One new and three known species of the genus Filenchus with two lateral lines were found in the rhizosphere of wild and cultivated plants from Iran. Filenchus paravesiculosus sp. n. is characterised by its small size, 425-510 μm; lateral field with two lines; cuticle coarsely striated; conoid-rounded head with 1-2 annuli, and amphidial apertures longitudinal slits, relatively short ovary, offset and elongate spermatheca, and elongate-conoid tail with broadly rounded terminus. F. paravesiculosus sp. n. differs from F vesiculosus by having shorter stylet (6.0-7.5 μm vs 9-11 μm). It can be distinguished from F. facultativus, F. acris and F. neoparvus by the shape of tail terminus (broadly rounded vs filiform to finely rounded) and having different head shape. Variation of the amphidial apertures is discussed. Filenchus fortis is a new record for Iran.
{"title":"Descriptions of Filenchus Paravesiculosus Sp. N. and Three Other Species of the Genus Filenchus Andrássy, 1954 (Nemata: Tylenchidae) From Iran","authors":"A. Karegar, E. Geraert","doi":"10.1163/005425998X00017","DOIUrl":"https://doi.org/10.1163/005425998X00017","url":null,"abstract":"One new and three known species of the genus Filenchus with two lateral lines were found in the rhizosphere of wild and cultivated plants from Iran. Filenchus paravesiculosus sp. n. is characterised by its small size, 425-510 μm; lateral field with two lines; cuticle coarsely striated; conoid-rounded head with 1-2 annuli, and amphidial apertures longitudinal slits, relatively short ovary, offset and elongate spermatheca, and elongate-conoid tail with broadly rounded terminus. F. paravesiculosus sp. n. differs from F vesiculosus by having shorter stylet (6.0-7.5 μm vs 9-11 μm). It can be distinguished from F. facultativus, F. acris and F. neoparvus by the shape of tail terminus (broadly rounded vs filiform to finely rounded) and having different head shape. Variation of the amphidial apertures is discussed. Filenchus fortis is a new record for Iran.","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82854221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
White clover grown in pots of low or high fertility soil was inoculated with Heterodera trifolii, pulse-labelled with 14 C and after 14 days the distribution of 14 C was investigated. In the presence of many H. trifolii, soil fertility did not affect the root/shoot distribution of 14 C. With few H. trifolii in high-fertility soil, there was significantly less 14 C translocation to the roots. The 14 C content per pot of the microbial biomass carbon was significantly greater in those pots with many H. trifolii at both soil fertility levels. Not only was there a significant increase in the size of the microbial biomass in pots with many nematodes but also the micro-organisms had a greater 14 C concentration. This may indicate increased nutrient cycling in pots with plants infected by H. trifolii.
{"title":"Impact of Clover Cyst Nematode (Heterodera Trifolii) Infection On Soil Microbial Activity in the Rhizosphere of White Clover (Trifolium Repens) - a Pulse-Labelling Experiment","authors":"G. Yeates, S. Saggar, C. S. Denton, C. Mercer","doi":"10.1163/005225998X00082","DOIUrl":"https://doi.org/10.1163/005225998X00082","url":null,"abstract":"White clover grown in pots of low or high fertility soil was inoculated with Heterodera trifolii, pulse-labelled with 14 C and after 14 days the distribution of 14 C was investigated. In the presence of many H. trifolii, soil fertility did not affect the root/shoot distribution of 14 C. With few H. trifolii in high-fertility soil, there was significantly less 14 C translocation to the roots. The 14 C content per pot of the microbial biomass carbon was significantly greater in those pots with many H. trifolii at both soil fertility levels. Not only was there a significant increase in the size of the microbial biomass in pots with many nematodes but also the micro-organisms had a greater 14 C concentration. This may indicate increased nutrient cycling in pots with plants infected by H. trifolii.","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86578744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Identification of Meloidogyne naasi Franklin, 1965 from Argentina.","authors":"M. Echeverría, E. Chaves","doi":"10.1163/005325998x00090","DOIUrl":"https://doi.org/10.1163/005325998x00090","url":null,"abstract":"","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83828450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The anhydrobiotic potential of the free-living mycophagous nematode Ditylenchus myceliophagus was examined. Both individuals and small aggregates (mixed larvae and adults) were able to survive anhydrobiotically if dried slowly enough and exhibited those behavioural (swarming) and morphological (coiling) adaptations normally associated with dehydration stress. Comparison of biochemical profiles of nematode aggregates cultured on Agaricus bisporus or Rhizoctonia cerealis mycelia and exposed to 97% rh for three days (preconditioning) showed similar decreases in lipid and glycogen contents but trehalose contents increased to about 3.65% and 9.25% dry wt, respectively. Trehalose content had no effect on the abilities of the nematodes to survive exposure to reduced rh levels following preconditioning, with no nematodes surviving after 24 hr at 0% rh. Nematodes reared on R. cerealis and allowed to dehydrate naturally in culture for 6 weeks post-swarm showed an unexpected increase in lipid during swarming (28% to 42% dry wt), glycogen levels declined and trehalose levels increased from 2.0% to 4.0% dry wt. None of these changes were associated with dehydration stress. After 3 weeks nematodes began to coil and had lipid and trehalose contents of about 32% and 16.65% dry wt, respectively. At the end of the six week period lipid contents declined to 26% dry wt and trehalose contents remained stable. Naturally dehydrated nematodes showed an almost identical pattern of survival to preconditioned ones when exposed to reduced rh levels. The anhydrobiotic capabilities of D. myceliophagus are discussed in relation to other nematode anhydrobiotes and to the importance of trehalose as either a necessity for successful anhydrobiotic survival or a general adaptive response to environmental stress.
