PA and DA meter – providers of the new ripeness index?

New ripening instrumentation like the PA analyser and the DA meter offer non-invasive tools based on degradation of chlorophyll in the fruit peel; their values were compared with the Streif index measured by an ART system, as traditional ripeness viz., picking tool using 5-year-old ‘Braeburn Hillwell’ at Klein-Altendorf in autumn 2015, when environmental weather pattern delayed harvest by ca. 3 weeks.
Treatments included two reflective mulches and two biostimulants with an untreated control.
The study showed that: 1) DA meter values (IAD) gave consistent results for the four treatments at the six measuring dates before harvest; 2) DA meter values (IAD) highly correlated with r=0.84-0.94 with Streif indices (ART system); 3) when ‘Braeburn’ stopped ripening at Streif=0.18 (harvest window for Streif 0.25-0.14 and for starch 3-5), DA meter values still continued to decrease; 4) fruit with reflective mulch (Extenday) appeared earlier ripe with the DA meter but later ripe with the ART system; 5) if we start to manipulate ripening e.g., by chemicals (phosphates, biostimulants, reflective mulches, 1-MCP), Streif values may reflect those changes in ripening, whereas DA meter values (IAD) still continue to decline at the same rate, unless the treatment has a direct chlorophyll effect, where DA values may be tricky to use.

XI International Symposium on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems

M.M. Blanke, A. Kunz

apple (Malus domestica Borkh.), Extenday, fruit quality, harvest, reflective mulch

https://doi.org/10.17660/ActaHortic.2018.1228.54