Genomic Innovations for Next-Generation Perennial Grain Crops

The most drought resistant among the five most important cereal crops and a key dual-use (grain and biomass) crop in regions containing some of the world’s most degraded soils, the importance of sorghum might be further elevated by the development of productive genotypes that increase the extent and duration of soil cover beyond those of conventional annual crops, mitigating or even reversing losses of ecological capital through multiple crops from single plantings. Ratoon or perennial grain crops may provide smallholders in particular with additional tools that can support their hard-won agricultural skills to feed their families despite the challenges of climate change and soil degradation -- deeper roots and longer growing periods mean more harvests, better protected soil and more resilience to fluctuations in rainfall. Ratoon cropping is routine in closely related sugarcane and is occasionally practiced with some sorghum genotypes, however little attention has been given to systematic improvement of sorghum for this production system. Spreading seed and soil preparation/sowing costs over multiple cropping cycles may significantly change production economics, perhaps permitting smallholders to broaden utilization of hybrids to further increase productivity. Modern genomics tools, particularly useful for improving perennial crops, can speed the process from lab to field. The Sorghum genus has become a model for dissecting the molecular control of perenniality, and rich resources are being developed to link sorghum biodiversity to its molecular basis. Nature has made sorghum perennial at least twice, and crosses between wild perennials and cultivated sorghums show the feasibility of developing genotypes with varying degrees of investment in perenniality while still providing harvestable food, feed, sugar and/or cellulose.  Genetic analysis of progeny from these crosses reveals ‘quantitative trait loci’ (QTLs) conferring traits related to ratooning and perenniality, and provides diagnostic DNA markers. One perennial Sorghum species has adapted to continents and latitudes far beyond the reach of its progenitors, surviving stresses year after year that are only periodically experienced by conventional (annual) sorghum, and we are also exploring the hypothesis that that it harbors novel alleles that may mitigate production challenges in conventional annual sorghums.