More accurate results with the DA index to determine AmbrosiaTM maturity stage

AmbrosiaTM apple has presented new challenges for maturity monitoring since it does not have climacteric ethylene rise in the initial stages of on-tree maturation. A starch-iodine index and background peel colour chart have been developed to aid in harvest decisions for AmbrosiaTM. While the starch-iodine index has been the primary indicator for making harvest decisions, the use of the colour chip comparators can be somewhat subjective in the variable lighting conditions of the orchard (personal observation).? The difference in absorbance or delta absorbance (DA) meter is a visible spectrometer that is designed to specifically measure chlorophyll a content in peel. The IDA (DA meter Index) is measured by the DAmeter?of T.R. TURONI?(Visit T.R. Turoni at Fruit Logistica 2017 - Hall 4.2/C-13). Starch-iodine index and IDA values were recorded during 3 years for AmbrosiaTM apples at harvest and compared with firmness retention after controlled atmosphere storage.? The starch-iodine index correlated with firmness retention only in 2012. Harvest IDA values were associated with firmness retention in all years. Seasonal differences in temperature patterns were possible factors affecting the starch-iodine index. The IDA showed a more consistent association with firmness retention in AmbrosiaTM apples in all 3 yr; conclusion is that the DA meter index was more consistent between seasons for monitoring maturity. SourceComparison of IAD and starch-iodine indices at harvest and how they relate to post-storage firmness retention in AmbrosiaTM apples over three growing seasonsPeter M. A. ToivonenAgriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Highway 97,?Summerland, British Columbia, Canada V0H 1Z0.Can. J. Plant Sci. (2015) 95: 1177[1]1180 doi:10.4141/CJPS-2015-185