Pyrus Ussuriensis Maxim Research Articles

Identification of differentially expressed genes in a spontaneous mutant of ‘Nanguoli’ pear (Pyrus ussuriensis Maxim) with large fruit

SummaryThe selection of mutants is one of the most important steps in horticultural breeding. Fruit size is an important breeding objective in pear (Pyrus spp.) because of its economic importance. The pear cultivar ‘Da Nanguoli’ (Pyrus ussuriensis Maxim) produces larger fruit than ‘Nanguoli’, from which ‘Da Nanguoli’ was a bud mutation. The molecular basis for this bud mutation remains unknown. In the present study, ploidy analysis showed that ‘Da Nanguoli’ did not exhibit any alteration in the overall ploidy level. Seventy-six transcript-derived fragments (TDFs) of genes that were differentially expressed between the two cultivars were sequenced using cDNA-AFLP technology. BLAST-X analysis showed that 26 (34.2%) of the TDFs had high sequence homology with known proteins in the non-redundant National Center for Biotechnology Information (NCBI) protein sequence database (i.e., E-values < –3.00). In total, 17 TDFs were chosen and their patterns of expression revealed using cDNA-AFLP and confirmed using quantitative real-time polymerase chain reaction (qRT-PCR). In addition, 98 TDFs, representing candidate genes, were studied in more detail to determine their functions in order to dissect the complex molecular mechanisms involved in the fruit-size mutation.

Genotypic difference for the susceptibility of Japanese, Chinese and European pears to Venturia nashicola, the cause of scab on Asian pears

Abstract Venturia nashicola, the cause of scab on Asian pears, is distinct from Venturia pirina, a causal fungus of European pear scab. Although scab caused by V. nashicola is one of the most serious diseases in the Japanese pear (Pyrus pyrifolia Nakai var. culta Nakai), information available regarding resistant breeding against V. nashicola is limited. In this study, 12 genotypes of Japanese pear, seven genotypes of Chinese pear (Pyrus ussuriensis Maxim.) and four genotypes of European pear (Pyrus communis L. var. sativa DC.) and/or their offspring were evaluated for susceptibility to V. nashicola with leaf and fruit inoculation tests. At 30–40 days after full bloom in their developmental stage, unfolded young leaves and fruit were inoculated with conidial suspensions of V. nashicola for each genotype, and the responses were rated at 30 days postinoculation for the inoculated leaves and at 42 days postinoculation for the inoculated fruits. No visible symptoms were found in European pear ‘Bartlett’ and ‘La France’ and their respective offspring ‘290‐36’ and ‘282‐12’, in the Japanese pear ‘Kinchaku’ and in the Chinese pears ‘Cangxili’ and ‘Hongli’; these genotypes were evaluated as highly resistant to V. nashicola. Necrotic lesions without sporulation were observed in the Chinese pears ‘Qiubaili’, ‘Manyuanxiang’, ‘Yuanbali’ and ‘Xiangyali’, which were regarded as resistant. Sporulating lesions were formed on the other genotypes, such as the major Japanese pear cultivars ‘Kosui’ and ‘Nijisseiki’, which were regarded as susceptible. The response of inoculated leaves coincided well with that of inoculated fruit for each genotype. When the severity of scab symptoms on scab‐susceptible genotypes was further rated with disease severity (DS) values, a genotypic difference was observed for overall DS values in a successive 2‐year measurement among the susceptible genotypes. Based on the DS values of leaf and fruit scabs, the Japanese pears ‘Niitaka’, ‘Shinko’, ‘Nijisseiki’, ‘Gold Nijisseiki’, ‘Osa Nijisseiki’ and ‘Shinsui’ were considered to be less susceptible to V. nashicola than the typical susceptible cultivar ‘Kosui’.

‘Hanhong’ Pear

‘Hanhong’ (Pyrus ussuriensis Maxim × P. bretschneideri Rehd.) is a new high-quality Asian pear with excellent firmness and crispness and a long shelf life. Fruit of ‘Hanhong’ are very attractive and the tree is very winter-hardy. The fruit and leaves are resistant to pear scab (Venturia pirina Aderh) and black spot (Alternaria kikuchiana Tannka) disease.

