Science - December 8, 2011

Biological control of peanut stem rot

PhD candidate Cuong Nhu Le has a solution for peanut farmers in Vietnam who are plagued by stem rot. The soil-borne fungus which causes this can be treated successfully with several useful soil-borne bacteria.

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Stem rot in peanut cultivation is mostly treated with fungicide currently, with varying results. Between 5 and 25 percent of peanut plants are infected, says Cuong Le, who tried to find a biological way to control stem rot. This infection is caused by the fungus Sclerotium rolfsii, a tough pathogen with a wide genetic diversity.
Cuong Le found two strains of the Pseudomonas family of bacteria which can inhibit the growth of the fungus. For this to happen, they have to produce the inhibitory substances phenazine or thanamycine.  Several Bacillus bacteria also appear to be able to inhibit stem rot in the fields. The use of these Bacillus types resulted in almost thirty percent more harvest, says the PhD candidate. Cuong Le found these useful soil-borne bacteria on the roots of the peanut plant when he was doing field experiments in Vietnam. Cuong Le, who is attached to the agriculture university in Hue, will make use of this acquired knowledge. 'You can cultivate these useful bacteria and apply them to peanut seeds so that the seedlings are directly protected against fungal infections,' says his supervisor Jos Raaijmakers.
Cuong Lee is due to receive his PhD on 16 December from Francine Govers, personal chair professor in Phytopathology.

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