Pyrus Serotina Research Articles

Diffusible and extractable auxins in young Japanese pear trees

Three-year-old trees of some Japanese pear ( Pyrus serotina Rehd.) cultivars of different growth habits (extent of apical dominance) were used. Scaffold branches were trained either vertically or laterally. Diffusible indole-3-acetic acid (IAA) levels in the terminal shoot were higher in the order of cultivars ‘Shinsui’ (strong), ‘Kosui’ (intermediate), and ‘Hosui’ (weak) in an early period, which was the reverse order of their branching ability. Scaffold branch orientation per se did not affect diffusible IAA levels in the various parts of the tree. In all cultivars, after bud break, diffusible IAA levels rapidly increased in all parts, especially in the upper part of the tree, showing a downward gradient from the shoot towards the root. A peak level in the shoot, or in the trunk, was reached prior to the period of most rapid extension growth or radial growth, respectively. The reduction of the level commenced first in the shoot, and spread basipetally towards the root. Diffusible IAA levels were associated with an increment of the growth rate rather than with the growth rate. During the growing season, extractable IAA in the cambial regions changed in a similar way to the diffusible IAA level. However, unlike diffusible IAA, extractable IAA increased and maintained a high level during the non-growing season. Removal of all shoots after cessation of the extension growth markedly decreased diffusible and extractable IAA levels in the rest of the tree.

‘Hosui’ fruit (Pyrus serafina) grown in New Zealand is nonclimacteric

Abstract Changes of fresh weight, flesh firmness, soluble solids, skin colour, respiration rate, internal ethylene concentration, and ethylene production were assessed for Japanese pear (Pyrus serotina cv. Hosui) fruits during maturation. Fruit fresh weight, soluble solids contents, and skin colour grade increased, firmness and respiration rates decreased with maturation, but internal ethylene and ethylene production remained undetectable. Ripening characteristics of ‘Hosui’ were investigated by measuring the respiration rate and ethylene production of fruit treated with propylene during maturation. Fruit respiration rate was enhanced in the presence of 0.5% propylene and declined upon removal of the gas. Ethylene production was not enhanced by exposure of fruit to propylene and remained at undetectable levels through the experiment. The results suggest that ‘Hosui’ fruit grown in New Zealand is nonclimacteric.

IRRIGATION MANAGEMENT AND FRUIT QUALITY IN ASIAN PEAR

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.

CONTAINER CULTURE OF HIGH-CHILLING PEAR AT TAIWAN'S LOWLAND

High-chilling pear cv. Shinseiki (Pyrus serotina Rehd.) were used to evaluate the cultivation potentiality at warm area via the decrement of supraoptimum temperature damage and the escape from dormancy. Several experimental results were obtained as follows: the media prepared by combination of peat and bark compost (1:1 in volume) inside nonwoven bag was lower in temperature than other media; both of the temperature of leaf surface and media decreased more than 2′C at noon by 25% shading favoring the CO2 exchange in the daytime; the foliage application of Aminofol increased leaf thickness and chlorophyll content; and BA or PP-333 treatment enhanced lateral buds development during the supraoptimum temperature period of summer, etc. An integrated management based on these results helped the 1-year old container-grown Shinseiki pear trees over-summer. The experimental trees were then forced to budbreak and flower by application of cyanamide in October. Eventually, the fruits were harvested in March. These results suggested that the production of high-chilling pears in warm area was technically feasible.

ASIAN PEAR (NASHI) TREE WATER RELATIONS IN LYSIMETERS.

