Asian Pear Research Articles

Characterization of aromatic volatile constituents in 11 Asian pear cultivars belonging to different species

Aroma is an important fruit sensory attributes that is influenced by the volatile compounds present in the fruit, and it determines whether a fruit is acceptable to consumers. The volatile compounds in 11 pear cultivars from different species were investigated by headspace solid phase microextraction and gas chromatography-mass spectrometry. In total, 70 volatile compounds, including three alcohols, six aldehydes, fifty-two esters, three acids, three terpenes and three ketones were identified and quantified. Ester was the dominant chemical class of which a total of 52 compounds were detected. Hexanal, hexyl acetate, ethyl hexanoate, ethyl 2-methylbutanoate and ethyl butanoate were the major volatile compounds. Pyrus ussuriensis Maxim showed a higher concentration of volatiles and higher ester content than in the other Asian pear species studied. Cultivars were clearly grouped into four clusters based on the concentration and number of different volatile compounds present in each cultivar. The clusters of different cultivars could be discriminated from each others using the first two principal components. The volatile profiles of the pears were qualitatively and quantitatively influenced by the cultivar. Key words: Pyrus, Asian pear, volatile compound, gas chromatography mass spectrometry (GC-MS), solid phase microextraction (SPME), multivariate analysis.

'한아름', '만풍배' 및 '신고' 배의 성숙 기간 중 과실특성 및 세포벽 관련물질의 변화

본 실험에서는 국내에서 육성한 조생종 '한아름'과 중생종 '만풍배'를 '신고' 품종과 대조하여 과실생장 기간 중의 과실 품질요인의 변화 및 세포벽 구성물질의 변화를 조사하였다. 세 품종 모두 생육기간 중 과육의 경도는 지속적으로 감소하여 과실성숙기의 경도는 '한아름', '만풍배' 및 '신고'에서 각각 29.4, 33.5 및 27.4N으로 나타났다. 세 품종 모두 성숙기에 에틸렌발생량이 매우 낮았는데 '한아름'에서만 성숙일에 <TEX>$0.39{\mu}L{\cdot}L^{-1}$</TEX>를 보였고 '만풍배'와 '신고'는 성숙일에 에틸렌이 측정되지 않았다. 세 품종의 가용성당은 과당이 우점하고 있었고, 과실의 성숙과 더불어 공통적으로 자당의 비율이 증가하였다. 세 품종에서 성숙기에 조사한 알코올불용성 물질(EIS)의 함량은 조생종인 '한아름'의 경우, <TEX>$10.79mg{\cdot}g^{-1}$</TEX> FW로 '만풍배'의 12.72 및 '신고'의 <TEX>$12.75mg{\cdot}g^{-1}$</TEX> FW에 비해 낮았다. 총가용성 펙틴은 '한아름'이 성숙기에 <TEX>$81.05{\mu}g{\cdot}mg^{-1}$</TEX> EIS로 '만풍배'의 57.88 및 '신고'의 <TEX>$61.81{\mu}g{\cdot}mg^{-1}$</TEX> EIS에 비해 높은 수준이었다. 수용성펙틴 분획의 분자량 변화는 과실발육 초기에 공통적으로 유의하였다. 4% KOH 가용성 hemicelluloses 함량은 '신고'에서 <TEX>$28.05{\mu}g{\cdot}mg^{-1}$</TEX> EIS로 세 품종 중 유의하게 그 수준이 낮았고 과실 성숙에 따른 큰 변화를 보이지 않았다. 셀룰로오스 함량은 '한아름'의 경우 성숙기에 <TEX>$408.00{\mu}g{\cdot}mg^{-1}$</TEX> EIS, '만풍배' 및 '신고' 는 각각 538.67 및 <TEX>$612.33{\mu}g{\cdot}mg^{-1}$</TEX> EIS이었다. 세포벽 구성 중성당 함량은 품종에 관계없이 과실이 비대하고 성숙이 진행됨에 따라 그 함량이 감소하는 경향을 보였다. '한아름'의 경우 우점 중성당인 arabinose 및 galactose 함량이 성숙기인 만개 후 127일에 급격히 감소하였다. 조생종인 '한아름'에서 성숙과 더불어 4% KOH 가용성 헤미셀룰로오스 및 xyloglucan의 분해가 유의하였고 '만풍배' 및 '신고'는 과실발육 초기에만 변화가 나타났다. Chelator 및 <TEX>$Na_2CO_3$</TEX> 가용성펙틴과 24% KOH 가용성 헤미셀룰로오스 분획의 분자량 변화는 품종에 관계 없이 매우 제한적이었다. We investigated the changes of fruit quality parameters, polysaccharide contents and cell wall components during maturation and ripening of two Korean pear cultivar 'Hanareum' and 'Manpungbae' compared with 'Niitaka' pear (Pyrus pyrifolia Nakai) which showed different physiological maturity based on days after full bloom (DAFB). Flesh firmness decreased continuously with fruit development and maturation, reaching a final level of 29.4, 33.5, and 27.4N at maturity in 'Hanareum' (127 DAFB), 