UK PlantSci 2013 & the Journal of Experimental Botany

David Atkinson
British Crop Production Council

Running time: 00:15:14 min

The Science Delivering Organic Agriculture: Crop Protection Revisited


A key concept for organic food production set out by one of the founders of the movement Albert Howard is that “Plants when in health, posses a considerable power of defence against disease. A healthy soil is the prime agent of prevention. The practical basis for this was set out by Eve Balfour in the following terms”Many plant species and families benefit from the presence of specific soil fungi (Mycorrhizas) in a particular way”. Thus two of the basic tenets of organic production become that healthy plants will have resistance to pathogens and that a functioning mycorrhizal association is important to health. Implicit in both of these is the importance of features such as the rotational sequence. The choice of crop species and variety impact on the soil micro-flora and on the speciation and availability of key nutrients. The extent to which these propositions are either true or important is a significant component in many current crop protection debates. The association between plants and arbuscular mycorrhizal fungi (AMF) has existed for around 500 million years. In a very real sense plants with AMF are different to uninfected plants. AMF affect the structure of individual roots, the branching of the root system and the longevity of individual roots. Related to this AMF reduce both the severity of infection with soil born diseases such as Phytophthora species and their impact on production. At a molecular level AMF infection results in the up regulation of some plant genes, e.g. those related to calcium lipid binding proteins and the down regulation of others e.g. protein encoding defence molecules. In addition the fungal component takes over the control of some basic plant capacities such as nutrient uptake. However to view AMF in only a resource capacity is to minimise their role. They function as a major source of information for the plant and it is perhaps here that they impact most on health and so on crop protection strategies. The impact of AMF on plants during acute water stress provides an example of an information based impact. During a period of decreasing soil water potential infected plants reduced the water consumption earlier and more rapidly than was the case for uninfected plants so reducing the impact of stress. The ways in which these and related factors provide the basis of crop protection in organic systems will be discussed.


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