Comparative analysis of anatomical characteristics and phenolic compounds of two highbush blueberry (Vaccinium corymbosum L.) cultivars with different rooting ability of semi-hardwood cuttings

Abstract

There is no information on morphological, anatomical or phenolic concentration differences between blueberry cultivars that could be related to the differential rooting responses. In the present work, such differences were evaluated comparing the rooting zones of cuttings from two blueberry cultivars (‘Jewel’ and ‘Violeta’ with 4n and 2n ploidy level, respectively). The parameters were measured during 150 days of rooting (rooting day after cutting insertion; RAI) at 30-day interval after treatment with 3 g/L of IBA. Stem length, stem diameter and number of leaves and buds were measured and tissue sections from cuttings were stained to measure tissue thickness. Also, the total phenolic content (TPC) by Folin-Ciocalteu method and the phenolic profile by liquid chromatography coupled to a diode array detection were also evaluated in rooting zones. ‘Jewel’ rooted earlier and in higher percentage than 'Violeta'. ANOVA showed that phenolic compounds, in a higher extent, and some morphological and anatomical parameters, in a lower extent, had a positive effect on rooting capacity. In both blueberry cultivars, the cuttings with the highest phenolic content presented an early rooting capacity. The multivariate analyses allowed us to corroborate these results. FiPLS selected common variables (coumaric acid and stem diameter) and specific variables depending on the cultivar (gallic acid, stem length and number of leaves for ‘Jewel’; and, vanillic acid, rutin, and cortex thickness for ‘Violeta’). PCA allowed to group the ‘Violeta’ samples (unrooted and rooted at 60, 90, 120 and 150 RAI) in compact homogeneous clusters with an adequate explanation rate (44.7 %). From all parameters, stem diameter seems to be inversely related, and cortex thickness and p-coumaric acid and rutin seems to be positively related to the earliest rooting day after insertion (RAI 60), while the largest the stem, the earlier the rooting. In future works, more cultivars and other parameters and phenolic compounds that can induce the rooting in cuttings, including their evolution over time, should be investigated.