The use of conjoint analysis to determine the relative importance of specific traits as selection criteria for the improvement of perennial pasture species in Australia

Despite the large number of active programs breeding improved forage plants, relatively little is known about the weightings that breeders consciously or subconsciously give to specific traits when selecting individual plants or that agronomists and producers use when assessing the relative merits of contrasting cultivars. This is in contrast to most modern animal breeding programs where the relative merits of novel genetics may be assessed against an index-based breeding objective. These technologies have not been widely used in crop or forage plant breeding but their use in forest tree breeding is relatively common. We have assessed the usefulness of discrete choice experiment techniques in the development of weightings for specific traits in forage plant improvement based on the views of an expert panel (plant breeders and non-breeders - agronomists, nutritionists, senior managers in breeding companies and consultants) asked to consider the requirements in four species (white clover, lucerne, perennial ryegrass and tall fescue). The results indicate that criteria related to abiotic stress tolerance, adaptation or the costs of pasture (root growth, drought tolerance, persistence, resistance to invertebrate pests, tolerance of hostile soil conditions) were deemed to be particularly important for white clover, while the highest-rated criteria for lucerne were not dissimilar, being tolerance of hostile soil conditions, persistence and tolerance of transient water-logging. For perennial ryegrass, three of the five highest-weighted criteria (drought tolerance, root growth, rate of recovery of pasture after water) are related to yield in environments where too much or too little water is a problem, highlighting the importance that the experts placed on the ability of the plant to withstand this important abiotic stress. For tall fescue, the highest-rated criteria were seedling vigour, drought tolerance, and persistence. Overall the preference weightings tended to reflect the perceived limitations of the various species, such as the priority of seedling vigour in tall fescue. This focus on the importance of abiotic stress is especially interesting as previous attempts to identify priorities have focused on the forage quality traits rather than analysing their importance relative to traits related to herbage yield or stress tolerance. This study highlights the importance of further work to help determine the focus of breeding objectives and selection criteria for different pasture species across production systems.