites (acetaldehyde, ethanol, ethyl acetate). `Shinko' pears did not benefit from CA storage and were best kept in air at 0 °C. An atmosphere of 2 kPa O2 with or without up to 5 kPa CO2 delayed flesh breakdown of `Shinsui' pears during storage 0 °C.

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T. Jones, J. Strang, G. Brown, and P. Wolfe

Kentucky is one of seven states in the southeast evaluating 13 Asian pear cultivars for suitability to the region. The cultivars were planted on a (20′ × 10′) spacing in 1989 at three separate locations. Data on time of bloom, tree growth, fire blight susceptibility and fruit quality and yield were collected. This study demonstrates the variability seen in Asian pear cultivars in response to site. There was a significant site by cultivar interaction for fire blight. The Princeton site had significantly more fire blight than either Lexington or Quicksand. Four cultivars, Niitaka, Shin Li, Shinko and Shinseiki had low fire blight ratings which were not significantly different between the three sites. Asian pear growth rates were significantly different between the three sites, but cultivar growth rates were not. Tree growth rate showed a significant negative correlation to fire blight rating. That is infected trees did not grow much. Initial findings show Shinko, Shinseiki and Niitaka to have some tolerance to fire blight spread and to produce good yields of attractive fruit. However, Niitaka had a very tough skin with a tendency towards fruit cracking. The cultivar Shin Li which also had fire blight tolerance did not produce fruit or flowers.

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Kathleen M. Griffiths, Mohammad H. Behboudian, and Melanie Dingle

Asian pear (Pyrus serotina Rehder) is endemic to southern China, Korea and Japan where it is an important fruit. Recent introduction into New Zealand has necessitated research to achieve high fruit quality. In this experiment three irrigation treatments were imposed on the cultivar Nijisseiki and the effect on fruit quality and storage life assessed. They were: a control for which soil water was maintained at 85% of field capacity (FC), “field” receiving only rainfall, and regulated deficit irrigation (RDI) in which soil water was depleted to 50% FC until rapid fruit growth started and then treated as in the control. Fruit weight and firmness were higher in the control and soluble solids were higher in the field treatment whose fruit matured earlier. Irrigation treatment showed no effect on the ripening pattern of the fruit in coolstorage or the incidence of the postharvest disorder flesh spot decay. Nitrogen and potassium levels were highest in the control fruit. However, levels of Mg, Ca, and P were not affected by irrigation.

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Nihal C. Rajapakse and William C. Newall

Changes in sugar composition during maturation and ripening of eight Asian pear cultivars were evaluated. Total soluble sugars (TSS) increased gradually throughout the maturation and averaged 10% to 13% in mature fruit. All cultivars, except `Shinko' and `Nijisseiki', had accumulated ≥10% TSS by 100 days after full bloom (DAFB). Starch accumulated during early stages of Asian pear fruit development but decreased as the maturity progressed coinciding with the rise in soluble sugars. Sorbitol, a sugar alcohol, was predominant in immature fruit and accounted for 35% to 60% of TSS fraction depending on the cultivar. Fructose rapidly increased during early maturation. Glucose increased during early maturation, but the increase was much smaller than that of fructose. Sucrose was low (<4%) in immature fruit but accumulated rapidly late in the maturation and continued to increase until harvest. In mature `Hosui', `Kosui', `Nijisseiki', `Shinsui', `Shinko', and `Ichiban' fruit, fructose was the predominant sugar which accounted for 47% to 60% of the TSS fraction. Glucose and sucrose accounted for 13% to 17% and 7% to 12%, respectively, in those cultivars. In mature `Shinseiki' fruit, sucrose was the predominant sugar (44% of TSS), while fructose and glucose accounted for 33% and 8%, respectively. Sucrose and fructose were present in equal amounts (29%) in mature `Chojuro' fruit. Late accumulation of sucrose in Asian pear cultivars suggest that sufficient time should be allowed before harvesting to obtain sweeter fruit.

