The nematode Heterorhabditis bacteriophora may be bred and selected, for a better resistance against environmental stress and longer shelf life. That is the conclusion of a lab study by researchers from the BIOCOMES-partner e-nema and colleagues from the universities of Kiel and Ghent, published in the latest issue of Nematology. Through this research, producers of nematodes for biological control may be able to increase the competitiveness of their products against traditional, synthetic products.
One of the targets of the BIOCOMES-project is to increase the economic feasibility of biological products for crop protection. In the case of entomopathogenic nematodes for plant protection, this could be done by prolonging the shelf-life and improving the persistence of marketable nematodes. For example, H. bacteriophora has commercial potential as a biological control agent against various harmful insects, such as the western corn rootworm. However, the number of larvae needed to effectively treat a rootworm plague is still too high to be able to compete commercially with synthetic alternatives. Therefore, larvae with a better endurance are needed.
Together with colleagues, Nanette Hope Sumaya of the Christian-Albrechts-University in Kiel and of the German producer of nematodes for plant protection, e-nema, tested H. bacteriophora nematodes in the lab. They exposed so-called ‘dauer juveniles’ – a resting stage of nematode larvae, named after the German word for endurance – to different levels of oxidative stress under different temperatures. At 25 oC, the survival under stressles conditions ranged from 21 to 57 days, whereas with stress, the survival was only 3 to a maximum of 22 days. Stored at 7 oC without stress, the survival increased to 94 days. Also, a high variability in the survival time was observed in the H. bacteriophora strains that were tested. There were groups of both good and bad survivors under all conditions.
Selection and breeding potential
There heritability of these traits appeared to be strong, as shown by using inbred, genetically identical lines of nematodes. Therefore, the researchers conclude that there is a potential of selecting and breeding only those nematodes that appear to have the best survival under a given circumstance.
Breeding for a better shelf life
The authors propose a selective breeding program, in which only the 10% best performing nematodes are used. Eventually, this could lead to nematodes with a better shelf life, that can be applied to crops that suffer form rootworm infections. Only when smaller numbers of larvae with a better shelf life can be applied in the field, they become an economically feasible alternative for larger groups of farmers. Therefore, this research has brought a concrete goal of BIOCOMES closer to application.
Nora de Rijk
Communication and dissemination BIOCOMES project