TY - JOUR T1 - Genomics of sorghum local adaptation to a parasitic plant JF - bioRxiv DO - 10.1101/633529 SP - 633529 AU - Emily S. Bellis AU - Victoria L. DeLeo AU - Elizabeth A. Kelly AU - Claire M. Lorts AU - Germinal Rouhan AU - Andrew Budden AU - Govinal Badiger Bhaskara AU - Zhenbin Hu AU - Robert Muscarella AU - Thomas E. Juenger AU - Michael P. Timko AU - Geoffrey P. Morris AU - Claude W. dePamphilis AU - Jesse R. Lasky Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/05/09/633529.abstract N2 - Host-parasite coevolution can maintain high levels of genetic diversity in traits involved in species interactions. In many systems, host traits exploited by parasites are constrained by use in other functions, leading to complex selective pressures across space and time. Here, we study genome-wide variation in the staple crop Sorghum bicolor (L.) Moench and its association with the parasitic weed Striga hermonthica (Delile) Benth., a major constraint to food security in many African countries. We hypothesize that sorghum landraces are subject to geographic selection mosaics within parasite-prone areas and selection against resistance where S. hermonthica is never found. Supporting this hypothesis, multiple independent loss-of-function alleles at sorghum LOW GERMINATION STIMULANT 1 (LGS1), a locus known to impact resistance, are broadly distributed among African landraces and geographically associated with S. hermonthica occurrence, suggesting a role in local adaptation to parasite pressure. However, the low frequency of these alleles within S. hermonthica-prone regions and their absence elsewhere indicates potential trade-offs restricting their distribution. LGS1 impacts stereochemistry of strigolactones, hormones controlling plant architecture, belowground signaling with other organisms, and abiotic stress tolerance. Supporting trade-offs, transcriptome profiling of nutrient-stressed roots revealed differential regulation of several strigolactone biosynthesis and signaling genes in LGS1-deficient sorghum compared to a susceptible line. Signatures of balancing selection surrounding LGS1 and candidates from analysis of genome-wide associations with parasite distribution support long-term maintenance of diversity in parasite resistance genes. Our study of host resistance evolution across smallholder agroecosystems provides a valuable contrast to both industrial farming systems and natural communities.SIGNIFICANCE STATEMENT Understanding co-evolution in crop-parasite systems is critical to management of myriad pests and pathogens confronting modern agriculture. In contrast to wild plant communities, parasites in agricultural ecosystems are usually expected to gain the upper hand in co-evolutionary ‘arms races’ due to limited genetic diversity of host crops in cultivation. Here, we develop a framework for studying associations between genome diversity in global landraces (traditional varieties) of the staple crop sorghum with the distribution of the devastating parasitic weed Striga hermonthica. We find long-term maintenance of diversity in genes related to parasite resistance, highlighting an important role of host adaptation for co-evolutionary dynamics in smallholder agroecosystems. ER -