• The Plant Pathology Journal
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• 제36권3호
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• pp.297-302
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• 2020

Root-knot nematodes (Meloidogyne spp.) are the most destructive group of plant-parasitic nematodes. Plants infected by Meloidogyne spp. develop above-ground symptoms, stunting, yellowing, nutrient deficiencies, and gall formations with typical hook-shaped root tips. Infected plants experience yield losses. During 2018-2019 survey, leaf chlorosis rice plants were found in 206 fields of 67 counties in Guangxi, China, around 30 days after transplanting. Galls and hooked tips on the roots and pear-shaped females were observed. About 32.04% of fields were infested with the nematode. The nematodes were identified as Meloidogyne graminicola base on morphological and molecular analysis. To the best of our knowledge, this is the first report of M. graminicola on rice plants in Guangxi, China. The results of this study urge the discovery of resistant cultivars and the development of management strategies.

• The Plant Pathology Journal
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• 제31권4호
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• pp.441-445
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• 2015

Carrot (Dacus carota var. sativus) is one of the top-ten most economically important vegetable crops produced worldwide, and the root-knot nematodes, Meloidogyne spp., are one of the most important pests in the carrot. In Korea, M. hapla and M. incognita are presumed to be the major root-knot nematodes distributing mostly in open carrot fields and greenhouses, respectively. In our study, currently-developed and commercial carrot cultivars and the parental lines were examined for their pathological responses to M. incognita and M. hapla 7 weeks after inoculation with about 1,000 second-stage juveniles (J2) of the nematodes. All the carrot cultivars and lines showed susceptible responses to both nematodes with the gall index (GI) of 2.4-4.4, which were always higher on the carrot plants infected with M. incognita than M. hapla. Gall sizes were remarkably larger with more serious reduction of the root growths in the plants infected with M. incognita than M. hapla, suggesting the carrot lines examined in our study were more susceptible to the former than the latter. In the infection sites of the root tissues, giant cells were more extensively formed, occupying larger stellar regions with the prominent destruction of adjacent xylem vessels by M. incognita than M. hapla. All of these results suggest M. incognita affect more seriously on the carrot plants that are grown in greenhouses, compared to M. hapla that has a major distribution in open carrot fields, which would be used for determining cropping systems based on target nematode species, their damage and pathological characteristics.

• 한국유기농업학회지
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• 제30권1호
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• pp.103-118
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• 2022

Photorhabdus is a bacterial symbiont of entomopathogenic nematodes of the genus Heterorhabditis in the family Heterorhabditidae. Photorhabdus is known to have nematicidal activity in addition to insecticidal activity. P. temperata isolated from Korean indigenous H. megidis Gwangju strain also produced high control efficacy against root-knot nematode Meloidogyne incognita and root-lesion nematode Pratylenchus penetrans. P. temperata has drawn interest as a potential bionematicide for the control of root-knot nematodes thereby. For the registration as an organic agricultural material, the toxicity of P. temperata was assessed by the acute toxicity test in carp (Cyprinus carpio) and acute oral and dermal toxicity tests in Sprague-Dawley rat (Rattus norvegicus) in compliance with the guidelines of the Rural Development Administration (RDA). In the acute toxicity test in fish, neither lethality nor abnormal responses of carp were observed. Body length and weight of carp and changes in DO concentrations and pH values were not significantly different between the treated group and the untreated control. In the acute oral and dermal toxicity tests, clinical signs, abnormal behavior, mortality, and pathological findings were not observed in all the experimental rats. The weight increment of all rats was normal. Acute toxicity results of P. temperata in fish and rats belonged to categories III, IV, and IV of RDA, respectively. Toxicity results of the present study indicated that P. temperata could be a safe and promising bionematicide against root-knot nematodes and root lesion nematode.

• The Plant Pathology Journal
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• 제34권1호
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• pp.35-43
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• 2018

Root-knot nematodes (Meloidogyne spp.) are parasites that attack many field crops and orchard trees, and affect both the quantity and quality of the products. A root-colonizing bacterium, Pseudomonas chlororaphis O6, possesses beneficial traits including strong nematicidal activity. To determine the molecular mechanisms involved in the nematicidal activity of P. chlororaphis O6, we constructed two mutants; one lacking hydrogen cyanide production, and a second lacking an insecticidal toxin, FitD. Root drenching with wild-type P. chlororaphis O6 cells caused juvenile mortality in vitro and in planta. Efficacy was not altered in the fitD mutant compared to the wild-type but was reduced in both bioassays for the mutant lacking hydrogen cyanide production. The reduced number of galls on tomato plants caused by the wild-type strain was comparable to that of a standard chemical nematicide. These findings suggest that hydrogen cyanide-producing root colonizers, such as P. chlororaphis O6, could be formulated as "green" nematicides that are compatible with many crops and offer agricultural sustainability.

