• Korean Journal of Plant Resources
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• v.32 no.4
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• pp.296-302
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• 2019

This study was accomplished to select breeding materials among the pear germplasm 6 species 43 accessions and check out the expression of scab incidence of inter specific hybrids of 5 crosses 609 seedlings for scab resistance breeding. Fruitlets scab incidence of P. pyrifolia, P. bretschneideri and P. ussuriensis were 59.5, 73.4 and 63.0% respectively, and also fruitlets scab incidence of interspecific hybrid cultivars between P. pyrifolia and P. bretschneideri were 77.7%. However, fruitlets scab incidence of P. communis and interspecific hybrid accessions between P. pyrifolia and P. communis were significantly less than 15%. As a result of the Duncan test, scab resistance of pear accessions were classified into two groups: P. communis and their hybrid were resistance and P. bretschneideri, P. pyrifolia, P. ussuriensis, and among their hybrid were susceptible. Also, it showed the same trend in the seedlings. Scab incidence of 'Seolwon' ${\times}$ 'Chuwhangbae' and 'Supergold' ${\times}$ 'Mantienhong' in P. pyrifolia seedlings showed more than 80%, while that of interspecific hybrid between P. pyrifolia and P. communis showed about 2%. It showed scab resistance of P. communis transferred to hybrid seedlings and expressed to be dominant in their seedlings. Namely, P. communis was good breeding materials for scab resistance.

• Korean Journal of Organic Agriculture
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• v.21 no.4
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• pp.617-627
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• 2013

This study was conducted to survey the current pest occurrence and grower's pest management practices, and to investigate biodiversity including birds, snakes, rodents, and amphibians in organic pear orchards. From the questionnaires and field survey of 22 organic orchards in 2010, the materials such as lime sulphur, plant extracts and their mixtures with microorganisms, and oils were preferred over insecticides. Scab, mealybugs, woollybugs and barkminers were the major pests for organic pear growers. Environment-friendly fungicides and insecticides were applied 9 to 10 and 5 to 6 times respectively. Incidence and severity of scab on Niitaka pear fruits in organic orchards was higher than in conventional ones. Whereas for mealybugs there was no significant difference between organic and conventional orchards. Pear fruits in organic orchards were significantly smaller than those of non-organic orchards. For the biodiversity of amphibians, snakes, pheasants, and rodents, there was no significant difference between organic and conventional orchards, but Rufous turtle doves were monitored more in organic areas than in conventional ones.

• The Plant Pathology Journal
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• v.24 no.2
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• pp.118-124
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• 2008

Skin sooty dapple disease, a fungal disease that lowers Asian pear fruit quality, has emerged recently in Korea but has not yet been thoroughly characterized. This disease affects the surface of fruit, leaves, and young shoots of the Asian pear, typically appearing as a dark or pale black dapple on the fruit surface. The disease initiates on the fruit with small circular lesions that become bigger, eventually spreading to form large circular or indefinite lesions. Sparse dark or flourishing white-greyish aerial mycelia and appearance of a dark or pale black dapple on the fruit surface are typical signs of this disease. The disease was severe during cold storage of the Niitaka and Chuhwangbae varieties, but more limited on the Gamcheonbae and Hwangkeumbae varieties. To identify causal pathogens, 123 fungal isolates were obtained from lesions. The fungi that caused typical skin sooty dapple disease symptoms in our bioassay were identified. Based on their morphological characteristics, 74% of the isolates were Cladosporium sp. and 5-7 % of the isolates were Leptosphaerulina sp., Tripospermum sp., or Tilletiopsis sp. None of the isolates caused severe soft rot by injection to a wound plug, but some of the Cladosporium sp. isolates caused mild maceration. Therefore this microbiol complex cannot account for the soft rot also observed in stored fruits. The high frequency of isolation of Cladosporium sp. from disease tissues and bioassay on pear fruit surface suggest that Cladosporium sp. could be a major pathogen in the microbial complex associated with skin sooty dapple disease of the Asian pear in Korea.

