The three C's — competition, coexistence and coevolution — and their impact on the breeding of forage crop mixtures

Abstract

The role of competition, coexistence and co-evolution in the formation of plant communities is discussed, particularly in relation to the breeding of improved grass/legume mixtures. Competition occurs whenever the demand for a particular resource outstrips supply, with the pressures generated within a species expected to exceed those between species. These pressures must be withstood before populations can coexist within a community. This is accomplished by a process of niche diversification, arising from temporal or spatial differences between the populations, that enables them to draw on resources not readily available to their competitors. Coexistence is crucial to the success of any breeding programme designed to raise the productivity of grass/ legume pastures, because it enables components to adapt not only to the environment which they share, but also to each other. A strategy that improves the "general ecological combining ability" of one or both components by a process of recurrent or reciprocal recurrent unilateral adaptation may prove successful, particularly if existing niche differences are increased thereby. Although both processes may give rise to populations which have apparently coevolved, only those resulting from reciprocal recurrent selection will meet the criteria of specificity and reciprocity.

Promising options for improving performance and proanthocyanidins of the forage legume sainfoin (Onobrychis viciifolia Scop.)

“…This result stresses the importance of 187 cultivars with increased performance, especially with increased competitive ability (against weeds 188 and the mixture partner). Strategies to achieve this include breeding for high yields in general 189 (independent of monoculture or mixture) and breeding for high performance derived from the 190 adaptation to specific mixture partners (Hill 1990 Protein precipitation in the rumen also reduces fermentation gas accumulation and the formation of 232 stable foams, which both lead to bloat and may cause animal death (Sottie 2014;Wang et al 2012). 233…”

Inbred Development

“…The plant breeding strategy for cultivar (or crop) mixtures differs from that aiming to improve and select superior lines, hybrids or clones in pure stands. Coexistence, competition, and coevolution with any pathogen(s), pest(s), and other plants affect a plant breeding program aiming raising productivity in mixtures (Hill 1990). Demand for a particular resource outstrips supply under competition because the pressures generated within a species exceed those between species.…”

Intergenotypic interactions in plant mixtures

“…John Hill (1990) has well articulated the problem before us when he says that `coexistence is crucial to the success of any breeding programme designed to raise the productivity of grass/legume pastures . .…”

“…First, is a straightforward systematic search for good combinations of species or cultivars that are high yielding . Often this has lead to attempts to identify characteristics, and to their subsequent inclusion in breeding programs, of the components of the high-yielding mixtures (Hill & Michaelson-Yeates, 1987 ;Hill, 1990 ;Collins & Rhodes, 1990 ;Annicchiarico & Piano, 1994) . Conventional variety improvement programs endeavor to identify superior i .e .…”