Background and Aims The susceptibility of winegrape cultivars to Botrytis cinerea is a debated topic, and the available classifications are based on professional experience rather than on experimental data. The main aim of this study was to compare and classify the susceptibility of several winegrape cultivars to B. cinerea and its relation to fruit maturity under two contrasting climatic and cropping conditions. Methods and Results Between 2011 and 2015, three field trials were undertaken in Chile and France, including 13 common cultivars. Both the incidence and severity of the disease were evaluated at harvest, and indices of susceptibility and maturity were calculated on a per site basis. The significant difference in incidence and severity observed among cultivars led to a similar susceptibility classification in both countries. Cabernet Sauvignon, Cabernet Franc, Grenache Noir and Petit Verdot were the most resistant cultivars, whereas Gewürztraminer and Sauvignon Blanc were the most susceptible. Moreover, an exponential and positive relationship was established between indexes of susceptibility and maturity. Conclusions The classification of cultivars according to the susceptibility to B. cinerea was similar in both countries, despite the contrasting climatic conditions and cropping practices. Significance of the Study These findings might be of interest for choosing cultivars that are more resistant to B. cinerea to reduce the number of fungicide applications.

Gray mold is the primary postharvest disease of ‘Hayward’ kiwifruit (Actinidia deliciosa) in Chile, with a prevalence of 33.1% in 2016 and 7.1% in 2017. Gray mold develops during postharvest storage, which is characterized by a soft, light to brown watery decay that is caused by Botrytis cinerea and B. prunorum. However, there is no information on the role of B. prunorum during the development and storage of kiwifruit in Chile. For this purpose, asymptomatic flowers and receptacles were collected throughout fruit development and harvest from five orchards over two seasons in the Central Valley of Chile. Additionally, diseased kiwifruits were selected after storage for 100 days at 0°C and 2 days at 20°C. Colonies of Botrytis sp. with high and low conidial production were consistently obtained from apparently healthy petals, sepals, receptacles, and styles and diseased kiwifruit. Morphological and phylogenetic analysis of three partial gene sequences encoding glyceraldehyde-3-phosphate dehydrogenase, heat shock protein 60, and DNA-dependent RNA polymerase subunit II were able to identify and separate B. cinerea and B. prunorum species. Consistently, B. cinerea was predominantly isolated from all floral parts and fruit in apparently healthy tissue and diseased kiwifruit. During full bloom, the highest colonization by B. cinerea and B. prunorum was obtained from petals, followed by sepals. In storage, both Botrytis species were isolated from the diseased fruit (n = 644), of which 6.8% (n = 44) were identified as B. prunorum. All Botrytis isolates grew from 0°C to 30°C in vitro and were pathogenic on kiwifruit leaves and fruit. Notably, B. cinerea isolates were always more virulent than B. prunorum isolates. This study confirms the presence of B. cinerea and B. prunorum colonizing apparently healthy flowers and floral parts in fruit and causing gray mold during kiwifruit storage in Chile. Therefore, B. prunorum plays a secondary role in the epidemiology of gray mold developing in kiwifruit during cold storage.

In organic phytosanitary management of vineyards, it is crucial to understand the available pathogen control alternatives in order to progress towards a more sustainable form of viticulture. The objective of this study was to evaluate the efficacy of seven biofungicides registered in Chile for the prevention and treatment of Botrytis Bunch Rot (BBR), and to test a novel fungicide composed of chitosan and riboflavin (CH-RF). Biofungicides including Trichoderma spp., Aureobasidium pullulans, and Melaleuca alternifolia were evaluated using biotests with grapevine berries. Registered products (specifically biological control agents) significantly reduced the in vitro growth of B. cinerea. However, the degree of pathogen control varied significantly among products in grapevine berries of the Chardonnay cultivar, and disease incidence and severity changed depending on the inoculation time. High control effectiveness was achieved with two biofungicides, A. pullulans (average efficacy 34%) and M. alternifolia oil (average efficacy 29%). In vitro tests showed CH-RF significantly reduced mycelial growth of B. cinerea. Noticeable differences between the new CH-RF fungicide (incidence under 50% and infection score under 1) and A. pullulans- and M. alternifolia-based products were detected in grapevine berries. Therefore, the new experimental formulation CH-RF constitutes a promising alternative for the control of B. cinerea and provides a basis for further research.

Penicillium digitatum is the causal agent of green mold, a primary postharvest disease of citrus fruits. This study evaluated the efficacy of a novel photoactive chitosan–riboflavin bioconjugate (CH-RF) to control green mold in vitro and in lemon fruit. The results showed total inhibition of P. digitatum growth on APDA supplemented with CH-RF at 0.5% (w/v) and a significant reduction of 84.8% at 0.25% (w/v). Lemons treated with CH-RF and kept under controlled conditions (20 °C and 90–95% relative humidity) exhibited a noteworthy reduction in green mold incidence four days post-inoculation. Notably, these effects persisted, with all treatments remaining significantly distinct from the control group until day 14. Furthermore, CH-RF showed high control of green mold in lemons after 20 days of cold storage (5 ± 1 °C). The disease incidence five days after cold storage indicated significant differences from the values observed in the control. Most CH-RF treatments showed enhanced control of green mold when riboflavin was activated by white-light exposure. These findings suggest that this novel fungicide could be a viable alternative to conventional synthetic fungicides, allowing more sustainable management of lemon fruit diseases.

Stem end rot (SER) caused by Botrytis cinerea is the primary postharvest disease in the Chilean kiwifruit industry. Relationships between the postharvest occurrence of SER in ‘Hayward’ kiwifruit and the temporal dynamics of earlier B. cinerea colonization of the floral parts (petals, sepals, receptacles, styles) was studied in five orchards over two consecutive seasons in Chile. Weather conditions in the first season favored B. cinerea infection with roughly constant colonization of floral parts up to about 120 days after full bloom, but colonization then increased up until harvest. In the second season, colonization was roughly constant throughout. Latent infections of the fruit occurred in both seasons but were high in the first season and low in the second. Incidence of latent infections at harvest were the best predictors (r > 0.8) of postharvest SER. The number of preharvest infection periods calculated using temperature, leaf wetness, and relative humidity satisfactorily predicted SER incidence by an exponential model, R²= 0.90, P < 0.001. Results indicated environmental variables play key roles in the temporal dynamics of B. cinerea colonization. Quantification of latent B. cinerea infections in asymptomatic fruit close to harvest, is a practicable way to predict later incidence of SER during storage.