{"title":"Trehalose: Its Role in the Anhydrobiotic Survival of Ditylenchus Myceliophagus","authors":"L. Higa, C. Womersley","doi":"10.1163/005425998X00044","DOIUrl":"https://doi.org/10.1163/005425998X00044","url":null,"abstract":"The anhydrobiotic potential of the free-living mycophagous nematode Ditylenchus myceliophagus was examined. Both individuals and small aggregates (mixed larvae and adults) were able to survive anhydrobiotically if dried slowly enough and exhibited those behavioural (swarming) and morphological (coiling) adaptations normally associated with dehydration stress. Comparison of biochemical profiles of nematode aggregates cultured on Agaricus bisporus or Rhizoctonia cerealis mycelia and exposed to 97% rh for three days (preconditioning) showed similar decreases in lipid and glycogen contents but trehalose contents increased to about 3.65% and 9.25% dry wt, respectively. Trehalose content had no effect on the abilities of the nematodes to survive exposure to reduced rh levels following preconditioning, with no nematodes surviving after 24 hr at 0% rh. Nematodes reared on R. cerealis and allowed to dehydrate naturally in culture for 6 weeks post-swarm showed an unexpected increase in lipid during swarming (28% to 42% dry wt), glycogen levels declined and trehalose levels increased from 2.0% to 4.0% dry wt. None of these changes were associated with dehydration stress. After 3 weeks nematodes began to coil and had lipid and trehalose contents of about 32% and 16.65% dry wt, respectively. At the end of the six week period lipid contents declined to 26% dry wt and trehalose contents remained stable. Naturally dehydrated nematodes showed an almost identical pattern of survival to preconditioned ones when exposed to reduced rh levels. The anhydrobiotic capabilities of D. myceliophagus are discussed in relation to other nematode anhydrobiotes and to the importance of trehalose as either a necessity for successful anhydrobiotic survival or a general adaptive response to environmental stress.","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80233619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Deux nouvelles especes de Rotylenchus et deux populations de R. agnetis sont decrites et figurees. Rotylenchus troncapitatus sp. n. se caracterise par une region cephalique tronconique annelee. Il se differencie de R. capitatus et de R. indorobustus par une plus grande longueur de corps et de stylet et par l'absence d'areolation a la partie anterieure du champ lateral. R. sabarlyi sp. n. differe des especes possedant une region cephalique tronconique annelee, par une tete ne comportant que deux anneaux alors que toutes les especes decrites en possedent au moins trois.
{"title":"Description De Deux Nouvelles Especes De Rotylenchus Et Deux Populations De R. Agnetis Szczygiel, 1968 (Nematoda: Hoplolaimidae)","authors":"G. Germani, C. S. L. Massèse","doi":"10.1163/005225998X00046","DOIUrl":"https://doi.org/10.1163/005225998X00046","url":null,"abstract":"Deux nouvelles especes de Rotylenchus et deux populations de R. agnetis sont decrites et figurees. Rotylenchus troncapitatus sp. n. se caracterise par une region cephalique tronconique annelee. Il se differencie de R. capitatus et de R. indorobustus par une plus grande longueur de corps et de stylet et par l'absence d'areolation a la partie anterieure du champ lateral. R. sabarlyi sp. n. differe des especes possedant une region cephalique tronconique annelee, par une tete ne comportant que deux anneaux alors que toutes les especes decrites en possedent au moins trois.","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89531597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This first report on a collection of Xiphinema species from Kenya deals with three species. Xiphinema mwanzianum n. sp. is closest to X. paritaliae but differs in vulva position, body length, stylet length, sexual dimorphism in tail shape and structure of Z-differentiation. It is also compared with X. elongatum, X. savanicola, X. rarum and X. pongolense. Xiphinema simpliciforme n. sp. is compared with X. simplex and X. parasimplex, from both of which it can be differentiated by body size and tail shape. X. elongatum is also reported and briefly discussed.
