Quality fruit improvement in sweet pepper culture by bumblebee pollination

The percentage of ovules that set seeds per fruit has been used to evaluate the bumblebee activity of a two campaigns greenhouse trial. The experiment was carried out with two commercial cultivars of sweet pepper, 'bell' type, called Bardenas and Vergasa. The averages of the percentages of seed set per fruit of the two campaigns were 49.8% (Bardenas) and 40.7% (Vergasa) on the pollination treatment, whereas the averages of the control (self-pollination) treatment were 27.5% and 25.7%, respectively. Percentages of seed set per fruit was strongly related with the number of bee visits, but weakly with duration of visits. The number of pollen grains deposited on stigmas by pollinators or by self-pollination was assessed by staining and microscopy, resulting in a higher number of pollen grains on the bumblebees-pollinated flowers than on the control (self-pollination) ones. As a consequence of this, the number of seeds set on the bumblebees-pollinated fruits, was always higher than in the control. Flowers visited by bumblebees produced larger and heavier fruits than non-visited flowers. Because fruit external maximum diameter, length and weight were highly dependent on seed set, the use of pollinators seems to be required to obtain sweet pepper fruits with improved quality characteristics. Percentage of seed set per fruit was correlated with the number of bumblebee visits to the flowers, seeds per fruit, number of pollen grains on stigma, and the quality fruit traits. The number of pollen grains per stigma was correlated with the number of seeds per fruit. (c) 2006 Elsevier B.V. All rights reserved.