Year and enclosure effects on fruit set in an autogamous almond

Fruit set was studied over 2 years in ‘Guara’, an autogamous almond (Prunus amygdalus Batsch) cultivar, following four different pollination treatments: open pollination, open pollination of a reduced number of flowers, self-pollination, and cross-pollination with a cross-compatible pollen. The treatments were applied to trees growing in the open air, to a tree inside an insect-proof cage, and to bagged branches in the open air. Fruit sets inside the cage were in general lower than at the open air, thus pointing to the possibility that a reduction of the light intensity inside the cage may reduce the level of fruit set. However, artificial pollinations resulted in higher sets inside the cage than in the open air in one of the years. Fruit sets on bagged branches after artificial pollinations were always lower than for the open air and inside the cage, showing that besides a general enclosure effect, as observed inside the cage, a bag effect is responsible for the reduction of sets, possibly due to the branch manipulation and flower damage by the bag. The reduction of the number of flowers did not always result in an increase in set of the remaining flowers. There were no consistent differences between the two types of artificial pollination, confirming ‘Guara’ self-compatibility. Year effects were observed, but not affecting all the treatments in the same direction nor at the same level, thus stressing the need for multiyear evaluation of autogamy.