Nashi pear (Pyrus serotina Rehder, cv. Hosui) trees were planted in 12 computerized 1m-wide drainage lysimeters in September 1987. During the 1990 season tree water use was monitored via lysimeter and neutron probe readings. Diurnal leaf water relations were studied using a pressure chamber for water potential (ψ) and a porometer for leaf conductance (gs). Xylem sap trunk flow velocities were measured with an experimental heat pulse device and converted to xylem flux. Close agreement existed between 24 hr xylem flux and lysimeter water use when comparing trees with different soil water content. Xylem flux also was very sensitive to changes in evaporative demand. During 9–13 day drying cycles pre-dawn ψ became progressively lower, morning decline more rapid, and afternoon recovery slower. The diurnal gs pattern also shifted during drying cycles, such that gs of water stressed trees always decreased from time of first measurement of sunlit leaves rather than increasing during the morning as on non-stressed trees. Late afternoon was the best time to distinguish between fully irrigated and stressed trees using gs measurements.

Detection and inheritance of a stylar protein associated with a self-incompatibility genotype of Japanese pear

Stylar proteins in 6 cultivars of Japanese pear (Pyrus serotina Rehd.) with different self-incompatibility alleles were examined by isoelectricfocusing polyacrylamide gel electrophoresis (IEF-PAGE). Cultivars used involved 1 self-compatible mutant ‘Osa-Nijisseiki’ obtained from ‘Nijisseiki’ (S2S4). Banding patterns of proteins were almost the same among the 6 cultivars except for 3 bands; one of which associated clearly with self-incompatibility S2-allele (hereafter the protein referred to as S2-protein) and was easily detectable because of its large amount and its pI value differed from many other proteins. Two other bands were seemingly associated with S3- and S4-alleles, respectively. The S2-protein was apparently present in the styles of ‘Osa-Nijisseiki’.

Performance of Drainage Lysimeters for the Evaluation of Water Use by Asian Pears

The design of a type of drainage lysimeter, as tested with trees of Pyrus serotina Rehder var. culta Rehder `Hosui' is described. All lysimeter operations and monitoring of irrigation and drainage volumes were managed by a “multi-tasking” controller/datalogger. It was possible to apply different irrigation levels to each of three sets of four random lysimeters. Evapotranspiration (ET) was calculated using a conservation of water equation, with differences between irrigation inputs and drainage outputs corrected for changes in soil-water content. ET ranged between 3.3 and 10.7 liters/tree per day in well-watered, noncropped trees in late Summer and Fall 1990. These rates correspond to ET of 0.13 to 0.43 liter·cm-2·day-1 and 0.96 to 3.10 liters·m-2·day-1 on trunk cross-sectional area and canopy area bases, respectively. The correlation coefficient between ET and Class A pan evaporation was >0.9 during this period. Weekly crop coefficients for the well-watered trees averaged 0.52 when calculated on a canopy-area basis. When irrigation was withheld for 18 days, the crop coefficient declined to 0.38. There were no differences in ET between trees growing in the two soil profiles, despite significant differences in soil water distribution.

Seasonal Changes in the Susceptibility of Japanese Pear (Pyrus serotina Rehd.) cv. "Kosui" Fruit to the Japanese Pear Scab Fungus, Venturia nashicola.

The effects of the fruit growth stage on the susceptibility to and the latent period of scab fungus on Japanese pear cv. “Kosui” were investigated. The degree of fruit susceptibility to the scab disease was high from the fruit receptacle stage (before bloom) to the young fruit stage (about 2 weeks after bloom). Susceptibility to the disease quickly decreased from mid May (about 25 days after bloom) and was low until early June (about 50 days after bloom) then gradually increased again. Susceptibility reached its highest during early to mid July (about 75 to 90 days after bloom). The latent period of the disease was short, 14 to 21 days, during the stage of high susceptibility and long, about one month, during the stage of low susceptibility. The percentage of cracked fruits was highest in fruits inoculated during early to late May (about 15 to 30 days after bloom), and was little lower during mid June. From the standpoint of orchard management, fruit cracking caused by fungus infection during early May and mid to late June is practically important because of high fruit susceptibility to the disease. This indicates that the best time for controlling the disease on fruit of cv. “Kosui” with fungicides in the Kanto district is from prebloom to early May and again from mid June to mid July (about 55 to 90 days after bloom). The results obtained from this work may be revised for an earlier calendar timing to be adapted in the Kyushu district, warmer area in Japan, and for a later calendar timing to be adapted in the Tohoku district, cooler area.

