Biochemical Identification of the Two Races of Radopholus similis by Polyacrylamide Gel Electrophoresis

Analysis of proteins of the banana and citrus race of Radopholus similis was carried out by several different types of polyacrylamide gel electrophoresis. These included standard slab gel, SDS slab gel, gradient slab gel, and two-ditnensional slab gel electrophoresis. A major band difference was detected between the two races by slab gel electrophoresis. However, several other poorly resolved but consistent hands of high molecular weight proteins near the gel origin also were considered as diagnostic. Resolution of protein bands was greatly improved by SDS and gradient slab gel electrophoresis, but no differences could be detected among the proteins resolved between the two rares with these techniques. Two-dimensional gels revealed a large number of proteins, but background staining obscured them hindering interpretation. When nematode races were reared on three different host plants, no differences in protein patterns were detected between them, indicating host preferences does not play a role in determining the types proteins occurring in these nematodes.     

Population Development of Pratylenchus hexincisus in Eight Corn Inbreds

Of eight corn inbreds tested in the greenhouse and field, three (H60, H95, and H84) supported lower populations of Pratylenchus hexincisus than other inbreds included in this study. No apparent differences existed among inbreds in nematode invasion or development in the roots, or in population structure. Differences in population were therefore attributed to differential reproduction.     

Phocanema decipiens: Growth,reproduction, and survival in seals

Captive harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus) were fed infective larvae of Phocanema decipiens, an anisakine nematode from the flesh of Atlantic cod (Gadus morhus). Ova of P. decipiens were first detected in the feces of harbor seals 21(17–30) days after exposure; the patency period was 15 to 45 days. In gray seals, the prepatent period was 19(16–23) days; patency 20–60 days. By the sixth week of infection in harbor seals, mean body lengths of adult females and males of P. decipiens were 60.8(40.8–76.2) and 54.3(45.5–60.8) mm, respectively; mean fecundity of female nematodes was 156,000 ova. In infections of similar duration in gray seals, females and males of P. decipiens were 82.1(69.7–104.3) and 64.4(53.8–72.7) mm in length, respectively; mean fecundity of females was 366,000 ova. In sensitizing infections in harbor seals, 28% of P. decipiens survived to early patency (Days 25–30) while only 9% of the nematodes survived to midpatency (Days 35–45). In sensitizing infections in gray seals, 56% of P. decipiens survived to early patency (Days 20–30) and 48% survived to midpatency (Days 35–50). Seals with existing or recent P. decipiens infections resisted reinfection; <50% of the nematodes in challenge infections in gray seals survived to Day 3 and <10% survived to patency. Growth of the nematodes, however, was not retarded in the challenge infections and resistence to reinfection subsided when seals were maintained anisakinefree for 2–6 months after loss of prior natural or experimental infections. Natural anisakine infections were surveyed in 16 harbor and 53 gray seals from the Nova Scotia mainland. The mean incidence of P. decipiens was 62(5–177) in harbor seals and 577(11–1694) in gray seals; incidence varied seasonally and with age of host. Adult females of P. decipiens from harbor seals were 64.0(49.2–79.8) mm in length and contained 1.68(0.87–2.73) × 10⁵ ova; females from gray seals were 78.3(62.3–92.1) mm in length and contained 2.39(0.69–4.39) × 10⁵ ova.     

Changes in blood leukocytes,bone marrow and lymphoid organs in sheep infected with Haemonchus contortus

Haemonchus contortus infection, which causes a blood loss anaemia in sheep, depleted leukocytes and produced leukopenia and a mild lymphopenia. Thymus atrophy, a decreased size of spleen and enlargement of adrenal glands occurred concomitantly in infected sheep which suggested that they were caused by the stress of infection. The overwhelming change in bone marrow of infected sheep was a 4-fold increase in erythroid series cells.Primary immunization with rat erythrocytes produced similar haemagglutinating antibody responses in infected sheep and in sheep allowed to recover from infection after treatment with thiabendazole. This suggests that extant infection with H. contortus was not associated with a secondary immunodeficiency. Blastogenic responses of blood lymphocytes from infected sheep to larval antigen correlated with faecal egg counts but not with haematocrit or leukocyte values. These results suggest that the unresponsiveness of lymphocytes to worm antigen which occur during infection with H. contortus is more closely related to contact with the parasite than to the pathological effects of infection.     

