Differences in zonal starch are most likely related to starch accumulation during fruit development, rather than differences in rates of starch degradation during ripening

Patterns of starch hydrolysis in stem, equatorial, and calyx zones of ?Honeycrisp? and ?Empire? apples (Malus sylvestris(L.) Mill var.domestica(Borkh.) Mansf.) during maturation and ripening, and in ?Gala? apples in response to propylene or 1-methylcyclopropene(1-MCP) treatments after harvest, were studied. Differences in zonal starch concentrations were found for ?Empire? and ?Gala? fruits, butnot for ?Honeycrisp?. During maturation and ripening of ?Empire?, the concentration of starch was highest in the calyx end and lowest inthe stem region. Differences in rates of starch hydrolysis among zones were not detected. ?Honeycrisp? and ?Empire? had the highest concentration of sorbitol in the calyx region, whereas it was highest in the stem-end region in ?Gala?. The distribution differences ofglucose, fructose, and sucrose were similar in all three cultivars; higher fructose and glucose concentrations in the stem region, and higher sucrose concentrations in the calyx end of the fruit. Postharvest treatment of ?Gala? with propylene did not affect the internalethylene concentration of the fruit but 1-MCP markedly inhibited it. Starch concentrations were highest in the calyx end but gradientsof starch among zones were not changed by postharvest treatment. The rate of hydrolysis was slowed by 1-MCP treatment, but was unaffected by propylene. Postharvest treatments influenced sorbitol, glucose, and fructose concentrations. Patterns of starch concentration among the zones did not confirm differences in ripening, but reflected its uneven distribution throughout the fruit during development. Therefore, measured differences in zonal starch are most likely related to starch accumulation during fruit development, rather than differences in rates of starch degradation during ripening. SourcesVariations in zonal fruit starch concentrations of apples ? adevelopmental phenomenon or an indication of ripening?Franziska C Doerflinger1,2, William B Miller1, Jacqueline F Nock1and Christopher B Watkins11 Horticulture Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA 2 School of Agriculture, Food, & Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, AustraliaHorticulture Research(2015)2,15047doi:10.1038/hortres.2015.47; published online: 14 October 2015 Picture, Amilon, automatic starchmeter for controlling the ripeness of apples and pears, by?ISOLCELL