Abstract/Summary

Future climate change will change the UK’s top fruit production environment further. The impact of three modified temperature environments (Ambient, +2°C, and +4°C) on annual apple (Malus domestica Borkh.) production was investigated within a purpose-built field research facility in Kent. Fruit production showed bienniality: high in 2017, -19, -21; low in 2018, -20, -22, which was greatest in ‘Fuji’. Analysis of data from fruit production over six years (2017-22) revealed unique temperature production responses across a genetically-diverse pool of 20 apple cultivars. A sequence of events triggered by seasonal temperature variables (Tmean, Tmax, and Tminmaxdiff) and crop load were primarily responsible for variation in yield and fruit quality. Temperature variables and crop load were negatively associated with floral bud production (p<0.05) in the subsequent season, which enhanced alternate bearing in the two warmer environments, causing an overall reduction in mean fruit yield across many cultivars (p<0.05). Fruit yield and fruit number per tree, sunlight, and precipitation were subsequently identified to affect fruit quality (firmness, soluble solids content (SSC), red colour coverage (RCC), dry matter content (DMC), and fruit weight). Warmer temperature environments had a positive effect on SSC and DMC, a negative effect on RCC, and a mixed effect on firmness (p<0.05) across most cultivars. These alterations in fruit quality had a minor effect on the subsequent storability of ‘Gala’ fruit. Differences in firmness and SSC were identified (p<0.05) amongst different treatments. However, reductions in RCC (p<0.05) substantially reduced the marketability of fruit from warmer environments. Warmer temperatures will influence many aspects of UK apple production, and cultivar selection will be key in mitigating negative effects of increased seasonal temperature. Crop management practices will also need to adapt to enhance resilience against lower winter chill, earlier fruit development, increased tree vegetative growth, and increased pest prevalence.