Efeito do frio na brotação e níveis de prolina em macieiras e uso de indutores na quebra de dormência em pereira Everton Sozo de Abreu Pelotas,

Abstract

The cultivation of temperate fruits crops represents an important section of the Brazilian agribusiness, but several obstacles must be overcome to promote the development of this sector. One of the main obstacles for these crops is related to the mild winter conditions found in Brazil, where the lack of winter chilling can cause several disturbances to the trees, harming the development, and consequently, yield and quality of these orchards. Thus, this work aimed to study aspects related to the budbreak of temperate fruit trees. Three studies were carried out. In the first chapter, budbreak for formation of 'Eva' and ' Maxi Gala' apple nursery trees was approached when they were submitted to 260, 596 and 932 chilling hours. Higher accumulation of chilling hours caused a decrease in the time for budbreak, greater budbreak in an acrotony pattern, while low accumulation of chilling hours caused sparse budbreak in 'Gala' trees. The second chapter was composed of two experiments with the objective of evaluating amino acid proline levels in apple dormant buds of 'Eva' and 'Gala' cultivars. In the first experiment, proline was determined in buds of branches subjected to artificial chilling to evaluate the levels of this amino acid during dormancy. Proline reduced to low levels after being subjected to cold and, after its cessation, there was an increase in proline levels just moment before budbreak. In the second experiment, proline levels in apple tree buds were evaluated after being subjected to contrasting thermal regimes. When subjected to 260 chilling hours, proline levels remained unchanged in both cultivars. When submitted to 596 and 932 chilling hours, proline levels increased close to budbreak. Thus, amino acid proline may be a marker of dormancy in dormant buds. The third chapter evaluated the budbreak and the average budbreak time of 'Hosui' pear cuttings treated with budbreak promoters hydrogen cyanamide, mineral oil, hydrogen cyanamide with mineral oil and Erger submitted to different thermal regimes. Budbreak promoters decreased budbreak time and increased budbreak rate with hydrogen cyanamide and hydrogen cyanamide with mineral oil being more effective in overcoming dormancy. Results obtained allow to conclude that the environmental conditions can interfere in apple and pear tree architecture and techniques to mitigate the effects of the lack of chilling should be used, such as the use of cultivars with low chilling requirement and budbreak promoters.