Adaptability and phenotypic stability of apple cultivars in a subtropical climate.

Breeding programmes have selected cultivars with a lower chill requirement. Apple production in these regions is socioeconomically valuable since fruit is harvested earlier than cooler regions. Understanding the adaptability and phenotypic stability in subtropical climate regions across multiple cropping seasons is important to ensure high productivity. The aim here was to evaluate the adaptability and phenotypic stability of seven apple cultivars that have been selected for a subtropical climate region. Phenology and productivity was measured including the mean number of fruit per plant, fruit weight, production per plant, mean estimated yield, and sum of chill hours, from four production cycles. Fruit quality was assessed for fruit from two production cycles. The genotype × environment interaction was analysed by the GGE biplot method. The Z selection index, the seasonal variation contributed significantly to the performance of each cultivar. Eva had the highest accumulated yield during the four production cycles and Imperatriz and Gala, had the lowest yields. Chilling requirements were the lowest for the cultivars Princesa, Eva and Julieta. Eva, Princesa and Julieta were the most stable for yield and also for the Z index. Eva and Julieta were the most adaptable and stable in subtropical climate regions. [ABSTRACT FROM AUTHOR]