1. The challenge Drought during grain filling is a common challenge for sorghum production in north- eastern Australia, central-western India, and sub-Saharan Africa. We show that the stay- green drought adaptation trait enhances sorghum grain yield under post-anthesis drought in these three regions. ABOVE : Sorghum plants of near-isogenic lines (NILs) differing for the parental allele at the stay-green2 (Stg2) QTL. Lines stg2/stg2 NIL (left) and Stg2/Stg2 NIL (right) were grown in the same conditions and were exposed to terminal water deficit. Shifting water use from pre- to post-anthesis Physiological studies in Australia found that introgressing four individual stay-green (Stg1–4) quantitative trait loci (QTLs) into a senescent background reduced water demand before flowering and hence increased water supply during grain filling, resulting in higher grain yield relative to the senescent control (1). Stay-green Drought Adaptation Trait Enhances Sorghum Production in Sub-tropical Australia, Central-Western India and Sub-Saharan Africa A Borrell 1, B George-Jaeggli 1, E van Oosterom 2, G Hammer 2, E Mace 3, V Vadez 4, J Kholova 4, H Talwar 5, S Deshpande 4, S Coulibaly 6, N Teme 6, C Barro-Kondombo 7, S Souley 8, A Tirfessa 9, A Adugna 9, C Kamau 10, A Mohamed 11, D Jordan 1 | a.borrell@uq.edu.au Stay-green positively correlated with grain yield A positive relationship between stay-green and yield was generally found in breeding trials in north-eastern Australia that sampled 1668 unique hybrid combinations and 23 environments (2). ABOVE: Grain yield of Stg NILs is enhanced relative to RTx7000 under post- anthesis drought in a rain-out shelter study; data are mean±2SE. Central-western India Studies in India found that various Stg QTLs affected both transpiration and transpiration efficiency, although these effects depended on the interaction between genetic background (S35 and R16) and individual QTLs. The yield variation unexplained by harvest index was related to transpiration efficiency in S35 (R 2 = 0.29) and R16 (R 2 = 0.72), and was related to total water extracted in S35 (R 2 = 0.41) but not in R16 (3). Sub-Saharan Africa Sixty-eight stay-green enriched lines were evaluated in six countries in sub-Saharan Africa during the 2013/14 season. Analysis of the data from Kenya indicates that stay-green and grain size were positively correlated at two sites: Kiboko (high yielding, r 2 =0.25) and Masongaleni (low yielding, r 2 =0.37). Together, these studies suggest that stay-green is a beneficial trait for sorghum production in the semi-arid tropics and is a consequence of traits altering the plant water budget. References 1.Borrell AK, Mullet JE, George-Jaeggl, B, van Oosterom EJ, Hammer GL, Klein PE and Jordan DR (2014). Journal of Experimental Botany, 65, 6251–6263 (doi:10.1093/jxb/eru232). 2.Jordan DR, Hunt CH, Cruickshank AW, Borrell AK, and Henzell RG (2012). Crop Science 52:1153-1161. 3.Vadez V, Deshpande SP, Kholova J, Hammer GL, Borrell AK, Talwar HS and Hash CT (2011). Functional Plant Biology, 2011, 38, 553–566. Author affiliations 1 The University of Queensland, Queensland Alliance for Agriculture and Food Innovation, Hermitage Research Facility, Warwick, Australia; 2 The University of Queensland, Queensland Alliance for Agriculture and Food Innovation, St Lucia, Australia; 3 Department of Agriculture and Fisheries, Hermitage Research Facility, Warwick, Australia: 4 International Crops Research Institute for the Semi-Arid Tropics, Patancheru, India; 5 Indian Institute for Millet Research, Hyderabad, India; 6 Institut d’Economie Rurale, Mali; 7 Institut de l'Environnement et de Recherches Agricoles of Burkina Faso, Burkina Faso; 8 Institut National de la Recherche Agronomique du Niger, Niger; 9 Ethiopian Institute of Agricultural Research, Adama, Ethiopia; 10 Kenya Agricultural Research Institute, Katumani, Kenya; 11 ARC, Mad Mwedani, Sudan Water conserved Water utilised Rain-out Shelter ABOVE: The lysimetry facility at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Hyderabad, India, was used to evaluate transpiration and TE in two populations varying in Stg QTLs. ABOVE: Stay-green enriched lines were evaluated in West Africa (1, Mali; 2, Burkina Faso; 3, Niger) and East Africa (4, Sudan; 5, Ethiopia; 6, Kenya). ABOVE: Dr Niaba Teme, a sorghum breeder, inspects his field trial in Mali. ABOVE: Stg3 uses less water than RTx7000 before anthesis and more water after anthesis. The temporal pattern of cumulative crop water use for RTx7000 (open squares) and Stg3 (filled squares) grown under a low water high-density treatment in a rain-out shelter study. The black vertical arrow marks anthesis.