Removal of flowers or inflorescences affects ‘Barnea’ olive fruitlet post-anthesis abscission

A typical olive (Olea europaea L.) inflorescence consists of about 20 flowers. However, in many cultivars, only one fruit develops. This is due to massive abscission of flowers and fruitlets, which occurs during the first month after anthesis. In this study, we used the olive cultivar 'Barnea' to characterize the abscission mechanism and to try to increase fruit set by increasing the number of developed fruit per inflorescence. Removing the lateral flowers 3 weeks before anthesis increased fruit set by more than 50%. Removing all inflorescences but one from a branch increased the number of developed fruits from 0.93 to 2.8 during 2017 and from 0.91 to 3.34 fruits per inflorescence in 2018. Sugar quantification in the pistil revealed that starch level is high on the day of anthesis and low 25 days later in abscised as well as in developed fruit. Soluble carbohydrates are low on the day of anthesis, low in abscised flowers/fruitlets 25 days after anthesis and high in developed fruit. Screening the natural variation found in the Israeli germplasm collection revealed that in most cultivars less than one fruit per inflorescence has developed. However, there are unique cultivars with a higher fruit set.     

In vitro propagation of olive (Olea europea sativa L.) ‘Kalamon’

A micropropagation method is described for olive (Olea europea sativa L.) ‘Kalamon’ using single-node explants collected from shoots produced from olive ovules grown in a growth chamber. Shoot proliferation was obtained on OM modified medium supplemented with 0.5 mg r¹ cystine, 10 mg I^-1 pantothenic acid calcium, 0.5 mg I^-' gibberel- lic acid (GA₃), 0.1 mg T¹ indole-3-acetic acid (IAA) and 10 mg I^-1 zeatin riboside, or 7.5 mg I^-1 benzyladenine (BA), or 10 mg I^-1 N⁶-2-isopentenyladenine (2ip). Explants were rooted on a medium similar to that for shoot development, but without cytokinins and with a-naphthaleneacetic acid (a-NAA), and indole-3-butyric acid (IBA) at 1, 2 and 3 mg I^-1 for both auxins. a-NAA at all concentrations was more effective than IBA. Shoot proliferation and rooting were improved by the addition to the nutrient media of 20 mg I^-1 and 50 mg I^-1 crude extract from olive ovules, respectively. Rooted explants were transferred to pots containing equal volumes of peat and vermiculite; about half survived.