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BSPP Break Crop Workshop – 24 June 08, PGRO
This one day BSPP workshop was held in conjunction with HGCA & PGRO and was part of a series of Presidential meetings being held in 2008. The workshop was designed to give an overview of current and future threats from diseases to the production of oilseed rape, field peas and faba beans.
The workshop comprised seven presentations, a poster session over lunch and a PRGO field tour. The meeting was chaired by the BSPP president Graham Jellis who was pleased to see that there is still a small enthusiastic community of researchers working on break crops. Key research is still needed to address important issues relating to diseases, which will enable growers to be fully aware of all the factors they need to consider when choosing their break crops.
The first session kicked off with a keynote presentation on ‘Phoma stem canker and light leaf spot in a changing climate’ by Bruce Fitt from Rothamsted.
These are the two main disease of oilseed rape in the UK and cause annual losses of up to £160 million and £60 million, respectively. Current risk forecast software is available for both these pathogens and with a bit of additional information they can be used to predict likely changes in these diseases with climate change. Under high carbon emissions (e.g. in 2020, stem canker onset could move forward by ~50 days and by 2070 by ~70 days.
The prediction is that severity of epidemics will increase and canker will spread further north, which will create a new problem for growers in Scotland. However, the converse is true for light leaf spot where projected climate change patterns indicate that it will decline, with very little left in the south by 2050, so not all Doom and Gloom. Bruce also commented that disease control plays an important contribution to climate change mitigation, because if diseases are well controlled we will need less nitrogen per tonne of crop to achieve our yield requirements.
Jon West from Rothamsted then followed Bruce’s theme talking about how we can forecast oilseed rape diseases from airborne inoculum. As we can use PCR to detect the presence or absence of pathogens from spore trap tapes, and also quantify the amount of pathogen present, there is a real chance that air sampling could be a very useful tool for routinely monitoring pathogen populations in the future. This could be especially useful where risk models are primarily based on rainfall data, which for sclerotinia in 2007 failed in some areas where there had been a very dry spring.
Sclerotinia was then discussed further, along with clubroot and Verticillium wilt, by Peter Gladders from ADAS. Peter commented that the increase in oilseed rape diseases is largely as a result of more intensive use of this crop in the rotation. Traditionally OSR was grown once in every five years but it is common today for this to be one in three, which has meant an increase in soil-borne diseases. A 10°C rise in temperature in the future could result in sclerotinia spores being produced virtually all year round. Biological control and resistant varieties will be key to control. A new species of Verticillium wilt was confirmed in 2007 (Verticillium longisporum). Symptoms occur later in the season than other Verticillium species and the economic impact is still uncertain. It is probably influenced by rising temperatures and drought stress. Clubroot is a well-known disease of brassicas and has been an issue on oilseed rape in Scotland for many years but is now appearing on southern crops, especially when the autumn is wet and warm. New advances in spore detection means that quantifying soil inoculum could provide a useful management tool in the future.
It may give us information on whether soil management e.g. lowering the pH, will be sufficient to control the disease or whether, in more serious cases, a resistant variety is needed. A 2°C rise could result into infections spreading to the end of October and starting again in early April (instead of September and June at present).
The morning session was concluded by Sally Hilton from Warwick HRI who gave a presentation on the impact of shortened rotations of oilseed rape on the microbial diversity of the rhizosphere. Sally has been working on a two year Defra funded project that has been trying to fingerprint the microbial diversity of the rhizosphere.
The project took advantage of samples from an ongoing eight year HGCA funded project that has been looking at the impact of previous cropping on OSR yields. The bacteria in the rhizosphere were very similar between continuous wheat and continuous OSR but some differences were seen in the fungal populations. Two pathogens were identified in the continuous OSR rotation that were not found in the wheat rotation. One of these has been identified as Olpidium brassicae. These results are very exciting and further sampling is being conducted to see whether this is a real effect resulting from increasing OSR in the rotation.
Lunchtime gave everyone a chance to chat through the morning session and look at the posters on display before starting the afternoon session, which left oilseed rape behind and focussed on peas and beans.
Anthony Biddle, the Technical Director or PGRO, started the afternoon session with a nice summary on pulse crops.
Anthony kicked off by stating that the area of spring peas in the UK is decreasing and the UK is now under supplied with peas, which is of great concern. However, the spring bean area has increased which is largely due to varieties that are being grown for export to Egypt for human consumption. Winter beans are a good break crop for heavy land farmers, and the area of winter beans has also steadily increased. In 2008 there has been a 30% increase in the pulse area planted, which is largely due to the high price of nitrogen fertiliser and static OSR yields. Many diseases are controlled with fungicides but this can be very expensive and ideally more new disease resistant varieties are needed, but progress in this area in the UK is slow.
Downy mildew in peas and beans was the next subject for discussion by Jane Thomas of NIAB. Oospores of downy mildew can survive for 5-10 years therefore, rotation, hygiene, seed treatments, foliar sprays & cultivar resistance are very important in controlling this disease. The overall mean resistance rating on the recommended list for pea downy mildew is increasing and there is currently some screening of new Pisum germplasm where some lines show complete resistance. Bean downy mildew occurs in all major growing areas in the UK and there is no evidence of different pathotypes for beans like there is for peas. There are no UK based breeding programmes focusing on new resistant varieties of beans but there are a few cultivars with partial resistance.
The final presentation of the day was given by Natalia Stawniak from NIAB which focused on the race structure of the stem nematode Ditylenchus dipsaci and its interaction with the faba bean crop. Stem nematodes are more common under cool conditions and less common under warm, dry conditions.
All commercial field bean varieties on the UK market are susceptible but resistant lines of field beans have been identified in France. Glasshouse tests have been developed to detect stem nematodes, which could be a useful pre-screening test for new variety development in the future.
The day was concluded with a trailer trip to view the PGRO variety trials along with some exotic germplasm lines from JIC. This was an excellent end to the day as the sun stayed shining for us.
Dr Vicky Foster, Senior Research Manager, HGCA
