Inoculation with two Oidiodendron maius strains differentially alters the morphological characteristics of fibrous and pioneer roots of Vaccinium virgatum ‘Tifblue’ cuttings

Abstract

Fine root systems of blueberries contain different individual fine roots suitable for absorptive or structural functions. However, there is limited information regarding how ericoid mycorrhizal fungi morphologically modify individual roots. Here, we focused on different individual roots that were classified into fibrous and pioneer roots based on whether their apical parts were smaller or larger than 100 μm in diameter. To develop root growth promoting techniques for cutting propagation of blueberries, we examined the hypothesis that inoculation with different Oidiodendron maius strains, EF1409 and EF1453, would alter the length and branching of pioneer and fibrous roots of the rabbiteye blueberry ‘Tifblue’ (Vaccinium virgatum) cuttings. Significant inoculation effects on individual root morphology were shown (P < 0.05); EF1409 significantly increased the length and branching of pioneer roots, whereas EF1453 moderately increased the branching of both root types, which supported our hypothesis. However, total root length and adventitious root number were not significantly affected by the different inoculations. There were positive correlations between total root length, adventitious root number, pioneer root length, and lateral root number of pioneer root. The best regression model suggested a dominant association between adventitious root number and total root length, although lateral root number of pioneer root was the second contributor to total root length. The differences in morphological alteration between the two strains suggested inter-strain or interspecific variation in function that modified morphology of different individual roots. Such variation is an important aspect for future techniques used to control the root systems of cuttings of blueberries and other ericaceous horticultural crops.