本文首次报道了来自肯尼亚的西菲纳蝇种的收集，涉及三个种。mwanzianum n. sp.与X. paritaliae最接近，但在外阴位置、体长、柱头长度、尾形性别二态性和z分化结构上存在差异。并将其与长叶竹、大叶竹、稀有叶竹和长叶竹进行了比较。单纯形Xiphinema simpliciformme n. sp.与单纯形X.和副形X.相比，两者都可以通过身体大小和尾巴形状来区分。此外，还报道并简要讨论了长叶竹。
{"title":"New and Known Species of Xiphinema (Nematoda: Longidoridae) From Kenya","authors":"A. Coomans, J. Heyns","doi":"10.1163/004725997X00052","DOIUrl":"https://doi.org/10.1163/004725997X00052","url":null,"abstract":"This first report on a collection of Xiphinema species from Kenya deals with three species. Xiphinema mwanzianum n. sp. is closest to X. paritaliae but differs in vulva position, body length, stylet length, sexual dimorphism in tail shape and structure of Z-differentiation. It is also compared with X. elongatum, X. savanicola, X. rarum and X. pongolense. Xiphinema simpliciforme n. sp. is compared with X. simplex and X. parasimplex, from both of which it can be differentiated by body size and tail shape. X. elongatum is also reported and briefly discussed.","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75929941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The first comparative study of head patterns in tylenchs was that of Sher & Bell (1975). De Grisse (1911) and Coomans & De Grisse (1981) srudied rhe underlying nervous system. The new information added since then is reviewed in this paper to see if the various patterns are characteristic of higher groupings (e.,9. families) within the Tylenchoidea. Therefore I used published and unpublished scanning electron micrographs (sEM) to produce schematized drawings. Comparing the photographs it was obvious that variation was found in the expression of pattems and sensilla. The schematized drawings give the maximum infbrmation obtained: e.g. whatever sensillum, distinct on a single photograph of a species or genus, was added on the drawing. In contrast to other nematodes there are no distinct lips in tylenchs. The head is an amalgamated lip region, internally strengthened by a cephalic framework and often including annuli, perhaps derived from ones formerly part of the body. The head can be continuous with the body, or variously offset but is always small to very small and unspectacular. It bears the mouth opening, which is nlinute and situated apically and centrally. There are two consecutive openings: the mouth opening seen at the outside is the prestoma opening: small, rounded to oval in Tylenchoidea and Aphelenchina, dorso-ventral slit to I-shaped slit in Criconematoidea. The stoma opening is found less than a micrometer to the
第一个对泰伦克斯头部图案的比较研究是谢尔和贝尔(1975)的研究。De Grisse(1911)和Coomans & De Grisse(1981)研究了潜在的神经系统。本文回顾了自那时以来增加的新信息，以确定各种模式是否具有较高分组的特征(例如，9)。泰伦科内的科)。因此，我使用已发表和未发表的扫描电子显微图(sEM)来制作原理图。比较照片，很明显，在图案和感受器的表达中发现了变化。图表给出了获得的最大信息:例如，在一个物种或属的单个照片上不同的任何感觉器官都被添加到图纸上。与其他线虫不同的是，蒂伦线虫没有明显的嘴唇。头部是一个合并的唇区，内部由头侧框架加强，通常包括环空，可能来自以前身体的一部分。头部可以连续与身体，或各种偏移，但总是小到非常小，不引人注目。它有开口，开口很小，位于顶端和中央。有两个连续的开口:在外面看到的开口为口前开口:小，在Tylenchoidea和Aphelenchina为圆形到椭圆形，在Criconematoidea为背-腹缝到i形缝。发现气孔开口小于1微米
{"title":"Comparison of the head patterns in the Tylenchoidea (Nematoda).","authors":"E. Geraert","doi":"10.1163/005025997X00049","DOIUrl":"https://doi.org/10.1163/005025997X00049","url":null,"abstract":"The first comparative study of head patterns in tylenchs was that of Sher & Bell (1975). De Grisse (1911) and Coomans & De Grisse (1981) srudied rhe underlying nervous system. The new information added since then is reviewed in this paper to see if the various patterns are characteristic of higher groupings (e.,9. families) within the Tylenchoidea. Therefore I used published and unpublished scanning electron micrographs (sEM) to produce schematized drawings. Comparing the photographs it was obvious that variation was found in the expression of pattems and sensilla. The schematized drawings give the maximum infbrmation obtained: e.g. whatever sensillum, distinct on a single photograph of a species or genus, was added on the drawing. In contrast to other nematodes there are no distinct lips in tylenchs. The head is an amalgamated lip region, internally