'Manpungbae' (163 DAFB), and 'Niitaka' (170 DAFB), respectively. The level of ethylene production was very low in early season 'Hanareum' pear which showed at most 0.39 <TEX>${\mu}L{\cdot}L^{-1}$</TEX> at maturity and no ethylene was detected in 'Manpungbae' and 'Niitaka' at maturity. Fructose was the most abundant soluble sugar during fruit maturation in the pears tested and an increase of sucrose was observed during fruit ripening in the Asian pears commonly. Ethanol insoluble solids (EIS) content decreased gradually with different levels among the pear cultivars as fruit ripens consisted of 10.79, 12.72, and 12.75 <TEX>$mg{\cdot}g^{-1}$</TEX> FW. The amount of total soluble polyuronides was higher in early season cultivars 'Hanareum' than those of mid-season cultivar 'Manpungbae' and 'Niitaka'. In 'Niitaka' which harvested most late season, the level of 4% KOH soluble hemicelluloses was lower than 'Hanareum' and 'Manpungbae' and maintained constantly during fruit ripening period. Cellulosic residues were determined high level in 'Niitaka' which showed 612.33 <TEX>${\mu}g{\cdot}mg^{-1}$</TEX> EIS at maturity when compared with 'Hanareum' (408.0 <TEX>${\mu}g{\cdot}mg^{-1}$</TEX> EIS) and 'Manpungbae' (538.67 <TEX>${\mu}g{\cdot}mg^{-1}$</TEX> EIS). The main constituents of cell wall neutral sugars which consisted of arabinose, xylose, galactose, and glucose were decreased gradually with onset of fruit ripening regardless of cultivar. Arabinose which was predominant in 'Hanareum' pear decreased at the last stage of ripening, but the changes of cell wall neutral sugar during ripening were not occurred in 'Niitaka' pear. The change of molecular mass distribution in water soluble pectin observed dominantly at the early stage of fruit development. Depolymerization of 4% KOH-soluble hemicelluloses and degradation of xyloglucan showed in early-season cultivar 'Hanareum' during fruit maturation, and degradation of those fractions were detected only at the early stage fruit development in mid-season cultivar 'Manpungbae' and 'Niitaka'. The molecular mass profile of CDTA soluble pectin, <TEX>$Na_2CO_3$</TEX>-SP and 24% KOH soluble hemicelluloses showed no significant change during fruit maturation regardless of cultivar.

Use of thiamine for controlling Alternaria alternata postharvest rot in Asian pear (Pyrus bretschneideri Rehd. cv. Zaosu)

SummaryThe effects of thiamine (vitamin B1) against Alternaria rot caused by Alternaria alternata and its possible mechanism in harvested Asian pear fruit were investigated. Thiamine strongly inhibited spore germination and mycelial growth of A. alternata in vitro. Thiamine at a concentration of 100 mm effectively inhibited the development of Alternaria rot, enhanced the activities of defence‐related enzymes, such as phenylalanine ammonia‐lyase (PAL), polyphenoloxidase (PPO) and peroxidase (POD), and increased the content of flavonoids, phenolics and lignin. Thiamine also affected reactive oxygen metabolism of the pear fruit by increasing its production and H2O2 content, and enhancing the activities of major detoxifying enzymes, such as superoxide dismutase (SOD). These findings suggest that the effects of thiamine on Alternaria rot in pear fruit may be associated with its direct fungitoxic property against the pathogens, and the elicitation of biochemical defence responses in the fruit.

