Investigating the cause and potential treatment of coriander yield decline

The Problem:

Annually around 1500 hectares of coriander are grown in the UK. Unfortunately coriander suffers from a severe decline in yield if grown in successive years in the same soil; the effect can last up to 8 years and has been observed throughout the UK. This yield decline (often above 50%) coupled with the fact that many growers lack enough available growing area to enable crop rotation means that the commercial production of coriander in the UK is problematic. The causes of this decline in yield are unknown but the observational evidence suggests a problem of biological origin (most likely microbial).

This project aims to determine the cause of coriander yield decline by combining microbiology and plant sciences expertise. Initial work will use a variety of soil types to grow coriander in greenhouse conditions to establish a yield decline effect. Plant performance will be assessed using a range of approaches including the monitoring of photosynthetic carbon gain, light use efficiency and above/below ground biomass productivity. Soils that impose a yield decline will be examined for microbial population changes by a series of increasingly complex microbiological and molecular based techniques. In particular, bulk soil will be compared with rhizosphere, root residue and plant root surface microbial populations. Parallel experiments will be carried out to investigate potential remedies to the issue. If no microbial cause is found then work will focus on other possibilities, including root exudation of inhibitory chemicals and other soil organisms.

Aims and objectives: