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Quantification of the genetic variation for phosphorus use efficiency in Brassica napus - WQ0119

Description
UK agriculture contributes over 12,000 tonnes of phosphorus (P) to surface waters annually (White & Hammond, 2006). With crop production relying on large inputs of P fertilisers, and most crops recovering less than 10% of the P fertiliser applied, the losses of P to surface waters from arable production accounts for 1,259 tonnes of P per annum. This mainly results from excess soluble inorganic phosphate (Pi) fertilisers added to crops, which are leached or eroded from the soil into surface waters. In addition, the processing of arable crops into feeds for animal production results in secondary losses of P to the environment via the animals. These P losses can result in nutrient enrichment of adjacent environments, with a consequent loss of habitats and decline in biodiversity. There are also financial costs involved in the use of P fertilisers, which will increase in the future as a result of i) unsustainable production of P fertilisers due to the depletion of cheaply available non-renewable reserves of phosphate rock, which are only predicted to last 50-100 years, ii) unstable energy prices, which will impact on the mining and transport of phosphate rocks, and iii) potential introduction of financial instruments associated with meeting climate change, the EU water framework directive and other soil management targets. Thus, there are both environmental and financial benefits in reducing our reliance on inorganic P fertilisers.

Our models of crop P requirements (Greenwood et al., 2001) and soil P dynamics (Karpinets et al., 2004) show that several UK crops could be grown without substantial P fertilisation (Greenwood et al., 2005). These crops include the arable rotation crops oilseed rape (OSR; Brassica napus) and wheat (Triticum aestivum). Thus, in the UK, P fertilisation in the OSR/wheat rotation should only be used to maintain soil P status. To maintain soil P status, the amount of inorganic Pi fertiliser applied should equal the P losses to the environment plus the P removed by the crop. In the UK, OSR currently occupies 11% of arable land and consumes over 7% of inorganic P fertilisers used in the UK. The area of OSR currently grown in the UK has increased nearly 30% in the last 5 years (Defra Statistics 2006, http://statistics.defra.gov.uk/esg/) and is set to continue increasing as demand for bio-diesel and bio-plastic production grows. During the 2004/2005 season, the OSR crop in UK received over 21,000 tonnes of P fertilisers (BSFP, 2006). The amount P in crop material harvested from OSR is the highest of all crops listed in RB209 (15.1 kg per tonne of fresh material; Potash Development Association). Thus, growing OSR varieties with higher tissue phosphate use efficiency (PUE = yield/tissue P concentration) will reduce the P removed by crops, thereby reducing P fertiliser requirements and losses to the local environment. In B. oleracea genotypes (Brassica C genome), PUE varies by 25-fold when plants are grown with sufficient P (Defra Project HH3501SFV). Comparable variation in PUE amongst varieties of OSR is anticipated. This project will therefore provide strategic information for developing novel strategies to reduce P inputs to the OSR / wheat rotation with the potential to reduce P loads to UK surface waters.

The general objective is to address the issue of diffuse P pollution affecting water quality, by determining the scope for developing OSR varieties with improved PUE. This will involve characterising the genetic variation for PUE in B. napus and elucidating regions of the genome that contribute to this trait, with the aim of identifying current commercial varieties and accessions with high PUE and informing future strategies for breeding new OSR varieties with improved P use efficiency.

This research will generate strategic information that will directly benefit Defra, industry and the scientific community. This will include information on the PUE of commercial OSR varieties with the ability to match varieties to their nutritional environment, and regions of the B. napus genome that impact on PUE traits. This will demonstrate the potential for breeding OSR varieties with improved PUE and provide knowledge to develop molecular markers associated with improved PUE and explicit strategies for breeding programmes. The dissemination of information through the scientific literature will benefit the international scientific community by advancing the understanding of plant mineral nutrition, and the genetics of an important model crop, at both the applied and fundamental levels. The development of OSR varieties with improved PUE would reduce the use of P fertilisers in arable agriculture in the UK. The adoption of such varieties may ultimately lower production costs, and reduce P pollution to, and enhance biodiversity in, UK waters.

This project will contribute to Defra`s policy objective to minimise the adverse impacts of UK agriculture on water quality. It will deliver to the specific scientific objective in WQ01, to mitigate transportation of pollutants into watercourses with specific emphasis on the management of fertiliser nutrient additions to mitigate losses to water systems and the development of novel germplasm for more efficient use of nutrients in the field and by the animals that consume them.

Objective
7. (b) Objectives

The General Objective is to address the issue of diffuse phosphorus (P) pollution affecting water quality, by determining the scope for developing oilseed rape (OSR) varieties with improved phosphorus use efficiency (PUE). This will involve characterising the genetic variation for PUE in Brassica napus and elucidating regions of the genome that contribute to this trait, with the aim of identifying current commercial varieties and accessions with high P use efficiency and informing future strategies for breeding new OSR varieties with improved P use efficiency.

Objective 01 To determine the extent of genetic variation in PUE and P response of current commercial OSR varieties under field conditions (48 months).

Objective 02 To determine assay conditions for characterising the genetic variation in PUE and P response of OSR to external soil P concentrations under glasshouse conditions (12 months).

Objective 03 To characterise the genetic variation in PUE of Brassica napus (AC genome) using reference experimental materials and commercial OSR varieties grown under glasshouse conditions. The contribution of previously identified candidate C-genome and Arabidopsis loci on PUE and P response traits will be determined using comparative genomics approaches (48 months).

Added to project in June 2008

Objective 03a To use a genetical genomics approach to identify expression QTL (eQTL) for PUE in A-genome Brassica (24 months).

Objective 04 To confirm results from genetic screens under field conditions using a subset of lines from Objective 03 (48 months).

Objective 05 To monitor the progress of the project at regular intervals and ensure appropriate transfer of knowledge gained during the project (48 months).
Time-Scale and Cost
From: 2007

To: 2011

Cost: £554,232
Contractor / Funded Organisations
Warwick - HRI
Keywords
Allocated - WHRI              
Sustainable Farming and Food Science              
Water Quality              
Water Quality and Use