Normal ripening cultivars of Pyrus serotina are either climacteric or non-climacteric

The climacteric status has been investigated in two cultivars of Pyrus serotina (Rehder). Both cultivars are chance seedlings. The fruit displayed a high respiration rate early in development that declined as fruit matured. Both ripened, as seen by skin degreening and softening, at similar times after flowering. Yet only in cultivar ‘Chojuro’ were the ripening changes associated with increased rates of ethylene and carbon dioxide production. In cultivar ‘Nijisseiki’ ethylene and carbon dioxide did not increase as fruit ripened. Continuous exposure of fruit to propylene accelerated skin degreening in cultivar ‘Nijisseiki’ but did not induce ethylene production or a climacteric peak of respiration. Whereas, in ‘Chojuro’, skin degreening, and ethylene and carbon dioxide production were all advanced after exposure to propylene. We conclude that although fruit development and ripening of both cultivars are similar, ‘Chojuro’ ripens with an associated respiratory climacteric, whereas ‘Nijisseiki’ does not.

Use of hydrogen cyanamide to improve flowering and fruit set in nashi (Pyrus serafinaRehd.)

Abstract Hydrogen cyanamide use was investigated as a means of improving flowering and fruit set in nashi (Asian pear, Pyrus serotina Rehder var. culta Rehder) cultivars. The onset of flowering and shoot extension were advanced, and the length of the flowering period was shortened in all cultivars tested. Most response was shown by the later-flowering cultivars ‘Shinseiki’ and ‘Nijisseiki’, Best results were achieved at application rates of 3% a.i. Applications of hydrogen cyanamide at 6 and 9% a.i, caused serious bud and wood damage, regardless of time of application. Application at 3% a.i. caused damage only if applied within 3 weeks of natural flowering. At 1.5%, no damage occurred, but the effects on flowering were uneven and the results inconsistent. For the pollinator, ‘Shinseiki’, best results were achieved with a single application of 3% a.i. at c. 30–50 days before natural flowering, substantially improving overlap with the flowering periods of the other nashi cultivars. Early applications were s...

Physiology and Prediction of Fruit Tolerance to Low-oxygen Atmospheres

Fruits of `Granny Smith' and `Yellow Newtown' apples (Malus domestica Borkh), `20th Century' pear (Pyrus serotina L.), and `Angeleno' plum (Prunus domestica L.) were kept in air and in 0.25% or 0.02% O2 at 0, 5, or 10C for 3, 7, 14, 25, or 35 days to study the effects of low-O2 atmospheres on their postharvest physiology and quality attributes. Soluble solids content (SSC), pH, and external appearance were not significantly influenced, but resistance to CO2 diffusion was increased by the low-O2 treatments. Exposures to the low-O2 atmospheres inhibited ripening, including reduction in ethylene production rate, retardation of skin color changes and flesh softening, and maintenance of titratable acidity. The most important detrimental effect of the low-O2 treatments was development of an alcoholic off-flavor that had a logarithmic relation with ethanol content of the fruits. The ethanol content causing slight off-flavor (Eo) increased with SSC of the commodity at the ripe stage, and it could be estimated using the following formula: (Log Eo)/SSC = 0.228. Using SSC of ripe fruits and average ethanol accumulation rate per day (VE) from each low-O2 treatment, the tolerance limit (Tl) of fruits to low-O2 atmospheres could be predicted as follows: Tl = Eo/VE = (100.228SSC)/VE.

Induction of Deformed Pollen Tube Tips and Their Morphological Characteristics in Self-incompatible Japanese Pear.

