Papers by Hideaki Iwahori
Nihon Senchū Gakkaishi, 2014
The influences of continuous ridge use (CRU) on root-knot nematode (RKN) damage to sweet potato w... more The influences of continuous ridge use (CRU) on root-knot nematode (RKN) damage to sweet potato was investigated in a double cropping system that uses radish in winter and sweet potato in summer. The CRU system tended to show reduced RKN damage to sweet potato relative to the conventional system (TR system), in which the field was tilled and ridged before sweet potato cultivation. RKN population density after the radish harvest was low in the upper area of the ridge in both the CRU and the TR systems. In the TR system, density in the upper area of the ridge was slightly increased after tillage and ridging. Low density in the upper area of the ridge is suggested as one of the reasons for the decrease in damage to sweet potato in the CRU system. Adoption of the CRU system would be one method of reducing RKN damage to sweet potato. Nematol. Res.
Jarq-japan Agricultural Research Quarterly, Jul 1, 2020
Sweet potato (Ipomoea batatas (L.) Lam.) is a major crop in Japan and worldwide. The sweet potato... more Sweet potato (Ipomoea batatas (L.) Lam.) is a major crop in Japan and worldwide. The sweet potato cultivar 'Koganesengan' is susceptible to damage by the southern root-knot nematode Meloidogyne incognita in Japan. We investigated the effects of cropping new resistant cultivars on the suppression of nematode population density and subsequent damage to the succeeding 'Koganesengan' crops. 'Koganesengan' was cropped with two resistant cultivars ('Daichinoyume' and 'Konamizuki'). The tuberous roots of 'Daichinoyume' and 'Konamizuki' were seldom damaged, whereas 'Koganesengan' was heavily damaged. In the next spring, the nematode population density in the plow layer soil (10 cm-15 cm) was lower after 'Daichinoyume' and 'Konamizuki' cropping than after 'Koganesengan' cropping. Nematode damage to 'Koganesengan' tuberous roots after 'Daichinoyume' and 'Konamizuki' cropping was slightly suppressed compared to that after 'Koganesengan' cropping. Cropping of these cultivars is an effective method of suppressing nematode density and reducing damage to sweet potatoes. By clarifying the capability of resistant cultivars even overseas, it will be possible to use sweet potato as a nematode-suppressive crop.
Applied Entomology and Zoology, May 11, 2023
Report of the Kyushu Branch of the Crop Science Society of Japan, May 15, 2005
Acta horticulturae, Jul 1, 2007
Southern root-knot nematode (SRKN), Meloidogyne incognita, causes severe damage to yield and qual... more Southern root-knot nematode (SRKN), Meloidogyne incognita, causes severe damage to yield and quality in sweetpotato, Ipomoea batatas, production. Resistance against SRKN has been intensively evaluated and enhanced in the sweetpotato breeding program in Japan. In this study, the genetic basis of multi-race resistance against SRKN in the sweetpotato cultivar 'J-Red' was investigated using F 1 progenies derived from the cross between 'J-Red' and the susceptible cultivar 'Choshu'. The two SRKN populations used were those collected from the central part of Kyushu Island (race SP1) and those from the southeastern part of the Kanto plain, Japan (race SP4), both of which showed a differential host reaction against the sweetpotato cultivars 'Norin-2', 'Tanegashimamurasaki-7' and 'Elegant Summer'. The distribution frequency of the progenies, based on the mean numbers of egg-masses was continuous but nearly bimodal, with approximately half of the 57 total progenies having less than 10 egg-masses. Segregation of resistant and susceptible progenies fit the expected ratio of 1:1, based on the assumption that the threshold for SP1 roughly ranged from 5 to 15 egg-masses per plant and that the threshold for SP4 from 10 to 30. These results showed that the resistance of 'J-Red' is controlled by multiple genes, including a single gene with a major phenotypic effect. A significant positive correlation was observed between the mean numbers of egg-masses produced by SP1 and by SP4, and a differential reaction to different SRKN races was not obvious among the F 1 progenies. Thus, the genes that control resistance to SP1 and to SP4 in 'J-Red' were considered to be closely linked to one another on the same chromosome or possibly identical.