strengthened by a cephalic framework and often including annuli, perhaps derived from ones formerly part of the body. The head can be continuous with the body, or variously offset but is always small to very small and unspectacular. It bears the mouth opening, which is nlinute and situated apically and centrally. There are two consecutive openings: the mouth opening seen at the outside is the prestoma opening: small, rounded to oval in Tylenchoidea and Aphelenchina, dorso-ventral slit to I-shaped slit in Criconematoidea. The stoma opening is found less than a micrometer to the","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79337996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Observations are reported on the fine structure of the cuticle of Paratrichodorus minor, P. nanus, P. rhodesiensis and Trichodorus eburneus. The ultrastructure of the cuticle was similar in Paratrichodorus and Trichodorus species; six layers were observed, the innermost layer consisting of three multilaminate units. The anatomy of the cuticle in Trichodorids was quite different from previous observations in other orders of Adenophorea. Two sets of intracuticular canals were observed as well as a peculiar type of junction between cuticle and somatic muscles. These results confirm previous studies on the anatomy of trichodorids and support the withdrawal of the family Trichodoridae from Dorylaimida. Siddiqi's (1983) classification of the trichodorids under the order Triplonchida should be considered with attention.
{"title":"Tem Observations On the Body Cuticle of Trichodoridae Thorne, 1935 (Nematoda: Enoplia)","authors":"D. Mounport, P. Baujard, B. Martiny","doi":"10.1163/005025997X00012","DOIUrl":"https://doi.org/10.1163/005025997X00012","url":null,"abstract":"Observations are reported on the fine structure of the cuticle of Paratrichodorus minor, P. nanus, P. rhodesiensis and Trichodorus eburneus. The ultrastructure of the cuticle was similar in Paratrichodorus and Trichodorus species; six layers were observed, the innermost layer consisting of three multilaminate units. The anatomy of the cuticle in Trichodorids was quite different from previous observations in other orders of Adenophorea. Two sets of intracuticular canals were observed as well as a peculiar type of junction between cuticle and somatic muscles. These results confirm previous studies on the anatomy of trichodorids and support the withdrawal of the family Trichodoridae from Dorylaimida. Siddiqi's (1983) classification of the trichodorids under the order Triplonchida should be considered with attention.","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87581677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Morphology and taxonomy of 14 species in 11 genera of plant parasitic nematodes collected from the Solomon Islands, are presented and discussed. Besides Eutylenchus vitiensis, Cephalenchus daisuce, Helicotylenchus erythrinae, H. hydrophilus, Criconema longulum, Ogma decalineatum, O. melanesicum, Discocriconemella limitanea, D. mauritiensis, Hemicriconemoides strictathecatus, Hemicycliophora litoralis, Xiphinema ensiculiferum and Aphelenchus isomerus, an undescribed species of Boleodorus was found, which is described here. All the species except O. decalineatum and X. ensiculiferum are new records for the Solomon Islands and four of them (Eutylenchus vitiensis, Helicotylenchus hydrophilus, Ogma melanesicum and Hemicycliophora litoralis) are rare and were found for the first time after their original descriptions. Boleodorus (Neobasiria) solomonensis n. sp. is characterized by its almost straight body, 550-650 μm long, head conical, lightly sclerotized, stylet 12.0-14.5 μm long, ovary with oocytes in one row, vulva at 53-58% of body length and tail elongate with rounded tip. Cephalenchus chilensis is synonymized with C. daisuce and Discocriconemella discolabia with D. mauritiensis. Scanning electron microscopy studies of Discocriconemella mauritiensis, Ogma melanesicum and Hemicycliophora litoralis are also included.
