Asian Pear Research Articles

The Potassium to Magnesium Ratio Enables the Prediction of Internal Browning Disorder during Cold Storage of Asian Pears

'Taichung No. 2' is a new Asian pear cultivar developed in Taiwan with low chilling requirement; however, is likely to develop internal browning disorder under low temperature storage conditions. We investigated the impact of storage time on flesh browning disorder in pears harvested from 22 orchards in 2010 and 2011, and analyzed the levels of nutrients in different fruit parts such as the peel, flesh, and core. Calcium and potassium contents were higher in the flesh and peel, respectively, of more severely browned fruits, whereas a lower magnesium content was recorded in the peel and core of these fruits. Nitrogen and potassium contents in the peel, and calcium content in the flesh were positively correlated with browning disorder severity. By contrast, the magnesium content in the core was negatively correlated with browning disorder severity. However, the nutrient contents in fruits varied between the two sampling years considered. Only the K/Mg ratio was an effective predictor of the browning disorder severity and showed a positive linear correlation in the two years. We recommend that the K/Mg ratio should be lower than 10 to avoid severe browning disorder in pears.

The Potassium to Magnesium Ratio Enables the Prediction of Internal Browning Disorder during Cold Storage of Asian Pears

‘Taichung No. 2’ is a new Asian pear cultivar developed in Taiwan with low chilling requirement; however, is likely to develop internal browning disorder under low temperature storage conditions. We investigated the impact of storage time on f lesh b rowning d isorder in p ears harvested f rom 22 orchards in 2 010 a nd 2 011, and analy zed the levels o f nutrients in different fruit parts such as the peel, flesh, and core. Calcium and potassium contents were higher in the flesh and peel, respectively, of more severely browned fruits, whereas a lower magnesium content was recorded in the peel and core of these fruits. Nitrogen and potassium contents in the peel, and calcium content in the flesh were positively correlated with browning disorder severity. By contrast, the magnesium content in the core was negatively correlated with browning disorder severity. However, the nutrient contents in fruits varied between the two sampling years considered. Only the K/Mg ratio was an effective predictor of the browning disorder severity and showed a positive linear correlation in the two years. We recommend that the K/Mg ratio should be lower than 10 to avoid severe browning disorder in pears.

Fruit quality and core breakdown of ‘Wonhwang’ pears in relation to harvest date and pre-storage cooling

‘Wonhwang’ Asian pear (Pyrus pyrifolia Nakai) is an early ripening pear cultivar, therefore requiring cultural and postharvest practices to retain commercial marketability. The present study included two experiments. The first was to investigate fruit characteristics and physiological disorder of ‘Wonhwang’ pears harvested at 120, 125, 130, and 135 days after full bloom (DAFB) and stored at room temperature for 21 days. The second was to evaluate the effects of 24h of pre-storage cooling at 0°C, 10°C, and 23°C followed by three weeks of room temperature storage on fruit storability and taste. Early fruit harvest increased fruit firmness, titratable acidity, and starch, with light fruit weight and low soluble solids content. Fruits harvested at 130 DAFB were in mid-climacteric phase. Free sugar composition was not consistently affected by DAFB. Harvesting at 125 DAFB retained fruit storability and suppressed occurrence of core breakdown compared to 130 DAFB or 135 DAFB at room temperature for 21 days. Pre-cooling at 10°C produced firmer fruits, lower core breakdown, and better taste compared to pre-cooling at 0°C and 23°C or untreated control (no pre-cooling).

