• Korean Journal of Plant Resources
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• v.28 no.6
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• pp.697-703
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• 2015

Twenty apple germplasm accessions from the Korean Genebank were successfully cryopreserved using two-step freezing to back up genetic resources maintained by field collections. This study examined the morphological and genetic stability of cryopreserved dormant apple buds that were stored in liquid nitrogen, and then rewarmed and regrown. Whole plants were regenerated directly from dormant buds through budding without an intermediary callus phase. The cryopreserved buds produced high levels of shoot formation (76.2-100%), similar to those of noncryopreserved buds (91.3-100%), with no observed differences between cryopreserved and noncryopreserved materials. Three of the twenty cryopreserved apple germplasm accessions were used to assess morphological and genetic stability. No differences in morphological characteristics including shoot length, leaf shape, leaf width/length ratio, and root length were observed between controls (fresh control and noncryopreserved) and cryopreserved plantlets. The genetic stability of regenerants (before and after cryopreservation) was investigated using inter simple sequence repeat (ISSR) markers. The ISSR markers produced 253 bands using four primers, ISSR 810, SSR 835, ISSR 864, and ISSR 899. These markers showed monomorphic banding patterns and revealed no polymorphism between the mother plant and regenerants before and after cryopreservation, suggesting that cryopreservation using two-step freezing does not affect the genetic stability of apple germplasm. These results show that two-step freezing cryopreservation is a practical method for long-term storage of apple germplasms.

• Korean journal of applied entomology
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• v.16 no.1 s.30
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• pp.33-39
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• 1977

The Present survey was conducted to clarify species of moths infesting apple and the general biology of the dominant species as a basis for effective control. From the results of a survey in Suweon area, 24 species of leafrollers, 3 species of fruit-moths, 4 species of leaf-miners, 4 species of fruit-piercing moths and 28 other leaf-feeders were identified as pests of apple or apple trees.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.531-538
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• 2011

This study was carried out to investigate the influence of defoliation by Marssonina blotch (Diplocarpon mali Harada et Sawamura) on vegetative growth and fruit quality in 'Fuji'/M.9 apple tree. Soluble solid contents decreased when the defoliation percentage by Marssonina blotch was over 10% before the end of September, and fruit weight decreased when percentage of defoliation was over 30%. Fruit red color and starch contents tend to decrease as percentage of defoliation near the fruit increased. Return bloom, fruit weight, and shoot growth the following year tend to decrease as percentage of defoliation increased. Photosynthetic rate of healthy leaves in bourse shoot during the end of September was maintained about $10{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, effects in increasing fruit growth and soluble solid contents after the end of September. Photosynthetic rates for the damaged leaf, damaged area was over 50% on the leaf surface, while 30% of the photosynthetic rates of healthy leaf are without damage applied with Marssonina blotch at the end of September. The results show that the decrease of fruit quality in defoliation treatments may be caused by the decrease of starch contents in fruit, and that was caused by the photosynthetic rates of leaves near fruit was decreased by Marssonina blotch in the wake of August.

• Research in Plant Disease
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• v.27 no.2
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• pp.79-83
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• 2021

The aim of the present study was to develop a sensitive and specific detection method for the rapid detection of apple scar skin viroid (ASSVd) in apple leaves. The resulting reverse transcription recombinase polymerase amplification (RT-RPA) assay can be completed in 10 min at 42℃, is 10 times more sensitive than conventional reverse transcription polymerase chain reaction, and can specifically amplify ASSVd without any cross-reactivity with other common apple viruses, including apple stem grooving virus, apple stem pitting virus, and apple chlorotic leaf spot virus. The reliability of the RT-RPA assay was assessed, and the findings suggested that it can be successfully utilized to detect ASSVd in field-collected samples. The RT-RPA assay developed in the present study provides a potentially valuable means for improving the detection of ASSVd in viroid-free certification programs, especially in resource-limited conditions.

