The protective mycorrhiza Rhizophagus irregularis, available from the EU project REFERTIL, can be introduced into unrooted strawberry cuttings grown in potting compost from plants without mycorrhiza fungi in their roots. An investigation carried out by researchers Joeke Postma and Marieke Förch from Wageningen UR has demonstrated this. By administering the mycorrhiza genus Rhizophagus, it was possible to reduce Phytophthora infection by around 50%. This is a promising way of preventing crown rot in strawberries.
Mycorrhizas are regarded as having a number of beneficial properties, such as making phosphates available to the plant or limiting the effects of infection by means of competition. However, mycorrhiza fungi are not present in substrates in which no plants have grown – clean potting compost, for example. Even including 10% soil from arable land in the potting compost did not lead to any mycorrhizas in the roots.
A trial was performed in which two types of mycorrhiza (Rhizophagus irregularis and Glomus etunicatum), supplied by the EU project REFERTIL, were added to unrooted Elsanta cuttings placed in potting compost. In the strawberry plants treated with the mycorrhiza genus Rhizophagus, 40% of the roots contained mycorrhizas after 6 weeks. In the Glomus-treated plants, only 10% of the roots contained mycorrhizas. In the control strawberries, not one single root had been colonised by the fungus.
Crown rot in strawberries.
Some of the strawberry plants were infected with Phytophthora cactorum, the cause of crown rot in strawberries. The mycorrhiza genus Rhizophagus was able to reduce infection with Phytophthora by around 50% when compared with the control plants without mycorrhiza. There were fewer plants with brown roots and also fewer with internal symptoms of crown rot. The other type of mycorrhiza was not really effective.
Which mycorrhiza types are the most effective?
The effects discovered in the trial now need to be evaluated in practice. It will be particularly important to consider repeatability, the method of administration and the circumstances in which mycorrhizas are effective. It is also essential to know which mycorrhiza types are the most effective and whether administering them would be economically viable.