Soybean could be made more tolerant of acidic soils through new breeding approaches to improve its root systems, according to scientists in China.
In a review of research on legumes to date, the team pointed to evidence suggesting that crops could be selected for root adaptations which include improved nutrient efficiency in the face of phosphorus (P) deficiency and tolerance of aluminium (Al) toxicity, both of which are common characteristics of acidic soils.
Developments could mean that soybean farmers can maintain yield, even when their crops are exposed to stress, the researchers wrote in The Crop Journal. They noted that a number of what are known as quantitative trait loci (QTLs), regions of DNA linked to specific variable traits, have been identified as involved in P efficiency and Al toxicity.
Promising discoveries
Some of the work established that certain genes improved P acquisition by controlling root length and architecture. Scientists have also identified several biological mechanisms which link root growth and P efficiency, while others have demonstrated that genes not inherently linked to P pathways or nutrient starvation can also improve both of these traits.
Further work linked legumes’ ability to tolerate Al toxicity to genes controlling both root length and the production of antioxidants, while a set of genes directly linked to Al detoxification was described in another study.
The key relationship between roots and soil microorganisms may also have the potential to be effectively manipulated through the use of genetic techniques, the authors said, pointing to research linking root-associated bacterial communities with crop genotypes.
More focused work to come
Despite the growth in knowledge around the molecular basis of tackling these stresses of acidic soils, very few of the discoveries have gone on to be used in breeding programmes or genetic engineering work, they stressed. Another issue they identified was that P efficiency and Al toxicity have tended to be studied in isolation, even though these are coexisting stresses in acid soils and improvements in both traits would maximise the vigorousness of soybean crops under such environmental conditions.
While QTLs linked to both P efficiency and Al toxicity tolerance have yet to be discovered, it may be possible to use QTLs linked with root architecture to find molecular links between the two qualities. Genes have also been found which are involved in plant mechanisms in response to both P starvation and Al toxicity.
“The molecular and genetic processes underlying P-Al interactions need to be studied and explored further. Once clearly investigated, these traits may be filtered through efficient screening or tagged with markers, and then incorporated into breeding programs through marker-assisted selection or transgenic engineering,” the scientists added.