Optimum extraction conditions for arbutin from Asian pear peel by supercritical fluid extraction (SFE) using Box-Behnken design

Asian pear (Pyrus pyrifolia cv. Niitaka) peel, a by-product that results from juice processing, is a good source of arbutin, a polyphenol, which has a whitening effect on the skin. The objective of this study was to investigate the optimum extraction conditions for arbutin from Asian pear peel by supercritical fluid extraction (SFE) using response surface methodology (RSM) based on Box-Behnken experiment design. Arbutin was extracted using co-solvent, methanol and ethanol. A three-level four-factor Box-Behnken experiment design was performed to evaluate the combination effect of four independent variances, co-solvent concentration (22 to 30%), extraction pressure (250 to 300 bar), extraction temperature (30 to 60°C) and extraction time (30 to 60 min), coded for X1, X2, X3 and X4, respectively. The coefficients of determination (R2) of response surface regression equations were 0.89 (p<0.01) for methanol as a co-solvent and 0.84 (p<0.01) for ethanol. Arbutin content by SFE with methanol was the highest with 3.35 mg/g at 26%, 275 bar, 45°C and 45 min. In conclusion, arbutin from Asian pear peel would be extracted from the most efficiently combination of 26% methanol as co-solvent, extraction pressure of 275 bar, extraction temperature of 45°C and extraction time of 45 min in the SFE. Key words: Asian pear, arbutin, response surface methodology, supercritical fluid extraction, Box-Behnken experiment design.

Identification of Chinese white pear cultivars using SSR markers

109 Pyrus accessions including 92 local Chinese accessions of P. bretschneideri were identified genetically using nine microsatellite loci developed from apple and pear. The nine SSR loci revealed 129 alleles in 109 pear accessions and 114 alleles in 92 Chinese white pears. Among the 92 local Chinese accessions of P. bretschneideri, 70 could be differentiated successfully except for 10 sets of synonymous or mutants. For the 92 accessions, the number of putative alleles per locus ranged from seven to 18, with an average of 12.67; the average values of observed heterozygosity and Shannon’s Information index were 0.60 and 1.85, respectively. A phenogram based on the SSR (simple sequence repeat) genotypes was obtained. The 109 accessions clustered into 11 groups based on geographical origin. The European pears and the Asian pears did not form independent two groups, but three P. communis cultivars grouped together independently. The Japanese P. pyrifolia cultivars mingled together with the Chinese P. bretschneideri cultivars, but four P. ussuriensis cultivars except for one (Jianbali) grouped together independently. The results indicated that the relationship of P. bretschneideri cultivars and P. pyrifolia cultivars was much closer than others.

Ethylene Analog and 1-Methylcyclopropene Enhance Black Spot Disease Development in Pyrus pyrifolia Nakai

Black spot disease is one of the most serious diseases in Asian pear cultivation, with the commercial cultivar Nijisseiki being susceptible. Ethylene is known to play major roles in regulating plant defense responses against various pathogens. We investigated the relationship between ethylene synthesis and black spot disease in ‘Nijisseiki’ pear leaves by treatment with an analog of ethylene and 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action. Interestingly, both treatments enhanced black spot disease symptoms. Both treatments also increased ethylene production in accordance with disease symptoms through altered gene expression of ethylene biosynthetic enzymes, especially 1-aminocyclopropane-1-carboxylate (ACC) synthase genes (PpACS3 and 4). Chemical names used: 1-methylcyclopropene (1-MCP), 1-aminocyclopropane-1-carboxylate (ACC).

