S02 - Session O4 - II - Genotype, environment, and interactive effects on olive tree photosynthesis and fruit ripening

Authors: Anna Volakaki, Ioanna Manolikaki, Georgios Koubouris *

Multi-environment trials are used to efficiently quantify the relative influence of genetic and environmental factors and their interaction on agronomic traits. In this sense, the effect of genetic and environmental factors on olive tree physiology and fruit maturity is critical to determine the variation of the cultivars and their stability across environments. The response to environmental conditions, such as temperature, can determine olive tree physiological events and fruit ripening. To this end, we established a multi-environmental trial (plants grown in the field under ambient conditions and other plants grown in a greenhouse with enhanced air temperature) to investigate the impact of air temperature on tree height, trunk diameter, photosynthetic activity, and fruit ripening in a set of six Greek olive cultivars, i.e. 'Chalkidikis', 'Koroneiki', 'Maronias', 'Mastoidis, 'Megaritiki' and 'Valanolia'. Most of the variability found for growth parameters (tree height and trunk diameter) was attributed to environmental conditions. Specifically, we observed a higher increase in tree height and trunk diameter in the field compared to greenhouse conditions. On the contrary, most of the variability was due to the genetic nature of photosynthetic parameters. 'Koroneiki' showed the highest photosynthetic rate, while 'Megaritiki' the highest stomatal conductance, intercellular CO2 assimilation, and transpiration. Concerning the phenological stages, all the cultivars in both environmental conditions reached about 50% of the final fruit size in July. 'Koroneiki', 'Maronias' and 'Mastoidis' reached 90% of the final fruit size in both treatments in August, while 'Megaritiki' and 'Chalkidikis' reached the same stage sooner in the greenhouse conditions compared to the field. In September, 'Chalkidikis' and 'Maronias' reached the harvest maturity stage in both conditions, while 'Koroneiki' was found in the same stage faster in the greenhouse than in the field. In conclusion, multi-environmental trials enhance the identification of genotypes adapted to environmental threats.