Arable: Emerging disease threats in the high-value speciality oilseed crop 'Ahiflower'

NIAB and Natures Crops International have worked together for over 15 years in a collaboration to develop the Buglossoides arvensis plant from an arable weed into a speciality oilseed crop (tradename: Ahiflower), which is grown exclusively in the UK. Ahiflower is the richest plant source of combined omega fatty acids, health-giving compounds also found in oily fish. The crop is a vegan-friendly, sustainable omega source: it is estimated that one acre of Ahiflower can yield as much omega-rich oil as 320 000 anchovies, thus reducing pressure on threatened marine ecosystems. There is increasing global demand for Ahiflower oil, especially in North America, the UK, the EU and Southeast Asia, where it is mainly used in healthy dietary formulations for both human and animal nutrition, plus new applications in cosmetics and personal care products.

This project will build on our existing collaboration and investigate some emerging disease problems seen by growers of the crop. The first of these is foot rot, which is thought to be caused by a complex consisting of several fungi in the soil, and is often associated with soils that become waterlogged during late autumn and winter when the crop is still establishing as small, slowly growing plants. Foot rot can cause damage to the roots and the bottom of the stem so that plants snap off completely and do not produce any seed. We will look in inoculated pots, trial plots and farmers crops for signs of foot rot, and send soil, root and stem samples from diseased plants for lab testing. These tests will tell us which organisms appear to be causing the disease, an important first step in working out how to control it better in the future.

The second disease is powdery mildew, which is also caused by a fungus. Mildew is often seen in Ahiflower crops later in the season when it causes the leaves to turn white, dry up and die prematurely. This results in lower yields and poor seed quality. Our previous work has suggested that some Ahiflower plants from our collection are more resistant to mildew than the best varieties farmers are currently growing. We will check if these results can be repeated in the field, and if they are true, will make crosses between resistant plants and high-yielding varieties as a first step in improving their disease resistance. We will also carry out an experiment to see how well screening plants in the glasshouse can accurately predict mildew resistance in the field. If it can, then this will also help us to breed future resistant varieties for farmers more effectively.

We will also grow field trials to test if there are any ways to reduce the risk of these diseases affecting farmers crops. We will test different combinations of fungicides, seed treatments and plant feeds, and grow trials at contrasting locations with different soils. This will build up a picture of which treatments work best in different situations. Our trial results will influence the advice we give to farmers so that they can continue to get the most out of their crops while still protecting the environment.

As well as looking at these diseases, this project will also begin to develop some new breeding technologies for the first time in this young crop. We will identify genetic markers (differences in the DNA sequence between distinct varieties), which will allow us to track the inheritance of genes and chromosomes back from parents and forwards through the generations in future breeding work. We will test that these markers work by looking at their inheritance in seedlings from the crosses we made between mildew resistant and mildew susceptible parents. The library of DNA sequence differences that we develop can be used for many more projects in the future which will all help to increase the yield, quality and disease resistance of this new crop.

NIAB and Natures Crops have collaborated for >15 years to develop the arable weed, Buglossoides arvensis, into a speciality UK oilseed crop (tradename: Ahiflower). There is increasing global demand for Ahiflower oil which is the richest plant source of omega-3-6-9 fatty acids, anti-inflammatory compounds usually sourced from fish.

We will investigate two emerging Ahiflower diseases:
1. Foot rot, often later seen in fields previously waterlogged and/or anaerobic during the autumn. We will monitor trial plots and farmers' crops, testing soil and plant samples with molecular diagnostics to identify the causal organisms, as a first step towards disease control.
2. Powdery mildew, which often causes premature senescence and losses in yield and quality. NIAB's diverse Buglossoides collection includes some partial resistance, but elite varieties are largely susceptible. A subset (low, medium and good resistance) will be grown in untreated field plots and pot tests, to see if high-throughput pot tests can predict field resistance. To improve their mildew resistance, elite varieties will be crossed with resistant lines.

We will test combinations of fungicides, seed treatments and stimulants in the field at contrasting locations and soil types, to assess disease control and any impact on yield, oil content and fatty acid profile. Results will feed into updated grower guidelines.

We will also develop the first Buglossoides genetic markers. Skim sequence for 94 diverse accessions will be aligned to identify SNPs and indels. Some will be converted to high-throughput KASP markers and used as a proof-of-concept to identify rare F1s amongst parental selfs harvested from our mildew resistance crosses. The SNP / indel database will form the basis of future marker development for the first Buglossoides genetic linkage maps, marker-trait associations, and applications in quality control, provenance tracking and IP protection in variety registration and seed multiplication.