title: Genotypic Variation in Grain P Loading across Diverse Rice Growing Environments and Implications for Field P Balances.
abstract: More than 60% of phosphorus (P) taken up by rice (Oryzaspp.) is accumulated in the grains at harvest and hence exported from fields, leading to a continuous removal of P. If P removed from fields is not replaced by P inputs then soil P stocks decline, with consequences for subsequent crops. Breeding rice genotypes with a low concentration of P in the grains could be a strategy to reduce maintenance fertilizer needs and slow soil P depletion in low input systems. This study aimed to assess variation in grain P concentrations among rice genotypes across diverse environments and evaluate the implications for field P balances at various grain yield levels. Multi-location screening experiments were conducted at different sites across Africa and Asia and yield components and grain P concentrations were determined at harvest. Genotypic variation in grain P concentration was evaluated while considering differences in P supply and grain yield using cluster analysis to group environments and boundary line analysis to determine minimum grain P concentrations at various yield levels. Average grain P concentrations across genotypes varied almost 3-fold among environments, from 1.4 to 3.9 mg g-1. Minimum grain P concentrations associated with grain yields of 150, 300, and 500 g m-2varied between 1.2 and 1.7, 1.3 and 1.8, and 1.7 and 2.2 mg g-1among genotypes respectively. Two genotypes, Santhi Sufaid and DJ123, were identified as potential donors for breeding for low grain P concentration. Improvements in P balances that could be achieved by exploiting this genotypic variation are in the range of less than 0.10 g P m-2(1 kg P ha-1) in low yielding systems, and 0.15-0.50 g P m-2(1.5-5.0 kg P ha-1) in higher yielding systems. Improved crop management and alternative breeding approaches may be required to achieve larger reductions in grain P concentrations in rice.
authors.affiliation: Africa Rice Center Dar es Salaam, Tanzania.
authors.forename: Elke
authors.initials: E
authors.lastname: Vandamme
authors.affiliation: Crop Production and Environment Division, Japan International Research Centre for Agricultural Science Tsukuba, Japan.
authors.forename: Matthias
authors.initials: M
authors.lastname: Wissuwa
authors.affiliation: Southern Cross Plant Science, Southern Cross UniversityLismore, NSW, Australia; Southern Cross GeoScience, Southern Cross UniversityLismore, NSW, Australia.
authors.forename: Terry
authors.initials: T
authors.lastname: Rose
authors.affiliation: Africa Rice Center Bouaké, Côte d'Ivoire.
authors.forename: Ibnou
authors.initials: I
authors.lastname: Dieng
authors.affiliation: Africa Rice Center Dar es Salaam, Tanzania.
authors.forename: Khady N
authors.initials: KN
authors.lastname: Drame
authors.affiliation: Africa Rice Center Ibadan, Nigeria.
authors.forename: Mamadou
authors.initials: M
authors.lastname: Fofana
authors.affiliation: Africa Rice Center Dar es Salaam, Tanzania.
authors.forename: Kalimuthu
authors.initials: K
authors.lastname: Senthilkumar
authors.affiliation: Africa Rice Center Ibadan, Nigeria.
authors.forename: Ramaiah
authors.initials: R
authors.lastname: Venuprasad
authors.affiliation: National Agricultural Research Institute Brikama, Gambia.
authors.forename: Demba
authors.initials: D
authors.lastname: Jallow
authors.affiliation: Programme Riz et Riziculture, CNRST/INERA Bobo Dioulasso, Burkina Faso.
authors.forename: Zacharie
authors.initials: Z
authors.lastname: Segda
authors.affiliation: Department of Crop Science, Faculty of Agriculture, University of Peradeniya Peradeniya, Sri Lanka.
authors.forename: Lalith
authors.initials: L
authors.lastname: Suriyagoda
authors.affiliation: Rice Research and Development Institute Ibbagamuwa, Sri Lanka.
authors.forename: Dinarathna
authors.initials: D
authors.lastname: Sirisena
authors.affiliation: Crop and Environmental Sciences Division, International Rice Research Institute Metro Manila, Philippines.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Kato
authors.affiliation: Africa Rice Center Cotonou, Benin.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Saito
keywords: P cycling; P removal; P utilization efficiency; grain P concentration; rice genotypes