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Mwamula, Abraham Okki,Ko, Hyoung-Rai,Kim, Youngjoon,Kim, Young Ho,Lee, Jae-Kook,Lee, Dong Woon The Korean Society of Plant Pathology 2018 Plant Pathology Journal Vol.34 No.4
The sugar beet cyst nematode, Heterodera schachtii is a well known pathogen on Chinese cabbage in the highland fields of Korea. However, a race of cyst forming nematode with close morphological resemblance to H. trifolii was recently isolated from the same Chinese cabbage fields. Morphological species differentiation between the two cyst nematodes is challenging, with only minor differences between them. Thus, this study described the newly intercepted H. trifolii population, and reviewed morphological and molecular characteristics conceivably essential in differentiating the two nematode species. A comparison of morphometric measurements of both infective juveniles and vulval cones of cysts showed significant differences between the two cyst nematodes. When total RNA and genomic DNA were extracted from a mixed field population, COI genes and ITS regions were clearly amplified with primers of the two Heterodera species, suggesting that Heterodera population collected from the Chinese cabbage field consisted of a mixture of two species. COI and ITS of H. trifolii were predominantly amplified from nucleotides prepared from H. trifolii monoxenic population whereas those of H. schachtii were strongly detected in H. schachtii monoxenic cultures. Thus, this study confirms the coexistence of the two species in some Chinese cabbage fields; and the presence of H. trifolii in Korea is reported here for the first time.
Mwamula A. Okki,Youngjoon Kim,Young Ho Kim,Jae Kook Lee,Hyoung Rai Ko,DongWoon Lee 한국응용곤충학회 2017 한국응용곤충학회 학술대회논문집 Vol.2017 No.10
The sugar beet cyst nematode (SBCN), Heterodera schachtii is a well known pathogen on Chinese cabbage in thehighland fields of Korea. However, recent reports have shown a coexistence of SBCN with the clover cyst nematode,H. trifolii in Korea. This study aimed at detailing and reviewing morphological and molecular characteristics conceivablyessential in differentiating the two nematode species. A comparison of morphometric measurements of both infective juvenilesand vulval cones of cysts showed significant differences between the two cyst nematodes. Indeed, using assorted cystsfrom field populations for molecular analysis resulted into a mixture of bands after gel electrophoresis, indicating a combinationof the two species. Thus, this study confirms the coexistence of the two species on Chinese cabbage fields in Korea.
Mwamula Abraham Okki,DongWoon Lee,Hyeong Hwan Kim,Jung Beon Yoon 한국응용곤충학회 2018 한국응용곤충학회 학술대회논문집 Vol.2018 No.04
Aphelenchoides composticola is an economic pest in mushroom cultivation, with a potential to cause heavy losses in the commercial production of Agaricus spp. Recently, A. composticola was intercepted on cultivated mushrooms in Korea and herein, this newly recorded species is morphologically and morphometrically characterized, and symptoms of mushroom damage are equally illustrated. The offset head, a prominent muscular median bulb, oval to round in shape, lateral field with three incisures, tapering truncate tail and average body length of 612.8μm, characterize females. Males are slightly smaller (561.2μm), characterized by well-developed paired spicules, ventrally curved tail, and conoid tail terminus posed with a terminal mucro.
Abraham Okki Mwamula,Oh-Gyeong Kwon,Chanki Kwon,Yi Seul Kim,Young Ho Kim,이동운 한국식물병리학회 2024 Plant Pathology Journal Vol.40 No.1
Identification of Helicotylenchus species is very challenging due to phenotypic plasticity and existence of cryptic species complexes. Recently, the use of rDNA barcodes has proven to be useful for identification of Helicotylenchus. Molecular markers are a quick diagnostic tool and are crucial for discriminating related species and resolving cryptic species complexes within this speciose genus. However, DNA barcoding is not an error-free approach. The public databases appear to be marred by incorrect sequences, arising from sequencing errors, mislabeling, and misidentifications. Herein, we provide a comprehensive analysis of the newly obtained, and published DNA sequences of Helicotylenchus, revealing the potential faults in the available DNA barcodes. A total of 97 sequences (25 nearly full-length 18S-rRNA, 12 partial 28S-rRNA, 16 partial internal transcribed spacer [ITS]-rRNA, and 44 partial cytochrome c oxidase subunit I [COI] gene sequences) were newly obtained in the present study. Phylogenetic relationships between species are given as inferred from the analyses of 103 sequences of 18S-rRNA, 469 sequences of 28S-rRNA, 183 sequences of ITS-rRNA, and 63 sequences of COI. Remarks on suggested corrections of published accessions in GenBank database are given. Additionally, COI gene sequences of H. dihystera, H. asiaticus and the contentious H. microlobus are provided herein for the first time. Similar to rDNA gene analyses, the COI sequences support the genetic distinctness and validity of H. microlobus. DNA barcodes from type material are needed for resolving the taxonomic status of the unresolved taxonomic groups within the genus.
