Back to perennials: Does selection enhance tradeoffs between yield and longevity?

Abstract

Perennial plants allocate more resources belowground and have longer-lived leaves than their annual counterparts, which are the basis for the promotion of perennial crops towards a more sustainable agriculture. On the downside, perennial plants selected for high seed-yield might show tradeoffs between current reproduction and long-term reproduction or survival, raising the questions of whether this high yield can be sustained over time and whether such tradeoffs can be overcome through selection. We compared growth, reproduction and the storage of reserves, over 3 years in wild and high-yielding accessions of Physaria mendocina. We found evidence of a tradeoff between current and future reproduction, responsible for a decrease in yield with age, in selected accessions. Selected accession had 76% more accumulated seed-yield in relation to wild accessions, but they also concentrated seed-yield and had an enhanced harvest index in the first year. Wild accessions maintained seed production over time. Resources allocated to reproduction were limited for both root allocation and carbohydrate accumulation after the second year. Wild and selected accessions consumed half of their storage carbon during reproduction, but replenishment of storage organs was 60% lower in selected accession compared to wild ones. This response could be related to a lower recovery of the root system after senescence. Empirical information about the pattern of use of reserves and their relationships with the ontogenetic changes in leaf functioning and root architecture is crucial when defining new criteria of selection of perennial species, since they will influence longevity and yield stability.