Abstract

Solar UV irradiation allows life on Earth, but becomes harmful at high levels due to UV-B and UV-A irradiation, generating negative effects for all organisms, including plants. We determined the effects of solar UV irradiation on photosynthetic performance, biochemical markers, and gene expression in five-year-old plants of two highbush blueberry (Vacciniam corymbosum L.) cultivars, Legacy and Bluegold. Plants growing under field conditions were subjected to three solar UV irradiation filter treatments: UV-transmitting filter ( + UV-A/13), UV-B blocking filter (-UV-B), and UV-A/B blocking filter (-UV-A/B) during two seasons. Net photosynthesis did not change among solar radiation filter treatments in either cultivar. Bluegold showed a significant reduction in stomatal conductance (g(s)) during both seasons under + UV-A/B compared to -UV-A/B (control treatment); while effective quantum yield (Phi PSII) and electron transport rate (ETR) did not change in Legacy, Bluegold showed a reduction in Phi PSII and ETR during the 2014 season. The highest significant increase (P <= 0.05) in total phenol concentration was observed in Bluegold (40%) under + UV-A/B in the 2013 season compared to Legacy. A similar tendency in flavonoids and anthocyanin was observed but in both seasons. In conclusion, an interaction genotype-environment was observed, where Legacy and Bluegold cultivars were differentially affected by solar UV irradiation and seasons in field conditions. Although Bluegold maintains CO2 assimilation, activating antioxidant defense, gene expression (MYBPAI, CHS, and F3'H) and metabolites (fiavonoid and anthocyanins) to counteract + UV-A/B treatment, this cultivar was no able to reduce oxidative stress and to recover photochemical efficiency of PRI compared to Legacy. Our findings contribute to the understanding of blueberry responses to solar UV irradiation at physiological, molecular, and metabolite levels under field conditions.