Forage breeding programs aimed at increasing productivity of marginal lands

Abstract Text: The definition of "marginal lands" is highly contentious, subject to a wide range of opinions and contexts.  For the purposes of this paper, I define marginal land simply as land with one or more problems that reduce crop productivity or economic sustainability. Numerous production and sustainability problems may be caused by land, soil, or atmospheric issues, including drought, nutrient imbalance, toxicity, pH imbalance, air pollutants, and temperature extremes. Forage crops, particularly perennials, are often relegated to these lands, particularly when crop productivity or sustainability falls below an economic viability threshold. As such, forage breeders have been faced with numerous challenges to breed both grasses and legumes that will tolerate these stresses, providing the basis for profitable and sustainable livestock production on lands that are "marginal" for crop production.  The foundation of plant breeding is genetic variation, which has been observed for nearly all of the major stresses that have presented themselves as challenges for forage breeders. Genetic variation often must be coaxed out of a species by designing the proper challenge and screening method for the plants, such as an acid soil that is sufficiently acidic to cause measurable or observable stress, but not so much as to kill all the plants.  For many stresses, it is quite common to find very low frequencies of tolerant or resistant plants, sometimes as low as <1 in 10,000.  For this reason, forage breeding is often a "numbers game" in which genetic improvements are directly proportional to the population sizes and efforts expended. Numerous cultivars have been developed and released to the public, often expanding the geographic range and broadening the environmental circumstances under which a forage species can be used for livestock production.

Keywords: Forage breeding, genetic variation, stress tolerance, adaptation