• The Plant Pathology Journal
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• 제33권1호
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• pp.66-74
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• 2017

This study was conducted to examine infectivity (penetration and gall and egg-mass formations) of the root-knot nematodes, Meloidogyne incognita and M. hapla, on carrots grown in soil conditions of 5 different soil textures consisting of bed-soil (b) and sand (s) mixtures (b-s mixtures) at the ratios of 10:0, 7:3, 5:5, 3:7, and 0:10. For M. incognita, the nematode penetration rates in b-s of 0:10 (100% sand) were significantly higher than in the other b-s mixtures, more greatly at 2 and 5 days after inoculation than at 10 DAI, while no significant differences in the penetration rates were mostly shown for M. hapla at the above DAI. However, for both nematodes, gall and egg-mass formations were remarkably increased in the b-s mixture of 0:10, compared to the other b-s mixtures, which is coincided with the general aspects of severe nematode infestations in sandy soils. This suggests the increased gall and egg-mass formations of M. incognita should be derived from the increased penetration rates in the sandy soil conditions, which provide a sufficient aeration due to coarse soil nature for the nematodes, leading to their mobility increased for the enhanced root penetration. For M. hapla, it is suggested that the sandy soil conditions affect positively on the healthy plant growth with little accumulation of the inhibitory materials and sufficient aeration, enhancing the nematode growth and feeding activities. All of these aspects provide information reliable for the development screening techniques efficient for the evaluation of the nematode resistance in the breeding programs.

• 한국응용곤충학회지
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• 제45권1호
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• pp.79-85
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• 2006

국내 주요감자재배지의 식물기생선충 발생상을 밝히기 위해 2004년과 2005년에 제주, 예산, 김천, 고령, 홍천, 평창, 김제, 밀양, 남원, 강릉, 인제 등 11개 감자 주산지를 대상으로 선충속별 종류와 밀도를 조사하였다. 채집한 토양시료 50개 중 30개에서 뿌리혹선충 유충이 검출되었으며 밀도는 12-69마리/토양 100cc 정도로 비교적 낮았다. 식물기생선충류 중 Pratylenchus sp., Helicotylenchus sp, Ditylenchus sp., Tylenchus sp., and Tylenchorhynchus sp.가 지역별로 검출되었으나 대부분 밀도는 매우 낮게 나타났다. 채집한 토양을 토마토 뿌리에 접종 후 뿌리혹선충을 배양하여 PCR-RLFP에 의한 정밀동정 결과 제주, 밀양, 고령에서 채집한 뿌리혹선충 암컷에서 500 bp의 PCR 산물을 얻었으며 제한 효소 Dra I을 처리한 결과 290 및 230 bp의 밴드가 형성되어 당근뿌리혹선충(Meloidogyne hapla)으로 동정하였다.

• 한국식물병리학회지
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• 제3권3호
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• pp.164-167
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• 1987

우리나라에서 발생하는 뿌리혹선충의 주요 종인 Meloidogyne hapla, M. arenaria, M. incognita 그리고 M. javanioa의 피해정도를 알기 위하여 pot당 0, 1,000, 10,000마리의 선충접종한 결과 감수정도는 M. javanica($Rutgers\;:\;80\%$, 복수2호 : $59\%$), M. incognita(Rutgers : $78\%$, 복수 2호 : $50\%$, M. arenaria($Rutgers\;:\;65\%$, 복수2호 : $24\%$), M. hapla($Rutgers\;:\;7\%$, 복수2호 : $15\%$)의 순이었고, M. hapla는 아열대인 필리핀에서의 Rutgers보다 우리나라에서의 Boksu 2에서 더 심한 피해를 나타내는 반면 M. arenaria, M. incognita 및 M. javanica는 필리핀에서의 Rutgers에서 더 피해가 심했다. 토마토의 생육에 미치는 영향은 풋트당 선충 10,000마리 접종구에서 Rutgers의 지상부 무게가 뿌리 무게나 초장보다 더 컸지만 선충 밀도가 낮은 1,000마리 접종구에서는 초장이나 지상부 무게가 감소하는 반면 뿌리 무게는 오히려 증가하는 경향이었다.

