Reproductive biology of the olive (Olea europaea L.) cultivar 'Nabali Baladi'

'Nabali Baladi' is the most common olive cultivar in Jordan. The final frui t set is very low, specially in orchards planted only with this cultivar. T his problem is very common in olive cultivars. Thus, the investigations foc used on the development and the morphology of the reproductive organs: poll en grain quality and quantity, pollen germination and pollen tube growth, f ertilisation and fruit set. Another two olive cultivars 'Grossa de Spagna' and 'Rasie' were used for cross-pollination. One month before anthesis, the two tetrasporangiate anthers were developed. About three weeks before anthesis, the microspore mother cells were observ ed clearly. Through a week, they developed to the microspore tetrade stage. Finally, the fully developed pollen grains could be observed about five da ys before anthesis. The pollen grain number of the pollinizers was higher than in 'Nabali Balad i'. The normal pollen grains were more than 82% for the three cultivars in both years. The pollen viability was tested on an agar medium 0,8%, contain ing 10% sucrose and 50 ppm citric acid. Immersion of the pollen grains in o live oil before spreading them on the medium improved this test significant ly. The pistil consists of a superior ovary, short style, and wet papillate sti gma. It was developed about six days before anthesis. A protuberance struct ure arised from the placenta of the ovary about four weeks before anthesis which developed to the anatropous ovule. Each carpel contained two ovules a nd only one ovule developed to the seed. The first embryo sac mother cell c ould be recognised in the middle of the ovule about two weeks before anthes is. The embryo sac with eight nuclei was completed about two days before an thesis. The pollen tubes grew intercellularly through the stigma and the tr ansmitting tissue in the style. One pollen tube entered the ovary to fertil ise one ovule through the micropyle. The stigmas with a high pollen grain number had also a high number of germi nated pollen grains. The flowers which had less than ten germinated pollen grains on the stigma had low percentage of fertilised ovaries. In most of s elf-pollinated flowers, all germinated pollen grains could not penetrate th e transmitting tissue in the style, while in open-and cross-pollination, mo st of the flowers had germinated pollen grains, and the tubes grew through the transmitting tissue in the style. In open and cross-pollination, the po llen tubes started to enter the ovules two to three days before in self-pol lination. In addition to that, the percentage of the fertilised ovules in o pen- and cross-pollination was about three times higher than in self-pollin ation. One week after anthesis, there was no difference in length between the fert ilised and the non-fertilised ovules. Two weeks after anthesis, the ovule l ength doubled and the non-fertilised ovules degenerated. From the third wee k till the seventh week after anthesis, the ovule grew almost logarithmical ly. Eight weeks after anthesis till the mature stage, there was no further increase in the ovule size. The nuclear endosperm started to develop five days after anthesis. It becam e cellular 15 days after anthesis. The absorption of the nucellus tissue an d the endosperm was very clear during the embryo development. The zygote was observed nine days after anthesis. Four and five weeks after anthesis, it developed to a long narrow suspensor. Six weeks after anthesi s, the embryo reached the globular stage. One week later, it started to dev elop two cotyledons (heart-shaped) which developed quickly to the full leng th 12 weeks after anthesis. Finally, the embryo and the partly absorbed end osperm reached the final stage about 22 weeks after anthesis. The perfect flowers abscised in two ways: the non-fertilised perfect flower s abscised through the second week after anthesis, and part of the fertilis ed flowers abscised from two to six weeks after anthesis. After that, there was no significant fruit drop. The fruit set in open-and cross-pollination was significantly higher than in self-pollination. According to these resu lts,'Nabali Baladi' can be considered as a partial self-compatible cultivar . Its self-incompatibility is gametophytic. Therefore, in 'Nabali Baladi' o rchards, two other pollinizers are recommended. 'Rasic' and 'Grossa de Spag na' are good pollinizers for 'Nabali Baladi'. In old 'Nabali Baladi' orchar ds, it is recommended to graft the olive trees with at least two pollinizer s.