Genotype, environment and their interaction effects on olive tree flowering phenology and flower quality

Flowering is one of the most critical processes in the reproductive phenology in fruit trees including olive. Under Mediterranean climate, olive flowering period normally occurs from early to late spring. Therefore, flowering time could be affected by environmental conditions such as water availability and temperature, thus influencing flower quality as well. Previous works have demonstrated the effect of genotype and environment on olive flowering, but those factors have never been compared in a single study nor their interaction evaluated. In the present work, we used a multi-environment trial established in four different agro-climatic conditions of Andalucía, Southern Spain, to test the genetic and environmental influences on flowering timing (flowering period, full bloom period, and full bloom date) and flower quality (flower number, perfect flower number and perfect flower percentage). Most of the variability found for flowering phenology parameters was due to environmental influence. On the contrary, for flowering quality parameters, most of the variability was of a genetic nature. In all cases, the genotype-environment interaction was significant. In this sense, the genotype by environment effects biplot model used to analyse the interaction showed that most of the genotypes evaluated have low stability for most of the parameters evaluated, except ‘Picual’ for flowering phenology parameters and ‘Koroneiki’ for quality. This emphasize the benefits of multi-environment trials on olive in order to select the best genotypes adapted to different environments and as a tool to face the future variability of environmental conditions caused by the climate-warming scenario. In conclusion, multi-environment trials allowed to efficiently quantify the effects of genetic and environmental factors and of their interaction on flowering phenology and on flower quality in olive.