Methyl Bromide Fumigation of Pratylenchus brachyurus in Peanut Shells

Five dosages of methyl bromide were used to fumigate peanut (Arachis hypogaea L.) shells and whole pods of peanuts in 1-liter flasks for 24 hr at 25 C. Methyl bromide dosages as low as 24.5 mg/liter killed all Pratylenchus brachyurus (Godfrey) Filip. &Sch. Stech. in peanut shells. Dosages of 44.6 and 50.9 mg/liter killed all but one or two nematodes in shells of whole pods. A 15% reduction in seed germination occurred at the 50.9-mg/liter dosage.     

Acetylcholinesterase secretion by parasitic nematodes. 3. Oesophagostomum spp

Acetylcholinesterase (AChE) activity in Oesophagostomum radiatum increased markedly during the fourth and early fifth stages of parasitic development and thereafter remained relatively constant in the mature parasites. Fourth stage Oe. radiatum maintained in vitro in a saline medium released AChE steadily for 4 h. Whereas the excretory glands of Oe. radiatum appeared to be the major site of AChE secretion, the highest concentration of the enzyme in Oe. venulosum was found in the cephalic tissues.Antibodies to Oe. radiatum AChE appeared in the serum of calves three weeks after primary infection with the parasite and were also found in the serum of neonatal calves and in the colostrum of their dams.Several soluble non-specific esterases were present in homogenates of adult Oe. radiatum and Oe. venulosum. In Oe. radiatum these esterases occurred both in gut tissue and excretory glands, and were present in secretions released in vitro by fourth-stage larvae. However, no antibodies against the esterases were detected in host serum.     

Relative DNA Content and Chromosomal Relationships of some Meloidogyne, Heterodera, and Meloidodera spp. (Nematoda: Heteroderidae)

The relative DNA content of hypodermal nuclei of preparasitic, 2nd-stage larvae was determined cytophotometrically in 19 populations belonging to 13 species of Meloidogyne, Heterodera and Meloidodera. In Meloidogyne hapla, M. arenaria, M. incognita and M. javanica, total DNA content per nucleus is proportional to their chromosome number, indicating that chromosomal forms with high chromosome numbers are truly polyploid. M. graminicola, M. grarninis and M. ottersoni have a DNA content per chromosome significantly lower than that of the other Meloidogyne species. Within Heterodera, species with high chromosome numbers have proportionally higher DNA content, indicating again polyploidy. DNA content per chromosome in Meloidogyne is one third that of Heterodera and one haft that of Meloidodera floridensis. The karyotypic relationships of the three genera are still not clearly understood.     

Disc-Electrophoretic Studies of Soluble Proteins and Enzymes of Meloidogyne incognita and M. arenaria

Soluble-protein and eight enzyme profiles obtained by polyacrylamide-gel electrophoresis were compared between Meloidogyne incognita and M. arenaria. Esterase, malate dehydrogenase, and α-glycerophosphate dehydrogenase patterns were distinctly characteristic for each species. Peroxidase and α-glycerophosphate dehydrogenase isoenzyme patterns varied when nematodes were propagated on different host plants. Similar profiles were obtained for two populations within each species. Antigenic proteins of these two species were compared following separation by electrophoresis.     

Effects of Selected Carbamate and Organophosphate Nematicides on Hatching and Emergence of Heterodera schachtii

Ethoprop, oxamyl, PP 156, fenamiphos, carbofuran , AC 64,475, Bunema M®, CG 12223, aldicarb, aldicarbsulfoxide, and aldicarbsulfone were tested for their effects on hatching and emergence of larvae from cysts of Heterodera schachtii. The oxime carbamates and carbofuran inhibited hatching , but this response was reversed by removing the chemical treatment . Inhibition of hatching by Bunema M and all organophosphates tested was irreversible .     

Breeding for nematode and virus resistance in potato via anther culture

Summary In Solanum tuberosum the production by parthenogenesis of 2x plants with 24 chromosomes, and the regeneration of microspores of such dihaploids to yield monohaploid (1x) plants is reproducibly possible, at least for some specific genotypes. Experiments are described using tissue culture techniques in an applied breeding program with the main aim of increasing the level of resistance to the potato cyst nematode Globodera pallida (Stone) and to the potato viruses X, Y and leaf roll. These resistances follow quantitative as well as qualitative modes of inheritance. Using anther culture it is demonstrated that doubled monohaploid clones can be produced which possess the resistance in the homozygous condition. In both ways of inheritance the ratio of resistant clones is rather high. The genotype of the anther donor plant has, however, a strong influence on the total number of androgenetic plants which can be regenerated. Therefore, experiments were initiated with the aim of integrating this capacity for regeneration (tissue culture ability) into valuable genotypes. The results show that the potentiality for regeneration is under genetic control and can be utilized by combination breeding. Its inheritance and physiological basis, as well as the behaviour of complete homozygous clones, is discussed.Dedicated to Prof. Dr. Joseph Straub on the occasion of his 70. birthday     

