The role of potato rooting and rhizosphere microorganisms in mineral nutrients acquisition

Potato rooting characteristics to enhance resource capture

Potatoes require large fertiliser inputs and often require irrigation. One way to reduce these inputs is to cultivate genotypes that use resources more efficiently, either because they require less mineral nutrient in their tissues or because they yield with smaller inputs.

These abilities are affected by many factors, but rooting characteristics (such as increased root growth rate, specific root length, and density and length of root hairs) and rhizosphere biochemical processes (such as the exudation of organic acids and enzymes) are of fundamental importance. Understanding the physiological and genetic control of changes in these characteristics as a natural response to limited resource may provide opportunities to improve the acquisition of soil mineral nutrients and water by plants in conventional and organic systems.

Our initial approach has been to assess the ability of potatoes to explore the soil volume, by screening genotypes for rooting characteristics in the field. We have found significant differences in root length between commercial varieties. In future research, this trait might be exploited in breeding programmes for improved resource acquisition.

Understanding the impact of rhizosphere microorganisms on the ability of potato plants to acquire mineral nutrients 

Roots have evolved in close association with fungi and bacteria in a complex soil ecosystem and the difficulty of studying these soil systems has biased our understanding in favour of above ground systems. We aim to improve our understanding of how fungal and bacterial associations with plants in soil enhance the plant’s ability to acquire resources often against steep concentration gradients or from closely associated soil particles which may have strong affinities for the same elements.

In association with the Plant Soil Interactions Group (Dr Tim Daniell), we are developing techniques for identifying the variation which exists amongst crop cultivars for associations with microorganisms related to enhanced nutrient uptake. This will increase our understanding of the processes which enable certain genotypes to be productive in low nutrient environments. The vast majority of terrestrial plants have enhanced acquisition of nutrients (most notably P and Zn) through mycorrhizal symbiosis, however little is known about the diversity of these fungi in arable systems.

Our initial studies have demonstrated genetic variation between the fungal colonisers of the roots of different genotypes of potato in the field. This may well relate to other rooting characters such as rooting depth which may act in concert to impact on function and efficiency of resource capture. We are now investigating these differing communities at the molecular level using their genetic code to identify relationships between them and potentially identify the best combinations for improved resource capture.