A comprehensive study on the effect of foliar mineral treatments on grapevine microbiota, flavonoid gene expression, and berry composition
Recently, foliar treatments with mineral-based compounds have shown positive effects on grapevine production by protecting grape from thermal excesses and reducing the decoupling between technological and phenolic maturity caused by climate change. Unraveling the effect of mineral particle applications on grape-associated microbes is pivotal for successful wine processing, due to the influence of the microbiota on wine composition and stability. To our knowledge, this is the first work that comprehensively studied the effects of kaolin and chabasite-rich zeolitites treatments on grape-related microorganisms (by real-time PCR quantification of total fungi, Hanseniospora uvarum, Metschnikowia pulcherrima, plant-associated bacteria and lactic acid bacteria), the expression of genes related to the flavonoid biosynthesis (PAL1, CHS1, F3H2, DFR, LDOX, UFGT, MYBA1, GST4, FLS4 genes) and the berry composition (°Brix, pH, acidity and anthocyanin concentrations) in cv. Sangiovese during ripening in two growing seasons (2019 and 2020). Here, we found both mineral treatments to cause elicitation of several flavonoid-related genes and development of higher anthocyanin concentration in berries without an alteration of the final technological maturity of grapes. Fungal and bacterial levels fluctuated over the growing season. Interestingly, we observed that in a climatic season characterized by mild temperatures and high rainfall (2020), no effect of the treatments was observed on the microorganisms analysed. Conversely, in a more stressful year (2019), chabasite-rich zeolitites treatments induced an increase in total fungi and H. uvarum populations 48h upon the second spray. Additionally, at the same sampling date, we observed higher M. pulcherrima population in kaolin treated berries in respect to control ones. However, treated grapes did not show significant differences on microbial composition at harvest. These results support the use of foliar mineral treatments to ameliorate anthocyanins concentration in grapes berries, protecting them from excessive heat without altering their native microbiota.
Issue: ICGWS 2023
1Department of Agricultural and Food Sciences (DISTAL), University of Bologna, Viale Fanin, 46, 3rd floor, 40127 Bologna, Italy