• The Plant Pathology Journal
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• 제33권3호
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• pp.249-263
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• 2017

This study aims to examine the potential reasons for the current prevalence of the fusarium wilt in the oriental melon. Twenty-seven Fusarium isolates obtained from oriental melon greenhouses in 2010-2011 were identified morphologically and by analysis of elongation factor-1 alpha gene (EF-$1{\alpha}$) and internal transcribed spacer (ITS) rDNA sequences as 6 Fusarium species (8 isolates of F. oxysporum, 8 F. commune, 5 F. proliferatum, 3 F. equiseti, 2 F. delphinoides, and 1 F. andiyazi), which were classified as same into 6 EF-$1{\alpha}$ sequence-based phylogenetic clades. Pathogenicity of the Fusarium isolates on the oriental melon was highest in F. proliferatum, next in F. oxysporum and F. andiyazi, and lowest in the other Fusarium species tested, suggesting F. proliferatum and F. oxysporum were major pathogens of the oriental melon, inducing stem rots and vascular wilts, respectively. Oriental melon and watermelon were more susceptible to F. oxysporum than shintosa and cucumber; and cucumber was most, oriental melon and watermelon, medially, and shintosa was least susceptible to F. proliferatum, whose virulence varied among and within their phylogenetic subclades. Severe root-knot galls were formed on all the crops infected with Meloidogyne incognita; however, little indication of vascular wilts or stem and/or root rots was shown by the nematode infection. These results suggest the current fungal disease in the oriental melon may be rarely due to virulence changes of the fusarium wilt pathogen and the direct cause of the severe root-knot nematode infection, but may be potentially from other Fusarium pathogen infection that produces seemingly wilting caused by severe stem rotting.

• 대한기계학회논문집
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• 제18권10호
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• pp.2797-2804
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• 1994

This paper analyzes the behaviors of corrugated membrane under the cryogenic liquid pressure and thermal loading using the FEM analysis program MARC. The FEM calculations were carried out on the basis of measured data of Technigaz membrane. It is very important to know the concentration levels and distributions of stress in the corrugated membrane. A quarter of the membrane sheet in place of the whole membrane was simulated because of its geometric symmetricity. The calculated results of the concentrated stress showed that the maximum stress occurs at the knot parts and at the root corner radius of the corrugations. The FEM calculated results indicated that the ring knot membrane which was developed in this study showed uniformly distributed stress and the lowest stress levels in the cross knot area in comparison with other two membranes. These results are very important to optimize the shape and improve the safety of membrane structure.

• 한국응용곤충학회지
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• 제17권2호
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• pp.89-98
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• 1978

경제작물증산에 크게 영향을 미치는 뿌리혹선충에 간하여 1977년 경상남, 북도 경기도 제주도 등의 4개도 46개 지역에서 66개의 재료를 채집하여 조사한 결과 뿌리혹선충 종두는 Meloidogyne hapla. Meloidogyne arenaria, Meloidgyne incognita 그리고 Meloidogyne javanica등 4종이 발견되었으며 동정된 4종의 뿌리혹선충의 중요 형태적 특징을 기술했다. 이 중에 Meloidogyne javanica는 우리나라 미기록종으로 경기도 수원시 이목동 원예시험장의 감자, 경북 대구시 검사 동의 배추, 대구시 산격동의 오랑캐 꽃, 경남 남해군 초음리의 호박 등에서 발견되었다. 지역별 뿌리혹선충 종류별 분포상태는 제주도에서는 전부 Meloidogyne incognita만 발견되었고 다름 3종은 발견도지 않았다. 그러나 경기도에서는 Meloidogyne incognita는 전연발견되지 않았다. 경상북도와 경기도에서는 Meloidogyne hapla가 가장 많이 발견되었으며 경상남도에서는 4종 모두 발견되었으나 Meloidogyne hapla와 Meloidogyne incognita가 비슷하게 분포하고 있었다. 전반적으로 우리나라에서 가장 빈번히 광범하게 분포하고 있는 종은 Meloidogyne hapla로 전체 조사수의 $50\%$를 차지하고 있으며 다음이 Meloidogyne incognita로 $33.3\%$, Meloidogyne arearia $10.6\%$, Meloidogyne javanica $6.0\%$의 순으로 나타났다. 지역별 피해상태는 제주도가 가장심하게 나타났고 다음이 경남, 경북, 경기 등의 순이었다. 뿌리혹선충의 피해를 받고 있는 직물은 24종이 발견되었으며, 그 중에 특히 중요한 농작물로는 콩, 땅콩, 감자, 토마토, 오이, 당근, 호박, 수박, 우엉, 고추, 가지, 배추, 상치, 담배, 인삼 등이었다. 전반적으로 뿌리혹선충방제를 위한 지도 계몽이 시급히 요구된다.