Salicylic acid and Cinnamomum verum confer resistance against Penicillium rot by modulating the expression of defense linked genes in Citrus reticulata Blanco

Abstract

Penicillium digitatum and Penicillium italicum are potentially important post-harvest pathogens of citrus fruit causing huge economic loss. In this study salicylic acid (SA) and Cinnamomum verum were tested to control the infection of P. digitatum (green mold) and P. italicum (blue mold) as an alternative to chemical control. In an in vitro assay methanolic extracts of five plants were tested for antifungal activity where C. verum exhibited the highest colony growth inhibition 74.6 and 76.4 % of green and blue mold respectively. Moreover, during In Planta assay the combination of C. verum and SA produced the lowest disease incidence (20 and 33.3%) and severity (13.1 and 6.1%) of green and blue mold respectively compared to stand-alone treatments without affecting the fruit quality considerably. Furthermore, an upsurge in the the activity of polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia lyase (PAL) encoding genes of citrus fruit was recorded during transcriptional profiling. The highest gene expression was recorded in fruit treated with C. verum and SA in combination compared to healthy control. Similar results were observed during quantification of corresponding gene products. This unveils the fact that the enhanced expression of defense-linked genes might be associated with the disease suppression. Conclusively, our findings indicate that C. verum and SA in combination can suppress green and blue mold of Citrus by modulating the expression of defense-linked genes. The combined use of plant extracts and resistance inducers is a safer alternate to chemicals to suppress green and blue mold during storage.