EFFECT OF CONTROLLED ATMOSPHERE STORAGE ON QUALITATIVE PARAMETERS OF ASIAN PEAR CULTIVAR 'ZAOSULI'

The effect of ambient atmosphere composition on the physico-chemical parameters of Asian pear cultivar ‘Zaosuli’ (weight loss, skin colour, firmness, titratable acidity, soluble solids, antioxidant capacity, acetaldehyde, methanol and ethanol content) were investigated. Fruit were stored at 1°C under conditions of RA (normal air), CA-1 (2% O2 + 7% CO2) and CA-2 (0.5% O2 + 1% CO2) for 40 days. At 10 day intervals, fruit were removed from storage for analysis immediately, and after 5 days in shelf-life conditions (18°C). The highest weight losses during storage were observed in fruits stored in RA atmosphere. In this atmosphere, considerable change of colour from green to yellow (highest increase in a* values in the CIE L*a*b* system) were detected. Tissue firmness significantly decreased within the first 10 days of storage for all treatments. There was no significant effect of the atmosphere on the content of titratable acidity and soluble solids content during storage. The antioxidant capacity of fruits decreased during storage, with the largest decline occurring in the CA-1 atmosphere, while less pronounced reduction was monitored in fruit stored in RA atmosphere. Pears stored under RA atmosphere had statistically significantly higher ethanol levels, measured at the end of the shelf life, than fruits stored under CA-1 and CA-2. During the monitoring period, no significant influence of the atmosphere on the flesh firmness, titratable acidity and soluble solids content was observed.

Comparison of bioactive compound contents and in vitro and ex vivo antioxidative activities between peel and flesh of pear (Pyrus pyrifolia Nakai)

We compared chemical constituents and antioxidative activities between the flesh and peel of two Asian pears (Pyrus pyrifolia Nakai cv. Niitaka and Chuhwangbae). Total phenolic, flavonoid, and ascorbic acid contents in the peels were higher than those in the flesh. However, total tocopherol content between peels and flesh was not different. The peels exhibited higher free radical scavenging activities in the in vitro models of DPPH, ABTS+, nitrite radicals, and reducing capabilities than those of the flesh. Pear fruit extracts significantly prevented 3T3-L1 cells from undergoing H2O2-induced oxidation and the effect was higher by the peel extract than by the flesh extract. In addition, blood plasma of rats administered the peel extract showed higher antioxidative activity than that of rats administered the flesh extract. These results suggest that consumption of unpeeled Asian pear fruit may effectively increase antioxidant activity in the body.

English

The present study characterized and identified pear cultivars growing in the southern region of Minas Gerais State, Brazil, using microsatellite markers. Nineteen (19) pear cultivars were collected from two sites of Southern Minas Gerais State: Ribeirao Vermelho and Lavras. DNA was extracted from newly formed leaves and amplified using 21 simple sequence repeat (SSR) markers (NH001c, NH002b, NH005b, NH007b, NH008b, NH009b, NH011b, NH013b, NH012a, NH014a, NH015a, NH017a, KA4b, KA5, KA14, KA16, KB16, KU10, BGA35, BGT23b and HGA8b). The data was analyzed by examining unweighted pair group method with arithmetic mean (UPGMA) clustering, principal coordinate analysis, the Shannon index, and the expected heterozygosity for each primer. The markers used were efficient in separating the Asian and European cultivars as well as hybrids. The primer KA16 was noteworthy in distinguishing the species Pyrus communis , Pyrus pyrifolia and Pyrus betulaefolia by its different banding patterns. Grouping by principal coordinates was similar to UPGMA clustering, forming two distinct groups among the Asian and European pears. The Shannon index and the expected heterozygosity had medium values of 0.440 and 0.300, respectively. The pear cultivars from Southern Minas Gerais usually show low productivity, mainly due to the lack of improved strains for less-demanding weather (warmer) conditions. The selection of the most suitable materials would contribute considerably to overcoming this problem, and the markers selected here can be used in separating cultivars - and presumably contribute to the selection of better matrices. Key words: Pyrus sp., Rosaceae, microsatellite, heterozygosity.