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Rodulfo O. Pacumbaba Jr. and Caula A. Beyl

The growing popularity of Asian pears in the open market has generated a need for more information about their fireblight resistance and stress tolerance. In 1994, Alabama A&M Univ. established a large research planting of 10 cultivars of Asian pear on three different rootstocks. The cultivars included Kosui, Korean Giant, 20th Century, Hosui, Shinko, Ichiban Nashi, Shinseiki, Chojuro, Okusankichi, and Shinsui. The three rootstocks used were Pyrus betulaefolia, Pyrus calleryana, and Old Home × Farmingdale 333. The planting was arranged as a randomized complete block replicated 10 times with a total of 300 trees planted. Mortality was scored in late 1995 and data was subjected to Chi-square analysis. Rootstock did have a significant effect on mortality. P. betulaefolia had the lowest frequency of mortality of 11%, with Old Home and P. calleryana at 24% and 31% respectively. Cultivars also had a significant effect on mortality. Korean Giant and Shinseiki had the lowest mortality of 3.33% and 6.67%, respectively. Kosui and Hosui had the highest mortality of 46.67% and 36.67%. Stress conditions that occurred during 1995 and environmental factors that contribute to the development of fireblight were responsible for the mortality of the Asian pear.

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Fenton E Larsen and Stewart S. Higgins

The influence of five Old Home × Farmingdale (OHF) rootstocks on tree size with 10 Asian pear scion cultivars was examined after 10 years in an experimental orchard in central Washington state. The effect of rootstock on tree size varied among scion cultivars. Within `Chojuro', `Hosui', `Niitaka', and `Seigyoku', trunk cross-sectional areas were similar regardless of rootstock. Within `Li', OHF 333 produced larger trees than OHF 282 and OHF 217. `Okusankichi' trees, which were generally the same size as `Hosui', were significantly larger on OHF 217 and OHF 97 than on OHF 333. `Kikusui' trees, which were generally similar in size to `Niitaka' and `Seigyoku', were larger on OHF 217, OHF 97, and OHF 282 than on OHF 333. `20th Century', which was similar in size to `Chojuro' and `Shinseiki', appeared to be the cultivar most sensitive to rootstock. `20th Century'/OHF 217 were significantly larger than trees on OHF 97 and OHF 282, which were larger than trees on OHF 51. `Shinseiki'/OHF 97 were larger than trees on OHF 333. The smallest trees were `Shinko', with trees on OHF 217, OHF 97, OHF 333, and OHF 51 all being larger than trees on OHF 282. Contrary to research with some European pear scions, consistent trends did not emerge from this research that would allow a general prediction of the relative influence of these five OHF clonal rootstocks on Asian pear tree size.

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A. Richard Renquist, Horst W. Caspari, M. Hossein Behboudian, and David J. Chalmers

Stomatal conductance (g s) of `Hosui' Asian pear (Pyrus serotina Rehder) trees growing in lysimeters was characterized for trees in well-watered soil and after brief water deficit. The measures of water status used to interpret g s data were soil-water content, leaf water potential (ψl), and instantaneous water use (trunk sap flow by the compensation heat-pulse technique). The diurnal course and range of g s values of well-irrigated Asian pear trees were similar to those reported for other tree fruit crops. Soil moisture at the end of a midsummer deficit period was 60% of lysimeter pot capacity, and diurnal ψl reflected this deficit predawn and in the late afternoon compared to well-irrigated trees. The g s was sensitive to deficit irrigation during more of the day than ψl, with g s values <3 mm·s-1 for most of the day; these were less than half the conductances of well-irrigated trees. The reduction of g s in response to a given soil-water deficit was not as great on days with lower evaporative demand. After a water deficit, g s recovered to predeficit values only gradually over 2 to 3 days. The low g s of trees in dry soil was the apparent cause of reduced transpiration, measured by trunk sap flow, and reduced responsiveness of sap flow to fluctuations in net radiation.