Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

In the UK the most problematic pests of the potato crop are the potato cyst nematodes Globodera rostochiensis and G. paUida. A structured survey of potato growing land in England and Wales was undertaken to reassess their occurrence and distribution. peN were present in 64% of sites sampled and of the populations found, 67% were G. pallida, 8% were G. rostochiensis and 25% contained both species. Just over 50% of the sites sampled had a rotation length of 1 in 5 or less and cultivars with partial resistance to G. paUida represented only 6% of the total number of plantings while those with resistance to G. rostochiensis represented 43%. The results show an increase in the incidence of peN compared with previous surveys and confirm the perceived shift towards G. paUida as the predominant species. Two field experiments were done to look at the integration of methods for the control of peN and subsequent reduction in yield loss in situations of very high peN levels. The first experiment assessed the use of 1,3-dichloropropene (1,3-D) with the granular nematicides aldicarb, oxamyl and fosthiazate when growing the susceptible cultivar Estima. The second experiment assessed the use of the resistant cultivar Sante with 1,3-D and oxamyl at full and half-rates. 1,3-D significantly advanced emergence, increased percentage ground cover, root invasion, yield, tuber numbers, and improved tuber size distribution. Nematode multiplication was significantly reduced by fumigation in the first experiment. The use of 1,3-D for the control of weed seeds was assessed and the results show a reduction in germination of weed seeds in soil after fumigation. The use of 1,3-D for the control of Rhizoctonia solani was also assessed and a trend in reduction in R. solani was observed after fumigation although the differences were not statistically significant.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: A molecular, morphological and biological characterisation of the genus Globodera (Nematoda: Heteroderidae) in South Africa is presented. The aims of the study were to determine the spread of the genus in South Africa; to study the systematics and describe the characteristics of the group and to gain a more complete understanding of the biology of the group as agricultural pests. Surveys were conducted in the Cape Floristic Region and in all the potato-producing areas of South Africa. The surveys unearthed new species of cyst nematodes and determined the spread of Globodera rostochiensis in the country. Phylogenetic analysis of sequences from ITS-rDNA was used to infer phylogenetic relationships among cyst nematodes from South Africa. The analyses established the distinct phylogenetic positions of cyst nematode populations from South Africa relative to an array of other cyst nematode species and indicated the existence of four new species of cyst nematodes. Analysis of random amplified polymorphic DNA (RAPD) banding patterns revealed intraspecific genetic variation amongst populations of Globodera rostochiensis. In order to provide molecular protocols for the accurate identification of South African cyst nematodes, species-specific primers and restriction enzymes were tested for their ability to discriminate between local Globodera spp. A combination of the molecular, morphological and morphometric characteristics of these populations were used to describe three new species of cyst nematodes. Experiments to determine the effect of storage temperature on the viability and hatching of South African populations of G. rostochiensis, showed differences in the responses of different populations to different storage temperatures. Experiments to determine the effect of field conditions on the viability and hatching of South African populations of G. rostochiensis, indicated that a decline in viable eggs in cysts from different populations occur, but suggests that the cysts will be able to survive for much longer in these soils than was expected. Spontaneous