Effect of Boron and Putrescene on Russet Asian pear (Pyrus spp. L.) under Subtropical Condition of Jharkhand Province of India

Effect of Boron and Putrescene on Russet Asian pear (Pyrus spp. L.) under Subtropical Condition of Jharkhand Province of India

De novo assembly, functional annotation, and marker development of Asian pear (Pyrus pyrifolia) fruit transcriptome through massively parallel sequencing

This study investigated the Asian pear transcriptome using the RNA-Seq normalized fruit cDNA library to create a transcriptomic resource for unigene and marker discovery. Following the removal of lowquality reads, 127,085,054 trimmed reads were assembled de novo to yield 37,649 non-redundant unigenes with an average length of 599 bp. Alternative splicing events were detected in 4121 contigs. A total of 30,560 single nucleotide polymorphisms (SNPs) and 7443 simple sequence repeat (SSR) makers were obtained. Approximately 21,449 (56.9%) unigenes were categorized into three gene ontology groups; 3682 (9.8%) were classified into 25 cluster of orthologous groups; and 10,451 (27.8%) were assigned to six Kyoto Encyclopedia of Genes and Genomes pathways. Differentially expressed genes were investigated using the reads per kilobase of the exon model per million reads methodology. A total of 546 unigenes showed significant differences in expression levels at different fruit developmental stages. Gene ontology categories associated with various aspects, including carbohydrate metabolic processes, transmembrane transport, and signal transduction, were enriched with genes with divergent expressions. These Pyrus pyrifolia transcriptome data provide a rich resource for the discovery and identification of new genes. Furthermore, the numerous putative SSRs and SNPs detected in this study will be important resources for the future development of a linkage map or of marker-assisted breeding programs for the Asian pear.

Tree growth and fruit production of various organic Asian pear (Pyrus pyrifolia Nakai) cultivars grown under a rain-shelter system

SUMMARYA study was conducted to compare the effects of an open-field or rain-shelter system on the physiological responses of four Asian pear (Pyrus pyrifolia Nakai) cultivars (‘Hanareum’, ‘Wonhwang’, ‘Manpungbae’, and ‘Niitaka’) in an organic orchard in 2013 and in 2014. The rain shelter was covered with polyethylene film between 31 March–4 July each season, then uncovered during the remainder of each growing season. The incidences of fruit disease and insect pests, and fruit quality were measured in 2013. The rain-shelter system increased leaf chlorophyll contents to a SPAD value of 44.0 and rates of CO2 assimilation to 17.0 μmol m−2 s−1 in all four cultivars. It also increased leaf total nitrogen concentrations and dry weights in ‘Wonhwang’ and ‘Niitaka’ trees compared to the open field. Freezing temperatures were observed in the open field during flowering. The rain-shelter system resulted in a 10.3% delay in completion of current year shoot extension in all cultivars on 7 August 2014. It also significantly increased fruit yields (22,900 kg ha−1), mean fruit fresh weights (582 g), fruit size (94 mm in length and 105 mm in diameter), and total soluble solids contents (12.7°Brix) in 2013 and 2014. The incidence of scab on fruit was reduced by 3.3% in the rain-shelter system in 2013, but scab and rust on leaves and fruit were not completely prevented by this system in September 2014. The incidence of green chafers on leaves was significantly reduced from 23.3% to 51.0% by the rain-shelter system on 15 July 2014. The average income from fruit production in both seasons increased by approx. 138%, 167%, 326%, and 215% for rain-sheltered ‘Hanareum’, ‘Wonhwang’, ‘Manpungbae’, and ‘Niitaka’ trees, respectively, compared to open-field production.

Evaluation of Physiochemical Changes of Asian Pear Cultivars During Winter Season

Evaluation of Physiochemical Changes of Asian Pear Cultivars During Winter Season

Xanthan gum based edible coating enriched with cinnamic acid prevents browning and extends the shelf-life of fresh-cut pears