Aberrations in pollen tube tips of Japanese pear, Pyrus serotina, in vivo studies following pollen-incompatible and -compatible pollinations; and in vitro studies on the effects of chemical additives to the growth medium were investigated.Incompatible and compatible pollen/stigma-style combinations resulted in pollen tubes with deformed tips which were mainly detected as a swelling. The incompatible combinations developed approximately twice as many swollen tips. Their surface structure revealed irregular features such as concave and unusual furrows, whereas a smooth surface was observed in normally growing tips.In in vitro trials, ABA, ovarian extract (OE), polyethylene glycol (PEG), H3B03 and fusicoccin (FC) increased the number of abnormal pollen tube tips. The tip surfaces of these tubes were considerably irregular, except in the case of H3BO3, which seemed to be similar to those deformed tips observed in incompatible styles. Boric acid caused regular fine furrows along the tube axis but CaCl2 had no effect on the deformed tip formation; the tube surface structure was relatively smooth. Thus, the growth inhibitors tend to induce irregularities on pollen tube surface similar to those observed on pollen tubes growing in an incompatible style, whereas growth promoters did not induce such symptoms. The similarities in tip morphology may indicate that cell wall synthesis in pollen tubes growing in incompatible styles is altered by inhibitors or water stress following a specific recognition reaction on the stigmatic surface and/or in the transmitting tissue. This alteration causes cessation of tube growth.

ニホンナシの自発休眼覚醒期から開花期までの発育速度モデルについて

In order to estimate flowering dates of fruit trees by the developmental rate (DVR) and the developmental index (DVI), the relations between the DVR and temperature were experimentally examined, and the DVR from rest break to flowering was modeled.Cultivars of Japanese pear (Pyrus serotina Rehd.), ‘Housui’ and ‘Kousui’ planted on pots were exposed to eight constant temperatures (31°C, 26°C, 22°C, 18°C, 16°C, 13°C, 10°C and 6.8°C) from January 24, 1989. We assumed that DVI of the initiation of temperature treatment was 0 and of flowering 1.0. The measured DVR at each temperature can be calculated in the form of reciprocals of the number of days from the initiation of temperature treatment to the flowering. The relations between natural logarithms of the measured DVR and reciprocals of the absolute temperatures became linear, but the parameters in the model changed around 20°C (Fig. 1).The models and their parameters obtained from the experiment was validated to the data observed in the open field. The difference between the observed and the estimated days to flowering was less than 3 days. The estimated time course of DVI was shown in Fig. 2.To study the locational difference in the model parameters, the twigs of Japanese pear (‘Housui’ and ‘Kousui’) collected from 13 prefectures were exposed to several different constant temperatures. The DVR in this experiment was determined from the date of germination to the flowering date. The result did not show a clear difference of the model parameters (Fig. 4, Table 3).In order to compare our model with the model of effective accumulated temperature, the latter was applied to measured DVR. MSR (mean square residual) of the former was less than of the latter.

Survival and Shoot Formation in Vitro of Pear Winter Buds Cryopreserved in Liquid Nitrogen

Vegetative buds of pear (Pyrus serotina Rehder, cv. Senryo) associated with shoot tissue were frozen stepwise to – 40C, immersed in liquid N, and thawed either at 37C in water or at 0C in air. Survival and shoot formation on thawed material was higher when preliminary cooling lasted 12 to 48 h rather than 0.5 to 2 h. The proper thawing temperature depended on the degree of cooling before cryopreservation. A few whole plants were recovered from the cryopreserved buds.