Nihon Senchū Gakkaishi, 2015
Species of root-knot nematode (RKN) from green pepper fields in Miyazaki, Kagoshima, Kochi, and I... more Species of root-knot nematode (RKN) from green pepper fields in Miyazaki, Kagoshima, Kochi, and Ibaraki prefectures were surveyed. Ten to second juveniles (J s) and female adults were collected, respectively, from each field and the species were identified individually by PCR-RFLP method. As a result, all RKN specimens, except one, were Meloidogyne incognita. Then each infested soil sample from of the fields was inoculated to breeding lines of nematode-resistant chili peppers (CM , LS and PI). Many galls and egg masses were observed after the inoculation in (ca. %) of the infested soils. This indicates that resistance-breaking nematodes dominated at a high frequency in these fields. Nematol. Res. (),-().
Japanese Journal of Crop Science, 2013
2000 2010 30 cm 75 cm 4. 8 g m-2 7. 2 g m-2 12. 0 g m-2 10 Jpn. J. Crop Sci. 82 1
Euphytica, Apr 7, 2012
The southern root-knot nematode (SRKN) Meloidogyne incognita severely damages yield and quality i... more The southern root-knot nematode (SRKN) Meloidogyne incognita severely damages yield and quality in sweetpotato production, and host plant resistance is one of the primary options for SRKN control. Segregation of F 1 progeny resistant and susceptible to the SP1 and SP2 races of SRKN suggested that the race-specific resistance of the sweetpotato cultivar ''Hi-Starch'' is mostly controlled by single genes and that the genes for resistance against each race are closely located. Bulked segregant analysis and subsequent analysis of 86 F 1 progeny plants identified nine amplified fragment-length polymorphism markers associated with SRKN resistance and a single linkage map consisting of seven of these markers. Quantitative trait locus (QTL) analysis using the segregating resistance data of the F 1 progeny allowed mapping of both a locus with a large effect on resistance to the SRKN race SP1 and another affecting resistance to SP2 to the region around E33M53_090 that was designated as qRmi(t). Two AFLP markers in the vicinity of qRmi(t), E33M53_090 and E41M32_206, were converted to locus-specific sequence-characterized amplified region markers based on their internal and adjacent DNA sequences. These markers might be useful for marker-assisted selection of SRKN resistance in sweetpotato breeding and as a first step to map-based cloning of the responsible QTL(s). Keywords Amplified fragment length polymorphism Á Bulked segregant analysis Á Ipomoea batatas Á Meloidogyne incognita Á Race Á Sequence-characterized amplified region
Report of the Kyushu Branch of the Crop Science Society of Japan, 2005
Japan Agricultural Research Quarterly: JARQ, 2020
Sweet potato (Ipomoea batatas (L.) Lam.) is a major crop in Japan and worldwide. The sweet potato... more Sweet potato (Ipomoea batatas (L.) Lam.) is a major crop in Japan and worldwide. The sweet potato cultivar 'Koganesengan' is susceptible to damage by the southern root-knot nematode Meloidogyne incognita in Japan. We investigated the effects of cropping new resistant cultivars on the suppression of nematode population density and subsequent damage to the succeeding 'Koganesengan' crops. 'Koganesengan' was cropped with two resistant cultivars ('Daichinoyume' and 'Konamizuki'). The tuberous roots of 'Daichinoyume' and 'Konamizuki' were seldom damaged, whereas 'Koganesengan' was heavily damaged. In the next spring, the nematode population density in the plow layer soil (10 cm-15 cm) was lower after 'Daichinoyume' and 'Konamizuki' cropping than after 'Koganesengan' cropping. Nematode damage to 'Koganesengan' tuberous roots after 'Daichinoyume' and 'Konamizuki' cropping was slightly suppressed compared to that after 'Koganesengan' cropping. Cropping of these cultivars is an effective method of suppressing nematode density and reducing damage to sweet potatoes. By clarifying the capability of resistant cultivars even overseas, it will be possible to use sweet potato as a nematode-suppressive crop.
Nematological Research (Japanese Journal of Nematology), 2017
Nematological Research (Japanese Journal of Nematology), 2005
To use resistant cultivars of sweetpotato effectively occurrence and distribution of pathogenic r... more To use resistant cultivars of sweetpotato effectively occurrence and distribution of pathogenic races of M incognita were examined. Five sweetpotato differential cultivars, 'Norin-1' ,'Norin-2','Tanegashimamurasaki-7','Elegant Summer' and Tred', which were selected from major Japanese sweetpotato cultivars based on resistance response to four M incognita populations with different virulence were used as differential hosts. A total of 129 M incognita populations were collected from mainly sweetpotato fields in Kyushu and Okinawa, Japan. Reproduction of the populations was assessed on the differentials based on production of egg-masses and pathogenic races were designated. Nine races, SP1 to SP9, were identified from these populations and 37.2%, 43.4% and 7.0% of the populations were, respectively, race SP1 that reproduces only on 'Norin-1', SP2 that reproduces on both 'Norin-1' and 'Norin-2', and SP4 that reproduces on four of the differential hosts but not on 'J-Red'. Region specific distribution was observed in these races. SP1 was widely distributed in Kumamoto and northern prefectures. SP2 was predominant in southern Kyushu, in both Miyazaki and Kagoshima Prefectures. SP4 was the major race in Okinawa Prefecture. Other races were detected from limited areas.
