We investigated the effect of heat exposure during olive inflorescence on reproductive development. We examined the response of olive inflorescence and flowering, to several heat scenarios: prolonged exposure to moderately high temperatures and a two-hour concentrated heat shock treatment during the inflorescences development stage, as well as heat stress during anthesis. We found that heat has a negative impact on the male reproductive system in olives, during early flower development and in mature pollen grains, which are relatively resistant to heat. Heat stress impaired pollen tube elongation capacity, and germination rate. Additionally, heat stress affected the ultrastructure of the external wall of the pollen grain, the exine, potentially impairing its ability to adhere to the stigma and fertilize the ovule.
We also examine the negative effect of summer high temperatures on oil yield and quality. We found that summer high temperatures, especially during July and August, repress the olive fruit development, the oil biosynthesis and several parameters of the oil quality. This repression is genotype depending.
The sensitivity of olive reproductive parameters to heat is a genotype-dependent trait, allowing for the identification of heat-resistant cultivars for use as pollen donors during anthesis, and for high oil yield and quality under warm summers. The development of new heat-resistant cultivars, as well as identify agriculture protocol to mitigate the negative effect of heat stress on the olive reproductive cycle is a crucial mission for the future of the olive cultivation.
