ABSTRACT The objective of this study was to evaluate the influence of the environment and the genetic factor on the the phenology of 16 advanced selections of peachtrees in the municipality of Urussanga, state of Santa Catarina. The experiment was conducted in two areas (360 m and 220 m above sea level) in 2017, 2018, and 2019 harvests. The selections are part of the EPAGRI fruit breeding program. The dates of beginning, full, and end of flowering and budding, percentage of flowering, budding and effective fructification were determined. The standard model (number of hours with temperatures below 7.2 °C) was not the most suitable. Full flowering was anticipated by five days, on average over three years, at the highest altitude due to the greater accumulation of cold. The 16 selections were classified into three groups: early (harvest in October), medium (harvest in November), and late (harvest in December). It is concluded that the environment and the genetic factor influence the phenology of advanced peach selections. Being the first, it influences the periods of flowering and budding and the percentages of flowering, budding and effective fruiting. The second with emphasis the maturation cycle and the harvest period. 1 Urussanga Catarina 360 (36 22 level 2017 2018 201 harvests program beginning full determined number 72 7 2 7. °C C suitable days years cold groups October, October , October) November, November November) December. December . December) first fruiting period 36 (3 20 3 (

RESUMO A dinâmica da dormência de espécies frutíferas de clima temperado é complexa e muito variável de acordo com o genótipo e o ambiente. Em razão desta variabilidade, muitos modelos fenológicos de unidades de frio não se têm mostrado adequados para as condições climáticas subtropicais brasileiras. Objetivou-se com o presente trabalho avaliar como a temperatura do ar influencia a dormência do pessegueiro em Urussanga- SC. Para isto, foram avaliadas as correlações entre as datas de plena floração de dezesseis variedades de pessegueiro e o total de horas em que as temperaturas permanecem em determinados níveis térmicos. Foram identificados dois grupos de variedades com respostas altamente diferenciadas às temperaturas, em diversos períodos. No primeiro grupo, constituído por dez variedades, o início da influência significativa (p<0,05) das temperaturas sobre a data de plena floração ocorreu mais precocemente, em fevereiro. Neste grupo, as temperaturas entre 16 e 25 oC, acumuladas de março a junho, foram as que mais contribuíram para a antecipação da floração. No segundo grupo, o início da influência significativa das temperaturas ocorreu mais tardiamente, em abril. Neste grupo, as altas temperaturas acumuladas do início de abril ao final de maio anteciparam a plena floração, mas a partir de 20/05 foram as temperaturas abaixo de 10 oC as responsáveis por esta antecipação. Este comportamento difere dos modelos fenológicos tradicionais, que consideram uma exigência sequencial de frio e de calor nesta fase de repouso hibernal. Os resultados obtidos indicam a possibilidade de que ocorra uma influência alternada e/ou paralela de diferentes níveis térmicos sobre a dormência.

ABSTRACT The dormancy dynamics of temperate fruit tree species is complex and highly variable according to genotype and environment. Due to this variability, many phenological models of cold units have not been suitable for subtropical climatic conditions in southern Brazil. The aim of this study was to evaluate the influence of air temperature on the peach dormancy in Urussanga-SC. For this purpose, the correlations between the date of full bloom of sixteen peach varieties and the total hours in which the temperatures remain in certain thermal levels were evaluated. Two groups of varieties with highly differentiated responses to temperature in various times were identified. In the first group, consisting of ten varieties, the beginning of significant influence (p<0.05) of temperatures on the date of full bloom occurred as earlier, in February. In this group, temperatures between 16 and 22 °C accumulated from March to June were those that most contributed to the flowering advance. In the second group, the beginning of the significant influence of temperatures occurred later in April. In this group, the accumulated high temperatures from early April to late May anticipated the full bloom, but from May 25, temperatures below 10 °C were responsible for this advance. This behavior differs from traditional phenological models that consider a sequential cold and heat requirement in the resting phase. The results obtained indicate the possibility of an alternating or parallel influence of different temperature levels on dormancy.