In crop breeding, choosing specific characteristics traditionally eliminates plants that fail to meet minimum standards for those traits. But this can make it difficult for breeders to develop crops which meet the standards for multiple characteristics at the same time.
Kiwi scientists have developed a simulation model to compare different strategies for managing priorities and tradeoffs in crop breeding programmes. Their results found that selecting plants based on the economic value of a combination of characteristics was more effective than using minimum standards on a trait-by-trait basis.
This could have important implications for crop improvement efforts around the world.
The results have been reported in a media release from AbacusBio Ltd, headed Genetic selection methods for crop breeding programmes – which is better?
The statement says AbacusBio consultants have been working on a study looking at how selection in multi-trait genetic improvement programmes can help plant and crop breeders better maximise efficiency and economic benefits.
Crop breeding programmes face an ongoing dilemma of how to prioritise their selection effort across many attributes and genetic traits of the crop they are working with. The selection of ryegrasses for grazing dairy cattle in New Zealand, for example, carries this same dilemma.
Independent culling and the use of a selection index are two commonly used methods in plant breeding programmes for improving cultivars. Independent culling involves establishing minimum standards for each trait and only selecting individuals that meet all these standards.
On the other hand, the selection index method involves selection for all traits simultaneously based on a combination of individual traits weighted by their importance for the breeding objective. This is analogous to their use in stock markets where indexes are used to weight together the prices of different stocks to determine how an overall market is performing.
The team including consultants Dr Peter Amer and Dr Tim Byrne have simulated a crop breeding programme, where clones of the selected variety are used as the commercial product, for 20 cycles of selection using either independent culling or an economic selection index with two unfavourably correlated traits under selection.
“Traits are often unfavourably correlated with each other,” Peter explains. “For example, crop yield and product quality are often unfavourably correlated.”
“When traits are unfavourably correlated, selection for one trait causes an undesired economic response in the other trait, which makes breeding to improve multiple traits simultaneously challenging.”
The results have shown that selecting using an index – compared to using individual culling criteria – produces at least equal, but more commonly higher genetic gains for overall performance, compared with strategies, where candidate parent plants are eliminated based on minimum performance for one attribute at a time.
To obtain higher genetic gains, accurately assessing the economic importance of the traits is essential. This feeds valuable information about the value of genetic gains into the whole process of designing and optimising the crop breeding programme.
AbacusBio is a world leader in advancing genetic improvement programmes through science and technology.
Since its merger with New Zealand plant breeding company Gemnetics, its team of consultants based in both New Zealand and the UK have worked with international groups to undertake a range of plant breeding projects including Cassava in Nigeria and Uganda (with Cornell University and the International Institute of Tropical Agriculture), sweet potato in Uganda (with the International Potato Center), and rice in Tanzania (with the International Rice Research Institute).
“This is an exciting growth area for our business,” Tim says.
“We have more than 20 years of experience working on trait prioritisation for livestock industries around the world. This has left us in an excellent position to inform a whole new approach to plant breeding.”