Variations in the molecular masses of the capsular exopolysaccharides amylovoran, pyrifolan and stewartan

Erwinia amylovora, causing fire blight of apple, pear and some ornamentals, Erwinia pyrifoliae, causing Asian pear blight, and Pantoea stewartii, causing Stewart's wilt of sweet maize, synthesize capsular extracellular polysaccharides (EPSs) with a high molecular mass. The EPSs are virulence factors and form viscous aggregates, which participate in clogging vessels of infected plants and causing wilting. The sizes of EPSs produced under different environmental growth conditions were determined by analysis with large pore HPLC columns. Their molecular mass of ca. 5MDa, when isolated from agar plates, decreases to ca. 1MDa for E. amylovora amylovoran from freeze-dried supernatants from liquid cultures and to 2MDa for freeze-dried preparations of P. stewartii stewartan. Size changes were also found following growth in various other media and for different strains. Stewartan, amylovoran and E. pyrifoliae pyrifolan were also shown to be completely degraded by a bacteriophage EPS depolymerase.

Development of cultivar-specific DNA markers based on retrotransposon-based insertional polymorphism in Japanese pear.

We developed retrotransposon-based insertional polymorphism (RBIP) markers based on the long terminal repeat (LTR) sequences of copia-like retrotransposon Ppcrt4 and flanking genome sequences, which were derived from 454 sequencing data from Japanese pear (Pyrus pyrifolia) ‘Hosui’. Out of 40 sequences including both LTR and flanking genome regions, we developed 22 RBIP markers and used them for DNA profiling of 80 pear cultivars: 64 Japanese, 10 Chinese (Pyrus ussuriensis) and 6 European (Pyrus communis). Three RBIP markers were enough to differentiate ‘Hosui’ from the other Japanese pear cultivars. The 22 RBIP markers could also distinguish 61 of the 64 Japanese pear cultivars. European pears showed almost no amplification of the 22 RBIP markers, which might suggest that retrotransposons had transposed during Asian pear evolution or reflect the genetic relationship between Asian and European pears. Sixteen of the RBIP markers could be positioned on a genetic linkage map of ‘Hosui’. The RBIP loci were distributed in 10 linkage groups, and some loci were very closely located within the same linkage group. The information obtained will be applicable to developing cultivar-specific RBIP marker sets in plants.

Inheritance of fire blight resistance in Asian &amp;lt;i&amp;gt;Pyrus&amp;lt;/i&amp;gt; species

Since several Asian pear species are considered to be potential source of fire blight resistance, we crossed “Doyenne du Comice”, the susceptible European cultivar, with four Asian pear species. The aim of the study was to establish the level of resistance of each genotype and the mode of transmission of fire blight resistance to each F1 full-sib progeny. The best sources of resistance were P. ussuriensis 18 and P. ussuriensis var. ovoidea 8 ranked to resistant and highly resistant, respectively. Although pear resistance to fire blight is suggested to be polygenic, distribution of phenotypes in “Doyenne du Comice” × P. ussuriensis var. ovoidea 8 hybrid family suggests the possibility of monogenic inheritance with the dominance of resistance derived from P. ussuriensis var. ovoidea 8. Polygenic inheritance of pear resistance to fire blight was identified in cross combinations of “Doyenne du Comice” with P. pyrifolia 6, and contributed by the major gene, with P. ussuriensis 18 and P. calleryana 12. Transgressive segregation was observed within the progenies of susceptible, moderately susceptible and resistant parents.

Changes in photosynthetic properties and antioxidative system of pear leaves to boron toxicity

Seedlings of the Cuiguan cultivar of the Asian pear ( Pyrus pyrifolia ) were used to study the effects of boron toxicity on leaf photosynthetic properties and lipid peroxidation. The plants were grown hydroponically and treated with four concentrations of boron: 10 (CK), 100, 300 and 500 μmol·L -1 . After 16 weeks of treatment, we measured the leaf contents of boron and chlorophyll (Chl), the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci), the concentrations of malondialdehyde (MDA), H 2 O 2 , ascorbic acid (ASA) and glutathione (GSH) and the enzymatic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR). Treatment with high levels of boron significantly increased the boron content of the pear leaves and reduced Chla, Chlb and carotenoid (Car) contents. Boron stress also reduced the Pn and Gs but increased the Ci. Furthermore, the leaf concentrations of MDA and H 2 O 2 increased with increasing concentrations of boron, whereas the enzymatic activities of SOD, APX, CAT and GR and the ASA and GSH levels first increased and then decreased. These results indicate that boron toxicity reduced the photosynthetic capacity of the pear plant, resulting in the accumulation of reactive oxygen species (ROS) and increased membrane lipid peroxidation. Moderate boron stress can therefore improve the vitality of a plant’s ROS scavenging system, but high concentrations will eventually overcome the system. Key words: Pear, boron toxicity, photosynthetic rate, lipid peroxidation.

