Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The genomic variability of sixty-nine populations of the potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis from Europe and South America were analyzed using the RAPD-PCR technique with sixty-six 10-mer primers. Large genomic differences were found between the two PCN species (i.e. 33%). The genomic pool of British G. pallida populations showed considerably less variation than the Peruvian populations, with 73% and 41% similarity between populations respectively. The genomic similarity among populations of G. rostochiensis was 89% for UK populations and 82% when the two continental European populations were included. Nevertheless, between populations within each species and from the same locality, genomic differences were still found. The RAPD-PCR technique proved to be useful for revealing the genomic variability between and within species using DNA extracted from 50 cysts, but it gave variable results when DNA extracted from individual females or cysts was used, suggesting that for evaluating the genomic variability of individuals it is better to use specific primers. RAPD-PCR was also used successfully to distinguish the two PCN species, individuals selected and selected for virulence and even biotypes using individual cysts. Based on the results found when comparing biotypes of Globodera pallida, it is suggested that all the biotypes considered in the International Pathotype Scheme could be grouped into Pa1 and Pa2/3 when classifying European populations, and Pa1A or Pa1B, P4A, P5A and P6A when analyzing South American populations. However, these groupings should be regarded just as a reference, because virulence bioassay results plus the data found using the RAPD-PCR technique suggested that, at least in G. pallida, virulence seems to be a polygenic trait ruled by several genes with additive effects. On the other hand, based on the same sort of data, virulence in G. rostochiensis seems to be ruled only by major genes. Selected and unselected populations of G. pallida, reared on either potato clone Solanum vernei (VTn)2 62.33.3 or a susceptible control, were distinguished using the RAPD-PCR technique and primers Operon A-07, E-06, G-16 and I-05. Three of the fragments that appeared to distinguish the unselected from the selected populations were cloned into an isolate of E. coli and their sequences obtained. Gpalpha, seems to be part of a promoter region of a gene probably related or linked to virulence. The use of differential clones to characterize PCN populations with different proportions of each virulence gene is a valuable tool. Whilst diagnostic probes for routine identification of virulent populations are being developed, the use of the “gene pool similarities” concept involving the DNA patterns of standard populations as genetic virulence types (i.e. virulence biotypes), integrated with information on their response to differential clones bearing genes for resistance, would represent the best approach towards devising a sustainable control strategy to optimize the usefulness of whatever resistance is available.

Oilseed rape has become an important weed in arable rotations and a feral plant of field margins, soil dumps and roadsides. Seed persistence in the soil following induced secondary dormancy is thought to perpetuate these weed and feral populations. Potential variation between cultivars has been suggested in previous work in the extent of secondary dormancy and other germination traits, and in underlying genetic heterogeneity. The aim of this work was to quantify in more detail inter- and intra- cultivar variation in germination traits for six oilseed rape cultivars, to confirm that variation was consistent in laboratory and field, and to ascertain whether there is a genetic base to this variation. The cultivars are Askari, Bristol, Gazelle, Libravo, Martina and Rocket, selected on the basis of their suspected heterogeneity. Laboratory germination tests were conducted at 4°C, 10°C and 19°C on a thermal plate and confirmed substantial inter-cultivar variation in germination rate, induction of secondary dormancy and the temperature stimuli required for dormancy break. The phenotypic traits were quantified by mathematical parameters and cultivars ranked in order of decreasing heterogeneity. DNA analysis was made on leaf tissue of early, middle and late germinating phenotypes using two simple sequence repeat primers. There was heterogeneity and phenotypic variability generally, but a direct association between phenotype and genotype was found only in the cultivar Martina. Field emergence trials revealed non-linearity in emergence and a strong similarity between laboratory germination and field emergence curves. Cultivar heterogeneity was found to be similar for emergence rate and post-winter emergence. Again there was evidence of an association between heterogeneity in emergence and genetic heterogeneity in the DNA markers. The results suggest that standard seed testing should be carried out at low temperatures to detect any hidden variability in germination. Plant breeders should be cautious about introducing variability into new breeding lines as this might increase the potential persistence of feral populations and the risk of gene transfer to later.

