Abstract
Abstract The objective of this work was to evaluate the effect of heat waves on the bud dormancy of grapevines with contrasting chilling requirements. ‘Chardonnay’, ‘Merlot’ and ‘Cabernet Sauvignon’ hardwood cuttings were collected in vineyards of Veranópolis, State of Rio Grande do Sul, Brazil, and were exposed to constant (7.2°C) or alternate (7.2 and 18°C for 12/12 hours) temperatures, combined with zero, one or two days a week at 25°C. Periodically, part of cuttings was transferred to 25°C for daily budburst evaluation. Endodormancy (dormancy controlled by cold) was overcome with 150 chilling hours (CH) at 7.2ºC in ‘Chardonnay’, 300 CH in ‘Merlot’ and 400 CH in ‘Cabernet Sauvignon’. Daily temperature cycles ranging from7.2ºC to 18°C did not affect the endodormancy process. Heat waves of 25°C resulted in increase in CH to overcome endodormancy. The negative effect of heat waves depended on their duration, with heat partially canceling out the chilling accumulation after 36 continuous hours on the dormancy. Such evidence shows that the dormancy evolution is affected by the impact of the heat interspersed with cold, and should be considered in the adjustment and/or development of better-adapted models for the prediction of the budburst potential of the grapevine culture in Southern Brazil.
Highlights
In temperate and subtropical climates, fruit species such as grapevine present bud dormancy in the autumn and winter, with temporary suspension of visible plant growth
Overcoming dormancy was considered when there were 70% or more sprouted buds (ANZANELLO; LAMPUGNANI, 2000). This chilling requirement was similar to that observed by Anzanello et al (2018), working with the same grapevine cultivars under constant thermal regime of 3oC
The alternating regime of 7.2°C and 18°C, for 12/12h, did not change the chilling requirement of cultivars, which remained at 150 chilling hours (CH) for ‘Chardonnay’, 300 CH for ‘Merlot’ and 400 CH for ‘Cabernet’ Sauvignon’ (Figure 1)
Summary
In temperate and subtropical climates, fruit species such as grapevine present bud dormancy in the autumn and winter, with temporary suspension of visible plant growth. Budburst inhibition results from a series of biochemical and physiological events at meristematic levels or close tissues, triggered by the perception of an environmental stimulus, which is usually caused by low temperatures, photoperiod changes or both. This type of dormancy can occur with different duration and intensity (depth), being overcome with the accumulation of a certain number of chilling hours (CH) during autumn and winter, ranging from 100 to 2000 CH, according to species and cultivar (HAWERROTH et al, 2010). Budburst depends on spring environmental conditions, especially temperature and water availability, in the state called ecodormancy
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