Biocontrol: Fungi as Nematode Control Agents

The fungal antagonists of nematodes consist of a great variety of organisms belonging to widely divergent orders and families of fungi. They include the nematode-trapping fungi, endoparasitic fungi, parasites of nematode eggs and cysts, and fungi which produce metabolites toxic to nematodes. The diversity, adaptations, and distribution of nematode-destroying fungi and taxonomic problems encountered in their study are reviewed. The importance of nemato-phagous fungi in soil biology, with special emphasis on their relationship to populations of plant-parasitic nematodes, is considered. While predacious fungi have long been investigated as possible biocontrol agents and have often exhibited spectacular results in vitro, their performance in field studies has generated little enthusiasm among nematologists. To date no species has demonstrated control of any plant pest to a degree achieved with nematicides, but recent studies have provided a much clearer concept of possibilities and problems in the applied use of fungal antagonists. The discovery of new species, which appear to control certain pests effectively under specific conditions, holds out some promise that fungi may be utilized as alternatives to chemical control after a more thorough and expanded study of their biology and ecology.     

Population Increase of Pratylenchus hexincisus on Corn as Related to Soil Temperature and Type

Population increase of Pratylenchus hexincisus on corn was tested over 3 months at 15, 20, 25, and 30 C in Marshall silt loam, Clarion silt loam, Buckner coarse sand, and Haig silty clay loam soils. The optimum temperature for increase was 30 C in all soils. The nematode population was significantly larger in Buckner coarse sand than in other soil types at 50 C. The recovered P. hexincisus populations equaled or exceeded initial inoculum levels at the two higher temperatures in Marshall silt loam and Haig silty clay loam and at 30 C in Clarion silt loam and Buckner coarse sand. P. hexincisus required 32,400 heat units in Haig silty clay loam and more than 40,000 heat units in the three other soil types to reach a level that is known to cause significant height and biomass reduction in corn under controlled condition.     

Biosynthesis of cytokinins by potato cell cultures

Potato cells grown in liquid culture incorporated mevalonic acid lactone-[2-¹⁴C] into free cytokinin (zeatin riboside and zeatin and the cytokinin of RNA (zeatin riboside). The cytokinin liberated by catabolism of RNA can account for no more than 40% of the free cytokinins.     

Effect of aging on the composition of mitochondrial membranes from potato slices

The phospholipid content of mitochondrial membranes from slices of potato tuber (Solanum tuberosum) remains stable during aging. The phospholipid compositions of whole mitochondria and inner membranes do not vary during aging whereas the concentrations of phosphatidylinositol and phosphatidyl-glycerol in outer membranes are slightly amplified. The saturation of outer membrane fatty acids is slightly increased during aging. Gel electrophoresis of mitochondrial membrane proteins show slight variations of one polypeptide in outer membranes and of three polypeptides in inner membranes. These results suggest parallel variations of lipids and proteins in membranes during aging, in marked contrast with the large modifications observed in mitochondrial activities.     

Genetic analysis of incompatibility in the diploid Ipomoea species closely related to the sweet potato

Summary In order to identify the genotypic constitutions of incompatibility in the diploid species, Ipomoea leucantha Jacq. (K221), which is most closely related to the sweet potato, the progenies derived from the reciprocal crosses, backcrosses and testcrosses were analysed. All the plants examined were self-incompatible, and pollen germination was inhibited on the stigma after incompatible pollinations. No reciprocal differences were found in the incompatibility reactions. In the progenies three incompatibility groups were observed which showed the rather simple segregation ratios. The homozygous plants for incompatibility alleles were obtained in the progenies. The experimental results demonstrated a sporophytic type of incompatibility controlled by a single locus with multiple S-alleles exhibiting a dominance relationship in both the pollen and the stigma. The plants obtained in the progenies had the following genotypes: S ₁ S ₂, S ₁ S ₃, S ₂ S ₂, S ₂ S ₃ and S ₃ S ₃.     

Pathological Differences in Heterodera schachtii Populations

Five populations of Heterodera schachtii Schm. from Oregon, Idaho, and Utah did not differ significantly in seedling penetration and rate of emergence and virulence. Another Utah H. schachtii population (Utah 2), however, differed from these five populations in all of the above-mentioned characteristics. More H. schachtii larvae of the Utah 2 population than the other populations penetrated sugarbeet seedlings at 10, 15, 20, and 25 C. Root and top weights of sugarbeet plants were signiticantly less when roots were parasitized by the Utah 2 population than when they were parasitized by larvae of the other nematode populations under similar experimental conditions. Also, the period of larval emergence was shorter in the Utah 2 population than in any of the other H. schachtii populations.