The prickly sculpin, Cottus asper, is a polytypic species characteristically represented by very prickly, fresh-water spawning "inland" forms, and less prickly, brackish-water spawning "coastal" forms. Its widespread geographic distribution, pronounced phenotypic variability, and the effects of the contrasting environments in which it occurs are the subject of this investigation. A complete nomenclatural history and synonymy of the species for the period 1836-1936 is presented. Morphological evidence is interpreted in the light of field and laboratory studies of the migration and reproductive behavior. Differences found in distribution and intensity of body prickles (modified scales), geographical distribution, and migratory behavior, support the contention that the polytypy of "coastal" and "inland" forms of Cottus asper has a genetic basis. Other morphological evidence is equivocal in support of this interpretation. Differences in fin ray counts, e.g., pectoral rays, between "coastal" and "inland" forms are correlated positively with the presence or absence of salinity in the environment. However, it is not known whether such differences are the result of individual modifications induced by the local environment, or due to long term genetic fixation. Evidence from studies of closely-related species supports the interpretation that Cottus asper is a polytypic species which has become, and is in the process of becoming, modified into several characteristic genotypes. Evolution within this “asper species group" probably occurred in three stages, each correlated with past geologic history. During the first stage, perhaps in the Pliocene or Late Miocene, "coastal" and "inland" forms were derived from an ancestral marine cottid. The second stage, during the Pleistocene, was characterized by fragmentation of the gene pool of the "inland" form into a series of geographically isolated populations which have since evolved into valid species. The third stage, in Recent Time since the retreat of the Cordilleran glaciers, has occurred primarily within the northern representatives of the "coastal" form. At least two derivatives can now be distinguished within the "coastal" form. / Science, Faculty of / Zoology, Department of / Graduate

Field collections and observations of Alaria (Order Laminariales) were made throughout the intertidal zones of the temperate areas in the Northern Hemisphere. In addition a study was made of all available herbarium material. Morphology was chosen as the basis of the systematic study of the genus. The systematics of the genus were studied by a discriminant and distance function analysis, using an IBM 1620 computer. From this analysis, the characteristics of 10 species were defined. Four other species were described from herbarium material, but were not sampled in sufficient quantity for statistical analysis. The dividing lines drawn between the various species are meaningful but essentially arbitrary. Confusion in the taxonomy of the genus has two main sources. First, the taxa are not completely differentiated into distinct species. Second, differences of environment appear to play a greater role as a cause of morphological variation than do differences of genotype. The names of 107 specific and subspecific taxa of the genus Alaria, including recombinations, were discovered in an exhaustive search of the literature. Of these 107 names, 19 were eliminated as illegitimate under the rules of the International Code of Botanical Nomenclature, or were removed from the genus. The genus Pleuropterum Miyabe et Nagai was reduced to synonomy under the genus Alaria. The conservation of the generic name Alaria was re-examined and found to be adequate. A thorough search was made for possible holotypes or lectotypes of the 88 taxa remaining. Material was either shown to be the holotype or found and designated as the lectotype for 66 taxa. No relevant material could be found for 11 more of these taxa and possible material for another 11 was judged inadequate for practical systematic purposes. / Science, Faculty of / Botany, Department of / Graduate

Five hundred wolf specimens were studied. They represent populations from Alaska to Keewatin and from Vancouver Island to Manitoba. Pelage color varies nearly from black to white. There are no discrete color phases. Pale wolves are more numerous and dark wolves less numerous toward the tundra (northeastward) between Great Slave Lake and Great Bear Lake. Judging from color variation, wolf populations intermingle by associating with caribou at migration. Male wolves are larger than females (approximately 4% in linear skull dimensions). Northeastern individuals have a shorter and relatively broader skull than southwestern ones. Multivariate divergence in twelve skull dimensions is approximately proportional to geographical separation. This may express genetic differentiation "by incomplete isolation. But the pronounced northeastward zonation of the environment may have direct influences upon growth processes. Interpretations in terms of genetic affinities are hypothetical and taxonomic conclusions are postponed. Simultaneous analysis of biometrical data appears indispensable to disclose major trends of geographic variation. / Science, Faculty of / Zoology, Department of / Graduate

