title: Stay-green traits to improve wheat adaptation in well-watered and water-limited environments.
abstract: A stay-green phenotype enables crops to retain green leaves longer after anthesis compared with senescent types, potentially improving yield. Measuring the normalized difference vegetative index (NDVI) during the whole senescence period allows quantification of component stay-green traits contributing to a stay-green phenotype. These objective and standardized traits can be compared across genotypes and environments. Traits examined include maximum NDVI near anthesis (Nmax), senescence rate (SR), a trait integrating senescence (SGint), plus time from anthesis to onset (OnS), mid-point (MidS), and near completion (EndS) of senescence. The correlation between stay-green traits and yield was studied in eight contrasting environments ranging from well watered to severely water limited. Environments were each classified into one of the four major drought environment types (ETs) previously identified for the Australian wheat cropping system. SGint, OnS, and MidS tended to have higher values in higher yielding environments for a given genotype, as well as for higher yielding genotypes within a given environment. Correlation between specific stay-green traits and yield varied with ET. In the studied population, SGint, OnS, and MidS strongly correlated with yield in three of the four ETs which included well-watered environments (0.43-0.86), but less so in environments with only moderate water-stress after anthesis (-0.03 to 0.31). In contrast, Nmax was most highly correlated with yield under moderate post-anthesis water stress (0.31-0.43). Selection for particular stay-green traits, combinations of traits, and/or molecular markers associated with the traits could enhance genetic progress toward stay-green wheats with higher, more stable yield in both well-watered and water-limited conditions.
authors.affiliation: The University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI), Leslie Research Facility, PO Box 2282, Toowoomba, QLD 4350, Australia j.christopher@uq.edu.au.
authors.forename: John T
authors.initials: JT
authors.lastname: Christopher
authors.affiliation: Department of Agriculture and Fisheries Queensland, Leslie Research Facility, PO Box 2282, Toowoomba, QLD 4350, Australia.
authors.forename: Mandy J
authors.initials: MJ
authors.lastname: Christopher
authors.affiliation: The University of Queensland, QAAFI, Hermitage Research Facility, 604 Yangan Road, Warwick, QLD 4370, Australia.
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Borrell
authors.affiliation: Department of Agriculture and Fisheries Queensland, Leslie Research Facility, PO Box 2282, Toowoomba, QLD 4350, Australia.
authors.forename: Susan
authors.initials: S
authors.lastname: Fletcher
authors.affiliation: The University of Queensland, QAAFI, 203 Tor St., Toowoomba, QLD 4350, Australia.
authors.forename: Karine
authors.initials: K
authors.lastname: Chenu
mesh_terms: D000222:Adaptation, Physiological; D000375:Aging / Q000502:physiology; D000069599:Crop Production; D003681:Dehydration / Q000503:physiopathology; D004777:Environment; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology*; D019655:Quantitative Trait, Heritable; D014908:Triticum / Q000254:growth & development / Q000502:physiology*
keywords: Crop adaptation; crop improvement; drought; genotype×environment interaction; leaf senescence; phenotyping; stay-green; water limitation; wheat.