hatch was the main contributor to the decline of viability of cysts in the soil. Recording of soil temperatures in different locations indicated that the average temperature at 20 cm depth was approximately 20°C, the optimum temperature for the reproduction of G. rostochiensis, as confirmed by in vitro reproduction tests, which also showed that multiplication and survival is influenced negatively when the temperatures rise above 25°C. Reproduction on differential potato clones confirmed the pathotype of all the South African populations of G. rostochiensis as Ro1. After assessing the reproduction of G. rostochiensis on indigenous solanaceous plants, it was concluded that none of these plants induce substantial hatch in G. rostochiensis, nor do they support multiplication of the nematode. The results of this project have an impact on inquiries at all taxonomic levels, while also having an essential practical application in nematology. Knowledge of the distribution, pathogenicity, survival potential and reproduction capacity of Globodera species in South African soils are valuable for the design of effective management strategies as well as regulatory measures. / AFRIKAANSE OPSOMMING: ‘n Molekulêre, morfologiese en biologiese karakterisering van die genus Globodera (Nematoda: Heteroderidae) in Suid-Afrika word aangebied. Die doelwitte van die studieprojek was om die verspreiding van die genus in Suid-Afrika vas te stel, om die sistematiek van die groep te bestudeer en om ‘n meer volledige begrip van die biologie van die groep te bekom. Opnames is in die Kaapse Floristiese streek en in al die aartappelproduserende gebiede in die land gedoen. Tydens die opnames is nuwe sist nematode spesies gevind en die verspreiding van Globodera rostochiensis in Suid-Afrika is vasgestel. Filogenetiese analises van die basispaar opeenvolgings van ITS-rDNS is gebruik om die filogenetiese verwantskappe tussen die sist nematodes van Suid-Afrika vas te stel. Die spesifieke filogenetiese posisies van die nematodes, relatief tot ander spesies het gedui op die teenwoordigheid van 4 nuwe spesies. ‘n Analise van “random amplified polymorphic DNA” (RAPD) bandpatrone het intraspesifieke variasie tussen populasies van G. rostochiensis uitgewys. Diagnostiese tegnieke, aan die hand van spesies-spesifieke inleiers en restriksie-ensieme, is geevalueer vir hul vermoë om Globodera spesies van mekaar te onderskei. ‘n Kombinasie van molekulére, morfologiese en morfometriese karaktertrekke is gebruik vir die beskrywing van drie nuwe Globodera spesies. Eksperimente om die effek van verskillende temperature op die lewenskragtigheid en uitbroei van Suid-Afrikaanse populasies van G. rostochiensis vas te stel, het verskille in die reaksies van die poulasies uitgewys. Eksperimente om die effek van veldtoestande op die lewenskragtigheid en uitbroei van Suid-Afrikaanse populasies van G. rostochiensis vas te stel, het gewys dat alhoewel ‘n afname in die lewenskragtigheid van eiers plaasvind, sal die siste nog steeds langer in die grond oorleef as wat verwag is. Spontane uitbroei van eiers was die grootste oorsaak van die afname in lewenskragtigheid van siste in die grond. Die monitoring van grondtemperature in verskillende lokaliteite, het gewys dat die gemiddelde temperatuur, 20 cm onder die grond, nagenoeg 20°C was. Die optimum temperatuur vir die aanteling van G. rostochiensis, soos gewys deur in vitro toetse is ook 20°C, maar ‘n skerp daling vind plaas by temperature hoer as 25°C. Aanteling op verskillende aartappel cultivars, het gewys dat die patotipe van plaaslike populasies van G. rostochiensis, Ro1 is. Toetse op inheemse Solanum plante het gewys dat die plante nie goeie gashere vir G. rostochiensis is nie. Die bevindings van hierdie studieprojek het ‘n impak op die taksonomie van die groep en kennis van die verspreiding, patogenisiteit en oorlewing van die nematodes onder Suid-Afrikaanse toestande is van waarde vir die daarstelling van effektiewe beheerstrategiee en wetstoepaslike regulasies.

No description available.

