Adaptation to temperature in entomopathogenic nematodes

• Main Author: Jagdale, Ganpati Baburao
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1997
• Subjects: Canada; Newfoundland
• Online Access: https://research.library.mun.ca/8624/; https://research.library.mun.ca/8624/1/Jagdale_GanpatBarurao.pdf

The effects of recycling over a two-year period at temperatures from 10 - 25 °C were studied in four strains of entomopathogenic nematodes: Steinernema carpocapsae All strain, Steinernema feltiae NF strain, Steinernema feltiae Umeå strain and Steinernema riobravis TX strain. The main objectives of this investigation were to study the capacity for, and mechanisms involved in. thermal adaptation of a native (NF strain) boreal steinernematid nematode and to compare it with strains of entomopathogenic nematodes originating from another boreal region (Sweden; Umeå strain), temperate zone (All strain) and subtropical zone (TX strain). -- On the basis of morphometry and restriction fragment length polymorphism in ribosomal DNA spacer, a nematode that was isolated from soil near St. John's, Newfoundland, Canada, was designated as a new strain, NF, of S. feltiae. To determine whether taxonomic separations of entomopathogenic nematodes could be accomplished on the basis of physiological properties other than DNA profiles, cellulose acetate electrophoresis was used to separate isozymes of eight enzymes in infective juveniles of five strains of Steinernema. These strains comprised the four listed above, together with S. feltiae L1C strain, isolated 14 years previously from Newfoundland. Based on comparisons of the relative electrophoretic mobilities (μ) of the isozymes, it was concluded that the five isolates could be distinguished. This finding suggests that cellulose acetate electrophoresis could be an important taxonomic tool for the identification of isolates of steinernematids, provided that a combination of enzymes is used. -- The capacities for high temperatures and freezing tolerance were determined and found to be affected by the temperatures at which recycling was carried out. In all the isolates, the UT₅₀, the temperature at which 50% of the infective juveniles died, increased with increase in recycling temperature. Freezing tolerance, as measured by times at which 50% of the infective juveniles were killed ...