Drought adaptation of stay-green sorghum is associated with canopy development, leaf anatomy, root growth, and water uptake.
Stay-green sorghum plants exhibit greener leaves and stems during the grain-filling period under water-limited conditions compared with their senescent counterparts, resulting in increased grain yield, grain mass, and lodging resistance. Stay-green has been mapped to a number of key chromosomal regions, including Stg1, Stg2, Stg3, and Stg4, but the functions of these individual quantitative trait loci (QTLs) remain unclear. The objective of this study was to show how positive effects of Stg QTLs on grain yield under drought can be explained as emergent consequences of their effects on temporal and spatial water-use patterns that result from changes in leaf-area dynamics. A set of four Stg near-isogenic lines (NILs) and their recurrent parent were grown in a range of field and semicontrolled experiments in southeast Queensland, Australia. These studies showed that the four Stg QTLs regulate canopy size by: (1) reducing tillering via increased size of lower leaves, (2) constraining the size of the upper leaves; and (3) in some cases, decreasing the number of leaves per culm. In addition, they variously affect leaf anatomy and root growth. The multiple pathways by which Stg QTLs modulate canopy development can result in considerable developmental plasticity. The reduction in canopy size associated with Stg QTLs reduced pre-flowering water demand, thereby increasing water availability during grain filling and, ultimately, grain yield. The generic physiological mechanisms underlying the stay-green trait suggest that similar Stg QTLs could enhance post-anthesis drought adaptation in other major cereals such as maize, wheat, and rice.
University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI), Hermitage Research Facility, Warwick, QLD 4370, Australia a.borrell@uq.edu.au.
Andrew K
AK
Borrell
Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA.
John E
JE
Mullet
Department of Agriculture, Fisheries and Forestry Queensland (DAFFQ), Hermitage Research Facility, Warwick, QLD 4370, Australia.
Barbara
B
George-Jaeggli
University of Queensland, QAAFI, Brisbane, QLD 4072, Australia.
Erik J
EJ
van Oosterom
University of Queensland, QAAFI, Brisbane, QLD 4072, Australia.
Graeme L
GL
Hammer
Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843, USA.
Patricia E
PE
Klein
University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI), Hermitage Research Facility, Warwick, QLD 4370, Australia.
David R
DR
Jordan
D000220:Adaptation, Biological; D018533:Biomass; D055864:Droughts; D018515:Plant Leaves / Q000033:anatomy & histology / Q000254:growth & development*; D018517:Plant Roots / Q000254:growth & development; D018526:Plant Transpiration / Q000235:genetics; D040641:Quantitative Trait Loci; D012639:Seeds / Q000254:growth & development; D045868:Sorghum / Q000033:anatomy & histology / Q000502:physiology*; D014867:Water / Q000502:physiology*
D014867:Water
Canopy development; crop water use; drought adaptation; leaf anatomy; root architecture; sorghum; stay-green.