Patterns of Morphophysiological Diversity and Their Implications for Selection of Grazing-Tolerant Lucerne

Abstract

Grazing-tolerant lucerne (Medicago sativa L.) has gained popularity for exploitation in pure stands or as a component of legume-grass mixtures in grazing systems of temperate regions. A challenge for breeders targeting mild-winter regions, such as Mediterranean Europe, is the selection of grazing-tolerant germplasm with low cold-season dormancy, because grazing-tolerant materials tend to possess marked autumn dormancy. It is unclear whether the relationship of persistence under grazing with autumn dormancy and low-growing habit is genetically based. In this study, four biparental populations of lucerne were evaluated for a set of morphophysiological traits and tolerance to heavily-stocked continuous sheep grazing. The populations originated from crosses between prostrate, dormant, grazing-tolerant germplasm and erect, non-dormant, little tolerant germplasm. The work aimed at exploring the patterns of morphophysiological variation in the populations, and assessing the relationships of plant morphophysiology with grazing tolerance. Great variation was found for all traits both among populations (except for grazing tolerance) and among F₁ progenies within populations. The correlations between survival after grazing and morphophysiological traits indicated better tolerance of genotypes with more prostrate habit and larger crown. The undesired correlation between grazing tolerance and cold-season dormancy did not occur consistently in all populations. The results can help understand to which extent different useful traits can be combined into a grazing-tolerant variety targeted to mild-winter environments.