The new mutation, synpalpi, which was found in the Xple Stock obtained from the Biological Supply House, Chicago, is so named because of the fusion of the antennae along the midline, all other Xple characteristics being normal except for a slight protrusion of the forehead. In stock cultures the mutant appears in greater numbers from normal Xple crosses than from synpalpi Xple crosses - with a predominance of female synpalpi. Experiments were carried out in order to determine the nature of the mutation, the type of inheritance involved, and the linkage group with which the mutation is associated. The mutant is not a gene mutation but a chromosomal aberration since Mendelian ratios were not observed to occur and since the mutation appeared irregularly but persistantly. A lethal factor is suggested by the small number of flies resulting from synpalpi crosses; the absence or small number of synpalpi in the F¹ of synpalpi crosses but its reappearance in 2-8% of the F² progeny; and by the death of flies in two different stages of development - early and late pupal stages. The association of the lethal factor with the "X" chromosome is assumed because few male synpalpi emerge. A deficiency of a part of the "X" chromosome would explain the death of the males and homozygous females. The possibility of a deficiency of a few bands at the tip of the “X” chromosome was substantiated by a review of the literature on deficient "X" chromosomes. It is believed that synpalpi flies are those deficient flies which do manage to survive and that the fused antennae are caused by the movements of the fly and forcing of fluid to the head in its efforts to extricate itself from the pupa case (its tracheae being attached posteriorly to the case). The Xple stock is very sensitive to variations from the optimum temperature of 25°C. Temperatures of 35°C., 29°C, and 15°C. increased the lethal effect of the deficiency - no synpalpi appearing in the F¹ or F² of temperature-treated cultures. In the test for linkage, the mutant appears to be associated with chromosomes I and III - therefore the mutant is not a simple deficiency of the "X" chromosome alone but appears to involve the third chromosome as well. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

Differences in progeny characteristics arising from differences in maternal age at time of birth are discussed as a possible source of ecologically important variation. The literature on effects of maternal age on progeny guality is reviewed. Experiments designed to document any effects of maternal age on two biological processes are described. The processes selected were production of alatae by an aphid, ASiSiioSiEiiOS. £isum , and incidence of diapause in a sawfly, Eriocamoa ovata . Maternal-age effects influenced the production of alatae by the aphid. Early-born progeny of wingless aphids were more likely to respond to a standard crowding stimulus by producing alatae than were late-born progeny. Early-born alata-producers also produced higher numbers of alatae than late-born ones. Maternal age affected the progeny of winged aphids, but in the opposite manner. Early-born progeny of this morph usually did not produce alatae at all, whereas late-born progeny did. The inhibition of alata-prcduction in the lineage of an alate aphid was satisfactorily explained by maternal age effects alone. A timing mechanism such as the "interval timer" proposed by Lees (1966) did not apply. Ho significant effects of maternal age on the incidence of diapause in the sawfly could be found. However, diapause was shown to be influenced by at least two factors. More animals diapaused at low humidities. Seven-instar larvae diapaused more frequently than did six-instar larvae. Larval developmental times varied with the number of instars, the occurrence of diapause, and the date of egg-laying. Length of the cccocn stage of ncn-diapausing individuals varied with the date of egg-laying. It is concluded that maternal age effects, although not universal, are a common biological phenomenon, and probably of ecological significance as a source of variation. / Land and Food Systems, Faculty of / Graduate

