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The Power of Genetic Diversityqrcode

May. 8, 2017

Favorites Print May. 8, 2017
 Kevin Cook
Kevin Cook

Crop productivity improvements at the turn of the 20th century was stagnant. Average yields in the United States plateaued around 20 bushels per acre for corn, 12 bushels for wheat, and 20 bushels for rice. The development of modern plant breeding, defined by the FAO as “the act of using genetic diversity to improve the agronomic performance of plants conducted as a formal endeavor and according to scientific principles”, led to several-fold improvements in productivity of these core crops over the ensuing century. These tools enabled plant breeders to identify germplasm with improved yield, standability, and pest resistance and to accumulate genes responsible for these traits from many different sources into new varieties and hybrids. Access to high performance germplasm comprised of diverse genes was required to realize this historic improvement in food availability and security.

A simple analogy will help to explain the role of genetic diversity in creating improved crop varieties. New colors are created by mixing different combinations of the primary colors red, yellow, and blue. The color range of an artist who has only red and yellow to work with will not be able to create all the color combinations required for most paintings. Each new crop variety is a unique combination of the genes possessed by its parental varieties. The more unique the gene combinations in potential parents, the more adaptable the potential varieties which can be derived from them will be. This diversity allows selection for improved characteristics and to address emerging agronomic issues faced by farmers. Developing improved varieties from a narrow genetic base is similar to attempting to produce purple paint from red and yellow.

Successful plant breeding has a natural outcome of reducing genetic diversity. The discovery of new high-performing varieties leads to the abandonment of the diverse but lower performance germplasm that it replaces (green may look great for a while —but if the blue paint is discarded the artist will not be able to adapt when a new option is needed). While the increased performance of these improvements benefits both farmers and the institutions that develop them, the resulting loss of genetic diversity makes the realization of future improvements more difficult. Declining genetic diversity among elite performing varieties is a bottleneck to future improvement of crop plants.

The negative impact of low diversity is most clearly visible in examples of severe production loss caused by emerging diseases at times of reliance on narrow genetic diversity. The Irish Potato Famine of 1845 to 1852 led to the death of as much as 40% of the population of Ireland when Late Blight ravaged the susceptible, highly homogeneous potatoes in use at the time. In 1969-1970, extensive use of the Texas male sterility system led to a devastating destruction of the maize crop in the U.S. when a race of Southern Corn Leaf Blight emerged which produced a toxin causing rapid death of hybrids carrying this male sterility system. In each case, the devastating effects could have been avoided by the growing of genetically diverse crop plants. The long-term impact of chronically diminished ability to make crop improvements because of limited diversity is far greater than the impact of these short-lived production interruptions. Reliance upon a narrow base of crop genetic diversity is a risk to global food security.

The FAO states that since the 1900s, some 75 percent of plant genetic diversity has been lost as farmers worldwide have left their multiple local varieties and landraces for genetically uniform, high-yielding varieties. Germplasm banks of most crop species are maintained by national and international institutions to protect existing diversity. Value capture from these sources is limited by imperfect characterization of the genes and agronomic traits of stored accessions. Further, these accessions are predominantly older and uncompetitive relative to those used in production and are primarily used as donors of individual genes or small numbers of genes associated with specific traits.
Addressing the “diversity ceiling”, seed companies have acquired businesses with diverse germplasm pools– to the tune of more than $10B over the last two decades (not taking into account the recent industry consolidation). The combining of these diverse pools unleashed impressive performance improvements. Unfortunately, they also resulted in the discarding of the crop diversity which had been actively maintained in small company breeding and commercial pipelines but which was unable to compete in the more selective competition of larger companies. In today’s consolidated seed market for the major agronomic crops, acquisition of competitive new germplasm pools is essentially no longer an option. Biotechnological developments (such as GMOs) brought and continue to bring new agronomic traits to plants that provide great value to growers, but do not address the inherent genetic potential of the crop for complex traits like yield, stress tolerance, and adaptation to changing environments.
How do we continue to break the genetic diversity barrier in order to develop new, elite varieties that will meet the global food production challenge? Recognition of the issue is the first step - and most large breeding organizations are very aware. The challenge is that the commercial marketplace rewards high-performance in the short-term and only values diversity when a problem emerges for which there are limited options. At this point, recovery may be costly and time-consuming.

Kaiima is taking a new approach to the diversity issue. EP™ is a technology which creates novel types of genetic diversity within the DNA of elite crop germplasm. The application of EP™ enables breeding programs to maintain the positive characteristics and performance of their elite varieties while creating novel new changes enabling additional improvements. Results to date have demonstrated ability to improve yield, harvest moisture, and disease tolerance in maize, canola, wheat, and sorghum. Demonstration of utility is underway in a range of new crop species. Resolution of the genetic diversity dilemma is complex and no single technology will resolve the issue. Nevertheless, EP™ is one great example of a new approach with high potential to contribute to the solution.

Please download AgroPages' latest magazine - 2017 Seed Special to see more.

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