Tobacco cyst nematodes (TCN), Globodera tabacum solanacearum, are one of the most serious pests for Virginia flue-cured tobacco (Nicotiana tabacum L.) farmers. These nematodes continue to spread to new farms every year and are now reported in 11 Virginia counties, seven North Carolina counties, and one farm in Maryland. The objectives of this study were to determine the ability of different populations of TCN to reproduce upon both a susceptible (K326) and resistant (NC567) cultivar, to compare TCN reproduction in non-infested soils with currently TCN-infested soils, and to examine reproduction and pathogenicity of TCN on other solanaceous crops. Tobacco cyst nematode reproduction on the TCN-resistant cultivar NC567 was significantly reduced when compared to the TCN-susceptible cultivar K326. Although significant differences among the populations were detected on both cultivars, the differences were not consistent across experiments. Results indicate similar pathogenicity among TCN populations on resistant and susceptible flue-cured tobacco cultivars. Plant breeders may use one population of the tobacco cyst nematode to screen tobacco germplasms for TCN resistance. Significant differences were noted in TCN reproduction among the various soils used in this study. However, the differences were inconsistent, making correlations between TCN reproduction and soil edaphic characteristics unreliable. Sterilizing the soils did not increase TCN reproduction. Reproduction in non-infested soils indicates that TCN will continue to spread throughout tobacco producing regions. Although traditionally an exclusive pest of tobacco, TCN's spread may threaten production of other solanaceous crops. Eggplant (Solanum melongena L.), pepper (Capsicum spp. L.), and tomato (Lycopersicon spp. L.) were confirmed to be hosts of TCN under field conditions. Eggplant was highly susceptible to TCN reproduction and yield suppression, exhibiting a 64% yield reduction in plots not treated with a nematicide compared to fumigated plots. Tomato allowed high rates of TCN reproduction but did not suffer yield loss. Tobacco cyst nematode reproduction was suppressed on pepper compared to the other two crops. No crop loss was noted in nontreated pepper plots compared to plots treated with a nematicide. Results would indicate that tobacco rotations including tomato or eggplant would be unacceptable due to high TCN reproduction rates. The tobacco cyst nematode does not seem to jeopardize the production of tomato and pepper in the southeastern United States, but does threaten profitability of eggplant production in this area. / Master of Science

Auksinis (Globodera rostochiensis) ir blyškusis (Globodera pallida) bulviniai cistiniai nematodai yra bulvinių (Solenaceae) šeimos kenkėjai, įrašyti į pasaulio, Europos ir Lietuvos karantininių organizmų sąrašą. Šio magistro darbo tikslas buvo identifikuoti G. rostochiensis, jo patotipus bei paplitimą, ištirti G. pallida būklę dirvos mėginiuose, paimtuose skirtingo ploto laukuose su skirtingais priešsėliais iš visų Lietuvos apskričių. Atlikus morfologinę ir pirmąkart Lietuvoje pritaikius DNR polimerazinės grandininės reakcijos (PGR) metodą bulviniams cistiniams nematodams G. rostochiensis ir G. pallida, Lietuvoje aptiktas tik G.rostochiensis, o G. pallida nerastas. Mažuose laukų plotuose - iki 5ha G. rostochiensis yra paplitęs labiau, nei dideliuose plotuose - nuo 5ha iki 30ha. Gausesniam paplitimui Lietuvos agroekosistemose įtakos turi lengvesnis dirvožemio tipas – smėliai ir priesmėliai, bei priešsėliai, kur didesnė tikimybė, kad augs augalai šeimininkai. Laboratorinis bandymas su diferenciniais augalais parodė, kad Lietuvoje paplitęs G. rostochiensis Ro1 patotipas. / Golden (Globodera rostochiensis) and pale (Globodera pallida) potato cyst nematodes are quarantine organisms. Potatoes are by far the most important host crop. Other Solanum spp. and their hybrids can also act as hosts. The aim of this study was to identify G. rostochiensis, G. rostochiensis pathotypes and distribution and also G. pallida status in soil samples from different field of different size and various forecrops in Lithuanian counties. Only G. rostochiensis was present in Lithuania after morphological identification and DNA polymerase chain reaction (PCR) which has been done in Lithuania for the first time. In small field areas up to 5 ha G. rostochiensis is more distributed than in bigger areas up to 30 ha. The presence of host plants in various forecrops, soil type – sands and sandy loams, also have influence on numerous distribution of G. rostochiensis. The experiment of G. rostochiensis pathotypes showed that only Ro1 pathotype is present in Lithuania.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniversitet, 2004. / Härtill 4 uppsatser.

