Proactive application of UV-B light could immunize strawberry fruits against gray mold (Botrytis cinerea) postharvest

Abstract

The severity of Botrytis cinerea growth could be significantly inhibited in mature strawberry fruits by priming fungal resistance in harvested berries after the proactive application of UV-B light (312 nm). Harvested fruits were irradiated by accumulative UV-B light amounts (0, 0.33, 0.65, and 1.3 mJoule/cm 2 ) before being artificially infected with B. cinerea. PCR assay could estimate a reduction ratio of 50 % in fungal DNA in fruits proactively exposed to 1.3 mJoule/cm 2 of UV-B light compared to non-UV-B treated fruits (0 mJoule/cm 2 ), which were harshly rotted with velvety gray mold growth. To reveal a side of possible molecular mechanisms behind UV-B induced immunity in ripe berries against B. cinerea, the expression profiles of some resistance-related genes were quantified using real-time PCR on day 1 and day 2 after infection. UV-B significantly sharpens the expression of strawberry defense gene FaBG2-1 which encodes the fungal cell wall degrading enzyme β-1-3-glucanase. Furthermore, jasmonic acid (JA) biosynthesis key gene FaAOS was strongly up-regulated after exposure to UV-B in infected or non-infected fruits on day 2. Equally important, the expression of FaNES1, volatile terpenoids linalool/nerolidol synthase gene, was moderately elevated. Abscisic acid (ABA) signaling gene FaPYR1 was found to be more responsive on day 2 after UV-B irradiation. Collectively, we hypothesize that UV-B proactive irradiation can encourage the enhancement of the molecular immune system in mature strawberry fruits against possible B. cinerea infection postharvest. Further empirical studies are needed to reveal UV-B potential as a sustainable priming agent to plant resistance against diseases.