South African scientist: “Speed breeding - the next step will be soybean”

08.03.2021

Rouxlene van der Merwe is working as Senior Lecturer at the University of the Free State in Bloemfontein, South Africa. Starting today, she will take part in the symposium "Seed Production in Times of Climate Change". In the run-up to the event, she talks about the effects of climate change in South Africa, her research on soybeans and the expectations she has for the symposium.

Rouxlene van der Merwe collecting data on flowering dates of 15 vegetable-type soybean genotypes. Photo: Werner van der Merwe

  • How is South Africa affected by climate change?

South Africa lies within a drought belt. The country is predominantly semi-arid with a variety of agro-ecological zones, ranging from desert and semi-desert areas to sub-humid and wet areas. The increase in climate variability and climate extremes are affecting both water quality and availability through changes in rainfall patterns, in soil moisture and the effects of increasing evaporation and changing temperatures on aquatic systems.

In rainfed farming systems, soil moisture limitations reduce crop productivity and increase production risk. Changes in summer rainfall patterns result in delayed planting of summer crops, such as maize, which ultimately affect yield, quality and the end-product. Although in some areas the production risk is reduced by irrigation, these farming systems depend on surface runoff or groundwater availability, which are also subject to change under climate change. Climate variability and drought spells also influence livestock production by generating disruptions in food (grazing) and feed supply or even limited freshwater for drinking.

  • Are there areas that even benefit from climate change?

Yes, especially during wetter years some areas benefit from climate change. During wetter years, localised floods and runoff have their advantages by increasing dam levels and groundwater levels while above average precipitation results in record high crop yields and restoring grazing capacity for livestock. These wetter years are coupled with lower mean maximum temperatures during summer, which further contribute to higher crop yields.

  • South Africa has several climate zones. Is the country therefore particularly suitable as a field of experimentation, for example for seed production?

South Africa is sub-divided into five aridity zones, which principally correspond to the country’s agricultural regions. Thus, crop breeding programmes and field experimentation coincide with the agricultural systems that take place in the different aridity zones. Currently a number of private seed companies, as well as several Institutes of Agricultural Research Council (ARC) are actively testing and developing improved varieties of agronomic and vegetable crops with the aims to optimise summer grains, winter cereals, oil seed and vegetable production for the benefit of producers, processors and end-use markets in South Africa.

In addition, close collaboration between some universities, respectively with private seed companies and the ARC, results in research-focussed projects that involves field experimentation. Some of these projects focuses on variety testing under different abiotic and biotic stress conditions (and production areas) and collect data on a number of variables including seed yield potential, end-use quality and stress resistance traits. The projects collectively aim to release top performing crops with reduce yield gaps and adequate nutritional value.

  • What hopes do you associate with the soybean as a crop? You deal with this topic in your lecture.

Two types of soybean are currently produced in South Africa, namely commodity type and vegetable-type soybean. Commodity type soybean production has shown a significant increase during the past eight years and surpassed sunflower production ever since 2015, making it the second most important summer grain crop. Vegetable-type soybean is only produced on a small scale since the crop was only introduced for research and production in 2009. Although the area planted with vegetable-type soybean is small, there remains potential for further growth through awareness and marketing.

There is scope to increase production and consumption through initiatives of the Edamame Development Programme and Fair Food Company in South Africa as well as crop improvement and adaptation through various breeding strategies. Finally, this alternative high protein crop can address homestead food security and malnutrition when produced supplementary to other vegetables currently grown in community gardens.

  • What results have you obtained from your research?

Drought tolerance indices, calculated from seed yield obtained under both stress and non-stress conditions in our field experiment, and used in correlation and multivariate analyses were useful to divide the 15 vegetable-type soybean genotypes into different groups based on yield production and tolerance. Genotypes selected from these groups were identified to be used in the breeding programme for drought tolerance. However, since seed yield is a quantitative trait, with a low heritability and likely to show significant genotype x environment interaction, another season’s data were needed.

Especially under South African production conditions, selection of genotypes across seasons, showing variable weather conditions and rainfall patterns, could largely affect inferences made from results obtained. Results obtained from the second experiment were similar to earlier results in terms of the correlation of drought tolerance indices but dissimilar in terms of the grouping of genotypes. This indicated that selection of drought tolerant genotypes would be more effective in severe drought stress environments.

  • Have you found varieties that produce high yields even under severe drought conditions?

Three genotypes, out of the 15, were identified that produced seed yields that were significantly higher than the genotype means, for the two water treatments respectively. However, only one genotype (AGS354) produced a seed yield under stress that was even higher than the genotype mean of the non-stress treatment.

  • Climate change leaves less and less time for the development of new varieties. How can methods like speed breeding or genome editing help?

Our plant breeding researchers are currently in the process of establishing a facility for speed breeding of wheat. If this is succesful, the next step will be soybean. With speed breeding not only will the breeding cycle be shortened but we will use less glasshouse space and probably improve the currently low success rate of our crosses.

In terms of genome editing, a wide range of tools and genomic resources has been developed. In addition, a variety of robust molecular tools, including CRISPR/Cas9 might be investigated for utilisation in our drought tolerance breeding programme. However, our research group are in need for the necessary infrastructure and skills in order to pursue these molecular applications.

In our genotype evaluation programme we have identified physiological traits that result from drought responses and contribute to the adaptation of plants under water-limited-induced stress conditions but an understanding of the molecular and physiological mechanisms behind these traits is essential for improving vegetable-type soybean through biotechnology. Thus, a collaborative network with partners, that can provide the necessary skills and that have the necessary equipment, that are willing to become involved in our drought tolerance breeding programme should be established. 

  • You work at the University of the Free State in Bloemfontein. What is the university's focus in plant research?

A variety of research projects are currently in progress under the supervision of 25 plant researchers within our Plant Sciences department. The Plant Breeders focus on improving yield, nutritional value and abiotic stress tolerance of maize, vegetable-type soybean, dry bean and cowpea, with additional research on biofortification of maize and sweet potatoes, pod-shattering resistance in soybean and nutritional quality of wheat.

The Plant Pathologists focus on improving Sclerotinia tolerance in soybeans and sunflower, while wheat research focus on breeding for resistance to Fusarium, stem rust and leaf rust pathogens. Sorghum research is focused on grain-mold pathogens and mycotoxigenic fungi,
with additional research on pecan scab. The Botanists focus on the phylogenetic and taxonomic relationships between Nemesia species that are endemic to southern Africa, as well as research in modern- and palaeo-ecology.

  • What do you hope to achieve at the conference?

The main reason for attending the conference would be to expand my knowledge on current and new methods that can be used in climate change research. This will assist to improve my current vegetable-type soybean breeding programme for drought and heat stress tolerance. Furthermore, I would like to meet with people who might be interested in collaborative research. We do not have the necessary expertise or equipment to expand our research in terms of molecular techniques that can assist with selection in drought tolerance breeding. Thus, by presenting at the conference, I am able to demonstrate our research focus and findings, and I hope that this will create opportunities for future collaboration.