Abstract
ABSTRACT Kiwifruit vines are an alternative approach to diversify Brazilian fruit farming because of the low supply and increase in the demand for their fruits. Hydrogenated cyanamide, which is the most common rest-breaking agent, is highly toxic and its use is not allowed in organic production systems. This study aimed at evaluating the efficiency of alternative rest-breaking agents in kiwifruit vines by using the biological method of single node cutting. Twigs of the cultivar Bruno were collected in an organic orchard in Pelotas, a city located in Rio Grande do Sul state, Brazil. Seven-centimeter-long cuts with a single shoot at the ends were segmented. Cuttings were placed on plastic trays with phenolic foam and soaked in water, at 85% relative humidity on average, and kept in bio-oxygen demand (BOD) incubators at 25± 1 °C and a 16-h photoperiod. Budbreak was evaluated in 2-day and 3-day intervals. The experiment was conducted in a completely randomized design with ten treatments and three replications of ten sampling units each. The following variables were analyzed: average budbreak time (ABT), final budbreak rate (FBR), vigorous budbreak rate (VBR), velocity of budbreak (VB), percentage of open buds (POB) and dormancy index (DI). The rest-breaking agent garlic extract (GE) 10% + mineral oil (MO) 2% was the most efficient one in budbreak induction in both production cycles. Thus, this dose is recommended for budbreak induction in kiwifruit vines grown in an organic system.
Highlights
Kiwifruit has had high demand in the Brazilian domestic market due to its therapeutic properties, such as its high content of vitamin C (Soqueta et al 2016)
Garlic extract resulted from peeled cloves of common white garlic (Allium sativum L.), which were triturated by a juice extractor, similar to a kitchen centrifuge, filtered through a cloth strainer and stored in containers wrapped in tin foil up to the application, right after the preparation; yield was in the ratio 3:1 (weight:volume)
In the experiment conducted in 2016 (Table 1), rest-breaking agents led to changes in the dynamics of budbreak, i. e., in the final budbreak rate (FBR), the percentage of open buds (OB), the average budbreak time (ABT), the dormancy index (DI) and the velocity of budbreak (VB)
Summary
Kiwifruit has had high demand in the Brazilian domestic market due to its therapeutic properties, such as its high content of vitamin C (Soqueta et al 2016). Every cultivar requires a certain number of cold hours below 7.2 °C to overcome dormancy, according to the model of dormancy evaluation proposed by Weinberger (1950). When chilling requirement is not totally supplied, the application of hydrogenated cyanamide is recommended at concentrations that range from 1 to 3%, depending on the cultivar, from three to five weeks before budbreak. There is a major problem related to the high toxicity of the commercialized product which has hydrogenated cyanamide in its formula. It is highly toxic to the environment and potentially carcinogenic to humans, and its use is prohibited in sustainable production systems such as the organic one (Ímrak et al 2016)
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