• Korean Journal of Breeding Science
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• v.41 no.2
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• pp.154-157
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• 2009

Pear has a gametophytic self-incompatibility (SI) system and its SI reaction is controlled by a single multi-allelic S-locus. 'Wonkyo Na-jasoojung 2' was selected from a cross between 'Wonwhang', early season major pear cultivar with high fruit quality and self-incompatible, and 92-18-79 (${S_4}^{sm}{S_4}^{sm}$) obtained from self cross of 'Osa-nijisseiki' (${S_2S_4}^{sm}$) (SM, stylar-part mutant), self-compatible bud mutant that originated from self-incompatible 'Nijisseiki' ($S_2S_4$) made in 2001 at the National Institute of Horticultural and Herbal Science, Rural Development Administration in Korea. '92-18-79' was selected as a self-compatible source through field investigation. It bloomed 1 day earlier than 'Osa-Nijisseiki' and similar to 'Wonwhang' in 2008. It is medium in tree vigor and spreading in tree habit. 'Wonkyo Na-jasoojung 2' is classified as highly susceptible to pear scab (Venturia nashicola) similar to 'Osa-Nijisseiki' and as resistant to black spot (Alternaria kikuchiana) similar to 'Wonwhang'. It had 65.7% fruiting rate by self pollination. The average optimum harvest time of 'Wonkyo Na-jasoojung 2' was 148 days after full bloom and it matured 2 days earlier than 'Osa-Nijisseiki' and 11 days later than 'Wonwhang'. The fruit is roundish oblate in shape and yellowish brown in skin color. Average fruit weight was 445 g and soluble solids content was 13.3 $^{\circ}Brix$. The flesh had abundant juice and negligible grit.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.5
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• pp.322-326
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• 2013

Many organic fruit growers adopt cover cropping in their orchards to improve soil properties. A field experiment was conducted to determine the effects of cutting frequency of cover crop (CF) and liquid manure application (LM) on green manure production (GMP) and returnable nutrient content (RNC) in pear orchard. The combined effects of CF and LM were tested at two levels, respectively, with liquid manure ($L_1$) and without liquid manure ($L_0$). After that, cover crops were cut once ($C_1$) and three times ($C_3$) in rye, and twice ($C_2$) and four times ($C_4$) in hairy vetch. The result showed that main factors related to green manure production were different depending on the species. In rye, LM was more effective in increasing the dry weight of cover crop and RNC than CF. In contrast, the parameters were more affected by CF rather than LM in hairy vetch. Thus, it is suggested that different management technique is needed depending on the cover crop species in order to maximize the green manure production in pear orchard.

• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.217-223
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• 1995

Nature of graft transmissibility of pear abnormal leaf spot disease was examined by various grafting methods in the greenhouse and field. When the diseased and symptomless twigs were collected in winter and grafted in the next spring to the seed-originated healthy root stock, the abnormal leaf spot was developed only in the case of the diseased twigs. Double grafting on a seed-originated healthy root stock, where the diseased and the symptomless twigs were used as 1st and 2nd scions, respectively, developed abnormal leaf spot lesions without exception on the 2nd scions. Tongue-graft with the diseased and the symptomless trees also incited abnormal leaf spots on the both trees. Abnormal leaf spots of were also developed on HN-39, an indicator pear tree, used as a 2nd scion in a double graft test, where the diseased twig and a seed-originated healthy tree were used as the 1st scion and the root stock, respectively. When the diseased twig was top-grafted to the healthy root stock, lesion development of abnormal spot was limited to the grafted twig itself in the 1st year, but expanded to the main branches in the 2nd year, and spread over the whole tree in the 3rd year. This result indicates that the causal agent of abnormal leaf spot disease is transmitted by graft.

