Jong-Han Park

In Korea, most of the grafted watermelons are a fusion of bottle gourd (Lagenaria siceraria) as a rootstock and watermelon (Citrullus lanatus) as a scionstock (Lee et al., 2010). Currently, we have collected several samples from grafted watermelon displaying symptoms of yellowing, withered and wilting leaves. When the symptomatic stem was excised, browning vascular tissues were observed due to the colonization of fungal pathogen. From the samples obtained, 25 fungal isolates were identified as species of Fusarium. Among 25 isolates, 18 were identified as Fusarium oxysporum, four as Fusarium solani, and three as Fusarium equiseti (F. equiseti) . Initial assessment showed that one of the F. equiseti isolates (NIHHS 16-126) was highly virulent to rootstock. Interestingly, this is the first time F. equiseti has been identified pathogenic to grafted watermelon. NIHHS 16-126 isolate was collected from watermelon cultivation field around Buyeo-gun (36.25951°N, 126.92044°E) county. Disease incident was estimated to infect approximately 10% of the watermelon plants cultivated in this area. NIHHS 16-126 isolate was examined to confirm its identity. On potato dextrose agar, colonies appeared yellowish-brown while the aerial mycelium was whitish to peach in color. Macroconidia were relatively long (20.21 - 51.13 × 2.30 - 4.5 μm, n=50), comprise of 3-6 septa, curvature shape and its conidiophores were with monophialides. However, microconidia formation was not observed. These morphological characteristics resemble F. equiseti characters as described by Hyun (2019). For molecular identification, an internal transcribed spacer of ribosomal DNA (ITS-rDNA), elongation factor-1α (EF-1α), and beta-tubulin (β-tub) genes were sequenced using primer pairs of ITS1/ITS4 (White et al., 1990), EF1-728F/EF1-986R (Glass and Donaldson 1995), and Bt2a/Bt2b (Carbone and Kohn 1999). BLASTN analysis revealed that ITS-rDNA (LC648248), EF-1α (LC648250), and β-tub (LC648249) sequences were 99-100% identical to F. equiseti reference sequences (KF515650, KF747331, and KF747330) infected Avicennia marina in China (Lu 2014). Phylogenetic analysis of concatenated ITS-rDNA, EF-1α and β-tub sequences showed that this isolate clustered in the same clade as F. equiseti, confirming its identity as F. equiseti. For the inoculation, roots of 12-days-old seedlings (watermelon and bottle gourd, n=10 each) were dipped in the conidia suspension (1x10⁶ conidia/µL) for 30 min. Inoculated seedlings were planted in the soil before being transferred to the greenhouse (temperature; 30°C, daylight; 14 hours). Control plants were inoculated with sterile water. Results showed that after 21 days post-inoculation, all inoculated bottle gourd seedlings (n=10) wilted and eventually died. In contrast, none of the inoculated watermelons or control seedlings were affected. Re-isolation of three fungal isolates (infected root) showed that their morphology and gene markers sequence were identical to the original isolates thus fulfilled Koch's postulates. Bottle gourd is the most preferred rootstock for grafted watermelons among Korean farmers due to its ability to resist Fusarium spp. infection. Therefore, the identification of F. equiseti as a fungal that is pathogenic to rootstock is crucial information to manage fusarium wilt disease among grafted watermelon. To our knowledge, this is the first report confirming F. equiseti infection in grafted watermelon plants in Korea.

Plumcot is an interspecific hybrid product between Japanese plums (Prunus salicina) and apricots (Prunus armeniaca) obtained by the NIHHS, Korea in 1999 [1]. At the early of 2017, black spots-like ...

Chinese cabbage (Brassica rapa L.) is one of the most important vegetables in Korea due to its role as the main ingredient for the making of Kimchi. In June 2014, disease symptoms of leaves wilt, d...

Muskmelons (Cucumis melo L.) are among the most popular cucurbits wordwide, and are cultivated in Korea for their sweet and juicy taste. In April 2018, wilting and damping-off symptoms were observe...

The use of conventional classification techniques to recognize diseases and pests can lead to an incorrect judgment on whether crops are diseased or not. Additionally, hot pepper diseases, such as “anthracnose” and “bacterial spot” can be erroneously judged, leading to incorrect disease recognition. To address these issues, multi-recognition methods, such as Google Cloud Vision, suggest multiple disease candidates and allow the user to make the final decision. Similarity-based image search techniques, along with multi-recognition, can also be used for this purpose. Content-based image retrieval techniques have been used in several conventional similarity-based image searches, using descriptors to extract features such as the image color and edge. In this study, we use eight pre-trained deep learning models (VGG16, VGG19, Resnet 50, etc.) to extract the deep features from images. We conducted experiments using 28,011 image data of 34 types of hot pepper diseases and pests. The search results for diseases and pests were similar to query images with deep features using the k-nearest neighbor method. In top-1 to top-5, when using the deep features based on the Resnet 50 model, we achieved recognition accuracies of approximately 88.38–93.88% for diseases and approximately 95.38–98.42% for pests. When using the deep features extracted from the VGG16 and VGG19 models, we recorded the second and third highest performances, respectively. In the top-10 results, when using the deep features extracted from the Resnet 50 model, we achieved accuracies of 85.6 and 93.62% for diseases and pests, respectively. As a result of performance comparison between the proposed method and the simple convolutional neural network (CNN) model, the proposed method recorded 8.62% higher accuracy in diseases and 14.86% higher in pests than the CNN classification model.

Zamioculcas zamiifolia (Lodd.) Engl., commonly known as the ‘ZZ plant’, belongs to the Araceae family. It is native to Africa, from Kenya to South Africa, and is considered an attractive indoor plant because of its dark green foliage and low light requirements. ZZ plants are also considered more effective than Sansevieria spp. in reducing BTEX contaminants (benzene, toluene, ethylbenzene and xylene) in indoor air (Toabaita et al. 2016). Additionally, the plants are tolerant to drought stress, have a unique appearance with minimal maintenance requirements, and are popular as ornamentals for display in offices and homes in Korea. In August 2016, ZZ plant samples from the Yongin nursery, Gyeonggi-do Province (37°12′01.8″N, 126°20′01.0″E) were submitted to the Horticultural and Herbal Crop Environment Division in Wanju, Korea. Initial symptoms included water-soaking of stems with lower leaf chlorosis followed by stem collapse and crown rot. White mycelia and brown sclerotia were observed on infected plant par...

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Cucumber (Cucumis sativus) possessed over 95% moisture content and low calorie. It is one of preferred vegetable and produces over 340,000 ton in South Korea. In 2013, we found necrotic water-soaked leaf and black spots from a commercial cucumber seeding areas in Yeongam-gun, Jeonnam Province, Korea. Fewer than 5 % of cucumber plants were appeared these symptoms. Severed symptoms on the leaves were turned black spots. Younger leaves were severed symptoms than cotyledons. Causal pathogen was isolated from black spot leaves. Bacteria isolate was formed circular, entire margin colonies with white to cream color colony on Luria-Bertani (LB) agar at 28°C. It appeared gram-negative bacteria using gram test kit. Pathogenicity tests were conducted with potted, greenhouse-grown cucumber plants. Inoculum grown on LB broth for 24 h at 28 °C was suspended in distilled water. Suspension (5.0 × 107 CFU/ml) was inoculated leaves using syringe. Inoculated plants were maintained at 28°C and over 90% humidity in a growth c...