Effect of Genetics and Climate on Apple Sugars and Organic Acids Profiles

Apple is widely cultivated in temperate regions. The beneficial properties of apple for preventing several illnesses are widely known. Nevertheless, qualitative variables such as sweetness or sourness may influence consumer satisfaction; they are critical factors for fruit consumption and essential in plant breeding. In the present work, 155 apple accessions were assessed during five consecutive years (2014-2018). Four individual sugars and seven organic acids were analysed by HPLC. A mixed-effects model was fitted with accessions and the years' climatic features as independent variables. A cluster analysis was applied on the mixed-effects model coefficients. Four groups were considered as optimum. Genetics seemed to have the strongest effect and showed clear differences between accession groups, while climate effects were strong only for certain compounds and had a more horizontal behaviour equally affecting the different accession groups. In fact, non-Spanish cultivars tended to concentrate, while autochthone accessions had a much wider spread. Individual sugars and acids concentrations correlated negatively with precipitation and positively with temperature range and solar radiation in all accession groups. The geographic region where the orchard is grown is thus very important in the resulting metabolites profiles. Moreover, apple genetics would also play a decisive role as highlighted in the cluster analysis.

Automated summary

This study evaluated 155 apple samples over a five-year period, analyzing four individual sugars and seven organic acids and studying the influence of genetics and climate on apple characteristics. The results showed that genetics had the strongest effect, with clear differences between different genetic groups, while climate had a more equal effect on different genetic groups for certain compounds. Precipitation, temperature range, and solar radiation were found to be negatively and positively correlated with the concentrations of sugars and acids. The study also highlighted the importance of the geographic region where the orchard is located.