Isolation and identification of phenolic compounds from an Asian pear (Pyrus pyrifolia Nakai) fruit peel

Eight phenolic compounds were isolated from the EtOAc-soluble acidic layer of methanol extracts of Asian pear (Pyrus pyrifolia Nakai cv. Chuhwangbae) fruit peels. These isolated compounds were identified to be arbutin (1), 4-(O-β-d-glucopyranosyl)-3-(3′-methyl-2′-butenyl)benzoic acid (2, malaxinic acid), 3,4-dihydroxybenzoic acid (3), trans-chlorogenic acid (4), cis-chlorogenic acid (5), isorhamnetin 3-O-β-d-glucopyranoside (6), 3,5-dicaffeoylquinic acid (7), and (-)-epicatechin (8) based on electronic spray ionization (ESI)-MS and NMR spectroscopic data. Of the isolated compounds, 2 and 5 were identified in pear for the first time.

Erwinia spp. from pome fruit trees: similarities and differences among pathogenic and non-pathogenic species

The number of described pathogenic and non-pathogenic Erwinia species associated with pome fruit trees, especially pear trees, has increased in recent years, but updated comparative information about their similarities and differences is scarce. The causal agent of the fire blight disease of rosaceous plants, Erwinia amylovora, is the most studied species of this genus. Recently described species that are pathogenic to pear trees include Erwinia pyrifoliae in Korea and Japan, Erwinia spp. in Japan, and Erwinia piriflorinigrans in Spain. E. pyrifoliae causes symptoms that are indistinguishable from those of fire blight in Asian pear trees, Erwinia spp. from Japan cause black lesions on several cultivars of pear trees, and E. piriflorinigrans causes necrosis of only pear blossoms. All these novel species share some phenotypic and genetic characteristics with E. amylovora. Non-pathogenic Erwinia species are Erwinia billingiae and Erwinia tasmaniensis that have also been described on pome fruits; however, less information is available on these species. We present an updated review on the phenotypic and molecular characteristics, habitat, pathogenicity, and epidemiology of E. amylovora, E. pyrifoliae, Erwinia spp. from Japan, E. piriflorinigrans, E. billingiae, and E. tasmaniensis. In addition, the interaction of these species with pome fruit trees is discussed.

Aumento da produção de pereira asiática pelo uso de fitorreguladores

The low fruit set in the Southern Brazil conditions is one of the limiting factors to pear production in the country. The use of plant growth regulators may minimize this problem. This study was carried out aiming to evaluate the effectiveness of different growth regulators and the combination of these substances on fruit set increase of ‘Shinseiki Asian pears. The application of growth regulators was performed when the pears have reached the full bloom stage. The experimental design was randomized blocks with four replications of one tree, with the following treatments: 1. control (no application); 2. thidiazuron (TDZ) 20mg L-1; 3. gibberellic acid (GA) 20mg L-1; 4. prohexadione calcium (PCa) 600mg L-1; 5. PCa 600mg L-1 TDZ + 20mg L -1 ; 6. PCa 600mg L -1 + AG 20mg L -1 ; and 7. AG 20mg L -1 + TDZ 20mg L -1 . When sprayed on full bloom stage, thidiazuron and gibberellic acid, and combinations of these substances, both at a concentration of 20mg L-1, increased significantly the fruit set and the fruit production of ‘Shinseiki’ pears. The use of prohexadione calcium, single or in combination with thidiazuron and gibberellic acid, did not increase the fruit production.