Development of Oxygen Concentration Gradients in Flesh Tissues of Bulky Plant Organs

Steady-state oxygen diffusion in flesh of apples (Malus domestics Borkh. cvs. Braeburn and Cox's Orange Pippin), Asian pears (Pyrus serotina Rehder. cvs. Hosui and Kosui), and nectarines [Prunus persica (L.) Batsch. cvs. Red Gold and Sunglo] was studied using a nondestructive method at 20C. Fruit flesh was found to exert a significant resistance to O2 diffusion resulting in measurable O2 gradients between tissues immediately beneath the skin and those at the fruit center for all these fruits. The magnitude of these O2 gradients varied between crops and cultivars and depended on the respiration rate and on effective O2 diffusivity in fruit flesh (De). Values of Dc varied with the cultivar and were broadly consistent with intercellular space volume. The range of De values obtained suggested that 02 diffusion in fruit flesh takes place in a combination of series and parallel modes in the intercellular space and fluid/solid matrix of the flesh. The results imply that O2 diffusivity in flesh tissues must be taken into consideration in the determination of critical external O2 level in controlled/modified atmosphere (CA/MA) storage.

Relationships between seed set and fruit weight and shape of nashi (Pyrus serotinaRehder varcultaRehder)

Abstract The relationships between seed set and fruit weight and shape were studied on four nashi (Pyrus serotina Rehder var culta Rehder) cultivars Hosui, Kosui, Nijisseiki, and Shinsui. The carpel number ranged between four and eight per fruit with each carpel having the capacity to carry two seeds. The number of seeds per fruit was significantly correlated with fruit weight with ‘Nijisseiki’ showing the highest fruit-weight increase per seed. The seed number per carpel and the total weight of seeds per carpel were related to fruit shape. Even seed distribution around the fruit core was related to evenly shaped fruit. On the basis of the levels of seed set observed, considerable potential exists for raising the nashi quality by optimising pollination and seed set.

Seasonal accumulation of mineral nutrients in leaves and fruit of Japanese pear ( Pyrus serotina Rehd.)

The concentrations of macro- and micro-nutrients within leaves and fruit of Japanese pear ( Pyrus serotina Rehder var. culta Rehder) trees were recorded over one growing season. Separate determinations were made for leaves on spurs and leaves on extension shoots. Numbers and dry weights of leaves and fruit on these trees were also measured to allow estimation of the quantities of nutrients accumulated within the deciduous organs of the tree. The cumulative canopy leaf dry weight increased until just prior to fruit harvest when leaf growth slowed considerably. There was relatively little increase in the leaf biomass after fruit harvest. Vegetative pruning, carried out on two occasions during the summer, appeared to have no significant effect on the subsequent rate of leaf growth. The dry weight of individual fruit increased exponentially until harvest. The rate of water accumulation within the fruit was more rapid than that for dry weight, with the ratio of dry weight:fresh weight declining during fruit development. Concentrations of N, P, K, Mg, S, Cu and B on spur leaves declined throughout the season. Concentrations of Ca, Mn and Zn increased during most of the growing season. There was no apparent seasonal pattern for Fe. For all nutrients, the seasonal trend within leaves on the extension shoots was in the same direction as that within the spur leaves, except for a transient inter-ruption or reversal of this trend for N, P, K, Mg, S, Cu and B at about 60–80 days after flowering. The concentrations of all the nutrients measured within the fruit generally declined during fruit development. The rate of nutrient accumulation within individual fruit appeared linear with time for Ca and Zn, while for N, P, K, Mg, Fe, Cu, Mn and B the accumulation was described better by a linear regression of the logarithm of nutrient content with time. The fruit represented a much larger sink than the leaves for P, K, Cu and B, while for Ca and Mn the leaves were a larger sink than the fruit, and for N, Mg, S, Fe and Zn the leaves and fruit were sinks of relatively similar dimensions. While there was some nutrient loss from the spur leaves during the later stages of fruit development, especially for N, the quantities involved could account for only relatively small proportions of the nutrients accumulated by the fruit during this time, e.g. 19% for N and 11% for Mg. The total quantities of nutrients accumulated within the deciduous organs were used to make provisional estimates of the uptake of macro-nutrients by the trees used in this study. Potassium was clearly the major nutrient in this regard, with an accumulation within the leaves and fruit exceeding that for all other nutrients by at least 75%. As most of the K accumulated was located in the fruit, this nutrient is likely to be a major component of maintenance fertiliser programmes.

