Conventional breeding with marker assisted selection succeeds where GM has failed. Report by Claire Robinson

Researchers at the Chinese University of Hong Kong (CUHK) have developed non-GM salt- and drought-tolerant soybeans using a combination of gene marker assisted selection and natural cross-breeding.

According to the university's website, "The achievement marked the culmination of two decades of collaboration between CUHK researchers and soybean breeders, as well as researchers in China, to improve soybean cultivation in adverse conditions such as drought and salinity. Through genomic analysis and cross-breeding, they have developed stress-tolerant soybeans and reclaimed abandoned land in remote areas for soybean cultivation."

A key breakthrough came when the research team, led by Prof Lam Hon-Ming, decoded the genomes of 31 wild and cultivated soybeans. They discovered that wild soybeans have more genetic biodiversity within themselves than cultivated ones, including stress-tolerance genes that have been lost during the historical process of soybean domestication. This highlighted the possibility of cross-breeding new varieties that combine the productivity and nutritional value of cultivated soybeans with the adaptability and stress tolerance of wild soybeans.

Prof Lam Hon-Ming

Using marker assisted selection, the researchers identified one gene that occurs naturally in some wild soybeans and which confers salt tolerance. GMWatch emphasises that even though just one gene was identified, this gene will operate within a context of gene families. This means that conventional breeding, which involves whole gene families, can succeed where genetic engineering, which isolates one or a few genes from their context, will fail.

From a collection of bred soybeans (resulting from artificial crossings using different parents), the researchers screened for the presence of this gene for salt tolerance and then performed selection for drought tolerance in dry regions. They worked with scientists in Gansu Province in China to develop and release three new stress-tolerance soybean cultivars. These cultivars passed provincial tests in Gansu and are now used by Gansu farmers on marginal lands.

GM unable to deliver desirable complex traits

GMWatch is not surprised that conventional breeding helped by marker assisted selection has succeeded where GM has failed in producing salt- and drought-tolerant soybeans. Conventional breeding has consistently outperformed GM in developing useful traits such as tolerance to environmental stresses. This is because these traits are genetically complex, meaning that they are the product of many genes working together. GM (including gene editing) can only manipulate one or a few genes at a time and is therefore incapable of delivering on desirable complex traits. In contrast, natural cross-breeding between different cultivars can bring together the families of genes to confer a complex trait, as is evidently so in the case of the salt- and drought-tolerant soybeans developed by the CUHK researchers.

But in spite of the successes of conventional breeding, we caution that developing crop plants with drought and salt tolerance is a band-aid approach that does not solve the wider problems of climate change and degradation of soils. Saline soils can be brought back to healthy life quickly and efficiently using agroecological methods, as shown in India following flooding from a devastating tsunami. The marginal lands which are being targeted by the new salt- and drought-tolerant soybeans could also be regenerated using these methods. These farming systems centre on incorporating organic matter into the soil – an approach that also enables soil to hold onto water and thus builds in drought tolerance.

In the meantime the new salt- and drought-tolerant soybean cultivars are no doubt a welcome advancement for farmers in regions with marginally fertile soils. And if they are grown within an agroecological farming system focusing on improving soil health, they could form part of the solution to the problems of saline soils and drought.