Differentiation of Seed, Sugar, and Biomass-Producing Genotypes in Saccharinae Species
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Springer Science+Business Media New York 2013. Plant sinks including grain, stem sugar, leaf, and stem biomass as well as roots and rhizomes are the primary Saccharinae products of interest to humans. While plants evolved particular ratios of these sinks in the wild, humans have selected for altered ratios to fit production needs. Through further selection, specialty cultivars have recently been developed to maximize grain, sugar, biomass, or rhizome production as well as specialty carbohydrate and nutrient compositions. In sorghum and other C4 grass crops these specialized cultivars continue to undergo differentiation and could become, to some extent, genetically isolated populations. There has been limited research on the genetics and diversity of morphologically different crop ideotypes but it appears that inadequate recombination and selection has occurred to genetically isolate such genotypes yet. Importantly, recent results have shown that genetic tradeoffs among these various plant products may be avoidable, because photosynthesis is often sink, rather than source, limited. By combining and selecting multiple product types as optimized in specialty cultivars, harvestable products and energy may be further increased. Here, I review molecular genetic and phenotypic evidence of ideotype differentiation and discuss how harvestable energy might be maximized by carefully selecting for multiple products. There are a wide range of potential confounding factors, such as flowering time, that may alter conclusions and some possible solutions are suggested. If an ultimate goal is maximum usable energy production per unit area to satisfy growing global demand for food, fiber, fuel, and land, then breeding for only single products may sacrifice potential productivity.