Growth Reduction of Apple Seedlings by Pratylenchus penetrans as Influenced by Seedling Age at Inoculation

Apple seedlings of different ages (1, 3, and 5 weeks) were inoculated with 6,900 Pratylenchus penetrans per seedling in 10-cm-diam pots in a growth chamber. Rate of growth suppression and total growth suppression of seedlings by P. penetrans were inversely proportional to seedling age at time of nematode inoculation. Younger seedlings were found to contain a higher number of nematodes per gram root.     

The Effects of Temperature on Pratylenchus scribneri and P. alleni Populations on Soybeans and Tomatoes

In soil temperature tests, rates of Pratylenchus scribneri and P. alleni reproduction were measured at various lemperatures on ''Clark 63'' and ''Cutler 71'' soybeans and ''Rutgers'' tomatoes. Recovered P. scribneri equaled or exceeded initial inoculum levels at temperatures of 27.5 C or higher on soybeans, and at 20 C or higher on tomatoes. Population increases were greatest at 3.5 C on both hosts. Populations increased on soybeans, but not on tomatoes, when soil temperature was raised from 25 to 35 C for either 3 or 9 days. Recovered P. alleni were less than the initial inoculum at 27.5 C but higher at 32 and 37.5 C and at 27.5 C on tomatoes, the lowest temperature tested for this nematode. In the field, soil temperatures 10 cm deep in eastern Kansas soybean growing areas reach 27.5 C only occasionally and for relatively short periods, which probably explains the relatively low and variable populations of P. scribneri and P. alleni on soybeans there.     

Genetic Structure of Races of Heterodera glycines and Inheritance of Ability to Reproduce on Resistant Soybeans

Four field populations of Heterodera glycines tested for ability to reproduce on three host differentials were each classified into one of the recognized races. A fifth population represented a new race. Genetic analysis indicated that the designated races are actually field populations that differ from each other primarily in the frequencies of three groups of genes (genes for parasitism) that act quantitatively and control the ability of the nematode to reproduce on resistant P.I. 88788, Pickett, and P.I. 90763 soybeans. Populations of race-3 have none of these genes for parasitism, or they have some in low frequency that results in an index of parasitism of less than 10 on any one of the resistant soybeans. Race-1 has a high frequency of one group of genes that enable it to reproduce on P.I. 88788. Race-2 has two groups of genes for parasitism in high frequency; one for P.I. 88788, and one for Pickett. Based on these findings, it was assumed that race-4 has three groups of genes for parasitism; one for P.I. 88788, one for Pickett, and one for P.I. 90763. Additional races may be recognized when new genes are identified, or when new gene combinations are discovered. The ability to reproduce on P. I. 88788 is inherited independently from the ability to reproduce on Pickett. Although the genetic structure of field populations does not provide a solid foundation for race designation, recognizing races under the present system may be useful when it clearly characterizes the behavior of field populations. Race designations, however, should be regarded as provisional since gene frequencies change with time in response to selection forces and, therefore, the race status of a population may change accordingly.     

Population dynamics of the parasitic stages of Ostertagia spp. in sheep

Callinan A. P. L. and Arundel J. H. 1982. Population dynamics of the parasitic stages of Ostertagia spp. in sheep. International Journal for Parasitology12: 531–535. The development and survival of continuing infections of Ostertagia spp. in weaner sheep were studied in order to develop a general model of the parasitic stages of the life cycle of these sheep nematodes. After 10 days, 13.8% of infective larvae (L₃) given at the rate of 1 dose of 1000 L₃ twice per week (group 1) and 20.8% of L₃ given at the rate of 10,000 L₃ twice per week (group 2) were recovered in the first of the serial nematode counts. In the final counts at 137 days, 7.7 and 0.7% were recovered in these groups. The build up and maintenance of nematode populations was regulated and related to the level of infection. A model in which the death rate of the parasitic stages was a function of the time of exposure to infection and rate of infection was used to describe the serial total nematode counts. During the experiment there was no noticeable trend in numbers of fourth stage larvae (L₄) in nematode counts, the size of adult nematodes, nematode egg counts (EPG) and egg output per female nematode (EPF). After 112 days, liveweight gains were significantly reduced in group 2 only, but increases in wool lengths were significantly reduced in both groups.