The story behind seeds is in many ways the single greatest key to understanding the extraordinary success of vegetables as a commodity. Of course, seeds are not unique or restricted to the vegetable industry, and growing vegetables also involves many other technological and creative achievements. However, the role of seeds in the vegetable world is one of the great stories of humanity’s agricultural success.
Sharing The Seed
In today’s worldwide vegetable seed production system, a dizzying number of cultivars for hundreds of vegetable commodities are bred, developed, tested, and brought to market for farmers around the globe. Scientific breakthroughs and innovations have resulted in outstanding varieties, excellent seed quality and vigor, and high levels of uniformity in the lots.
The extensive research behind these innovations is a model of fruitful collaboration between public and private entities. Government and university investigators have achieved greater success due to cooperative efforts with industry; likewise, private industry researchers have moved forward rapidly with the help of publicly funded plant physiologists, geneticists and breeders, plant pathologists, and others.
An example of such a successful collaboration can be found with the Seed Biotechnology Center at the University of California, Davis (http://sbc.ucdavis.edu). The Center is a partnership between Seed Biotechnology Center (SBC) scientists, seed industries, and private companies located throughout the world.
Through this partnership, new techniques and methods are developed to advance plant breeding, find novel traits, increase seed quality, and integrate new technologies. The SBC is also dedicated to providing ongoing education and training for people in the seed industry. Workshops, courses, and published materials are intended to train newcomers to the seed world as well as update those already working in this field.
It is not only the actual seed that illustrates this high level of technology, for seed researchers, plant breeders, producers, and handlers have learned how to best prepare seed so that it is optimally ready for the grower to use. Seeds are grown and harvested so as to be of the highest quality possible. Then seeds can be handled, manipulated, and stored in various ways so as to be in peak physiological condition for rapid and uniform germination.
In addition, seeds are treated in various ways so as to add protectant chemicals, such as fungicides and insecticides, to guard against pests and pathogens in the ground.
The critical field of seed pathology, defined here as the study of pathogens that are carried in and on seed and which can result in infected plants, is another aspect of the success story involving humanity’s handling of seed. Seed pathology boasts a number of notable historical landmarks in which investigators discovered that the source of damaging diseases was found in the seed itself. Examples of such findings include mosaic virus of lettuce, the bacterium that causes black rot of crucifers, the watermelon fruit blotch bacterium, the bacterial speck, spot, and canker pathogens of tomato, and dozens of others.
Elegant experiments have pinpointed how the pathogens enter seeds and where they are found in seed tissues, how the pathogens can be detected, and how to treat infested seed so as to eliminate the agents or reduce the risk of significant disease and resulting crop losses. The science of seed pathology also demonstrates how investigative methods can improve and change over time. At one time the detection of seedborne pathogens was completely dependent on the actual culturing and growing out of pathogens from infested seed.
Today, extremely sensitive, DNA-based molecular methods are often used to find these invisible hitchhikers that have attached themselves to seed. This and all technologies, however, are never perfect. Presently, most DNA based methods cannot differentiate DNA from live versus dead cells of a pathogen, which limits the utility of these assays, particularly for testing seeds that have been treated (with hot water or chemicals) so as to kill pathogens in and on the seed.
Safeguarding The Seed
Despite the success story of seed development, production, and handling to date, the seed world must continue to conduct research, search for new genetic resources, develop yet newer techniques, and deal with novel challenges as they appear. New diseases or new strains of pathogens periodically occur on crops, and in some cases these problems are found to be seedborne.
For example, in the past two years, two newly documented pathogens of parsley (Pseudomonas, Stemphylium) have been associated with seeds. A different, perplexing dilemma has recently implicated spinach seed.
While not causing a disease on spinach, the fungus Phomopsis has been detected on spinach seed by federal inspectors. This finding has created a complicated, controversial situation. The significance of the Phomopsis species, whether or not they cause disease on spinach or other crops, is undocumented. Yet, authorities have designated two species of this fungus as quarantine pests because these species apparently have not been detected in the U.S.
Rejection of spinach seed at U.S. ports of entry threatens to result in significant economic losses by seed companies and possible seed shortages for growers in California and elsewhere. This spinach Phomopsis case illustrates that our understanding of the seed world is not complete, and that more research is needed so that policies can be based on scientific information and findings.