Nematological Research, 2014
The influences of continuous ridge use (CRU) on root-knot nematode (RKN) damage to sweet potato w... more The influences of continuous ridge use (CRU) on root-knot nematode (RKN) damage to sweet potato was investigated in a double cropping system that uses radish in winter and sweet potato in summer. The CRU system tended to show reduced RKN damage to sweet potato relative to the conventional system (TR system), in which the field was tilled and ridged before sweet potato cultivation. RKN population density after the radish harvest was low in the upper area of the ridge in both the CRU and the TR systems. In the TR system, density in the upper area of the ridge was slightly increased after tillage and ridging. Low density in the upper area of the ridge is suggested as one of the reasons for the decrease in damage to sweet potato in the CRU system. Adoption of the CRU system would be one method of reducing RKN damage to sweet potato. Nematol. Res.
Kyushu Plant Protection Research, 2010
Nematological Research, 2012
Euphytica, 2012
The southern root-knot nematode (SRKN) Meloidogyne incognita severely damages yield and quality i... more The southern root-knot nematode (SRKN) Meloidogyne incognita severely damages yield and quality in sweetpotato production, and host plant resistance is one of the primary options for SRKN control. Segregation of F 1 progeny resistant and susceptible to the SP1 and SP2 races of SRKN suggested that the race-specific resistance of the sweetpotato cultivar ''Hi-Starch'' is mostly controlled by single genes and that the genes for resistance against each race are closely located. Bulked segregant analysis and subsequent analysis of 86 F 1 progeny plants identified nine amplified fragment-length polymorphism markers associated with SRKN resistance and a single linkage map consisting of seven of these markers. Quantitative trait locus (QTL) analysis using the segregating resistance data of the F 1 progeny allowed mapping of both a locus with a large effect on resistance to the SRKN race SP1 and another affecting resistance to SP2 to the region around E33M53_090 that was designated as qRmi(t). Two AFLP markers in the vicinity of qRmi(t), E33M53_090 and E41M32_206, were converted to locus-specific sequence-characterized amplified region markers based on their internal and adjacent DNA sequences. These markers might be useful for marker-assisted selection of SRKN resistance in sweetpotato breeding and as a first step to map-based cloning of the responsible QTL(s). Keywords Amplified fragment length polymorphism Á Bulked segregant analysis Á Ipomoea batatas Á Meloidogyne incognita Á Race Á Sequence-characterized amplified region
Nihon Senchū Gakkaishi, 2002
Differences in the resistance of sweet potato cultivars and lines to Melodogyne incognita populat... more Differences in the resistance of sweet potato cultivars and lines to Melodogyne incognita populations. Zen-ichi Sanol, Hideki Iwahoril, Yasushi Tateishil and Yumi Kai2. Differences in resistance of sweet potato cultivars to some populations of Meloidogyne incognita were examined in greenhouse assays. Twenty-four major sweet potato cultivars rooted in 200 g of potted soil were inoculated with approximately 500 juveniles of four M. incognita populations collected from different areas. Reproduction rates (eggs produced per J2 inoculated) were determined after 35 days of growth at 27t. Nine cultivars with reproduction rates higher than 11 were rated as susceptible and five cultivars with reproduction rates lower than one were rated as highly resistant to the four populations. However distinct differences were observed in reproduction rates of those populations on the other 10 cultivars. In an assay similar to the one described above with 13 newly developed cultivars or breeding lines, all four populations produced many egg-masses on three and produced only a few egg-masses on 6 of those cultivars or breeding lines. However, the remaining cultivars or breeding lines did not have a consistent response to the four populations. Among purple sweet potato cultivars grown primarily in Okinawa and Tanegashima Island, two similarly shaped cultivars, Bise and Tanegashima-murasaki 7, exhibited different levels of resistance to two populations as indicated by a marked difference between the numbers of egg masses produced. These results clearly demonstrate that resistance of sweet potato to populations of M. incognita distinctly differs with cultivars or breeding lines. Jpn. J. Nematol. 32 (2), 77-86 (2002).
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Papers by Hideaki Iwahori