A morphological and morphometrical study was made of the tobacco cyst nematode complex, Globodera tabacum sspp. tabacum (GTT), virginiae (GTV), and solanacearum (GTS) including observations of eggs, second-stage juveniles (J2), males, females, and cysts. Observations focused on the anterior region including head shape, lip pattern, stylet morphology, and the tail region including tail shape in J2 and spicules in males. The head region of J2 was set off from the body and consisted of three head annules, six lips, and an oral disk. The shape of the head seen in lateral view showed little variability within or among the subspecies. Stylets of J2 were robust and had three anchor-shaped, rounded knobs. They varied slightly in width and height within each subspecies. The lip region consisted of a central oral disc surrounded by two lateral and two submedial lips. The oral disc varied from rectangular to elliptical. The submedial lip pairs were not fused in all specimens. The tail of J2 was finely pointed and the tip was rounded in all subspecies. The head of the male was set off and contained five head annules, six lips, and an oral disc. The head region was similar in lateral view in all three subspecies. The stylet was robust and had three rounded knobs that slope posteriorly. The dorsal knob of males of GTV appeared to slope more posteriorly than in the other two subspecies. In the SEM, the head region had a large central rounded to elliptical oral disc with two lateral and two submedial lip pairs. The submedial lips were rounded or rectangular. The submedial lip pairs were fused in most specimens, but not all. The spicules of GTT showed a slightly more enlarged head region than the other two subspecies. The three subspecies could not be separated on the basis of any character or group of characters of J2 or males.The anterior region including body shape, head shape, lip pattern, stylet morphology, and the terminal area in females; and body shape and terminal area of cysts were observed. The most useful characters to separate the three subspecies were female body shape, stylet knobs, perineal tubercles, cyst shape, anal-fenestral ridge pattern, anus, and tail region. GTT was characterized by rounded females and cysts with sharply back sloped stylet knobs, clumped perineal tubercles in the vulval region, tight parallel ridges in the anal-fenestral region of the cyst, and a distinct tail region not shaped like a crescent. GTV was characterized by its ovoid to ellipsoid female and cyst shape, the "Dutch shoe" shape of the dorsal stylet knob, the more individualized perineal tubercles, a maze-like pattern of ridges in the anal-fenestral region, and an indistinct anus. GTS was characterized by its ovoid to ellipsoid female and cyst shape, moderately backward sloped stylet knobs, more widely separated ridges, a distinct anus, and a tail region usually shaped like a crescent. Much variability in shape and patterns was visible among all the isolates of the different subspecies. Tubercles in the neck as well as bullae were reported and discussed. A morphometric evaluation of second-stage juveniles (J2), males, females, and cysts was performed for several characters. Morphometrics of eggs, J2, and males were considerably less variable than in females and cysts. No measurements of eggs and J2 were useful for identification of the three subspecies. The distance of the median bulb to the head end and the distance of the excretory pore to the head end in J2 and males were quite reliable and useful. The stylet knob width of males was useful for identifying GTV isolates. Tail length was useful in separating males of GTT isolates from GTV and GTS. The body length/ width (L/W) ratio of females and cysts discriminated GTT from GTV and GTS. Stylet knob width of females was an auxiliary character useful for identifying GTV. This subspecies complex has a continuum of values for the majority of the characters observed. The data suggests a closer relationship between GTV and GTS which is likely because these two subspecies occur in very close proximity in Virginia, 38 km separation between closest adjacent geographical ranges; whereas GTT occurs 700 km away in the northeastern U.S. / Ph. D.