Multigene phylogenetic analysis of inter- and intraspecific relationships in Venturia nashicola and V. pirina

Isolates of Venturia species isolated from pear in Japan, China, Taiwan and Israel were used in this study to analyze their molecular phylogenetic relationship. The nucleotides of rDNA-ITS, partial β-tubulin and elongation factor 1α genes were sequenced directly after PCR. Based on these sequence data two phylogenetic groups could be distinguished. Isolates collected from Asian pears such as Japanese and Chinese pears formed a distinct evolutionary lineage from those derived from European and Syrian pears. This result corroborated the early taxonomic separation of V. nashicola from V. pirina. In addition, trees from single-locus data sets and the combined data set showed that all isolates of V. nashicola were included in a monophyletic group and representative isolates of five pathological races originating from different locations and cultivars formed a single lineage. In contrast, two distinct evolutionary lineages were revealed in V. pirina and isolates of five races were scattered in two lineages. Israeli isolates of race 2 as well as two Japanese isolates of V. pirina formed a distinct lineage from other isolates of this species, while other Israeli isolates belonging to races 1, 3, 4, and 5 were closely related to each other and formed another lineage. It was indicated that the evolution of pathological races in V. nashicola might have occurred relatively recently as compared with V. pirina.

Chemical composition and antifungal activity of cuticular wax isolated from Asian pear fruit (cv. Pingguoli)

In order to understand the cuticular wax properties of Asian pear fruits (cv. Pingguoli), a series of assays was conducted on extraction, fractionation and determination of composition. The results showed that the maximum yield of wax from the fruit was obtained by chloroform/methanol (3:1), and then by chloroform extraction. Polar and low polar fractions occupied 64.3% and 26.9% of total crude wax by column chromatography. 54 and 22 components were identified in polar and low polar fractions by GC/MS, respectively. Long-chain fatty acids and triterpenoids predominated in polar fraction and n-alkanes were predominant in low polar fraction. In vitro tests indicated that polar fraction, low polar fraction and total crude wax inhibited spore germination and mycelial growth of Alternaria alternata, which is a causal agent of Alternaria rot of pears, and the maximum inhibition was obtained by polar fraction. These findings indicated that n-alkanes in low polar fraction and triterpenoids, fatty acid in polar fraction might have contributed to the antifungal properties of pear fruit cuticular waxes.

Estimate of Leaf Chlorophyll and Nitrogen Content in Asian Pear (Pyrus serotina Rehd.) by CCM-200

In many cases evaluation of chlorophyll and nitrogen content in plants need to destructive methods, more time and organic solvents. Application of chlorophyll meters save time and resources. The aim of this study was estimating of chlorophyll and nitrogen content in Asian pear leaves using non-destructive method and rapid quantification of chlorophyll by chlorophyll content meter (CCM200). This study was conducted on 8 years old Asian pear trees during June 2008 in Tehran, Iran. To develop our regression model, the chlorophyll meter data were correlated with extracted chlorophyll and nitrogen content data obtained from DMSO and Kejeldal methods, respectively. The results showed that, there was positive and linear correlation between CCM-200 data and chlorophyll a (R²=0.7183), chlorophyll b (R²=0.8523), total chlorophyll (R²=0.90), and total nitrogen content (R²=0.76) in Asian pear leaves. Thus, it can be concluded that, CCM-200 can be used in order to predict both chlorophyll and nitrogen content in Asian pear leaves.

The fading distinctions between classical patterns of ripening in climacteric and non-climacteric fruit and the ubiquity of ethylene—An overview

The process of fruit ripening is normally viewed distinctly in climacteric and non-climacteric fruits. But, many fruits such as guava, melon, Japanese plum, Asian pear and pepper show climacteric as well as non-climacteric behaviour depending on the cultivar or genotype. Investigations on in planta levels of CO2 and ethylene at various stages of fruits during ripening supported the role and involvement of changes in the rate of respiration and ethylene production in non-climacteric fruits such as strawberry, grapes and citrus. Non-climacteric fruits are also reported to respond to the exogenous application of ethylene. Comparative analysis of plant-attached and plant-detached fruits did not show similarity in their ripening behaviour. This disparity is being explained in view of 1. Hypothetical ripening inhibitor, 2. Differences in the production, release and endogenous levels of ethylene, 3. Sensitivity of fruits towards ethylene and 4. Variations in the gaseous microenvironment among fruits and their varieties. Detailed studies on genetic and inheritance patterns along with the application of '-omics' research indicated that ethylene-dependent and ethylene-independent pathways coexist in both climacteric and non-climacteric fruits. Auxin levels also interact with ethylene in regulating ripening. These findings therefore reveal that the classification of fruits based on climacteric rise and/or ethylene production status is not very distinct or perfect. However, presence of a characteristic rise in CO2 levels and a burst in ethylene production in some non-climacteric fruits as well as the presence of system 2 of ethylene production point to a ubiquitous role for ethylene in fruit ripening.