• Horticultural Science & Technology
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• v.34 no.4
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• pp.655-661
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• 2016

To develop scab-resistant pear (Pyrus spp.) varieties with fruits that are as crisp and juicy as Asian pears, a cross was made between 'Whangkeumbae' and 'Bartlett' varieties (P. pyrifolia ${\times}$ P. communis) at the Pear Research Institute of the National Institute of Horticultural & Herbal Science, Rural Development Administration, in 1994. Among the 285 seedlings, 'Greensis' was first selected in 2006 for its good eating quality and named in 2012 after regional adaptation tests in nine regions and ten experimental plots from 2007 to 2012. The tree showed a vigorous growth habit and semi-spreading characteristics, like 'Whangkeumbae'. The optimum fruit harvest date was also around Sept. 26 and fruit was round in shape and green in skin color at maturity. Average fruit weight was 470g, and the soluble solids content was $12.4^{\circ}Brix$. The flesh was very crisp and juicy, and had good eating quality. Its' leaf size was similar with 'Bartlett' and smaller than 'Whangkeumbae'. The average of full bloom date of 'Greensis' was determined as Apr. 26, which was six days later than 'Whangkeumbae' and similar with 'Bartlett'. S genotypes of 'Greensis' were identified as $S_4S_e$ by S-allele PCR product sequencing analysis. It seems that the $S_4$ allele was inherited from 'Whangkeumbae' and the Se allele from 'Bartlett'. 'Greensis' displayed strong resistance to scab disease caused by Venturia nashicola, similar to European pear cultivars like 'Beurre Hardy' and, 'Conference'. 'Greensis' was also highly resistant to black leaf spot (Alternaria kikuchiana) in the field

• The Korean Journal of Pesticide Science
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• v.12 no.4
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• pp.375-381
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• 2008

A new disease causing skin sooty dapple symptoms on fruits, leaves, and young shoot of Asian pear occurred in Korea. However, no chemical control approaches has been developed to control this disease. To investigate ecological aspects of this disease, we conducted field surveys in the high or low disease occurred orchards. The years with heavy rainfall caused severe occurrence of the skin sooty dapple disease than the years with lower rainfall during all growth stages of pear fruit. Different fruit-wrapping bags did not prevent occurrence of skin sooty dapple disease, and lesion numbers were higher in lower parts of fruit equatorial line inside of fruit-wrapping bags. There is a direct correlation between occurrence of the skin sooty dapple disease and frequency of fungicide application in the orchards. Among the tested commercial fungicides, thiophanate-methyl WP and penconazole WP completely inhibited the growth of the Cladosporium sp. in in vitro studies but little protection was observed in the field following fungicide applications. However, application of lime sulfur combined with the use of fruit-wrapping bags most effectively reduced incidence of the disease in the field. Our results suggest that skin sooty dapple disease could be a serious problem in sustainable organic pear farms and effective control methods for this disease urgently required.

• Korean Journal of Agricultural Science
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• v.38 no.1
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• pp.39-44
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• 2011

The changes in major moth populations were monitored by sex pheromone traps in pear orchards at Yuseong-Gu, Daejeon from 2008 to 2010. Among four major moths, Grapholita molesta and Caposina sasakii occurred most frequently. Their occurrences peaked 2 to 3 times during the growing season from May to September. G. molesta was exceptional, occurring until September. For the environmentally-friendly control of these moths, 9 control materials including insect pathogenic bacteria and environmentally-friendly agricultural materials, were examined on the larva of 4 kinds of moth and sprayed on pear leaves in the field. As the generalized results of bioassay, Bacillus thuringiensis subsp. kurstaki and Sophora flavescens extract were shown to have better control effects than any other control material.

• Korean journal of applied entomology
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• v.14 no.4 s.25
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• pp.215-219
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• 1975

The number of instars of pear sawfly larvae (Janus piri Okamoto) collected front field pear trees, were determined by measuring the width of head capsule, and the growth ratio in each instar was also studied. 1. The larval head width had six distinct peaks, which suggests that the larva of this insect passes six instars. 2. The head width tended to increase as the instars avdance, except in tile first and second instars. The coeffieient of variation decressed as the instars advanced. The growth ratio, which was similarly great in the first and second instars, decreased as the instars advanced. 3. Gains' and Campbell's formulae seemed to be more suitable than Dyer's for the determination of larval instars of this insect by the measurement of headwidth. 4. The larval instars could be inferred from the extent of damage to pear tree by this insect; that is the larvae in the second to fourth instars usually gave slight and invissible damage, while those in the fifth to sixth instars gave rapid and severe damage.