The 12-year journey to breeding a leading grass variety

Monday 02.12.2019 , events , news

Plant breeder Sarah Palmer gives a glimpse into the 12-year process of developing a new grass variety which involves continually selecting families  better than their predecessors.

This enables the Institute of Biological, Environmental and Rural Sciences at Aberystwyth University (IBERS) in Wales, to keep pushing through the ceiling for quality and yield in grass varieties.

Sarah describes how the key differentiators used at IBERS differ to most other grass breeding programmes and have led to the dominance of Aber varieties on the Irish Recommended List and Teagasc Pasture Profit Index (PPI).

For over thirty years the grass breeding programme at IBERS has focused on both quality (DMD) and yield among other traits. Many other grass breeding programmes only began to look at quality much more recently. This has helped ensure the quality of varieties being produced at IBERS is ahead of other grass varieties available in Ireland.
Leading grass varieties with the “Aber” prefix come from the IBERS grass breeding programme including AberGain, AberChoice and AberClyde to name but a few. From start to finish, it takes 12 years to develop a variety worthy of entering the marketplace, with stringent selection criteria; sometimes resulting in years of trials being scrapped, so the cycle can start over again with applied findings.

“In the first year, we sow 10,000 seedlings which are whittled down over the years to one commercial variety based on an elite combination of specific traits. This includes yield, persistency, quality, disease resistance, distinctness, uniformity, stability and seed production,” says Sarah. “It’s a very long process and requires a bit of luck mixed with a lot of science.”

Below, is a walk through the multi-year process of breeding a diploid perennial ryegrass.

Sarah Palmer, Forage Grass Breeder, Institute of Biological, Environmental and Rural Sciences at Aberystwyth University (IBERS)

Year 1 – 10K Progeny Sown

The process of developing a single variety starts by hand sowing 10,000 progeny seeds from 10 families to be narrowed down to the best four. “Only one seedling can be raised in each well of a tray. It’s fiddly, time consuming work, but essential,” explains Sarah.

Year 1 to 2 – 4K Progeny Selected

In late summer, 4,000 of the original 10,000 seedlings are transplanted into a field nursery. Rows comprise of plants belonging to the same family. Due to the more natural environment of a field nursery, the heading and flowering data is more reliable which contributes to the next key criterion for selection at this stage.

“Transplanting is again done by hand and is the most back-breaking part of the grass breeding process – it’s a job we save for a warm sunny day and everyone chips in to help. The next challenge is keeping the birds, rabbits and deer off – they know quality and home in on the most digestible plants for a snack!” says Sarah.

Year 2 – 400 Individual Plants Selected

In mid-summer, 400 plants are transferred from the field into pots and polycrossed in isolation chambers. Once the seed heads have filled, a month or so later, the seed from each plant is harvested separately. Grasses are wind-pollinated, so the filtration and positive air pressure of the isolation chambers mitigate the risk of cross contamination from wild pollen. This insurance of varietal purity is unique to the IBERS’ grass breeding programme; one that Sarah attributes to the success of varieties seen on the PPI above other breeders.

Sarah adds: “This is the busiest time of year for me as there is time pressure to get the seed threshed, cleaned and ready for sowing again – and the seed is too precious to me to trust this job to anyone else.”

Year 2 to 5 – 100 Half-Sib Plot Evaluation

Progeny of the 100 highest seed yielding plants are sown in replicated ‘mini-sward’ plots and assessed for yield, quality and persistency over a period of three and a half years.

“I spend many hours pawing over this data to ensure I choose the very best lines from which to make a new variety,” comments Sarah.
According to Sarah, “studies in the 1970s revealed that looking at how perennial ryegrasses performed in swards was far more accurate than simply looking at individual plant performance.” Sarah explained how this research and method was then adopted at IBERS and is considered a step that has led to the success of Aber varieties.

Meanwhile, the corresponding ‘mother plants’ from the breeding population are cloned, trimmed by hand and combined to make a new variety. It takes an additional year in isolation chambers to produce the seed.
“Our population improvement method of grass breeding is like managing a pedigree herd. By continually selecting families which better their predecessors we are able to keep pushing through the ceiling for quality and yield in our varieties; something that has shone through on the Irish PPI. This sets the bar for ourselves and also the rest of the industry.”

Year 4 to 9 – Four variety composition and evaluation

Candidate varieties are evaluated in test plots at IBERS for the following three and a half years to decide which, if any, are worthy of being entered into national list trials conducted by the Department of Agriculture, Food and the Marine (DAFM) in Ireland or the National Institute of Agricultural Botany (NIAB) in the UK.

Year 7 to 12 – 1 Commercial Variety

Any grass variety developed by IBERS must make it onto the DAFM Irish Grass and Clover Recommended List before it is made available to the Irish market. To make the cut, a variety is independently trialled by the DAFM for four years to test grass quality, persistence, seasonal and total yield; under both a simulated grazing and simulated silage protocol. The process is very competitive and only new varieties offering significant improvement will be added to this list. These varieties will receive a value on the PPI, providing farmers with additional information on the expected value of a variety.

Meeting the needs of Irish Farmers

Since the PPI was first released in 2015, Aber varieties have continually topped all categories (late tetraploid, late diploid, intermediate tetraploid and intermediate diploid) in terms of total PPI value (€ per ha/year). In 2019, AberGain is the leading late tetraploid, AberChoice leads the late diploids, while AberClyde and AberMagic, are the leading intermediate tetraploid and diploid varieties, respectively.

Sarah concluded that all of the steps taken above and the selection pressure enforced at IBERS for key traits such as seasonal yield, quality and persistency means that key performance indicators are recognized sooner rather than later. This ensures the best chance of breeding a variety for these selected traits and breeding the top varieties on the PPI.

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