Location
Development of an early warning test indicating the risk of Cavity spot in Carrot. Phase 2: Validation (Extension to FV 448)

Research

FV 448a - Development of an early warning test indicating the risk of Cavity spot in Carrot. Phase 2: Validation (Extension to FV 448)

Start Date: 
01/04/2017
Completion Date: 
31/10/2017
Project Leader: 
Nathalie Verhoef, Nsure B.V.
Code: 
FV 448a
Industry representatives:
James Bramley, M.H. Poskitt Ltd.
Ian Holmes, Strawsons Ltd.  
 
AHDB Horticulture Cost:
£53,020 
 
Summary
Cavity spot is a major carrot disease in the UK and is mainly caused by Pythium violae. Cavity spot reduces harvest quality. Visibly infected carrots are not acceptable for fresh produce market or processing.
 
An early indication for cavity spot would be of great value, because it can be used as a decision support system. The test has to assess risk on cavity spot at two cost adding moments: before distribution of straw and before fields are covered. A tool to select low risk fields will reduce losses and leads to less costs for labour and straw. 
 
Within this project, NSure aims to develop an early warning test to detect cavity spot at an early stage. In the 1st season, RNA sequencing (RNA-Seq) has been used to identify carrot specific indicator genes that change upon an early infection with Pythium violae. During the 2nd season, these indicator genes will be validated for reliable use in practice. The results of this project might be used in other projects regarding Pythium violae and cavity spot.
 
Aims:
In the first year of this project, possible genes were identified indicating stress as a consequence of an infection by Pythium. In the second year, these specific genes will be validated for their suitability to serve as indicator genes for the risk of the development of cavity spot. Most suitable genes will be used to develop a practical test that quantifies the expression of those genes in order to determine the risk of cavity spot at an early stage. At the end of this phase of the project, the test should be ready for use in practice.
 
Objective
1. Validation of carrot indicator genes in the most important carrot variety, Nairobi;
2. Validation of carrot indicator genes in various samples collected from 6 varieties which are intentionally infected with Pythium violae or Pythium sulcatum;
3. Selection of a final set of carrot indicator genes that will be used for the test to determine the risk of the development of cavity spot;
4. Development of a user friendly test format including decision criteria that will be beneficial to the growers;
5. Continuous and active two-way communication between growers and researchers.
 
 
Benefits to Industry
Carrot is one of the major crops in the UK. The total cultivated area exceeds 9.000 ha. 60% of the acreage, approx. 5.500 ha, is stored under straw. One hectare results on average in a gross income of £8.000. This means that the total turnover of covered carrots is approx. £44 million. Losses due to cavity spot vary between years and geographical regions. Untill recently, Scotland for example, had no occurrence of cavity spot. Other regions have more severe problems. In some fields the damage exceeds 40%. On average, cavity spot destroys 3% - 7% of the yearly yield, resulting in a loss between £1.25 and £3 million. However, this percentage seems to increase over the years. Last season for example, the percentage was estimated to be between 5% and 10%, which almost doubled the losses.
 
The average cost of covering consist of straw (£3.000 per ha) and logistics (transport and covering). In total the costs for covering are approx. £4.000 per ha. It is clear that a high cavity spot occurrence means that a grower will not earn (instead: will lose) money on those batches. A predictive test that determines high risk fields, will support a grower to pick only low risk fields for covering. A reduction of cavity spot occurrence of only 1% on average, already makes a difference in turnover of £440.000 per year. This is exclusive of extra costs for covering, logistics and sorting. A predictive test would make UK carrot industry much more profitable.
 
This project will result in a practical test to determine the risk on cavity spot. The test will consist of a simple sampling kit for the grower that enables him to collect samples. The samples have to be sent to a lab either in the UK (preferably) or to NSure’s facilities in Wageningen. Within 48 hours after the samples are received, the grower will receive an indication of the risk of cavity spot. Samples can be taken throughout the season in order to support decision taking at several crucial time points during the season. Growers will be informed about the test and its background in several meetings and by a user’s guide that will be delivered together with the test kit. 
 
Finally, the specific insight in development of Pythium violae during the season, will be shared with the growers and researchers involved in other projects concerning Pythium violae in carrots. This might be of help to better understand behaviour of Pythium violae. This better understanding could contribute to improvement of measures to prevent from Pythium violae infection and cavity spot occurrence.