The tobacco cyst nematode (TCN), Globodera tabacum solanacearum [(Miller and Gray, 1972) Behrens 1975] Stone 1983, is one of the most economically important pests of flue-cured tobacco (Nicotiana tabacum L.) in Virginia. Although TCN has been reported from other countries, the geographical distribution of G. t. solanacearum within the United States is limited to Virginia, North Carolina, and one county in Maryland. Approximately 30% of the tobacco acreage in Virginia is infested; average yield reduction is 15%, but complete crop failure can occur. The objectives of this research were to examine intraspecific variability within G. t. solanacearum and to evaluate the relative adaptability of G. t. solanacearum on a resistant (NC567) and a susceptible (K326) flue-cured tobacco cultivar. Nineteen geographic isolates of G. t. solanacearum, one isolate each of G. t. virginiae and the Mexican cyst nematode (G. "mexicana"), two isolates of G. t. tabacum, and five Heterodera species were characterized by DNA fingerprinting using the RAPD-PCR technique. Reproducible differences in fragment patterns allowed similar differentiation of the isolates and species with each primer. Hierarchical cluster analysis was performed to illustrate the relatedness between nematode isolates and species. In contrast to reports in the literature, we found a Miller isolate of G. "mexicana" to cluster more closely with G. t. solanacearum than with G. t. tabacum or G. t. virginiae. Although no pathotype differences have been found within G. t. solanacearum, the average Jaccard's similarity index among isolates of G. t. solanacearum was 74%, representing greater variation than that observed across different pathotypes of the closely related potato cyst nematode, Globodera pallida. This result suggests that the emergence of resistance-breaking biotypes is more likely than previous research suggests. If a new pathotype is reported, a RAPD marker associated with virulence against a specific host resistance gene could prove to be a valuable tool in population diagnosis, resistance screening, and overall TCN management. One isolate of G. t. solanacearum was cultured on a resistant (NC567) and a susceptible (K326) flue-cured tobacco cultivar over five generations. Variable TCN reproduction was observed on both cultivars over each generation. This variability in reproduction could be attributed to differences among generations in the time interval between inoculation and cyst extraction, temperature, possible diapause effects, and/or daylength. Ninety-eight cysts were produced in the fifth and final generation compared to the 14 to 50 cysts produced during each of the previous four generations. Increased reproduction on the resistant variety suggests that increased virulence might be selected, but research involving additional generations would need to be carried out in order to conclude whether or not TCN virulence is being selected. / Master of Science

Resistance to Globodera tabacum solanacearum in flue-cured tobacco was characterized in vitro, in the greenhouse, and field. The objectives of this study included evaluation of hatching of G. t. solanacearum as stimulated by root exudate, penetration and development of G. t. solanacearum on roots, and the effects of G. t. solanacearum on growth, yield, and quality of flue-cured tobacco. Root exudate from resistant (NC 567) and susceptible (K 326) flue cured tobacco cultivars had similar effects on hatching of G. t. solanacearum. Dilution of root exudate reduced hatching and hatching appeared to increase with increased temperature. More swollen and flask shaped nematodes developed in roots of K 326 than those of NC 567. Resistance reduced development of vermiform juveniles to swollen nematodes in NC 567. However, development of swollen nematodes to flask shaped nematodes was similar for both cultivars. Resistance to G. t. solanacearum was effective at 17, 22, 27, and 31°C. Infection by G. t. solanacearum suppressed number of leaves, plant height, fresh weight of leaves, and feeder roots. Reduction in fresh leaf weight at 11 weeks after transplanting was greater for the susceptible cultivar, K 326, than for the resistant cultivar, NC 567. However reduction in fresh feeder root weight and increases in the ratio of leaf weight to feeder root weight at 11 weeks after transplanting between both cultivars. Yield and grade index of cured leaves were negatively correlated with area under curves of total nematode population densities per gram of feeder root. The rate parameters of regression models suggested that the two cultivars responded similarly to infection by G. t. solanacearum in yield and quality reduction. However, K 326 had a higher yield potential in the absence of nematodes. / Ph. D.