Use of Gibberellic Acid for Management of Bunch Rot on Chardonnay and Vignoles Grape

Abstract

Harvest bunch rot of wine grape, caused primarily by Botrytis cinerea, is a perennial problem limiting the productivity of eastern vineyards, especially on cultivars with compact clusters. The aim of the present study was to evaluate the effectiveness of gibberellic acid (GA) sprays at reducing the compactness of Chardonnay and Vignoles clusters and minimizing bunch rot. Applications of GA reduced the number of berries per centimeter and the incidence and severity of bunch rots in Vignoles and, to a lesser extent, in Chardonnay over three consecutive years; however, the magnitude of GA effects often depended on the timing and rate of application. Bloom GA applications were more effective (P < 0.001) at reducing compactness and bunch rots than prebloom applications. Significantly, negative effects of GA applications on yield were negligible based on data from 4 years of trials on single vines and 2 years of data on 24-vine plots of Vignoles, provided the rates did not exceed 25 ppm. Regression analysis showed that berries per centimeter accounted for between 89 and 94% of variation in the incidence of Botrytis rot on Vignoles. On Chardonnay, compactness accounted for 53% of the variation in incidence, and the estimated compactness level at which no bunch rot would occur was 4.40 ± 1.05 (mean ± standard error) berries per centimeter. The relationship between cluster compactness and spray coverage of berries was also investigated in two separate experiments. Spray coverage of individual berries decreased linearly as cluster compactness increased within the range tested (3 to 18 berries per centimeter). Cluster compactness accounted for two-thirds of the variation in individual berry coverage, and coverage was reduced by 40 to 50% for clusters with about 18 berries per centimeter. These results strongly support the use of GA in integrated management of bunch rot on Vignoles and Chardonnay in eastern U.S. vineyards.

Differences in Flower Transcriptome between Grapevine Clones Are Related to Their Cluster Compactness, Fruitfulness, and Berry Size

“…The application of the gibberellins inhibitor prohexadione-Ca causes a loosening effect by reducing berry size and/or number of berries, likely through disturbing pollination and cell division processes (Molitor et al, 2011; Schildberger et al, 2011). The application of gibberellic acid pre-bloom promotes the growth of the inflorescence (Hed et al, 2011; Molitor et al, 2012a), while gibberellin treatments during bloom reduce fruit set and increase berry size (Ben-Tal, 1990). …”

Multicultivar and multivariate study of the natural variation for grapevine bunch compactness

“…(Leong et al 2006). This fact has been explained by the combined effect of an increased inner airflow and lower humidity, an improved coverage by fungicide spraying, and/or by showing less physical damage caused by berryto-berry contact (Hed et al 2011, Molitor et al 2012b) that may cause the appearance of microscopic cracks in the grape berry cuticle (Becker and Knoche 2012). In addition, compact bunches have more inner berries than loose bunches (Vail and Marois 1991), which may lead to an inadequate sun irradiation, affecting the phenolic ripeness of the bunch (Figueiredo-González et al 2013).…”

Gray mold caused by Botrytis cinerea limits grape production in Chile

“…In some wine grapes, cluster elongation, which can be achieved with the use of growth regulators (e.g., GA3 gibberellin, prohexadione-Ca), can reduce cluster compactness, improve airflow and considerably reduce microclimate conditions within the grape canopy that favor GM development (Ferree et al, 2003;Hed et al, 2011Hed et al, , 2015Molitor et al, 2011;Pearson and Riegel, 1983). However, this technique has not been used commercially in Chile, and its use appears to be quite limited in other countries.…”