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Ripe rot is one of the most important bunch diseases of grapes in the highlands of southern Brazil and a matter of concern for winegrowers. Sixty‐one strains isolated from berries of Vitis labrusca and V. vinifera varieties with symptoms were classified by phylogenetic analysis of the sequences of β‐tubulin, glyceraldehyde‐3‐phosphate dehydrogenase, D1/D2 domain of 28S rDNA, and rDNA internal transcribed spacer. They were also characterized by morphology, and their pathogenicity was evaluated. The combined molecular data allowed identification of six Colletotrichum species: C. fructicola, C. kahawae and C. viniferum (gloeosporioides complex), C. limitticola, C. nymphaeae (acutatum complex), and C. karstii (boninense complex). This is the first report of C. karstii and C. limitticola associated with the ripe rot of grapes. Morphological characteristics varied within and among species, confirming their separation at the complex level. Pathogenicity tests on V. vinifera berries showed that the most prevalent species, C. viniferum (37.8%) and C. fructicola (36.1%), were more virulent than the less prevalent species C. limitticola and C. karstii. Our findings indicate that there is a high diversity of Colletotrichum species associated with ripe rot disease of grapes in Brazil. There were no clear differences in the distribution of Colletotrichum species between V. labrusca and V. vinifera varieties. The determination of fungal species responsible for grape ripe rot in Brazilian vineyards may contribute to further epidemiological studies and the development of more efficient prophylactic methods for ripe rot management.

BACKGROUND Essential oils (EOs) are volatile natural compounds produced by plant secondary metabolism, and some of them exhibit antimicrobial activity. The objective of the present study was to determine the chemical composition the EOs of Eucalyptus staigeriana and Eucalyptus globulus, and their effect in vitro and in vivo against Botrytis cinerea and Colletotrichum acutatum, the most important fungal rot diseases of grapes. Moreover, grapes collected from field experiments were used to evaluate the impact of the alternative control on the alcoholic fermentation and wine composition. RESULTS The major compound of E. staigeriana EO were citral 30.91% (19.74% geranial, 11.17% neral), 1.8‐cineole (24.59%) and limonene (19.47%), while 1.8‐cineole represented 68.26% of E. globulus EO. The two EOs showed in vitro antifungal activity against both pathogens. Eucalyptus staigeriana EO exhibited the highest activity inhibiting mycelial growth (MG) and conidial germination at 0.5 μL mL−1. Moreover, this EO was able to reduce the incidence and severity of grey rot caused by B. cinerea and the severity of ripe rot caused by C. acutatum The alternative control did not significantly influence alcoholic fermentation, the physicochemical characteristics, and the volatile composition of wines. CONCLUSION These results are promising and indicate that E. staigeriana EO might be further investigated as a natural alternative for the control of fungal rots on wine grapes. © 2019 Society of Chemical Industry

Fungal rots, caused by Botrytis cinerea and Colletotrichum acutatum, are the main causes of postharvest decay of table grapes in Brazil. The aim of this study was to assess the chemical composition and the fungicidal effect of Foeniculum vulgare essential oil in vitro, on mycelial growth (contact and volatile phase) and conidia germination, and in vivo on postharvest grapes against both fungi. The major compounds found in F. vulgare essential oil were trans-anethole (79.14%), fenchone (11.94%) and estragole (5.76%). The mycelial growth (contact phase) and conidia germination of B. cinerea were inhibited completely at concentrations of 50 and 100 ppm (µL mL -1 ), respectively. For C. acutatum, mycelial growth (contact phase) and conidia germination were inhibited completely at concentrations of 100 and 200 ppm, respectively. The volatile phase had a fungistatic effect on mycelial growth of both fungi at different concentrations tested, and the pure essential oil (100%) presented fungicidal effect against B. cinerea. In vivo tests were carried out using grapes of Vitis spp. cv. "Isabella" and the concentrations of essential oil tested were efficient, reducing the incidence of disease caused by B. cinerea and C. acutatum at postharvest, both in preventive and curative treatment. The concentration 200 ppm completely inhibited the incidence of both fungi. In conclusion, F. vulgare essential oil presented fungicidal action against postharvest fungal rots on grapes.

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