Effects of Sowing Depth and Seed Orientation on the Germination and Seedling Growth in Shea Tree ( Vitellaria paradoxa C.F. Gaertn.) for Rootstock Production in Nursery

Abstract

The study aims to determine the effects of sowing depth and seed orientation on the germination and seedling morphological variability in nursery. The seeds used were collected from an elite shea tree coded P14 located at Boundiali. The two factors that are sowing depth (5 cm, 10 cm and 15 cm) and seed orientation (VH, VB, HH, HB and HL) were tested in a Fisher block design with three replications. Germination parameters and vegetative growing traits of the juvenile shea plants were evaluated in nursery. The results showed that the seeding depth of 5 cm got better final germination rate (84.6 %), a shorter latency time (51.3 days) and a lower median germination time (110 days). Vegetative vigour of shea seedlings was better for the horizontal seed orientation with hilum sidewards (HL). After 12 months in the nursery, the proportions of plants suitable for grafting varied from 20 % (vertical seed orientation with the apical end upwards) to 32.50 % (horizontal seed orientation with hilum sidewards). It appears that sowing the seeds at a depth of 5 cm in the horizontal orientation with hilum sidewards leads to good germination and better vegetative development of shea seedlings in the nursery.