2019 ASHS Annual Conference

Unlike most horticultural crops, blueberry (Vaccinium spp.) thrives in acidic soils (pH 4.2 – 5.5) and is stressed by higher pH soils. While it is well established that high pH stress reduces growth and yield in blueberry, root-level responses to high pH stress are notably absent from our current understanding of this problem. We investigated how high pH stress affects blueberry roots. For this means, we compared root oxidative status between ‘Emerald’ southern highbush blueberry (V. corymbosum L. interspecific hybrids) and V. arboreum Marshall genotype FL09-502. These genotypes have been previously characterized as high pH-sensitive (‘Emerald’) and high pH-tolerant (FL09-502), respectively. One year-old rooted cuttings were transplanted to a hydroponic growth system filled with a complete nutrient solution. After 14 days of acclimation at pH 5.5, plants were exposed to complete nutrient solutions buffered to pH 4.5 or pH 6.5. Relative membrane permeability was measured in fresh root samples. Proline content, lipid peroxidation, catalase and peroxidase activity were measured on root tip samples that were flash frozen and stored at -80 °C. Relative membrane permeability and proline content were not affected by pH treatment. On the other hand, pH treatment affected plant oxidative status. ‘Emerald’ exhibited significantly higher lipid peroxidation rates at pH 6.5 than at pH 4.5, while lipid peroxidation in FL09-502 was not affected. These results suggest that oxidative stress might play a role in Vaccinium spp. decline or resilience in high pH soils. This advances our understanding of high pH stress responses in this genus and provides a biological marker that can be used to identify additional high-pH tolerant genotypes.