• Journal of Plant Biotechnology
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• v.44 no.4
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• pp.379-387
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• 2017

Various sizes (0.2 ~ 1.2 mm) and developmental stages (referred to as Stage 1 ~ 3) of apical and lateral meristems were excised, together or separately, directly from dormant buds of apple 'Hongro'. They were mixed infected by Apple scar skin viroid (ASSVd), Apple chlorotic leaf spot virus (ACLSV), Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV), which are major viruses attacking apples. A total of 31 callus lines (> 10 mm in diameter) were obtained by culturing the explants on Murashige and Skoog (MS) medium supplemented with 3% sucrose, 3.0 mg/L benzyladenine (BA) and 0.1 mg/L indole-3-butyric acid (IBA), and they were subjected to RT-PCR analysis for virus detection. A high rate of virus elimination (expressed as the percentage of calli that did not amplify during RT-PCR, i.e., RT-PCR negative calli per total number of calli obtained) was achieved for ACLSV (100%), ASSVd (93.7%), and ASPV (93.7%), whereas it was only 25.8% for ASGV. ASPV was detected in the presence of 2 ~ 3 bracts. Simultaneous virus elimination of ASSVd, ASPV, ACLSV, and ASGV occurred during the meristem culture, in which the early stages of the dormant buds (Stage 1) were used, because ASGV was mostly eliminated during that stage. The results of the present study will be valuable for the production of virus-free apple trees.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.4
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• pp.259-265
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• 2004

A quicker method was developed for foliar analysis in diagnosis of nitrogen in apple trees based on multivariate calibration procedure using partial least squares regression (PLSR) and principal component regression (PCR) to establish the relationship between reflectance spectra in the near infrared region and nitrogen content of fresh- and dry-leaf. Several spectral pre-processing methods such as smoothing, mean normalization, multiplicative scatter correction (MSC) and derivatives were used to improve the robustness and performance of the calibration models. Norris first derivative with a seven point segment and a gap of six points on MSC gave the best result of partial least squares-1 PLS-1) model for dry-leaf samples with root mean square error of prediction (RMSEP) equal to $0.699g\;kg^{-1}$, and that the Savitzky-Golay first derivate with a seven point convolution and a quadratic polynomial on MSC gave the best results of PLS-1 model for fresh-samples with RMSEP of $1.202g\;kg^{-1}$. The best PCR model was obtained with Savitzky-Golay first derivative using a seven point convolution and a quadratic polynomial on mean normalization for dry leaf samples with RMSEP of $0.553g\;kg^{-1}$, and obtained with the Savitzky-Golay first derivate using a seven point convolution and a quadratic polynomial for fresh samples with RMSEP of $1.047g\;kg^{-1}$. The results indicate that nitrogen can be determined by the near infrared reflectance (NIR) technology for fresh- and dry-leaf of apple.

• Korean journal of applied entomology
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• v.43 no.1
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• pp.15-20
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• 2004

Leaf damage by apple leafminer, Lyonetia prunifoliella, was surveyed on Fuji apple orchards with seedling rootstock from 1992 to 2001 and with M.9 rootstock from 1999 to 2001. The damage was negligible in apple orchards with seedling rootstock as 0.15% in 1992 and 0.06% in 1993. However it sharply increased to more than 3.39% since 1994, reaching at peak damage of 6.28% to 7.78% in 1996 to 1998. Damages on apple orchards with M.9 rootstock from 1999 to 2001 were higher as 6.09% to 15.3%, compared with those with seedling rootstock in the same years. In seedling rootstock apple, the damage was highest on september but in M.9 rootstock apple, the difference was not significant. Leaf damage showed no differences between cultivars including 4 Korean cultivars and Fuji. These results may explain that increase of M.9 rootstock apple orchards is responsible for the recent outbreak of the leafminer in Korea.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.52-52
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• 2018

