When we save seeds, we pass on valuable plant genes that will aid the health and persistence of future plant generations. But that’s not all we are passing on. Packed tightly among the plant’s cells reside many thousands of cells and spores from bacteria and fungi, which will grow alongside and within the developing plant.
My research seeks to explore this exciting, unexplored area of the plant microbiome by focusing on the seed. Many of these seed borne microbes are much more than incidental hitchhikers, but have forged long-term alliances with their towering plant companions. In exchange for an exclusive, energy-rich habitat within the plant, many of these microbes increase the health and resilience of the plant host.
Seed-borne fungi and bacteria can benefit the plant in many ways, including:
-Resistance against plant pathogens
-Nitrogen fixation within the plant
-Protection against herbivores
-General increase in growth rate
-Resilience against drought and other extreme weather patterns
History of seeds
Seeds are the foundation of our entire food system. Without giving special care to seeds, our ancestors would not have been able to guide plant evolution to make agriculture a worthwhile lifestyle for humans. In fact, in English, the word “seed” (sed) only came after the verb “to sow” (sawan), which illustrates the fundamental importance of the act of planting. Over the years, we have seen a shift of sowing seed, from a highly diverse, decentralized activity, to one that is dominated globally by a handful of companies that produce the seed to be sown. There used to be as many seed varieties as there were human cultures and natural landscapes. With the centralization of our seed production comes the striking disappearance of the vast majority of our seed diversity – some estimates report that over 90% of agricultural diversity has gone extinct in the U.S. (75% globally, according to the FAO). With the loss of these seeds, we lose valuable genetic information and wisdom accumulated over many generations, and therefore we have decreasing potential to adapt our crops to changing ecosystems, pathogens, and climates.
Seeds have also been formative in our understanding of genes. Gregor Mendel (1822-1884), the father of modern genetics, experimented with generations of pea plants to discover that each plant contains fundamental units of instructions that are inherited generation to generation in the seeds, such as red or white flower color. Utilizing this scientific imperative, plant breeders have sought to isolate the very genes that cause certain desirable plant traits, such as a gene that causes high yield or resistance to a certain disease. Over the years, we have found that Mendel’s model of 1 gene = 1 trait is far more of an exception than the rule. As our crops continue to fall to weeds, diseases, and weather, breeders are expanding the search for genes to protect them against the elements. New technologies allow us to scan the entire genome for areas that are statistically associated with certain desirable traits, which means that breeding efforts are now devoted to coordinating the actions of multiple genes to get the desired result. Additionally, biotech has been putting foreign genes into our crops in a standard practice that society finds both dazzling and disturbing. Since the advent of genetic revolution in the 1900’s, seeds seem to represent little more than packets of genetic information.
Beyond genetic inheritance
The aim of my research is to explore the role of microorganisms in the breeding and evolution of our crops. Microorganisms bring a missing ecological dimension to our breeding efforts, when we understand that the traits of a plant are not only governed by its genes, but by its intimate interactions with its diverse microflora. Try as we might, we cannot separate plants from the microbes with which they have co-evolved for millions of years. Once discarded as “contaminants”, or environmental “noise” that gets in the way of “pure” plant science, plant-associated microbes are increasingly recognized as an essential piece of the plant’s story. Moreover, these microbes force us to consider the ecological forces that are setting the stage for their interactions with plants. We must call into question the ecosystems in which we are breeding these plants. Should these plants be bred in “controlled” environments without regard to their complex ecologies, or should we take seriously the ecological context of plant breeding? Are there general interactions between plants and microbes that can and should be packaged and sold across the world, or should plant breeding efforts necessarily be local and distributed, as they were historically?
We still have a lot to learn about the role of seed-borne organisms in our agriculture, and the nature or their inheritance. However, their presence within seeds calls into question the convention of treating seeds to remove pathogens, and force us to consider our seed storage and seed germination environments. We can be certain that seeds appear to pass on far more information than their genes alone.