Histological and cell wall polysaccharide chemical variability among apricot varieties

- Parenchyma tissue of 9 apricot varieties were phenotyped and chemotyped.
- Image analysis of tissue macrographs distinguished varieties on their histology.
- Cell wall sugar composition was a poor discriminant of the varieties.
- Cell wall polysaccharide esters substitution distinguished varieties.
- Pectin ester distribution and hemicellulose fine structure distinguished varieties.

The variability of histological and cell wall chemical characteristics of apricot were assessed in nine apricot varieties: Harogem, Goldrich, Hargrand, Iranien, Moniqui, Orangered® Bhart, Stark Early Orange, Ravicille and Rouge du Roussillon. For chemical analyses, Iranien and Moniqui were harvested twice at two weeks interval and Goldrich parenchyma was subdivided into inner and outer tissue.Image texture analysis of parenchyma tissue sections allowed distinguishing varieties on the basis of cell and vascular bundle size distributions and tissue organization. Whole parenchyma cell wall sugar composition failed to distinguish varieties. Goldrich outer tissue was richer in arabinose and mannose compared to inner parenchyma. Methyl and acetyl esterification of polysaccharides were better discriminants. The distribution of methyl and acetyl esters on pectin varied among varieties. The tissue regions studied in Goldrich and the different harvests studied in Moniqui and Iranien affected pectin esterification. Hemicellulose fine structure profiles discriminated varieties on the basis of xyloglucan and galactoglucomannan structures proportion.The results point to variations in chemical and histological characteristics that can be of importance in studies on the understanding the genetics of apricots texture variations.