Apple (Malus domestica) is one of the most economically important fruits in Korea. But virus infection has decreased sustainable production of apple and caused the serious problems such as yield loss and poor fruit quality. Virus or viroid infection including Apple chlorotic leaf spot virus (ACLSV), Apple stem pitting virus (ASPV), Apple stem grooving virus (ASGV), Apple mosaic virus (ApMV) and Apple scar skin viroid (ASSVd) has been also reported in Korea, furthermore, its damages and economic losses have increased constantly. In our research, we tried to survey virus infection for commercial nursery trees of major apple cultivars, especially dwarfing rootstocks 'M.9' and 'M.26' as well as scions. Trees were collected from 11 locations which have produced a great amount of apple nursery stocks in Korea. Infection degree was investigated in apple cultivars, 'Hongro' and 'Fuji' using RT-PCR method. In the scion of cultivar 'Hongro', infection ratio of ACLSV, ASPV and ASGV were 100%, 81.8% and 100% respectively. In the rootstock of cultivar 'Hongro', infection ratio of ACLSV, ASPV, ASGV and ApMV were 90.9%, 81.8%, 100% and 9.1% respectively. In the scion of cultivar 'Fuji', infection ratio of ACLSV, ASPV and ASGV were 81.8%, 90.9% and 100% respectively. In the rootstock of cultivar 'Fuji', infection ratio of ACLSV, ASPV, ASGV and ApMV were 81.8%, 90.9%, 100% and 9.1% respectively. Infection of ASSVd was not detected in both cultivars. From our results, it was found that most of apple rootstocks and scions had multiple infections by apple viruses which have caused economic damage in fruit production.

• Korean journal of applied entomology
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• v.26 no.4 s.73
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• pp.245-249
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• 1987

In the 82 apple varieties tested, the distribution of varieties grouped on the damage degree to Alternaria leaf spot were 15 varieties(l8.3%), which damaged above 50%, and 51 varieties(62.2%) damaged below 5%. Susceptible varieties to Alternaria leaf spot were Raritan, Indo, Winesap and Starkrimson, moderately resistant varieties Sekaiichi and Starking, and resistant Jonathan, Tsugaru, Molliies, Jonagold, Gala etc. The leaf hair density on the backside of leaf were rarer inresistant varieties than susceptible one. In inoculation test, penetration and infection of Alternaria mali were easier on the backside than surface of apple leaf at the same varity, and infection rate with Alternaria mali were higher at removal treatment than non-removal one of leaf hairs, so we can guess that leaf hair are related to resistance of variety to Alternaria mali.

• Korean Journal of Agricultural Science
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• v.43 no.1
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• pp.21-27
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• 2016

Apple stem grooving virus (ASGV), Apple chlorotic leaf spot virus (ACLSV), and Apple stem pitting virus (ASPV) have been known to induce top working disease causing economical damage in apple. Occurrences of these three viruses in pome fruit trees, including apple, have been reported around the world. The transmission of the three viruses was reported by grafting, and there was no report of transmission through mechanical contact, insect vector, or seed except some herbaceous hosts of ASGV. As RNA extraction methods for fruit trees, Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) and multiplex RT-PCR techniques have been improved for reliability and stability, and low titer viruses that could not be detected in the past have become detectable. We studied the seed transmission ability of three apple viruses through apple seedling diagnosis using RT-PCR. Nineteen seeds obtained from commercially grown apple were germinated and two of the resulting plants were ASGV positive. Seven clones of the amplified ASGV coat protein (CP) genes of these isolates were sequenced. Overall sequence identities were 99.84% (nucleotide) and 99.76% (amino acid). Presence of a previously unreported single nucleotide and amino acid variation conserved in all of these clones suggests a possible association with seed transmission of these 'S' isolates. A phylogenetic tree constructed using ASGV CP nucleotide sequences showed that isolate S sequences were grouped with Korean, Chinese, Indian isolates from apple and Indian isolates from kiwi.