The objective of this investigation was to elucidate the influences of xanthan gum-based edible coating (2.5 g/L) applied alone or enriched with cinnamic acid (1 g/L) on the quality attributes of fresh-cut Asian pear (Pyrus pyrifolia L. cv. ‘Nashpati’) and European pear (Pyrus communis L. cv. ‘Babughosha’) stored at 4 °C. The incorporation of cinnamic acid as antioxidant agent into xanthan gum based edible coating caused significant (p < 0.05) retardation of the oxidative browning, decline of ascorbic acid level, degradation of total phenolics content and reduction in antioxidant capacity as compared to fresh-cut pears coated only with xanthan gum and uncoated ones. The control slices of ‘Nashpati’ displayed greater rise in browning index (BI) and polyphenol oxidase activity (PPO) and consistent decline in lightness (L*) values than those of ‘Babughosha’ during 8 days of storage. Moreover, the lower proliferation of microorganism over the fresh-cut pear may be attributed to the combined influence of good processing conditions along with xanthan gum edible coating enriched with cinnamic acid. Thus the tested xanthan gum based edible coating plus cinnamic acid may contribute to reduce the surface browning and enhance the shelf-life of fresh-cut ‘Nashpati’ and ‘Babughosha’ for 4 days and 8 days, respectively at 4 °C.

Evaluation of susceptibility of pear and plum cultivars to winter frost

ABSTRACT The damage to pear and plum buds was investigated in Mashhad, after a period of unusually warm weather for a few days in March 2013 followed by a sudden drop in temperature to -12°C. Frost damages of vegetative and reproductive buds and spur-part below the buds of pear and plum cultivars were investigated based on visual observations. The following pear (Pyrus communis L.) cultivars were investigated: William’s, Bell de june, Ida, Spadona, Koshia, Domkaj, Dare Gazi, Mohamad Ali, Boheme, Shekari, Ghodumi and one Asian pear (Pyrus serotina Rehd.). Japanese plum (P. salicina L.) included ’Shiro’, ’Shams’, ’Computi’ and European plum (Prunus domestica L.) included ’Stanley’, ‘Early Santa Rosa’, ’Late Santa Rosa’, ’Shablon’ and ’Black Diamond’. Electrical conductivity (EC) and proline content were measured in reproductive buds. It was discovered that visual damages were different between cultivars, as the vegetative pear bud of ‘Ghodumi’ suffered the most damage and all parts of ‘Late Santa Rosa’ were the most susceptible in plum cultivars. On the other hand, ‘Computi’ had the most resistant reproductive bud and no damage was observed in the other parts. The EC and proline content of ‘Dare Gazi’ were the highest despite the fact that high proline content did not show high resistance, which was related to the phenological stage of ‘Dare Gazi’.

Rapid and nondestructive detection of watercore and sugar content in Asian pear by near infrared spectroscopy for commercial trade

Watercore and sugar content are internal qualities which are impossible for exterior determination. Therefore the aims of this study were to develop models for nondestructive detection of watercore and predicting sugar content in pear using Near Infrared Spectroscopy (NIR) technique. A total of 93 samples of Asian pear variety "SH-078" were used. For sugar content, spectrum of each fruit was measured in the short wavelength region (700–1100 nm) in the reflection mode and the first derivative of spectra were then correlated with the sugar content in juice determined by digital refractometer. Prediction equation was performed by multiple linear regression. The result showed Standard Error of Prediction (SEP) = 0.58°Bx, and Bias=0.11. The result from t-test showed that sugar content predicted by NIR was not significantly different from the value analyzed by refractometer at 95% confidence. For watercore disorder, NIR measurement was performed over the short wavelength range (700–850 nm) in the transmission mode. The first derivative spectra were correlated with internal qualities. Then principle component analysis (PCA) and partial least squares discriminant analysis (PLSDA) were used to perform discrimination models. The accuracy of the PCA model was greater than the PLSDA one. The scores from PC1 were separated into two boundaries, one predicted rejected pears with 100% classification accuracy, and the other was accepted pears with 92% accuracy. The high accuracy of sugar content determining and watercore detecting by NIR reveal the high efficiency of NIR technique for detecting other internal qualities of fruit in the future.

