Netting Impact on Fruit Characteristics in Apple - with novel Main Effects Meta-PCA analysis

In the light of climate change, netting (for hail, shade or pest protection) is on the increase with over 200 individual screened papers on the effects of netting on fruit quality. To differentiate the effects and attribute them to climate, hail net or cultivar, a meta-analysis of internationally published peer-reviewed articles after meeting strict selection criteria was conducted; this was based on seven varieties and twenty locations in the majority of fruit growing regions in a diverse range of climates on all continents, Northern and Southern hemisphere. Apple was used as a model crop to provide wide variation with its many varieties, but the results may be useful for other fruit crops. The meta analysis provided uniform results: Fruit colour was the fruit parameter most affected by netting, followed by starch breakdown (both adversely affected), and then to a much smaller extent, fruit firmness, TSS and acidity but small increase in fruit mass - all with a uniform trend, showing reasonable maintenance of fruit quality under netting over all seven varieties (Braeburn, Gala, Elstar, Jonagold, Pinova and Fuji) and locations. While Gala was most suitable, unaffected and stable in the netting effects in the PCA, Pinova was the least suitable for cultivation under netting. The late ripening cultivars Braeburn and Cripps Pink were both positively influenced by earlier ripening under netting, as desired at the end of the season. The changes in fruit quality are discussed with respect to alterations in microclimate, ecosystem and shade adaptation under the netting.