Younghyun Ryu

Resistance of Commercial Tomato Cultivars to Meloidogyne arenaria and M. incognita

Root-knot nematodes (Meloidogyne spp.) are among the main pathogens of greenhouse crops worldwide. Plant resistance is currently the method of choice for controlling these pests. To select resistant tomato against two common species of root-knot nematodes, M. incognita and M. arenaria, 36 commercial tomato (Lycopersicon esculentum Mill.) cultivars were screened. Seventeen tomato cultivars were resistant to both root-knot nematodes: six in cherry tomato, `Tenten`, `Cadillac`, `Cutti`, `Sweet`, `Ppotto`, `Lycopin-9`, eight in globe tomato, `Lovely 240`, `Dotaerang Dia`, `Cupirang`, `Dotaerang Master`, `Super Dotaerang`, `Dotaerang Season`, `Miroku`, `Hoyong`, and three in root stock, `Special`, `Fighting`, and `Magnet`.

Soil Nematode Fauna in Dokdo Island of Korea

Nematode fauna in Dokdo island was investigated for two years between 2008 and 2009. Population density and biomass were 239,500 m 2 (26,000�836,000) and 103.9 mg/m 2 (3.0�388.6), respectively. Total of 31 species of nematodes were identified : Acrobeloides is the most important genus with prominence value (PV) of 117.8, followed by Rhabditidae (PV = 81.9), Prismatolaimus (PV = 39.0), and Aphelenchoides (PV = 31.4). Among feeding group, bacteriovorus nematode composed 77% of density and 62% of biomass followed by plantparasitic and fungivorus nematodes. A species of Pratylenchus having distinctive tail terminus is under study as a new species. Biological indices, Shannon and Wiener index (2.46), Simpson’s diversity index (0.86), Species evenness (0.73), Species richness (1.30) indicate that nematode fauna in Dokdo island is diverse and unique. This study may give a general idea of nematode fauna at the Dokdo island.

Resistance of Newly Introduced Vegetables to Meloidogyne arenaria and M. incognita in Korea

To select resistant vegetables against two species of root-knot nematodes, M. incognita and M. arenaria, 39 vegetables belongs to 7 families, 13 genera, 25 species were screened in greenhouse pot test. Susceptible vegetables to both nematodes were amarath and leaf beet in Amaranthaceae, Malabar spinach in Basellaceae, Moroheiya in Tiliaceae, and Water-convolvulus in Convolvulaceae, Pak-choi in Brassica campestris var. chinensis, Tah tasai in B. campestris var. narinosa, B. campestris var. chinensis x narinosa, Leaf mustard, Mustard green in B. juncea, Kyona in B. juncea var. laciniate, Choy sum in B. rapa subsp. arachinenesis, Kairan in B. oleracea var. alboglabra, Arugula in Eruca sativa, Garland chrysanthemum in Chrysanthemum coronarium, Endive in Cichorium endivia, Artichoke in Cynara cardunculus var. scolymus, Lettuce in Lactuca sativa. Resistant to M. arenaria but susceptible to M. incognita were B. oleracea cv. Matjjang kale, B. oleracea var. gongyloides cv. Jeok kohlrabi, and C. intybus cv. Radicchio. Resistant vegetables to both nematodes were C. intybus cv. Sugar loaf, Grumoro, Radichio treviso, B. oleracea cv. Manchu collard, Super matjjang, B. oleracea italica, B. oleracea var. botrytis italiana, and Perilla in Lamiaceae. Vegetables resistant to both species of root-knot nematodes could be used as high-valued rotation crops in greenhouses where root-knot nematodes are problem.

Studies on HG Type of Heterodera glycines in Korea

Thirteen soybean cyst nematode (SCN) (Heterodera glycines) populations collected in Korea were examined in their HG type by their reproductivity on 7 Plant Introduction indicators for the identification of HG type. Six HG types were identified, HG type 0, 2, 5, 2.5, 1.2.7, and 2.5.7. HG type 2.5 was the most frequent (4 samples, 30.8%), followed by HG type 2.5.7 (3 samples, 23.0%). About 76.9% of SCN populations were reproduced on PI 88788, followed by PI 209332 (61.5%), PI 548316 (‘Cloud’) (30.8%), and PI 548402 (‘Peking’) (7.7%). No population could reproduce on PI 90763, PI 437654, thus, they could be used for resistant source for developing SCN resistant soybean in Korea.

