BioControl (2013) 58, 417-426

Prakaijan Nimkingrat, Shakhina Khanam, Olaf Strauch and Ralf-Udo Ehlers (2013)
Hybridisation and selective breeding for improvement of low temperature activity of the entomopathogenic nematode Steinernema feltiae
BioControl 58 (3), 417-426
Abstract: Steinernema feltiae is used to control overwintering larvae of the codling moth Cydia pomonella L. Application is in autumn when efficacy can be limited by low temperature. The objective of this study was to screen for low temperature activity among wild type populations of S. feltiae, hybridise most active strains and further improve low temperature activity by subjection of a hybrid strain to selective breeding. Significant variation was recorded among 22 S. feltiae strains. The temperature at which 50 % (AT50) and 10 % (AT10) of the dauer juveniles (DJs) were active ranged between 2.9 to 5.8 °C and 0.95 to 3.5 °C, respectively. The mean AT50 of 22 S. feltiae strains was 3.83 °C. The five most active strains were crossed. The hybrid strain HYB01 was more active at low temperature than parental and other hybrid strains with an AT50 of 0.52 °C and an AT10 of 0.09 °C. The tolerance was lost after few reproductive cycles in the insect Galleria mellonella, but was recovered after seven selection cycles with exposure to lowering temperatures. The heritability for the low temperature activity was calculated at h² = 0.45. Negative trade-off effects on virulence against C. pomonella and reproduction on the same insect were not reported. The most virulent strain was a commercial strain with an LD50 of 30.2 at 8 °C and 37.2 DJs per cocooned instar at 15 °C, followed by the selected hybrid with 48.1 and 47.4 DJs, respectively. Offspring production reached 15.000 DJs per instar at 8 °C and was only half at 15 °C. The results well document the potential of a breeding programme for enhancement of the activity of S. feltiae at lower temperature with the objective to improve the control potential of overwintering codling moth C. pomonella.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Ralf-Udo Ehlers

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
environment/habitat manipulation
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Cydia pomonella
Steinernema feltiae/Xenorhabdus bovienii (entomopathogen)	Cydia pomonella