Response of Early-season Asian Pear ‘Hanareum’ Treated with GA4+7 to Postharvest Application of 1-methylcyclopropene (1-MCP)

본 연구에서는 지베렐린(<TEX>$GA_{4+7}$</TEX>)을 0, 0.5, 1.2, 2.4% 농도로 조생종 '한아름' 배에 처리하고 수확 후 에틸렌 작용 억제제인 1-methylcyclopropene(1-MCP)를 <TEX>$1{\mu}L{\cdot}L^{-1}$</TEX> 농도로 처리한 후, 20일간의 상온유통기간 중 과실품질 및 생리장해 발생에 미치는 영향을 조사하였다. 상온유통 기간 중 감모율의 변화는 <TEX>$GA_{4+7}$</TEX> 농도와 관계없이 증가하는 경향을 보였으며, 1-MCP 처리의 경우 상온유통 기간이 증가함에 따라 감모율이 약간 감소하는 것으로 나타났고 <TEX>$GA_{4+7}$</TEX> 농도가 증가함에 따라 1-MCP 처리 효과는 떨어졌다. 상온유통 10일에 1-MCP를 처리하지 않은 모든 과실에서 경도가 급격하게 감소하였던 반면 1-MCP를 처리한 과실의 경우 상온유통 15일까지 30N 이상의 높은 경도를 나타내었다. 그러나 <TEX>$GA_{4+7}$</TEX> 처리 농도가 증가할수록 1-MCP 처리 효과는 떨어지는 것으로 조사되었다. 1-MCP를 처리한 과실의 경우 상온유통 기간 동안 가용성고형물과 산함량이 높게 나타났으며, 과피색의 경우 <TEX>$L^*$</TEX>(밝기) 및 hue angles은 높게 조사되었지만 <TEX>$a^*$</TEX>(적색도)의 경우 1-MCP 무처리에 비해 낮게 나타났다. 상온유통 중 에틸렌 발생량은 <TEX>$GA_{4+7}$</TEX> 처리 농도에 영향을 받지 않았고 1-MCP 처리는 에틸렌 발생량을 낮추지 못하는 것으로 조사되었다. 반면 1-MCP 처리 과실의 호흡률은 상온유통 20일간 유의하게 낮게 조사되었는데 1-MCP 처리 효과는 지베렐린을 처리하지 않은 구에서 가장 크게 나타났고 <TEX>$GA_{4+7}$</TEX>의 농도가 증가함에 따라 호흡률 감소 효과도 떨어졌다. 한편 1-MCP 처리는 상온유통 중 발생하는 과심갈변이나 분질과 같은 생리장해 발생 경감효과를 보여, <TEX>$GA_{4+7}$</TEX> 농도와 상관없이 상온유통 15, 20일 동안 과심갈변과 분질과의 발생을 억제하였다. This study was conducted to investigate the effect of 1-methylcyclopropene (1-MCP, <TEX>$1.0{\mu}L{\cdot}L^{-1}$</TEX>), a known ethylene action inhibitor, on fruit quality and incidence of physiological disorders during a simulated marketing period at <TEX>$25^{\circ}C$</TEX> for 20 days in early-season Asian pear (Pyrus pyrifolia Nakai) 'Hanareum' that had been treated with 0, 0.5, 1.2 or 2.4% <TEX>$GA_{4+7}$</TEX>. Weight loss of stored fruits increased with <TEX>$GA_{4+7}$</TEX> concentration, and the 1-MCP treatment slightly reduced the weight loss rates during the marketing period. Flesh firmness decreased abruptly in all 1-MCP-untreated fruits as the storage period extended to 10 d, whereas the firmness of 1-MCP-treated fruits remained high (> 30 N) during 15 days shelf-life. The effect of 1-MCP was significantly reduced when fruits were subjected to increased GA concentration. Higher soluble solids content and acidity during extended shelf-life were also apparent in 1-MCP-treated 'Hanareum' pears. The L-values (lightness) and hue angles of 1-MCP treated samples were higher than those of controls during 20 days shelf-life, but the a-value (redness) was lower in 1-MCP treated fruits. 1-MCP treatment did not decrease the level of ethylene evolution regardless of <TEX>$GA_{4+7}$</TEX> concentration during shelf-life in early-season Asian pear 'Hanareum'. By contrast, 1-MCP treatment decreased the respiration rate significantly during shelf-life. The efficacy of 1-MCP was greatest in the GA-untreated fruit and was reduced as the <TEX>$GA_{4+7}$</TEX> concentration increased. 1-MCP treatment influenced the severity of physiological disorders including core browning and mealiness: 1-MCP treatment completely blocked the incidence of core browning of during 15 days shelf-life, and reduced the severity of mealiness during 20 days shelf-life regardless of <TEX>$GA_{4+7}$</TEX> concentration. Based on our results, we conclude that the use of <TEX>$1{\mu}L{\cdot}L^{-1}$</TEX> 1-MCP can be of great benefit for maintaining quality and preventing physiological disorders in early-season pear cultivar 'Hanareum' pear, whereas its efficacy decreases with the concentration of <TEX>$GA_{4+7}$</TEX> whereas its efficacy gradually decreases when the concentration of <TEX>$GA_{4+7}$</TEX> paste increased.

