Breeding grass and white clover for improved phosphorus use

The study found variances in phosphorus use efficiency of different forage crops that was due to the plants genetics.  DNA mapping of both perennial ryegrass and white clover lines allowed those plants which performed well in low phosphorus soils to be identified.

The second part of the study investigated the phosphorus balance of livestock fed forage crops with high phosphorus use efficiency.  The results showed that the nutritional qualities of these low foliar phosphorus content lines had no detrimental effect on phosphorus digestibility or phosphorus balance in the ruminant animal.

This study has shown that selection for forage crops with improved phosphorus use efficiency is feasible and could lead to the production of commercial varieties being available, provided there are no detrimental effects on agronomic characteristics.

The Problem:

There is strong evidence for a major contribution from agriculture to diffuse water pollution problems, especially those related to nutrient enrichment (eutrophication).

Phosphorus inputs in fertilisers and animal feeds have been greater than phosphorus outputs in agricultural products by about 15 kg P/ha/year, with crops typically recovering less than 10% of applied fertiliser P. These excess inputs of phosphorus have lead to well documented problems with respect to water quality and the maintenance of critical ecosystem processes.

Project Aims:

1. Increase P acquisition, utilisation and retention efficiencies by at least 10% in elite germplasm
2. Improve variety performance on soils of low or moderate P status without further applications of P.
3. Optimise phosphorus use efficiency in ruminants when fed forage legumes.

Deliverables: 

• Production of varieties of PRG and WC which will show significant improvements over current varieties in terms of PUE over a range of soil P conditions
• Increased understanding of the genetic control of key traits relating to PUE
• Development of potential white clover varieties for use in low P status soils
• Determination of the suitability of white clover lines grown under low P conditions for ruminant livestock systems.

Approach:

• Identification of QTLs for components of phosphorus use efficiencies (PUE)
• Transfer to elite breeding lines and validation
• Direct selection of white clover and PRG on soils of moderate P status with and without addition of P fertiliser
• Seed production and field testing of potential new varieties