The eastern Africa region, Ethiopia and its surroundings, is considered as the center of origin and diversity for sorghum, and has contributed to global sorghum genetic improvement. The germplasm from this region harbors enormous genetic variation for various traits but little is known regarding the genetic architecture of most traits. Here, 1425 Ethiopian landrace accessions were phenotyped under field conditions for presence or absence of awns, panicle compactness and shape, panicle exsertion, pericarp color, glume cover, plant height and smut resistance under diverse environmental conditions in Ethiopia. In addition, F1 hybrids obtained from a subset of 1341 accessions crossed to an A1 cytoplasmic male sterile line, ATx623, were scored for fertility/sterility reactions. Subsequently, genotyping-by-sequencing generated a total of 879,407 SNPs from which 72,190 robust SNP markers were selected after stringent quality control (QC). Pairwise distance-based hierarchical clustering identified 11 distinct groups. Of the genotypes assigned to either one of the 11 sub-populations, 65% had high ancestry membership coefficient with the likelihood of more than 0.60 and the remaining 35% represented highly admixed accessions. A genome-wide association study (GWAS) identified loci and SNPs associated with aforementioned traits. GWAS based on compressed mixed linear model (CMLM) identified SNPs with significant association (FDR ≤ 0.05) to the different traits studied. The percentage of total phenotypic variation explained with significant SNPs across traits ranged from 2 to 43%. Candidate genes showing significant association with different traits were identified. The sorghum bHLH transcription factor, ABORTED MICROSPORES was identified as a strong candidate gene conditioning male fertility. Notably, sorghum CLAVATA1 receptor like kinase, known for regulation of plant growth, and the ETHYLENE RESPONSIVE TRANSCRIPTION FACTOR gene RAP2-7, known to suppress transition to flowering, were significantly associated with plant height. In addition, the YELLOW SEED1 like MYB transcription factor and TANNIN1 showed strong association with pericarp color validating previous observations. Overall, the genetic architecture of natural variation representing the complex Ethiopian sorghum germplasm was established. The study contributes to the characterization of genes and alleles controlling agronomic traits, and will serve as a source of markers for molecular breeding.

Following advances in genetics, genomics, and phenotyping, trait selection in breeding is limited by our ability to understand interactions within the plant and with the environment, and to identify traits of most relevance to the target population of environments. We propose an integrated approach that combines insights from crop modelling, physiology, genetics, and breeding to characterize traits valuable for yield gain in the target population of environments, develop relevant high-throughput phenotyping platforms, and identify genetic controls and their value in production environments. This paper uses transpiration efficiency (biomass produced per unit of water used) as an example of a complex trait of interest to illustrate how the approach can guide modelling, phenotyping, and selection in a breeding programme. We believe that this approach, by integrating insights from diverse disciplines, can increase the resource use efficiency of breeding programmes for improving yield gains in target populations of environments.

The Ethio-Sudan region is recognized as the center of origin and diversity for cultivated sorghum. All major races of the crop are widely grown in Ethiopia with durras being dominant. The objective of the present study was to determine the extent of morphological variability among the Ethiopian durras and examine the pattern of relationships among these traits and their association with yield and yield components. Two hundred accessions collected from major sorghum-growing regions of the country were evaluated during the 2007 season at two locations representing hot and dry low land and mild mid-altitude environments. A randomized complete block design with three replications was used. Data were collected on phenology, plant height, a range of leaf traits and yield components. Significant variation was observed among all traits measured. Phenological traits and plant height were significantly correlated with each other and with all leaf traits. There was positive correlation among leaf traits, and between leaf traits and yield components except thousand kernel weight (TKW) and panicle length (PL). Grain fill duration was negatively correlated with all traits except days to maturity, TKW, and leaf length. Yield components except PL and TKW were positively correlated with each other. Selection that focuses on key yield components, larger leaf area, and on enhancing the grain filling rate by reducing excessive grain fill duration may contribute to yield improvement.

Finger millet is one of the most neglected and underutilized crops worldwide, yet an important food cereal for millions of poor farmers in

Sorghum is an important food and feed crop in the dry lowland areas of Ethiopia. Farmers grow both early-sown long-duration landraces and late-sown short-duration improved varieties. Because timing and intensity of drought stress can vary in space and time, an understanding of major traits (G), environments (E), management (M), and their interactions (G×E×M) is needed to optimize grain and forage yield given the limited available resources. Crop simulation modeling can provide insights into these complex G×E×M interactions and be used to identify possible avenues for adaptation to prevalent drought patterns in Ethiopia. In a previous study predictive phenology models were developed for a range of Ethiopian germplasm. In this study, the aims were to (1) further parameterize and validate the APSIM-sorghum model for crop growth and yield of Ethiopian germplasm, and (2) quantify by simulation the productivity-risk trade-offs associated with early vs late sowing strategies in the dry lowlands of Ethiopia. Field experiments involving Ethiopian germplasm with contrasting phenology and height were conducted under well-watered (Melkassa) and water-limited (Miesso) conditions and crop development, growth and yield measured. Soil characterization and weather records at the experimental sites, combined with model parameterization, enabled testing of the APSIM-sorghum model, which showed good correspondence between simulated and observed data. The simulated productivity for the Ethiopian dry lowlands environments showed trade-offs between biomass and grain yield for early and late sowing strategies. The late sowing strategy tended to produce less biomass except in poor seasons, whereas it tended to produce greater grain yield except in very good seasons. This study exemplified the systems approach to identifying traits and management options needed to quantify the production-risk trade-offs associated with crop adaptation in the Ethiopian dry lowlands and further exemplifies the general robustness of the sorghum model in APSIM for this task.

Sorghum [Sorghum bicolor (L.) Moench] is an important dryland crop in the semiarid tropics, and temperature and photoperiod are the main environmental factors affecting its phenology and thus adaptation. The objectives of this study were to quantify the response of development rate to temperature and photoperiod for 19 diverse Ethiopian sorghum genotypes, and to determine if differences in these responses could be linked to racial grouping or agroecological adaptation. The genotypes, representing four major sorghum races and adaptation to four agroecological zones, were sown on 12 dates at two locations in Ethiopia with contrasting altitude. This created a range in photoperiod and temperatures relevant to Ethiopian conditions. Days from emergence to flag leaf appearance, anthesis, and maturity were recorded. A predictive phenology modeling framework was used to fit the effects of photoperiod and temperature on the rate of development for both the pre-and post-anthesis periods. Results indicated that the pre-anthesis development rate was independent of photoperiod for the range tested. This result differed from West African germplasm and likely reflects differences in agroecological adaptation and racial background. Significant genotypic differences were observed for the base temperature (0-9.8 • C) and for the optimum rate of development (0.011-0.022 d -1 , with low value indicating late anthesis), with differences related to agroecology and racial type. Post-anthesis differences in the temperature response were minor. The observed differences in pre-anthesis base temperature can positively affect sorghum breeding programs globally, especially in temperate regions where suitability for early spring plantings is often restricted by low temperatures.

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