Flowering responses of young olive trees (Olea europaea) to experimental warming during summer and autumn in Northwest Argentina

ANDREA MISERERE; PETER SEARLES; ANA FEDERICO; CARLOS HERRERA; MAGDALENA BRIZUELA; M. CECILIA ROUSSEAUX

Congreso; XXXIV Reunion de la Sociedad Argentina de Fisiologia Vegetal; 2023

Olive expansion into new growing areas and global warming require a better understanding of the effects of elevated temperature on flowering. This study aimed to assess how warming during summer and autumn affects the timing of flowering and its intensity in two olive cultivars. A field, warming experiment was conducted in La Rioja, using two-year-old, potted olive trees (‘Arbequina’, ‘Coratina’). Two temperature levels, a near-ambient control (T0) and an actively-heated (T+) treatment (+3°C), were established from December to mid-May of the 2014-15 growing season in open-top chambers (OTCs). The treatments were applied during the entire period, early (Dec-Feb), or late (Feb to mid-May). Additional trees located in an adjacent nursery received no temperature manipulation (NM). In spring, the full bloom date (FB, at least 50% of flowers open) and the flowering intensity (FI; % of lateral buds with inflorescences) were determined visually with weekly observations. The FB date was affected by the treatment period, but not by the temperature level. In ‘Arbequina’, entire and late trees had later FB dates (4-6 days) than NM and early trees. In ‘Coratina’, trees from the early, late, and entire periods flowered 2-3 days later than NM trees. The FI in ‘Arbequina’ was greater than 60% in NM and T0 trees from all treatment periods. T+ trees from the early period also had high FI. However, FI was significantly reduced to 10% in trees warmed during the entire or late periods. In ‘Coratina’, the FI was high in the NM and early trees, but FI was very low in both T0 and T+ trees from the entire or late periods. The results indicate that warm air temperatures during autumn will likely reduce FI substantially with climate change, even in cultivars with relatively low chilling requirements such as ‘Arbequina’ and ‘Coratina’. Thus, limiting olive production in Northwest Argentina unless more suitable cultivars can be found.