Understanding and mitigating against the causes of yield decline in pea

Pea is an important legume grown for human and animal consumption. Both vining and combining peas are grown in Europe, for fresh vegetable/frozen (vining) and the dried pulse crop (combining) markets. The intensive use of fields for vining pea production has led to yield declines of up to 40%, attributed to the build up of a complex of soil borne plant pathogens causing foot-rot. Pathogens involved in the complex include fungi such as Fusarium, Aphanomyces and Didymella spp. However, the relative abundance and dynamics of these is unknown. It is also difficult to identify and quantify many of these pathogens to predict yield decline and other than long rotations there are no strategies for mitigation. One approach is to use green manure/biofumigant crops in the rotation, which when incorporated into the soil, can improve soil health and reduce the impact of soil borne diseases in other systems.

This project aims to 1) understand the components and dynamics of the foot-rot complex as well as associated microbiota in the pea rhizosphere using both conventional and metagenomics approaches, 2) develop molecular diagnostics for key pathogens and 3) identify green manure / biofumigant crops that can suppress foot-rot. For 1), isolations of fungi from affected peas will be made and pathogenicity tested using established plant infection assays to determine the range of pathogens present in foot-rot affected fields. In a complimentary approach, DNA from root/rhizosphere samples affected/unaffected by foot-rot will be subjected to amplicon sequencing to identify, compare and understand the dynamics of the different microbial communities and pathogens across multiple field sites. For 2), multiple isolates of each pathogen will be identified and characterised through sequencing of appropriate housekeeping genes, and PCR diagnostics developed for those that are most prevalent. For 3), the effect of different biofumigant plants will be tested for their effect on selected pathogens in vitro, in plant based assays in the greenhouse and finally in the field.       

The project builds on an existing informal collaboration between Warwick and the Processors and Growers Research Organisation (PGRO) and directly addresses the BBSRC priority area of agriculture and food security, specifically to ‘increase the efficiency and sustainability of crop and animal production, reduce waste in the food chain’. Results of the research will potentially have a considerable impact on the sustainability of the UK pea industry, and therefore the potential to form the basis of a REF Case Study.

Study Summary

"Multilocus DNA sequencing analysis of both D. pinodella and F. solani isolates revealed the lack of genetic diversity within D. pinodella isolates from the UK and other countries, while DNA sequencing analysis of UK F. solani isolates challenged an idea that F. solani formae speciales are specific to single plant species. Both lab-based experiments (For F. oxysporum, F. solani f. sp. pisiand D. pinodella) and pot-based experiments using D. pinodellain the glasshouse established positive relationships between the concentration of fungal spores, pea foot rot disease development and plant mortality. A  further test tube assay revealed the additive nature of interactions between F. oxysporum, F. solani f. sp. pisi and D. pinodella when co-inoculated in terms of disease development in pea.

Preliminary quantitive polymerase chain reaction analysis of root colonisation in this experiment successfully quantified DNA for each of the three pathogens. Commercial biofumigant varieties of Brassica juncea (brown mustard) and Eruca sativa (rocket), bred for high glucosinolate concentrations significantly reduced mycelial growth of F. solani f. sp. pisi, F. oxysporum, D. pinodella and A. euteiches in plate-based lab experiments. These species were also successful at supressing D. pinodella foot rot disease development in a pot-based glasshouse experiment. Overall, this research has contributed substantial knowledge regardingthe genetic variation, disease development and interactions of PFRC pathogens, and the potential of biofumigationas a management strategy"

The full thesis can be accessed here >

Sponsors:

Warwick University MIBTP iCASE studentship and Processors and Growers Research Organisation (PGRO)

Student:

Lisa King - The University of Warwick, Coventry, CV4 7AL, UK

Start Date: September 2017

Duration of study: 4 years