“Genetic diversity – the key for improving drought stress tolerance in crops” - Expert meeting in Berlin

"Genetic diversity – the key for improving drought stress tolerance in crops“ – this was the subject addressed by an international expert meeting held in Berlin in November 2019 and attended by around 100 participants from home and abroad. The Julius Kühn Institute (JKI) and the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) extended invitations to this conference on behalf of the BMEL.

Importance of the subject for food security

Crop production is facing considerable challenges: by 2050, there will be an estimated 9.6 billion people to feed, and this despite the fact it will not be possible to significantly expand the amount of land used for agriculture. This situation is being exacerbated by climate change, changing dietary habits, and the increasing amount of land used for the production of bioenergy and by other uses in the context of the bioeconomy. Although the impact of climate change will differ from region to region, it can be assumed that it will have a considerable impact on the yield of the crops that are most important for human nutrition.  Experts reckon that by 2050 most regions around the globe will experience a reduction in yields or strong fluctuations. The reason for this is that the yields depend considerably on temperature and precipitation levels. Against this backdrop, experts are focusing on the following aspects first and foremost: how can drought stress tolerance and water use efficiency of crops be improved through targeted breeding, given that this is crucial for the stability of yields, for increases in yield and thus for food security?

As early as 2017, the BMEL and both research institutes gave centre stage to the subject at an international expert workshop held during the German G20 Presidency in Berlin entitled “Harnessing genetic resources to improve drought stress tolerance in crops”. The results of this workshop were then presented at the meeting of the Agricultural Chief Scientists (MACS) held from 12 - 15.11.2017.

At their meeting in November 2019, the participants then followed up on the outcome of 2017. Thus, experts from the fields of genotyping, phenotyping, plant breeding, plant physiology, data and information management, international cooperation and climate change adaptation focused on the following issues:

  • tapping plant genetic resources;
  • phenotyping and genetic mapping of drought stress tolerance;
  • breeding for drought stress tolerance; and
  • extending of international cooperation to improve the drought stress tolerance of agricultural crops.

Key outcome of the meeting

The experts documented the following as a key finding: the protection of plant genetic resources is still critical at a global level. Besides the many genebanks, mention should be given in this regard to the “Global Seed Vault” in Spitzbergen, which has already proven its worth in restoring the genetic resources stored in the genebank of Aleppo. 

Alongside the protection of plant genetic resources, it is, however, also necessary to improve the efficient use of these resources. The systematic conversion of genebank collections into bio-digital resource centres is a key element in this regard.

This needs to be supplemented by developing databases and web portals to facilitate access to and analysis of data.

Nowadays, the availability of our crops’ reference genomes and the development of corresponding high-throughput marker technologies enable the genetic variation for individual characteristics to be recorded at DNA level and used for breeding purposes in a targeted manner. The creation of new variations, for example by creating "synthetic wheat" from the original varieties, is also suitable to increase the genetic variation for drought stress tolerance, as is the targeted use of landraces from arid regions, e.g. the so-called "Spanish Barley Core Collection".

In addition to storing and recording genetic diversity at molecular level, the recording of drought stress tolerance, i.e. the reliable and repeatable phenotyping, is of paramount importance for breeding plant varieties with improved drought stress tolerance.

It was shown that, while methods under controlled conditions allow a reliable detection of corresponding differences, these were, however, only able to be transferred to the field to a limited extent. On the other hand, different adaptation strategies to drought stress, e.g. by determining the transpiration rate, were also demonstrated in the field.

The phenotyping of the root system will play an increasingly important role in the future. Here, too, there has been some notable recent progress. Nevertheless, it will still be necessary to develop more efficient and more precise processes, inter alia to analyse the root architecture more precisely and to record water use efficiency. 

Mention should be given in this context to the “Crop Hall” established at IPK, which allows a close simulation of field-like conditions. The recording of physiological parameters, such as the influence of drought stress on spikelet fertility, the influence of nutrient supply on drought stress tolerance, and the clarification of metabolic pathways that cause drought stress tolerance, is still seen as decisive for an improvement in drought stress tolerance.

 

A combination of the recording of molecular and phenotypical data in suitable populations makes it possible to identify loci and genes that are involved in causing drought stress tolerance. They can be efficiently used in the breeding process by means of molecular markers, as has been illustrated by different examples. If these genes are known, new and perhaps more effective gene variants can be directly produced in high-yielding varieties, for instance by using CRISP/Cas.

Conclusion

Improving drought stress tolerance is a major task of plant breeding, with a view to adapting the agricultural sector to future production conditions.

The existing variation in plant genetic resources must first be recorded in order to be able to produce new plant varieties with improved drought stress tolerance.

It is today possible to pre-select genebank accessions for analysis based on geographic and climatic information by means of suitable software (e.g. FIGS). The next step is for these provenances to then be genotyped with suitable high-throughput phenotyping technologies. There are a range of different low-cost technologies available for this purpose.

Processes have also been developed that enable phenotyping for drought stress tolerance, thus laying the foundations for the identification of genome regions/genes that are involved in causing drought stress tolerance.

The structured and globally concerted storage of the data of all genotypes that have been or are to be analysed worldwide poses a considerable challenge which, however, can be solved in the same way as genotyping and phenotyping, since the systems and capacities required for this are basically no longer a limitation. It is therefore essential to initiate and promote coordinated international cooperation, both on the genotyping and phenotyping of plant genetic resources and on their utilisation in breeding.

The JKI therefore assumed the coordination of the “Heat and Drought Wheat Improvement Consortiums (HeDWIC)”. HeDWIC is a programme that is associated with the Wheat Initiative initiated by the G20 Agriculture Ministers. It is aimed at enhancing the heat and drought stress tolerance of wheat via different international projects.

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