Abstract
The study describes the development and employment of plant tests based on artificial inoculation of seeds or the potting substrate for evaluating the potential of microorganisms to control seedling blight of maize caused by seed- and soil-borne fusaria. Nine strains of Fusarium were isolated from maize kernels and identified morphologically and by molecular methods as belonging to the species Fusarium verticillioides, F. subglutinans, F. cerealis, F. poae and F. proliferatum. In order to determine pathogenicity, maize kernels were inoculated by immersion in suspensions of conidia of these isolates and sown in a pasteurized substrate in seed trays. Based on plant dry weight, the isolates of F. verticillioides and F. subglutinans were more pathogenic than the other isolates. Using an isolate of F. subglutinans, the efficacy of a set of 25 potential fungal and bacterial antagonists was assessed using inoculation of maize kernels by placement in mixtures of the pathogen and the antagonists. The results obtained with this methodology indicate the potential of a number of different microorganisms applied as seed treatments, including some reported previously as biocontrol agents, to control seed-borne seedling blight of maize. In order to develop a method for the testing of biocontrol agents against soil-borne attack, isolates of F. subglutinans, F. cerealis and F poae from maize kernels together with isolates of F. avenaceum, F. culmorum and F. graminearum originating from maize silage and wheat were used to artificially inoculate the potting substrate. The results showed large differences in pathogenicity, with the most aggressive isolates belonging to F. culmorum and F. graminearum.
Highlights
In order to avoid damage during germination and early crop establishment by insect pests and plant pathogens, seeds of many agricultural and horticultural crops are routinely treated before they are sown
The isolates of Fusarium employed were obtained from the culture collection of Kiel University originating from maize silage (F. graminearum Ck3, F. graminearum Os12, F. culmorum Fu13, F. avenaceum To8) and wheat kernels (F. culmorum VIII18)
The isolates F. subglutinans (II), F. subglutinans (III) and F. cerealis were intermediate in pathogenicity, whereas F. proliferatum and F. poae had no effect or were only mildly pathogenic (Fig. 2)
Summary
In order to avoid damage during germination and early crop establishment by insect pests and plant pathogens, seeds of many agricultural and horticultural crops are routinely treated before they are sown. Driven by concern about adverse effects of chemical plant protection products on humans and the environment, efforts have been made in recent decades to replace chemical seed treatments by environmentally more friendly methods. With the continuing call by the public, consumers and authorities for a reduction in chemical pesticide use on the one hand, and discontinuation of authorisations for chemical active ingredients on the other, along with a lack of new registrations, it can be expected that non-chemical seed treatments will gain importance in the future. Non-chemical seed treatments are still not available in many economically important crops, necessitating further research in this field
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