Prediction of retrotransposons and assessment of genetic variability based on developed retrotransposon-based insertion polymorphism (RBIP) markers in Pyrus L.

Interspecific hybridization has been considered the major mode of evolution in Pyrus (pear), and thus, the genetic relationships within this genus have not been well documented. Retrotransposons are ubiquitous components of plant genomes and 42.4% of the pear genome was reported to be long terminal repeat (LTR) retrotransposons, implying that retrotransposons might be significant in the evolution of Pyrus. In this study, 1,836 putative full-length LTR retrotransposons were isolated and 196 retrotransposon-based insertion polymorphism (RBIP) primers were developed, of which 24 pairs to the Ppcr1 subfamily of copia retrotransposons were used to analyze genetic diversity among 110 Pyrus accessions from Eurasia. Our results showed that Ppcr1 replicated many times in the development of cultivated Asian pears. The genetic structure analysis and the unweighted pair group method with arithmetic mean (UPGMA) dendrogram indicated that all accessions could be divided into Oriental and Occidental groups. In Oriental pears, wild pea pears clustered separately into independent groups in accordance with their morphological classifications. Cultivars of P. ussuriensis Maxim, P. pyrifolia Nakai, and P. pyrifolia Chinese white pear were mingled together, which inferred that hybridization events occurred during the development of the cultivated Asian pears. In Occidental pears, two clades were obtained in the UPGMA dendrogram in accordance with their geographical distribution; one contained the European species and the other included species from North Africa and West Asia. New findings in this study will be important to further understand the phylogeny of Pyrus and origins of cultivated pears.

Response of 1-methylcyclopropene Treatment on Early season ‘Hanareum’ and Mid-season ‘Manpungbae’ Asian Pears (Pyrus pyrifolia Nakai)

Response of 1-methylcyclopropene Treatment on Early season ‘Hanareum’ and Mid-season ‘Manpungbae’ Asian Pears (Pyrus pyrifolia Nakai)

Genetic mapping of polygenic scab (Venturia pirina) resistance in an interspecific pear family

The need for chemical control of scab (Venturia pirina, V. nashicola) is the main barrier preventing sustainable pear production. As cultivars with durable resistance are not available yet commercially, the development of molecular markers for early selection is desirable to enhance the efficiency of breeding such cultivars. Interspecific pear progeny PEAR1 × PEAR2 derived from European (Pyrus communis) and Asian (P. pyrifolia and P. ussuriensis) pears was infected with three single-spore isolates of V. pirina using the droplet inoculation technique. Illumina Infinium® HD Assay technology was employed to genotype the progeny with single nucleotide polymorphism markers for map construction. With one linkage group missing in each parent, the parental maps covered 17 linkage groups in total, 1,132.3 and 1,136.8 centimorgan for the female and male parents, respectively. Resistance mapping resulted in the identification of seven quantitative trait loci (QTLs) by Kruskal–Wallis analysis. Parent PEAR1 contributed a QTL on linkage group (LG) 17 that was effective against all three scab isolates, while PEAR2 contributed one on LG7 that was effective against two isolates. The other five QTLs, on LG2 and LG5 of PEAR2, and LG7 and LG10 of PEAR1, displayed differential interactions, with each QTL being paired with a single incompatible isolate. Additive effects of combined resistance loci displayed a higher level of resistance than single loci, and the role of nonhost resistance is discussed.