Glycemia and peak incremental indices of six popular fruits in Taiwan: healthy and Type 2 diabetes subjects compared.

The aim of this study was to evaluate the glycemic index and peak incremental indices of six popular fruits in Taiwan, comparing healthy subjects (n = 20) and patients with Type 2 diabetes (n = 17). The six kinds of fruits tested were grapes, Asian pears, guavas, golden kiwifruit, lychees and bananas. Glycemic index values were tested according to the standard glycemic index testing protocol. The glycemic index and peak incremental indices were calculated according to published formulas. In Type 2 diabetes subjects, the glycemic index values of grapes, Asian pears, guavas, golden kiwifruit, lychees and bananas were 49.0 ± 4.5, 25.9 ± 2.9, 32.8 ± 5.2, 47.0 ± 6.5, 60.0 ± 8.0 and 41.3 ± 3.5. In healthy subjects, the glycemic index values were 49.1 ± 7.3, 18.0 ± 5.4, 31.1 ± 5.1, 47.3 ± 12.1, 47.9 ± 6.8 and 35.1 ± 5.6. There was no significant difference in glycemic index values between healthy and Type 2 diabetes subjects. There was also no significant difference in PII when comparing healthy subjects and subjects with Type 2 diabetes. In conclusion, glycemic index and peak incremental indices in healthy subjects can be approximately the same for Type 2 diabetes.

Cloning and Sequence Analysis of Endopolygalacturonase Genes in Venturia nashicola and Venturia pirina

Genes encoding endopolygalacturonase (endoPG) were isolated from pathogens of the Asian pear scab, Venturia nashicola races 1, 2, 3, and 4, and European pear scab, V. pirina. The Vnpgr1 gene of the V. nashicola race 1 consists of a 1,116-bp open reading frame, encoding a protein of 372 amino acids with an estimated molecular mass of 37.5 kDa and an isoelectric point (pI) of 6.56. The sequences of Vnpg genes from different races and Vppg gene from V. pirina showed high identities (95-100%). The deduced amino acid sequence of the V. nashicola race 1 endoPG showed 63-68% identity to the endoPG sequences of Penicillium olsonii, Colletotrichum lindemuthianum, Cryphonectria parasitica, Fusarium oxysporum, Sclerotinia sclerotiorum, and Alternaria citri. The deduced amino acid sequence of the race 1 endoPG was identical to the N-terminal amino acid sequence of the previously purified endoPG enzyme from the mycelia of this race. The results of a southern blot analysis indicated that V. nashicola race 1 (isolate JS-115) had a single copy of the Vnpgr1. Restriction fragment length polymorphism (RFLP) analysis of the polymerase chain reaction (PCR) products of the endoPG gene digested with HincII, BspEI, and BsrGI was performed; thereafter, agarose gel electrophoresis yielded race-specific RFLP patterns.

α-Farnesene and antioxidative enzyme systems in Asian pear ( Pyrus serotina Rehd.) fruit

The effects of 1-methylcyclopropene (1-MCP) on ripening, superficial scald and concentrations of α-farnesene, conjugated trienols (CTols) and antioxidant enzyme activity of ‘KS 6’ Asian pear ( Pyrus serotina Rehd.) were studied. 1-MCP treated (2 μL L −1) or untreated control fruit were stored at 1 °C and 90–95% RH for up to 120 days. 1-MCP treated fruit were firmer than untreated fruit. Application of 1-MCP delayed skin color change. Scald appeared after shorter storage duration and was reduced, but not entirely controlled, with 1-MCP. Accumulation of α-farnesene and oxidation were slower in skin of 1-MCP treated fruit compared with controls. Catalase and peroxidase activities in untreated fruit either increased while activities decreased in 1-MCP treated fruit. Superoxide dismutase activity remained stable. The treatment of Asian pears with 1-MCP followed by cold storage maintained textural characteristics with less scald incidence.