{"title":"Plant Parasitic Nematodes From the Solomon Islands With a Description of Boleodorus Solomonensis","authors":"W. Ye, E. Geraert","doi":"10.1163/005125997X00048","DOIUrl":"https://doi.org/10.1163/005125997X00048","url":null,"abstract":"Morphology and taxonomy of 14 species in 11 genera of plant parasitic nematodes collected from the Solomon Islands, are presented and discussed. Besides Eutylenchus vitiensis, Cephalenchus daisuce, Helicotylenchus erythrinae, H. hydrophilus, Criconema longulum, Ogma decalineatum, O. melanesicum, Discocriconemella limitanea, D. mauritiensis, Hemicriconemoides strictathecatus, Hemicycliophora litoralis, Xiphinema ensiculiferum and Aphelenchus isomerus, an undescribed species of Boleodorus was found, which is described here. All the species except O. decalineatum and X. ensiculiferum are new records for the Solomon Islands and four of them (Eutylenchus vitiensis, Helicotylenchus hydrophilus, Ogma melanesicum and Hemicycliophora litoralis) are rare and were found for the first time after their original descriptions. Boleodorus (Neobasiria) solomonensis n. sp. is characterized by its almost straight body, 550-650 μm long, head conical, lightly sclerotized, stylet 12.0-14.5 μm long, ovary with oocytes in one row, vulva at 53-58% of body length and tail elongate with rounded tip. Cephalenchus chilensis is synonymized with C. daisuce and Discocriconemella discolabia with D. mauritiensis. Scanning electron microscopy studies of Discocriconemella mauritiensis, Ogma melanesicum and Hemicycliophora litoralis are also included.","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87421132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
If only a few cysts are sampled from a large population and reproduced elsewhere, then the new isolated population may not be genetically representative of the original population. This phenomenon is called random genetic drift. The susceptibility of a cultivar to the new population could be significantly different from that to the original population. This deviation has been quantified for potato cyst nematodes via derivation of statistical equations. The standard deviation σ, caused by random genetic drift, is inversely proportional to the square root of the number of cysts sampled, decreases at increasing mating frequency per female, and attains its highest values at intermediate levels of cultivar susceptibility to the original population. Relative susceptibility of a cultivar is the reproduction factor P 1/P 2 on this cultivar relative to that on a susceptible reference cultivar, at a low inoculum density. If only one cyst is taken, then σ- equals 20-30% at a relative susceptibility to the original population of 20-80%, under assumptions given in the text. If more than 10 cysts are drawn, then σ is lower than 9%. Increasing the mating frequency from one to 25 decreases the random genetic drift by approximately the same extent as doubling the number of cysts per sample. Virulence based on two independent genes hardly changes drift compared to monogenic virulence. If the number of eggs per cyst is lower than 15, then additional random genetic drift arises. The results of this study may be used to judge how many cysts are needed in a sample to keep the sampling error sufficiently small, and for investigations on founder effects.
{"title":"Modelling the effect of random genetic drift on the virulence of potato cyst nematodes","authors":"H. Schouten","doi":"10.1163/004825997X00042","DOIUrl":"https://doi.org/10.1163/004825997X00042","url":null,"abstract":"If only a few cysts are sampled from a large population and reproduced elsewhere, then the new isolated population may not be genetically representative of the original population. This phenomenon is called random genetic drift. The susceptibility of a cultivar to the new population could be significantly different from that to the original population. This deviation has been quantified for potato cyst nematodes via derivation of statistical equations. The standard deviation σ, caused by random genetic drift, is inversely proportional to the square root of the number of cysts sampled, decreases at increasing mating frequency per female, and attains its highest values at intermediate levels of cultivar susceptibility to the original population. Relative susceptibility of a cultivar is the reproduction factor P 1/P 2 on this cultivar relative to that on a susceptible reference cultivar, at a low inoculum density. If only one cyst is taken, then σ- equals 20-30% at a relative susceptibility to the original population of 20-80%, under assumptions given in the text. If more than 10 cysts are drawn, then σ is lower than 9%. Increasing the mating frequency from one to 25 decreases the random genetic drift by approximately the same extent as doubling the number of cysts per sample. Virulence based on two independent genes hardly changes drift compared to monogenic virulence. If the number of eggs per cyst is lower than 15, then additional random genetic drift arises. The results of this study may be used to judge how many cysts are needed in a sample to keep the sampling error sufficiently small, and for investigations on founder effects.","PeriodicalId":18988,"journal":{"name":"Nematologica","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74924362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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