Genetic improvement of perennial ryegrass and red clover to increase nitrogen use efficiency and reduce N losses from pastures and silo

Project number:                    74302

Lead contractors:                 IBERS

Partners:                                   LINK: LK0686

DairyCo, EBLEX, HCC, QMS, LMC, BGS

Start & end date:                   April 2008 to March 2013

Actual end date:                    April 2013

 

The Problem:

Diffuse nitrogen (N) pollution of watercourses is a major water quality issue in the UK and increasingly the focus of EU legislation. Thus, reducing N pollution from livestock agriculture, within the context of profitable farming is an important component of greater sustainability of food production.

 

Project Aims:

  • Develop new varieties of perennial ryegrass (PRG)with nitrogen use efficiencies (NUE) 10-15% higher than in current varieties
  • Reduce N leaching losses from red clover by deployment of new varieties
  • Develop new red clover varieties with a 15% enhancement in polyphenol oxidase (PPO) activity and use a digestion study in steers to quantify the impact of differences in PPO activity on N losses to the environment.

 

Approach:

Forage breeding techniques will be used to identify new QTLs for NUE.  Elite populations of forages will be established combining NUE QTL and other desirable agronomic traits.  Seed will be produced from subsequent potential varieties to undergo field testing.

 

Results:

Enhancing nitrogen use efficiency (NUE) in perennial ryegrass by 10%

Seeds of five PRG populations with N uptake and N use efficiency QTLs, in an AberMagic background, were harvested for validating their effects under flowing solution culture conditions and under field conditions.  Their detailed evaluation under field conditions was carried out, and varieties with potential for national list testing developed.

 

Selection of red clover lines for reduced N leaching

Agronomic performance of a low leaching line red clover variety was evaluated in a field experiment alongside control varieties as well as 6 new selection lines. The plots were sown with perennial ryegrass (AberMagic) and a mixture of perennial ryegrass (AberMagic) and hybrid ryegrass (AberEcho) with 4 replicates. Data was collected after the end of the LINK project.  This additional field data may enable submission of the most promising variety to national list testing.

 

Develop new red clover varieties with enhanced PPO activity

Combined analysis of agronomic performance as well as PPO activity from field and glasshouse grown red clover plants was carried out. This resulted in 4 groups of plants, a low and high PPO activity group from both Pawera and Aa4494. Each of the four groups of plants were polycrossed during summer 2012 in isolation chambers using bumblebees. Field plots of these lines were sown in 2013 (after completion of the project) prior to entry into official trials.

 

Digestion experiments on the potential of high PPO RC silage to improve N use efficiency and polyunsaturated fatty acid duodenal flow in cattle

Two experiments were carried out to invesitage the impact of red clover silage with different levels of polyphenol oxidase activity on nitrogen use efficiency and protection of polyunsaturated fatty acids across the rumen against a control perennial ryegrass silage.  Both experiments showed a significant difference between perennial ryegrass silage and red clover silage in terms of C18 and N protection across the rumen. However, the first experiment showed little difference between high or low PPO red clover silage when levels of protein bound-phenol (measure of oxidation activity; PBP) were comparable. In contrast, the second experiment showed a significant improvement in N use efficiency when the differences in PBP were larger for the high PPO RC silage.

The experiments showed the potential of PPO’s substrate (di-phenols) to autoxidise during wilting and thus protect protein through the formation of protein-bound phenol. This highlights the importance of not only selecting for enzyme but also substrate. Both experiments failed to find any negative impact on methionine bioavailability which has been previously reported with PPO protected red clover silage protein.

 

Planned activity:

  • General messages about variety selection and new variety availability with novel traits is included in grassland management KT      events and material.
  • Press releases have been completed as have various KT articles.  Messages were communicated at Grass and Muck event in 2012 and further  activity is planned for the Grass and Muck event in 2014 (biennial event).
  • A number of academic publications have been published in international journals from this work.