Plant Parasitic Nematodes in Soybean in Korea and Their Importance Rating

Plant parasitic nematodes were isolated from 274 soil samples collected from soybean fields in Korea. Nematode importance rating in soybean is proposed based on this study and by reviewing other reports. Soybean cyst nematode, Heterodera glycines is the most important nematode species and rated as 1 st because it detected from 38%(range 25-51%) of soil samples with high density except Jeju province. Root-knot nematode, Meloidogyne spp. is rated 2 nd and is more widely distributed in southern provinces, Gyeongnam, Jeonnam, and Jeju province (detection rate ranged 16-44%). Pratylenchus is rated 3 rd and is more frequently detected from northern provinces such as Gyeonggi and Gangwon (detection rate ranged 10-13%). Helicotylenchus is rated 4 th and is particularly important in Jeju province (detection rate is 62% and numbers averaged 571 nematodes/300cm 3 soil), which is the main production area for sprouting soybean in Korea. Tylenchorhynchus, Paratylenchus, Criconema, Criconemoide, Mesocriconema, Ogma, Xiphinema, Paratrichodorus, and Trichodorus occur in low frequency and density, thus they are rated to 5 th . We propose to delete following nematode genus from the list of soybean parasitic nematode in Korea because their parasitism on soybean is unconfirmed or negligible; Tylenchus, Aphelenchus, Aphelenchoides, Ditylenchus, Hirschmanniella immamuri, Basiria graminophila, Psilenchus, and Pseudhalenchus. Therefore, we revised 30 species in 16 genera as soybean parasitic nematodes in Korea. Importance rating is 1 st Heterodera glycines, 2 nd Meloidogyne spp., 3 rd Pratylenchus spp. and 4 th Helicotylenchus spp. especially in Jeju province.

Resistance of Commercial Pepper Cultivars to Root-knot Nematodes

Ninety two pepper (Capsicum annuum L.) cultivars were screened for resistance to two common species of root-knot nematodes, Meloidogyne incognita and M. arenaria. All 92 pepper cultivars were resistant to M. arenaria (0-3 eggmass/plant) but were susceptible to M. incognita (76-678 eggmass/plant). Susceptibility to M. incognita were slightly differed; `Geomok` and `Shintaepung` had relatively less eggmass (300 eggmass/plant). Therefore, pepper is highly recommended as a high-valued rotation crop to only those greenhouses infested with M. arenaria, but should restrict for M. incognita.

Effect of Density of Helicotylenchus dihystera on Growth of Solanum lycopersicum

A greenhouse experiment was conducted to examine the effect of initial population density (Pi) of Helicotylenchus dihystera on six commercial tomato cultivars. Two-week-old tomato seedlings of six commercial cultivars were transplanted in d-10-cm clay pot and was inoculated with to give 0, 0.02, 0.2, and 2 nematodes/g soil. Plants were grown in a greenhouse for 60 days. Root and plant weights were unaffected but plant height declined only at inoculum level of 2 nematodes/g soil. At the highest initial population density (2 nematodes/g soil), plant height of tomato cv. Poseidon was reduced by 24%. Tomato cv. Hoyong produced the most nematodes with 7.0 nematodes/g soil and the least was tomato cv. Miniheuksu with 2.2 nematodes/g soil.

Identification and Characterization of Entomopathogenic Fungi Isolated from Bemisia tabaci in Korea

Entomopathogenic fungi were isolated from Bemisia tabaci in an Oriental melon field, and their growth characteristics, factors related to a natural outbreak, and infectivity against Bemisia tabaci, Tetranychus urticae, and Frankliniella intonsa were investigated. The isolates had erect conidiophores bearing whorls of 4-6 phialides with a swollen base where cylindrical conidia of were attached. The isolates were identified as Isaria fumosorosea on the basis of morphological characteristics and an ITS sequence with 99% similarity. I. fumosorosea IFs-08 grew well on Sabouraud dextrose agar+yeast extract medium(3.2 mm/day/); it grew better at than at . The isolates of I. fumosorosea-IFs were highly infective and killed 93.9-96.7% B. tabaci, 84.9-92.0% T. urticae, and 81.5-84.4% F. intonsa in bioassay, whereas three isolates (Isaria tenuipes, Isaria farinosa, and Isaria fumosorosea) from KACC showed a low infectivity of 10-20%. To the best of our knowledge, this is the first report of I. fumosorosea isolated from B. tabaci in Korea.

Resistance of Soybean Cultivars to Heterodera glycines HG type 2.5 in Korea

A total of 75 soybean cultivars developed in Korea was screened against soybean cyst nematode (SCN), Heterodera glycines HG type 2.5. Cysts developed on soybean cultivars ranged from 104 to 624 cysts per pot. There was no resistant cultivar but `Jangyeopkong`, `Saealkong`, `Miryangkong`, and `Mansukong` were moderately resistant; 33 cultivars were moderately susceptible and the other cultivars were susceptible. `Jangyeopkong`, `Saealkong`, `Miryangkong`, and `Mansukong` could be recommended for soybean fields infested with SCN until developing SCN resistant soybean.