An Update on Crop Modification
Several articles about genetic modification of crop plants have been posted on this website–e.g. here (Gene Editing), here (GMO’s), here (GEC’s vs. GMO’s), here (USDA policy on gene editing), and here (Genetics Terminology). Click here for a summary presentation of the various genetic techniques currently used to modify crop plants, and here for a pictorial presentation of those techniques.
A FarmProgress article that was posted in Feb. 2020 titled “Gene editing: Gateway to new future of plant breeding” provides an interview with Dr. Ponsi Trivisvavet, CEO of Inari Agriculture, Inc., a private genetics company that works to incorporate new techniques in genetics and data management with traditional plant breeding to impact the speed with which new and improved crop varieties can be brought to market. In the article, Dr. Trivisvavet discusses how gene editing is being used to 1) produce and understand genome sequences, 2) identify genes that are responsible for targeted traits, 3) limit or enhance the expression of a gene or genes, and 4) modify the expression of multiple genes that may be associated with a trait such as drought resistance. She also touches on epigenetics, or changes that modify gene expression without changing the genetic code of the target organism. This technology is being touted by some as the next breakthrough in genetic modification of crop plants (Click here for additional information about epigenetics).
The above linked articles indicate that there are numerous techniques that can be used to genetically alter a species such as soybean. Therefore, increased effort must be directed toward incorporating the many genetic enhancements that have already been identified as having the potential to improve the performance of soybeans in the field. Some examples of such identified improvements follow.
In a previous article on this website titled “Increased soybean nitrogen fixation: a potential game changer?”, an article about a recent discovery regarding enhanced nitrogen (N) fixation by soybean was summarized. In the cited research article, the authors concluded that enhancing N export from soybean nodules leads to increased N2 fixation, nodule metabolism, and shoot N nutrition in modified soybean lines, and promoted increased seed development which resulted in increased seed yield. In this case, the authors worked with two transgenic soybean lines that have the “over-expressor genes” that support this process. It was determined by this author that this discovery “could be a potential game-changer if it can be transferred to the soybean genome in general, and then can be translated into increased yield of newly developed varieties.” This of course will require a concerted effort by soybean breeders and geneticists using methods cited above.
In a set of articles that contain results from research conducted as part of the international RIPE (Realized Increased Photosynthetic Efficiency) project, authors report findings that implicate the shortcomings of photosynthesis in crop plants–e.g soybeans–for maximizing seed yield. A summary of results in these articles follow.
An article titled “Photosynthesis in the fleeting shadows: an overlooked opportunity for increasing crop productivity” (The Plant Journal 101:874-884 [2020]) states that leaves in crop fields experience frequent and erratic fluctuations in light intensity, and are slow to respond to both increased and decreased light intensity. This slow response (recovery from photoprotection or dissipation of damaging excess absorbed light energy as heat when light intensity is reduced and/or activation of Rubisco activase when light intensity increases) reduces the efficiency of carbon assimilation. The researchers calculated that these combined limitations resulted in a 13% reduction in crop carbon assimilation on both sunny and cloudy days. They found that over the course of a sunny and intermittently cloudy day, differences among soybean lines they used would translate to substantial differences in total crop carbon assimilation, and thus yield. The authors state that “These findings suggest an unexplored potential for breeding improved photosynthetic potential into our major crops. The approach is to genetically engineer or possibly breed the necessary photosynthetic apparatus into lines to accomplish faster adjustment to natural light fluctuations. We estimate that this faster adjustment to changing light intensity in the field could increase food production by 20% per acre, without a need for more water.”
An article titled “Improving photosynthesis and crop productivity by accelerating recovery from photoprotection” (Science 354:857-861 [2018]) describes the bioengineering of an accelerated response to field conditions of irregular or fluctuating light intensities in tobacco that results in increased leaf CO2 uptake and subsequent plant dry matter production by improved tobacco lines. The authors state that “the findings provide proof of concept for a route to obtaining a sustainable increase in productivity for food crops and a much-needed yield jump.”
An article titled “Chlorophyll Can Be Reduced in Crop Canopies with Little Penalty to Photosynthesis” (Plant Physiology176:1215-1232 [2018]) reports findings from simulations that soybean plants with 20% less chlorophyll theoretically require 9% less nitrogen with no penalty to carbon gain (biomass) and yield. Thus, these simulations show that soybean canopies can assimilate similar amounts of CO2 with significantly less chlorophyll. The authors state that “future efforts should focus on repartitioning nitrogen from excess chlorophyll into more beneficial investments.” It is likely that these efforts will involve genetic studies and plant breeding to develop advanced lines with the desired leaf chlorophyll trait. The end product will necessarily be soybean varieties with a leaf chlorophyll content that is sufficient to maximize photosynthesis while simultaneously allowing increased nitrogen partitioning to desired plant parts such as seed and seed components.
The above narrative leads to the following conclusions.
• It is obvious to this writer that future improvements in crop performance–e.g. improved pest resistance, more efficient use of water and fertilizer inputs, improved drought/stress tolerances, and improving yield potential by changing the chemistry/structure of plants –will most assuredly arise from the enhanced germplasm and improved crop varieties that can only come from advancements made by public and private sector crop geneticists and breeders.
• All genetic enhancement traits must eventually be incorporated into a revised soybean genome that can be used to develop new varieties that will be beneficial to growers.
• The required pace in the development of improved crop varieties through enhanced genetics can only result from increased investment by both public and private entities in this endeavor.
• The vast majority of current improved soybean varieties now originates from the private sector, which indicates that this sector has and continues to make a major investment in this effort.
• The public crop breeding sector is the major producer of enhanced germplasm that the private sector depends on for developing improved crop varieties. This germplasm will be developed by public geneticists and breeders using findings from studies such as those shown above.
• This then indicates to me that the public sector (commodity groups and public institutions) should reassess their commitment of funds to determine how they can best be used to increase support for the development of this enhanced germplasm that is needed to develop improved crop varieties.
• And finally, there needs to be a concerted effort by both public and private sector administrators to increase the cooperation and coordination among public and private breeders and geneticists so that all available resources and expertise are invested to support an increased effort to develop improved crop varieties.
• All enhancements to a crop’s genome, including those that may result from the results provided in the above cited research, must be incorporated into agronomically acceptable soybean varieties that contain these improved traits in order to be of value to producers and end users.