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A description of the establishment and proliferation of the biocontrol agent Clonostachys rosea on carrot seeds and the interaction with seedborne Alternaria

The development of Clonostachys rosea during seed germination and plant emergence and the interaction between C. rosea and A. radicina on carrot seed were studied in a time course experiment. A gfp transformant of a wildtype isolate of C. rosea was included in Fluorescence microscopy studies of the interaction. The results showed that Plectosporium tabacinum (IK1755), Clonostachys rosea f. catenulata (IK1878), C. rosea (IK1871) and C. solani (IK1889) multiply on seeds during biopriming to levels which are suitable for biocontrol of diseases. C. rosea grows and sporulates intensively on Alternaria infected seed, it coils around Alternaria spores and mycelium and restrict hyphal extension and sporulation of A. radicina.

In conclusion: C. rosea is a suitable biocontrol agent for controlling A. radicina. Based on microscopic evaluation of the growth and distribution of the antagonist during priming, C. rosea colonized the whole surface of the pericarp, including the apex of the seed where the primary root emerges. This is important for protecting the seedling against inoculum of pathogenic Alternaria spp. as well as other seedborne pathogens located on or in the pericarp. Furthermore, it provides an opportunity to protect the seedling from soilborne pathogens attacking the emerging seedling. The results can explain the efficacy of the biocontrol agents and support knowledge about mechanisms of biocontrol by C. rosea. This insight is an important background for further biocontrol studies in other disease/crop systems, especially for biological seed treatment in combination with other physiologically treatments.

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Reported by

The Royal Veterinary and Agricultural University
Thorvaldsensvej 40
1871 FREDERIKSBERG
Denmark
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