It is often thought that crops such as soybeans adapt to drought stress and become capable of withstanding drought. There is no evidence to support this view, when it is considered on the basis of producing an economic yield. The limited adaptation that does occur (through myriad biological and/or physiologial processes) only increases the plant's ability to survive during drought. This may be a valuable mechanism for a desert shrub, but it is of little value where production of a profitable seed yield is important for a crop such as soybean.
So is there potential for “real” drought tolerance in an important crop such as soybean where mere survival is not a viable option? The following recent developments indicate there is.
Bioceres Crop Solutions, an Argentinian company, has developed wheat with the drought stress tolerant technology labeled “HB4" (click here for HB4 White Paper). Scientists with the company added genetic material from sunflower (hahb-4 gene) to the wheat genome to produce this new wheat trait. The hahb-4 gene is a transcription factor that modulates the expression of several hundred genes and provides drought tolerance that is not related to stomatal closure.
Verdeca, a joint venture created between Bioceres and Arcadia Biosciences, is developing soybean varieties that incorporate the HB4 technology. The company states that HB4 wheat and soybean are compositionally and nutritionally equivalent to their conventional counterparts, and that there is no yield drag associated with the technology in years when there are no stress-related yield reductions in conventional varieties. Verdeca has completed the regulatory review process in the U.S. and has received approval from USDA for commercialization of HB4 drought tolerant soybeans in the U.S. market.
Producers of nonirrigated soybeans are encouraged to be on the lookout for forthcoming varieties with the HB4 trait. Such varieties have the potential to enhance the yield of soybeans that are produced in dryland environments. If the company’s claim of a 12-19% yield enhancement when soybeans are produced in conditions that promote drought stress is accurate, this could mean a significant advancement in profitability for dryland soybean producers.
Another key research finding was touched on in a July 13, 2022 FarmPress article titled “How onions could help corn, soybeans withstand drought stress” by Tom Bechman. This article highlights the work of Dr. Karen Tanino and colleagues at the University of Saskatchewan in Canada. The results of their research reported in an article titled “With a Little Help from My Cell Wall: Structural Modifications in Pectin May Play a Role to Overcome Both Dehydration Stress and Fungal Pathogens” that appears in the journal Plants, 2022, 11, 385 (https://doi.org/10.3390/plants11030385) indicates that pectin modifications in the cell wall of onion plants appear to play an important role in resistance to both dehydration and biotic stresses. They surmised that calcium application played a vital role in this modification of cell wall pectin to result in a strengthening of the cell wall as a physical barrier to both abiotic and biotic stresses. This preliminary work with onion indicates that shoring up cell walls could provide an additional line of defense against drought stress in other plant species.
The vast majority of both U.S. and global soybean acreage is nonirrigated. Thus, soybean productivity on these acres is subject to the vagaries of the weather, especially erratic and/or deficient rainfall. Since periods of drought occur on these nonirrigated acres in most years, the above technologies/findings could lead to alleviation of some of the stress associated with these drought periods. This should result in increased production of soybean on these acres.
Composed by Larry G. Heatherly, July 2022, email@example.com