Navigating trade-offs between increasing yield and perenniality

Perennial crops offer promise to maintain or enhance food security, while also reducing the environmental footprint of agricultural systems for improved system sustainability and ecosystem services. Progress in developing perennial crops has generally been slow, due to the need to overcome evolutionary and eco-physiological bottlenecks that limit yield potential and broader adoption. Nevertheless, species differ in the extent of these barriers, and in the approaches used to address them from a breeding and genetic perspective. As significant progress is now being made, further questions arise about the limits to crop improvement under a perennial growth habit. Must the performance of a perennial crop be limited relative to its annual counterpart, due to the need for the perennial to invest in regenerative structures. Conversely, the annual can devote resources towards yield without having to set aside resources for the next generation, other than to the seed itself. This paper examines data on dry matter production and allocation by perennial and annual counterparts in relation to their resource use. In particular, attention is drawn to changes in resource availability and capture under perennial Vs annual systems. Whether the perennial is more or less efficient in resource conversion or allocation is only part of the question, if the perennial were able to access additional resources not available to the annual. To address these complex questions properly requires long-term data, so systems performance and resource balance can be considered over crop cycles, and the merits and disadvantages of each system properly examined. This paper considers currently-available evidence to address these questions, and what is needed to show the way forward.