Pear (Pyrus Species) Genetic Resources in Iwate, Japan

Iwateyamanashi (Pyrus ussuriensis Maxim. var. aromatica (Nakai et Kikuchi) Rehd.) is one of the Pyrus species grown wild in Japan. The origin of the Japanese pear (P. pyrifolia) is uncertain but it has been suggested that Iwateyamanashi is the possible progenitor of the modern Japanese cultivar. During the last few decades, the number of Iwateyamanashi trees has been decreasing and therefore, conservation is urgently needed. After 13 explorations in the northern Tohoku region of Japan, 615 pear trees and 30 local names were recognized mainly in Iwate Prefecture. The center of the distribution seemed to be somewhere around Mt. Hayachine to the northern area of Kitakami highlands (from lat. 39 °20′ to 40 °10′N, and from long. 141 °20′ to 141 °50′E). Four morphological characters concerning fruit shape, measured for 85 trees, showed a wide range of continuous variation. For the skin colour of fruit, 51% of trees bore russet type fruits, 22% smooth and 27% intermediate ones. Most of the fruits had five loculi but Sanenashi fruits (seedless pear), one of the old cultivars, had three, and fruits of another two trees had four. More than 80% of trees tended to produce fruits with a calyx but some trees bore fruits without a calyx. These observations indicate a wide range of genetic diversity in Pyrus species which is caused, not only by high heterogeneity in Iwateyamanashi itself, but also by the coexistence of Iwateyamanashi, P. pyrifolia (Burm.) Nakai and hybrid progeny in this area. Already 250 trees have been conserved as genetic resources by grafting at Kobe University.

Resistance to Fire Blight among Flowering Pears and Quince

Fire blight, caused by the bacterium Erwinia amylovora (Burrill) Winslow et al., is one of the most destructive diseases of plants in the Rosaceae subfamily Maloideae. Artificial inoculations, using E. amylovora strain E2002a, were conducted to determine levels of resistance to fire blight among taxa of flowering pears (Pyrus L. spp.) and quince (Chaenomeles Lindl. spp.). The level of resistance was measured as the length of the fire blight lesion as a percentage of overall shoot length. Considerable variation in resistance was observed among both pears and quince. Pyrus ussuriensis Maxim. `Prairie Gem' was highly resistant with a lesion length of 1% of the total shoot length. Pyrus calleryana Decne. `Bradford' was intermediate with a 50% lesion length while P. calleryana `Chanticleer' was significantly more resistant with a lesion length of 31%. Nine pear taxa were highly susceptible and did not differ significantly from 100% disease severity (total shoot death). Chaenomeles speciosa (Sweet) Nak. `Contorta' was highly resistant with a lesion length of 15%. Six quince taxa, including C. × superba (Frahm) Rehd. `Cameo', `Texas Scarlet', and `Jet Trail' were highly susceptible while nine other taxa showed intermediate resistance.

Adaptive responses ofAcer ginnala, Pyrus ussuriensis and Prunus davidiana seedlings to soil moisture stress

One-year-old seedlings of Amur maple (Acer ginnala Maxim), Ussurian pear (Pyrus ussuriensis Maxim) and David peach (Prunus davidiana Carr) were planted in pots in greenhouse and treated with four different soil moisture contents (75.0%, 61.1%, 46.4% and 35.4%). The results showed that net photosynthesis rate (NPR), transpiration rate (TR) and stomatal conductance (Sc) of seedlings of the three species decreased with the decease of soil moisture content, and Amur maple seedlings had the greatest change in those physiological indices, followed by Ussurian pear, David peach. Amur maple and Ussurian pear seedlings also presented a decrease tendency in water use efficiency (WUE) under lower soil moisture content, whereas this was reversed for David peach. Under water stress the biomass allocation to seedling root had a significant increase for all the experimental species. As to root/shoot ratio, Amur maple seedlings had the biggest increase, while David peach had the smallest increase. The leaf plasticity of Amur maple seedlings was greater, the leaf size and total leaf area decreased significantly as the stress was intensified. No significant change of leaf size and total leaf area was found in seedlings of Ussurian pear and David peach. It was concluded that Amur maple was more tolerant to soil moisture stress in comparison with David peach and Ussurian pear.

チュウゴクナシ‘鴨梨’果実の低温障害発生と貯蔵性に及ぼす温度の影響

To establish a physiological basis for storage and transport of the Chinese pear 'Yali', (Pyrus ussuriensis Maxim. var. sinensis Kikuchi), the occurrence of chilling injury and storage life of fruit stored at 0°, 5°, 10°, and 20°C were investigated. Inhibitory effects of temperature-conditioning prior to low temperature storage on chilling injury were also studied; the mechanism of conditioning-effect is discussed.1. Browning and water-soaked appearance of flesh, which seemed to be symptoms of chilling injury, were observed in the fruit stored at 0° or 5°C, but not at 10° and 20°C. After an extended storage, browning of the core occurred at all temperatures, indicating to be a different symptom from that of chilling injury.2. The rates of respiration and ethylene production in the fruit decreased with the lowering of storage temperature. The rates of respiration in the fruit transferred to 20° from 5°C recovered at the level of the fruit stored throughout the experiment at 20°C. However, respiration rates of fruit injured by the low temperature treatment and then transferred to 20°C were higher than that of the control.3. The electrolyte leakage from flesh discs increased with the occurrence of chilling injury and continued to increase with the development of the injury symptoms.4. The occurrence of chilling injury in fruits stored at 5°C was inhibited by various temperature-conditioning lasting more than three weeks. As stepwise cooling and delayed storage both inhibited the occurrence of chilling injury, the mechanisms of conditioning effects seem to depend on aging rather than on cold-acclimatization of the fruit.5. The fruit stored at 5°C after an appropriate temperature-conditioning retained good eating quality even after 5 months of storage.