ナシ赤星病り病葉の光合成•呼吸特性

Net photosynthesis (Pn) and dark respiration (Rd) were determined on detached leaves of pear (Pyrus serotina, cvs. Suishu, Chojuro, Doitsu, Nijisseiki, Pyrus communis cv. Bartlett and Pyrus betulaefolia) infected by Japanese pear rust (Gymnosporangium asiaticum MIYABE et YAMADA).In the resistant cultivar (Bartlett), very few symptoms in leaves occurred. Pn and Rd were unaffected by infection. However, in susceptible cultivars (Suishu, Chojuro, Doitu) and P. betulaefolia, depression in Pn and stimulation of Rd accompanying an increase in size of lesions on leaves occurred.In Japanese pear cv. Nijisseiki, no significant differences were found either in Pn and Rd rate or in degree of infection by shading treatment.

ニホンナシの不和合性における柱頭の関与

A few fundamental experiments were carried out to increase information about the incompatibility of Japanese pear (Pyrus serotina R.). The results obtained are summarized as follows.1. Flowers of ′Kosui′ at anthesis were self- or cross-pollinated after emasculation, and pollen germination on stigmas at 6h after pollination was observed. Pollen grains in cross-pollination germinated well and their pollen tubes elongated into stigmas by that time. But in self-pollination, the number of pollen grains observed on the stigma surface was very small and few pollen grains stretched their tubes into stigmas. Tube growth of cross-pollen was smooth in styles and some of the pollen tubes penetrated into ovaries 72h after pollination. On the contrary, tube growth of self-pollen was very poor and most of the tube tips stayed around 2mm below the stigma surface at 72h after pollination.2. Flowers of ′Kosui′ and ′Chojuro′ at anthesis were emasculated, self- or cross-pollinated, fixed at intervals, stored in 70% Ethanol and processed for fluorescent microscopy through a routine procedure, where the number of pollen grains left adhered to the stigma surface was counted. On ′Kosui′, cross-pollination greatly surpassed self-pollination at 3h after pollination. But the difference decreased as time went on and there existed no difference between self- and cross-pollination at 12h after pollination. On ′Chojuro′, cross-pollination was superior to self-pollination from 6 to 12h after pollination.3. Pistils of ′Kosui′ that were sampled soon after pollination were analyzed for proteins by IEF electrophoresis in combination with a silver nitrate staining procedure. Clear difference was observed between self- and cross-pollination as to the band pattern of buffer-soluble proteins of ovaries as soon as at 3h after pollination.From these results, it was suggested that the stigma might play some significant role in the function of incompatibility of Japanese pear.

Incompatible pollen tube growth and protein composition in styles of Japanese pear following high temperature treatments

Immersing the excised-prepollinated styles of self-incompatible Japanese pear, Pyrus serotina Rehd., into distilled water at 45°C for 1.5–2.5 min promoted the growth of self-pollen tubes; both the number of styles penetrating the pollen tubes through styles to cut ends and of pollen tubes protruding from cut ends were increased. The subsequent growth of the protruded pollen tubes on agar media was also enhanced by the treatments. Treatments at 40°C did not promote the growth of self-pollen tubes and those at 50°C led the styles to necrosis. In the stylar proteins analyzed by isoelectricfocusing polyacrylamide gel electrophoresis, several changes in banding pattern were found following the heat treatment; one of the bands was a glycoprotein that increases in quantity in developing styles as self-incompatibility of the style becomes stronger (Hiratsuka et al., 1986). This protein band was stained more weakly by Coomassie Brilliant Blue-G250 dye. Antigenic substances in the styles examined by immunodiffusion seemed not to be denatured by high temperature treatments.