Study of reproductive behaviour in low-chill apples in warmer zones of Argentina

Abstract

The domesticated apple (Malus × domestica Borkh.) showsabnormalities in its flowering biology when it is growing in mild-winterareas. Hence, the flowering phenology and the mating system (e.g., open-,cross- and self-pollination, apomixis and parthenocarpy) of Caricia, Eva,and Princesa apple cultivars were studied in three consecutive growingseasons. The flowering period ranged between August and October with widevariation between years, especially in relation to the overlapping of thefull-bloom periods. Fruit set by selfing was significant, reaching a meanvalue of 20% with a minimum of 4.5% and a maximum of 43.7%, depending onthe growing season and the cultivar. The self-incompatibility indexshowed significant changes between years in Eva and Princesa but not inCaricia. Fruit and seed set were significantly greater in cross- andopen-pollination treatments than by self-pollination, apomixis orparthenocarpy. Those variables were affected by a growing season ×treatment interaction. The results indicated that Caricia, Eva, andPrincesa apples show partial to full self-incompatibility, dependingstrongly on the growing season. However, better fruit and seed set ratesare obtained by cross-fertilization