Leaf Conductance, Growth, and Survival of Willow and Deciduous Fruit Tree Species under Flooded Soil Conditions

Abstract Potted seedlings and cuttings of various tree species were submerged to 5–10 cm above the soil level for up to 20 months in order to determine flood tolerance based on leaf conductance (kl), growth, and survival. Flooding induced a decline in kl at soil oxygen diffusion rates of 30, 22, 20, and 15 × 10−8g cm−2 min−1 for Prunus persica (L.) Batsch, Halford seedlings (peach), Pyrus communis L. cv. Bartlett (Bart), Pyrus calleryana Decne (Call), and Pyrus betulaefolia Bunge (Bet), respectively. The leaves of some species, particularly Pyrus communis L. cv. Old Home × Farmingdale 97 (OH × F 97), abscised shortly after a decline in kl, yet leaves of most other Pyrus species did not abscise despite months of maintaining a kl near zero. Growth rates were reduced for all fruit tree species except Bet and Call after one month of spring flooding. One month of fall flooding reduced the growth of all fruit tree species the following spring. Bet survived 20 months of continuous submergence; however, only Salix discolor Muhl. (willow) grew well under these conditions. Flooding promoted adventitious rooting of willow, Cydonia oblonga Mill. cv. Provence BA 29 (quince) and Malus domestica Borkh. cv. MM 106 (apple); anthocyanin pigmentation in leaves of apple and all Pyrus species; leaf chlorosis of quince, apple, and peach; and hypertrophied lenticels on the submerged stems and roots of all species. The tolerance, based upon kl, growth, and survival, was: willow &gt; Bet &gt; Call = quince &gt; Bart &gt; OH × F 97 = Pyrus pyrifolia (Burm.) Nak. (Pyri) = Pyrus ussuriensis Maxim. (Ussuri) = apple &gt; peach. Although the survival of pear rootstocks with and without a ‘Bartlett’ scion were similar, flooding symptoms often were quite different.

果実&amp;bull;野菜の成熟生理と貯蔵に関する研究 (第2報)

The changes in respiration rates, ethylene production, internal ethylene concen trations and flesh firmness were investigated during the maturation and ripening periods of pear fruits, using 3 species and several cultivars, as follows: Pyrus communis L. var. sativa DC. (Bartlett, La France and Winter Nelis), Pyrus serotina Rehd. var. culta (Yakumo, Nijisseiki, Niitaka and Kikusui), Pyrus ussuriensis Maxim. var. sinesis Kikuchi (Ya-li, Rai-Yan-Tsu-li and Auto-li). The fruits were picked 2-3 times at different stages of maturity and stored at 20°C.1. Three cultivars of P.communis, Bartlett, La France, and Winter Nelis showed a typical climacteric pattern of respiration. Respiration and ethylene production in both La France and Winter Nelis were much lower than in Bartlett.2. Among P.serotina, Yakumo and Kikusui fruits picked at two different stages of maturity showed a rise in respiration; respiration didn′t rise in Nijisseiki and Niitaka fruits picked at commercial harvest maturity, but did in fruits picked at the immature stage. Ethylene production in Yakumo increased with rising respiration, but the other 3 cultivars maintained a very low level of production during the experimental period.In Nijisseiki, exogenous ethylene treatment caused a rise in respiration immedi ately after picking. This effect continued only in the presence of exogenous ethylene, and could be reproduced in the same fruit when re-treated with ethylene after a month of storage.It was concluded that Yakumo and Kikusui can be classified as climacteric fruits, while Nijisseiki and Niitaka are non-climacteric fruits.3. Three cultivars of P.ussuriensis; Ya-li, Rai-Yan-Tsu-li and Auto-li showed a typical climacteric accompanying a rise in ethylene production.

The Effect of Pear Psylla, Psylla pyricola, Control on Growth and Survival of Bartlett Pear Trees on Two Rootstocks1

The effect of pear psylla, Psylla pyricola Forster, feeding on the growth and survival of Bartlett pear trees on Bartlett seedling and Pyrus ussuriensis Maxim. seedling rootstocks, was studied in an orchard planting of 400 trees during the first 4 years after planting. Half the trees on each rootstock were exposed to uncontrolled populations while sprays were applied to the remaining trees to control this insect. Trees on Bartlett seedling rootstocks grew more than those on P. ussuriensis rootstocks in both the sprayed and unsprayed plots. Trees on both rootstocks grew more in plots sprayed to control psylla than comparable trees in unsprayed plots. The number of tree deaths owing to quick decline was greater for trees exposed to pear psylla than for those sprayed to control this insect.