Growth, fruit production, and disease occurrence of rain-sheltered Asian pear trees

Tree performance, fruit production, and disease occurrence were compared for ‘Niitaka’ Asian pear (Pyrus pyrifolia Nakai) trees grown under open-field or rain-shelter system in two organic orchards. The study was conducted in two provinces, Naju (orchard A) with young pear trees in 2012 and 2013 and Namwon (orchard B) with mature pear trees in 2012. Pear trees under the rain shelter showed higher overall tree canopy growth, number of leaves, and fruit set in both orchards, with less frost damage to flower clusters due to preventing decreasing canopy temperature during flowering in orchard A. Trees grown under the rain-shelter system had higher fruit yield, average fruit weight, crop density, fruit soluble solid contents, titratable acidity, and fruit skin color L*, as well as reduced disease incidence of leaves or fruit, all of which would likely contribute to higher economic return compared to those from open-field systems.

배 검은별무늬병균(Venturia nashicola)의 균사 생장에 대한 배지 조성의 영향

Pear scab caused by the fungus Venturia nashicola is the most devastating disease on Asian pear (<italic>Pyrus pyrifolia</italic>). However, mycological and biological traits of V. nashicola were rarely known because the artificial cultivation of the fungus is difficult using typical fungal growth medium in the laboratory. The main objective of this study, was to determine the best culture medium composition suitable for mycelial growth of V. nashicola. A new culture medium using pear extracts, various carbon and nitrogen sources were used to examine the best combination for mycelial growth of V. nashicola. The culture medium ammended with pear extracts showed higher mycelial growth than non-ammended PDA medium. Specifically, the culture medium ammended with pear ground young leaf extract showed the highest fungal mycelial growth. The increased mycelial growth of V. nashicola was observed in growth medium ammended with Ca(NO₃)₂ but mycelial growth was negatively influenced by supplement with calcium chelating agent, EGTA. Taken together, we invented a new growth medium ammended with pear extract or Ca(NO₃)₂ for growth of V. nashicola, and it could be helpful to study on ecological and mycological traits of the pear scab pathogen.

Penetration Behaviour of Venturia nashicola, Associated with Hydrogen Peroxide Generation, in Asian and European Pear Leaves

AbstractThe penetration behaviour of the pathogen Venturia nashicola, which causes scab disease in Asian pears, was studied at the ultrastructural and cytochemical levels in host and non‐host leaves. We show, for the first time, that before V. nashicola penetrated the cuticle of the epidermis of the pear leaf, the appressorial bottom of the pathogen invaginated to form a cavity that contains electron‐dense material. The leaf cuticle beneath the cavity also became highly electron dense following penetration by V. nashicola. The location of these electron‐dense materials at the sites of penetration of the pathogen into plant cell walls suggests that they might be related to enzymes capable of degrading cell walls and that the cavities might be needed for successful penetration of leaves by V. nashicola. The generation of hydrogen peroxide (H2O2) was observed in penetration‐related infection structures of V. nashicola, such as appressorial bottoms, infection sacs, penetration pegs and necks of subcuticular hyphae regardless of whether the interaction of V. nashicola with pear plants was compatible or incompatible. Nonetheless, more H2O2 was generated at the sites of the structures in scab‐inoculated susceptible leaves than that in scab‐inoculated resistant ones. Furthermore, the decrease in the level of H2O2 generation following treatment with the antioxidant ascorbic acid partially prevented the penetration of the cuticle. Therefore, the generation of H2O2 from the penetration‐related structures might be a pathogenicity factor that contributes to strengthening the penetration peg of V. nashicola.