Expert chat with Dr. Matthias Daub, Julius-Kuehn-Institute (JKI), Germany – July 2017

Dr. Matthias Daub (2)
Dr. M. Daub

Dr. Matthias Daub heads Field Station Research on sugar beet for the Julius-Kuehn-Institute (JKI) in Germany. The JKI serves as Germany’s Federal Research Center for Cultivated Plants. This institute conducts scientific assessment for European Union (EU) panels, as well as provides policy advice, independent research, research collaborations, registration of new crop protection compounds, and advice for the German Chamber of Agriculture.

Matthias studied agricultural sciences at the University of Bonn and later at the University of Hohenheim, Germany. He then worked as a Research Assistant at the Horticultural Research International in East Malling, England known today as East Malling Research (EMR). When Matthias learned about a Ph.D. position for a European project on population dynamics and pathogenicity of the Pine Wood Nematode, Bursaphelenchus xylophil, the high level of complexity caught his interest. Matthias joined the JKI in Elsdorf in 2006. From his experiences in England and completing his doctorate studies, Matthias recognized how important it is to be connected to other researchers – to discuss current research, solve problems, and develop new control methods.

Matthias, what are your main projects with the JKI?

At the research station in Elsdorf, we conduct mostly applied research on nematodes – such as Heterodera schachtii, Heterodera betae, Ditylenchus dipsaci – in the sugar beet pathosystem. This focus includes resistance testing of sugar beet and catch crops for national registration and detection of virulence groups and sources of resistance against the Beet Cyst Nematode (BCN). We develop integrated management strategies and damage prediction models, as well as new methods for damage detection and population density assessment. We work regularly in cooperation with the International Beet Research Institute, breeders, the crop protection industry, national and regional sugar beet working groups (unions, consultancies, and sugar industry), public federal state authorities, and universities and private research organizations.

Can you give us a bit of background about the relevance and challenges of nematodes for sugar beet in Europe?

Taking a very general view on Europe, one can say that, on average, probably one-fifth of all sugar beet fields will have a nematode problem; however, if we look more specifically at countries and regions which have a long history of sugar production – such as Germany, the Netherlands. Belgium and France – we would probably reach a level of fifty percent. In those countries, the White Sugar Beet Cyst Nematode Heterodera schachtii pose the biggest problem, followed by occasional problems with Heterodera betae, Diptolenchus dipsachii and Meloidogyne spp.. There are, of course, regional differences and changes over time. In the past, H. betae (also known as the Yellow Cyst Nematode) was mainly known in Italy and thought to be adapted to warmer climates. Nowadays, we know that this nematode is also a problem in the lighter soils of Scandinavia and Finland. On the other hand, free-living nematodes, a known problem in Scandinavia, are seen more and more also in Germany. It is important to be aware that changes in climate, or broad use of varieties that are tolerant or partially resistant to one nematode species, always also impact other nematode species by freeing space in the pathosystem.
Another important aspect is that the conditions for sugar beet production will change drastically from October 2017, when sugar production will be exposed to world market prices due to the end of quota management. Sugar factories will compete much more against each other, resulting in prolonged campaigns that require more acreage of sugar beet to provide the necessary biomass. This change creates a paradox because prices for sugar beets are low, which makes production less attractive to growers when compared to other field crops. At the same time, we have fewer and fewer registered crop protection compounds in Europe to ensure good yields and sufficient resistance management by alternating the active ingredient and mode of action used. This paradox puts the breeder under pressure to develop varieties with resistance or tolerance to different pathogens, which also cannot be too expensive if they are to be economically acceptable.

What is key to managing nematode problems in Europe?

Key is that the growers are aware of nematodes as a possible problem in their fields. Nematode damage is easily mistaken for nutrient deficiency and other diseases. Though tolerant cultivars do not show symptoms, it does not mean that nematodes do not impair potential sugar yield. The problem is, you do not see this impact. Growers and advisory services need to be educated. Yet less and less applied experts on nematodes are out there.

To manage nematodes in Europe there are several relevant factors that should be adopted:

A) It is important to make sure to rotate your sugar beet with other crops that are not susceptible to nematodes. Ideally, after sugar beet, the rotation with non-host crops should be wider than three years in the same field.
B) It is important to implement robust weed management to avoid nematodes using weeds as an alternative host that enables them to survive phases with non-host crops in the field (bridging). This weed management includes eliminating volunteer canola because it is a host that propagates BCN quite well.
C) Intermediate crops that are nematode resistant can also decrease the initial population in a field – a practice that is well-adopted in Europe due to governmental push (greening). To use this approach as a tool, the intermediate crop must be well managed (e.g. timely planting and optimal nutrient supply) and should be polygenetic in its resistance traits.
D) The time of sawing creates a big impact as well because early drilling under lower temperatures will reduce the risk of higher nematode infections, whilst late drilling increases the risk.
E) Last, but definitely not least, is the choice of a tolerant variety that is adapted to the expected pest pressure. We see the choice of variety as particularly complex because a tolerant variety that works in one location might not work equally well in another environment. Therefore, we need to always test varieties in a first step under controlled conditions and in a second step under field conditions.
F) We need more knowledge about local differences in the virulence of BCN and its genetical footprint to identify this in field populations

Matthias, what drives you in your research and what do you think is needed in the future to solve the many questions in the dynamic field of nematology?

Nematology – especially the applied side of it – needs innovative technologies. To develop these new approaches, experts of different disciplines and functions must talk to and collaborate with each other. Research innovation in applied nematology includes phenotyping nematodes based on their morphological characteristics to determine population specific characteristics and indicators for fitness. This research can serve as a complementary tool to the analysis of populations based on their genetic differences because we see that, even genetically, largely identical populations can behave very differently under certain circumstances. We are working on this type of field typology of nematode populations with Lemnatec and the TU in Aachen.

Another challenge we face is the number of soil samples required to predict initial populations in larger fields. Methods other than the classical soil sampling would drastically improve the accuracy. Entomologists have investigated new methods already 20 years ago, a path that nematology should follow. For example, near-infrared (NIR) studies to determine nematode densities were already used in the 80’s, yet with recent technology developments such as drones, NIR methods now become feasible to be used in the field. Other sensor technologies could also be used in the field, for example technologies that use chemotaxis to determine the presence of nematodes. Additionally, GPS data collected during harvest that can be matched with spots of lower yield would enable a later analysis of low-yield problem spots potentially caused by nematodes.
There are many exciting new technologies that can be, and need to be, adopted by nematology. A key challenge in nematology is that when viewing a field under optimal conditions for the crop, one will not be able to tell spots of 100 nematodes per cm3 apart from those with 6,000 nematodes per cm3, even if the variety is sensitive.

I love solving complex problems that are multi-factorial, which is in my opinion the key for being successful in solving nematode problems. We must think holistically and not mono-factorial. We need to use all tools that we have in an integrated approach to manage nematodes for the long run. And we need to work together, discussing our challenges between breeders, public and private research entities and the relevant, different disciplines.