TABLE CONTENTS

suggest that C. japonica DJs appear to have short longevity and weak desiccation tolerance
but they are able to extend their longevity by entering quiescent and being protected from
desiccation on the bug.
Morphological and Behavioral Variation in Infective Juveniles of Mutant
Steinernema feltiae
Tomalak, M.
Department of Biological Pest Control and Quarantine, Institute of Plant Protection, Wladyslawa Wegorka 20,
60-318 Poznan, Poland.
Mutagenesis is a powerful tool used in genetic improvement of cultivated plants and animals',
worldwide. New mutant alleles can change the organisms' phenotypes, including those of
commercial significance. As with the aid of a simple cross-breeding technique point
mutations can be easily transferred to existing strains, new recombinant genotypes can further
widen the range of phenotypic variation available for subsequent works on strain
improvement and their use in the practice.
In entomopathogenic nematodes from the genera Steinernema and Heterorhabditis the
process of spontaneous and chemically-induced mutagenesis has been explored for over 15
years. However, with the exception of Steinernema feltiae, only a few distinctive mutations
have been identified in the examined species. Our study on S. feltiae has revealed a marked
sensitivity of this species to chemical mutagens. Over sixty point mutations altering
morphology and/or behavior of infective juveniles (IJ) have been identified so far. Most of
them are maintained in mutant strains in the laboratory culture. All of the mutant phenotypes
(except for segmented - Seg)] fall into categories earlier described for C. elegans, such as
dumpy - Dpy, roller - Rol, twitcher and other uncoordinated -Unc, variable abnormal - Vab,
and long - Lon. The main advantage of the use of entomopathogenic nematodes in this
research is that all the new phenotypes presented by IJs can be related with their practical
significance, expressed as the nematode ability to disperse in the soil, find the host insect, and
penetrate into its hemocoel.
IJs of most of the identified mutants are less effective than wild-type S. feltiae in some or all
of these functions. However, mutations in two genes, i.e. Sflon-1 and Sfrol-1, showed to have
positive effects on the nematode activity: Increased body dimensions of IJs in the long mutant
(pn49) are associated with the improved ability to penetrate the soil and infect insects at
greater soil depths than the wild type. Also, the changes in the muscle arrangement of roller
mutants (pn16, pn36) positively influence the nematodes' penetration into the host. Crossbreeding
and transfer of these mutations to other strains helps to improve the nematode
activity in the soil. Reported findings suggest that these alleles present real value for genetic
improvement of IJs' efficacy in commercial strains of S. feltiae.
5 th International Congress of Nematology, 2008 225