Pollen Yield of Two CVS. of Olea Europaea L. (‘Manzanillo’ and ‘Swan Hill’)

Abstract

Airborne pollen concentrations (grains/m) under and near trees of two cultivars of Olea europaea were studied during the 30 day pollination period in Tucson, Az, USA. Airborne pollen concentration from Manzanillo, the dominant horticultural cultivar, was compared with that of the fruitless cultivar, Swan Hill using Burkard samplers. We conclude that airborne pollen is not produced by the Swan Hill cultivar of Olea. The values reported from the Swan Hill site reflect background levels of Olea pollen for the Tucson area. Peak atmospheric Olea pollen concentrations occurred at both sites on April 14, 1985. Pollen concentrations around the Manzanillo site ranged from 7 to 6,196 grains/m3/day. At the Swan Hill site daily totals were an order of magnitude less. Diurnal Olea pollen concentrations for the Manzanillo site on the peak day varied from 1,000 to 18,133 grains/m3/hour. Both sites exhibited rapidly increasing pollen concentrations at sunrise with a sharp increase between 1100 to 1300 hours MST for the Manzanillo site. Seasonal pollen capture was also measured using Tauber traps placed at various distances from each tree and within the tree canopy. Both cultivars produced the same number of pollen grains/anther (85,000). An unknown anatomical or physiological factor in ‘Swan Hill’ inhibits stomial rupture and thus pollen-shedding. Generally 15% of the anthers partially dehisce in the Swan Hill cultivar. The Swan Hill cultivar can be useful in reducing pollen concentrations in urban environments caused by planting of ornamental olive trees.