Abraham Okki Mwamula,Md. Faisal Kabir,이동운(DongWoon Lee) 한국식물병리학회 2022 Plant Pathology Journal Vol.38 No.2
The global nematicides market is expected to continue growing. With an increasing demand for synthetic chemical-free organic foods, botanical nematicides are taking the lead as replacements. Consequently, in the recent years, there have been vigorous efforts towards identification of the active secondary metabolites from various plants. These include mostly glucosinolates and their hydrolysis products such as isothiocyanates; flavonoids, alkaloids, limonoids, quassinoids, saponins, and the more recently probed essential oils, among others. And despite their overwhelming potential, variabilities in quality, efficacy, potency and composition continue to persist, and commercialization of new botanical nematicides is still lagging. Herein, we have reviewed the history of botanical nematicides and regional progresses, the potency of the identified phytochemicals from the key important plant families, and deciphered some of the impediments involved in standardization of the active compounds in addition to the concerns over the safety of the purified compounds to non-target microbial communities.
Abraham Okki Mwamula,Ho-wook Lee,Yi Seul Kim,Young Ho Kim,Dong Woon Lee 한국응용곤충학회 2023 한국응용곤충학회 학술대회논문집 Vol.2023 No.10
Rotylenchus pini Mamiya, 1968 was reported from rhizospheric soils of Zoysia japonica in Korea. Females and males of the characterized population conform to the original species description from Japan and also to other subsequent species descriptions with variations in a few details in morphometrics including the existence of pharyngeal gland overlap in some specimen. Bayesian analysis of all the three DNA markers consistently grouped R. pini together with Rotylenchus species including R. zhongshanensis, a morphologically close species. Additionally, the newly obtained sequences of R. pini were found to be almost identical to the sequences assigned to Rotylenchus aff. devonensis in GenBank. These Rotylenchus aff. devonensis isolates might be representatives of R. pini populations. The current and previous phylogenetic studies supported by the recorded morphological plasticity within populations of the genus validate the proposed synonymy of Pararotylenchus with Rotylenchus.
Abraham Okki Mwamula,고형래,김영준,김영호,이재국,이동운 한국식물병리학회 2018 Plant Pathology Journal Vol.34 No.4
The sugar beet cyst nematode, Heterodera schachtii is a well known pathogen on Chinese cabbage in the highland fields of Korea. However, a race of cyst forming nematode with close morphological resemblance to H. trifolii was recently isolated from the same Chinese cabbage fields. Morphological species differentiation between the two cyst nematodes is challenging, with only minor differences between them. Thus, this study described the newly intercepted H. trifolii population, and reviewed morphological and molecular characteristics conceivably essential in differentiating the two nematode species. A comparison of morphometric measurements of both infective juveniles and vulval cones of cysts showed significant differences between the two cyst nematodes. When total RNA and genomic DNA were extracted from a mixed field population, COI genes and ITS regions were clearly amplified with primers of the two Heterodera species, suggesting that Heterodera population collected from the Chinese cabbage field consisted of a mixture of two species. COI and ITS of H. trifolii were predominantly amplified from nucleotides prepared from H. trifolii monoxenic population whereas those of H. schachtii were strongly detected in H. schachtii monoxenic cultures. Thus, this study confirms the coexistence of the two species in some Chinese cabbage fields; and the presence of H. trifolii in Korea is reported here for the first time.