567 Effect of Temperature and Humidity on Strawberry Firmness at Two Different Sites in the Huelva Region of Spain S. Pyrotis, L. Abayomi a , D. Rees and J. Orchard Natural Resources Institute University of Greenwich Kent ME4 4TB United Kingdom Keywords: Candonga™, postharvest quality, pre-harvest conditions, climate change, strawberry Abstract The effects of ambient humidity and temperature on polytunnel grown straw- berries (Fragaria × ananassa ‘Sabrosa’-‘Candonga’™) and its impact on postharvest firmness were evaluated between March and June 2010 on two commercial sites in the Huelva region of Spain. Mean temperatures recorded during growth and development were between 11-21°C. Humidity varied between 56-81% and 60-86%, firmness was in the range of 3.2-9.9 N and 5.4-10.4 N for Lepe and Moguer growing sites, respectively. A significant (r=0.87, P<0.05) negative impact of growing temperature on firmness was observed. Increased temperatures of 1°C were found to decrease strawberry firmness by 0.5 and 0.7 N at each site. However, humidity levels greater than 75%, caused by high levels of precipitation, reversed that trend. INTRODUCTION Strawberries are one of the most popular berry fruits. Global production, including the UK, has increased over recent years (FAOSTAT, 2010). This is due not only to their distinct flavor and aroma, but also because of their nutritional value (Törrönen and Määttä, 2002). One of factors detrimental to strawberry quality is lack of firmness. Levels of UV radiation (Ordidge et al., 2008), humidity (Lieten, 2002), carbon dioxide (Harker et al., 2000), including cultural practices, such as fertilization (R. Vogels, 2010, pers. commun.) as well as postharvest conditions (Nunes et al., 2003; Shafiee et al., 2010) have been found to influence strawberry firmness. Firmness is a key quality attribute desired by marketers and also impacts the textural property experienced when eating the fruit, however, this can be affected by poor handling during harvesting and subsequent marketing. To counteract susceptibility to bruising, efforts have been made both in understanding and manipulating this aspect of strawberry physiology (Burkhurt, 1943; Manning, 1998). There are a number of factors associated with fruit firmness some of which include enzyme activity. Pectate lyase (Jimenez-Bermudez, 2002; Figueroa et al., 2008), polygalacturonase and pectin methylesterase, have been found to play a regulatory role in deterioration of strawberry firmness (Fraeye, 2009). A three-year study is presently underway to gain better understanding of the effects of pre-harvest weather conditions and their extremes on the postharvest quality of a major strawberry cultivar ‘Candonga’™, exported from Spain into the UK. Preliminary results are presented herein. MATERIALS AND METHODS Strawberry fruits of ‘Candonga’™ were grown using standard polytunnel practices at two commercial production sites, Lepe and Moguer in Huelva, Spain. Levels of precipitation (mm/day), mean temperature (°C) and average relative humidity (%RH) were recorded from two weather stations ~3 km from the production sites, at the field sites and within the polytunnels (using Tinytag Plus and Tinytalk data loggers) at Lepe and Moguer. Ripe fruit were harvested, packed into 400 g punnets and cooled to remove field heat. Fruit was then transported to the UK by road over 2 days at 3°C and subsequently stored under a l.abayomi@greenwich.ac.uk Proc. XXVIII th IHC – International Berry Symposium Eds.: B. Mezzetti and P. Brás de Oliveira Acta Hort. 926, ISHS 2012