Plectritis congesta and P. brachystemon are two very closely related species which grow sympatrlcally, and differ in their: breeding system, some associated morphological (floral) characters, and isozyme phenotypes. Plectritis congesta is approximately 70% outcrossed in nature, while P. brachystemon is less than 3% outcrossed in natural populations. Theory would predict that, all other things being equal, the outcrossed species would be more variable genetically than the selfed species. Since selection acts on genetic variability, the two species could be expected to respond differently to it. Six generations of plants of both species were grown under controlled conditions, and measured for a number of characters. Control and treatment (selection for tall and short height, and for early and late anthesis) populations were maintained. Two sets of P. congesta populations were maintained, one outcrossed (approximately 65%) and one selfed (outcrossed approximately 15%); the P. brachystemon populations were naturally self-pollinating. Selection pressure in the experiment was approximately 90%; 20 of the 200 plants in any population were selected to form the next -generation, on the basis of height or flowering time in the treatment populations, and at random in the control populations. The P. congesta populations responded to divergent selection for height at anthesis, indicating that genetic variability for this character was present in the populations. The outcrossed lines, PCO, diverged 66% or 148 mm from the control line; the selfed lines, PCS, diverged 78% or 175 mm. There were no significant differences between the outcrossed and selfed P. congesta lines over the course of the experiment. Two estimates of narrow sense heritability - realised heritability (b[sub=c]) and parent-offspring: regression (h²) - quantified this genetic variability: in PCO b[sub=c] = 0.53, h² = 0.45: in PCS b[sub=c] = 0.58, h² = 0.44. There was a decline in the phenotypic variance for height at anthesis in the P. corigesta lines selected for this character. In contrast, the P. brachystemon populations did not respond to selection for height at anthesis, and appear to have no detectable genetic variability for this character. Both species appear to have significant genetic variability for flowering time, as both responded to divergent selection for this character. The PCO lines diverged 33.5% or 31.8 days from the control line, the PCS lines diverged 28.7% or 27.3 days, and the P. brachystemon lines, PBS,-diverged 18.5% or 21.5 days. According to the heritability estimates, P. congesta is more variable genetically: in the PCO lines b[sub=c]=0.77, h² = 0.60; in PCS b[sub=c]= 0.75, h² = 0.72; while in PBS b[sub=c]= 0.49, and h²= 0.42. There was a decline in the phenotypic variance for flowering time in all three species groups. Of the other measured but unselected characters - number of days to emergence, number of nodes at anthesis, number of primary branches at anthesis, and fruit production - some responded to the selection pressure with divergence, notably those characters which were correlated with the selected characters (for example, number of nodes at anthesis, correlated with flowering time). With others there was no change which could be attributed to the selection procedure. There was no evidence from two qualitative characters - fruit wing phenotype and fruit pubescence pattern phenotype - for any response to selection; dispersion in both characters was not significantly different from that expected to result from random drift. The relatively high increase in aberrant characters in the P. congesta lines compared to the P. brachystemon lines is probably indicative of inbreeding depression in the normally outcrossed P. congesta. It appears that despite the difference in breeding system, the two Plectritis species are able to maintain variability by similar processes (genetic) in some characters, as in flowering time, and by different processes (genetic in P. congesta, phenotypic in P. brachystemon) in other characters, as in height at anthesis. Thus one quantitative character, height at anthesis, follows the pattern predicted by the breeding system difference, with the outcrossed P. congesta being much more variable genetically than the selfed P. brachystemon. This agrees with the levels of variability observed by Layton (1980) in electrophoretically detectable isozymes, and observed by Ganders and Maze (unpublished) in metrical fruit characters. The other quantitative character, flowering time, shows considerable genetic variance in the populations of the selfed P. brachystemon, though less than in the populations of P. congesta. The maintenance of such relatively high levels of genetic variability in the face of the strong inbreeding pressures which must be present in P. brachystemon populations is certainly adaptive, and probably comes about through occasional outcrossing and multiniche selection for variability among the segregating lines. / Science, Faculty of / Botany, Department of / Graduate