Abstract. The study was conducted for four years (2016 to 2019) in Olive germoplasm collection at Bouka, Latakia, Syria, to evaluate flower characteristics and sexual compatibility of olive cultivar Coratina under Syrian coast conditions. “Coratina” was characterized by low level of pistil abortion, average number of flowers per inflorescence and good pollen germinablity. ISI of “Coratina” showed that this cultivar was highly self- incompatible. A new threshold depends on flowering load and final fruit set were adapted to evaluate pollinizers. The two autochthonous olive cultivars “Khodeiri” and “Dermlali” were good pollinizers for “Coratina” but with some annual differences in pollination efficiency. Reverse pollination results confirmed that “Khoderi” is inter-compatible with „Coratina“ in both directions. It is suggested to plant “Coratina” in mixed orchards with “Khoderi” because they’re inter-compatible, having regular bearing habit and overlapping in flowering period.

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The study was conducted in Bouka center for research and plant production, Syria, in order to study flowering behavior of French olive cultivar 'Picholine'. Average number of flowers per inflorescence, pistil abortion (%) and fertile inflorescence (%) were studied in three positions of flowering shoots (apical, middle and basal position) in 2018 and 2019 seasons. Chilling units, flowering dates and growing degree days were also estimated in 2017, 2018 and 2019 seasons. Results showed that the number of flowers per inflorescence was not changing between seasons, but it was influenced by inflorescence position on the shoot. Pistil abortion was significantly lower in the basal position compared to inflorescences located in the apical and middle position of the shoots. Ratio between the number of flowers per inflorescence and the number of flowers with aborted pistils differed depending on inflorescence position on the shoot and season. In total, the number of flowers per inflorescence was responsible for 11% of the variation in pistil abortion in 2018, and 37% in 2019 season. Chilling units differed considerably among seasons, 2018 had the lowest chilling units, while 2017 had the highest. 'Picholine' flowered regularly even under low chilling conditions showing to have lower chilling requirements and consequently could adapt well to areas with relatively warm winters. This could be an advantage under global climatic change.

The research was conducted in 2017 and 2019 seasons in Bouka center for research and plant production, Latakia, Syria, in order to investigate the ability of using Syrian olive cultivar 'Khoderi' as polliniser for 'Tanche',' Picholine' (French) and 'Frantoio' (Italian) olive cultivars. Pistil abortion (%), pollen germination (%), flowering period, self, open and cross-pollination with 'Khoderi' were studied. Results showed that all cultivars were characterized by good pollen germination ratio. Both season and cultivar affected pistil abortion significantly. The flowering periods were overlapping for all studied cultivars but with some delay of 'Frantoio'. 'Picholine' was highly self-incompatible (ISI= 0.11), while 'Tanche' was partially self-incompatible (0.33-0.35). The highest self-compatibility was for 'Frantoio' (ISI= 0.52-0.73). Pollination results showed that using 'Khoderi' as polliniser increased final fruit set over open-and selfpollination for all cultivars and seasons. The results indicated that 'Khoderi' was efficient polliniser for 'Tanche', 'Picholine' and 'Frantoio' olive cultivars under Syrian Coast conditions.