Variability of Seed Germination and Seedling Growth Potential of Ricinodendron heudelotii (Euphorbiaceae) at Fine Scale in Southern of Benin

Abstract

Ricinodendron heudelotii (Euphorbiaceae) is an oilseed plant with high socio-economic value. Unfortunately, the seed’s tegumentary dormancy causes low germination and severely limits its large-scale spread. Germination and juvenile growth of eleven provenances from Benin and Central African Republics were tested under four different pre-treatments (control, lime scarification, soaking in water for seven days and scarification followed by soaking in water for three days) in order to provide information for use in the reforestation and improvement of R. heudelotii. In a Fischer block with three replicates of ten seeds, the daily and final germination (nine months) was recorded and the cumulative germination rate, average germination time and survival rate were calculated. In addition, total height, diameters at the collar and above the cotyledons, internode length, total number of leaves and seedling internodes were measured quarterly. Germination and growth of juveniles were significantly different between provenances and pre-treatments. The highest germination rate (%) in short duration (d) was recorded with seeds both scarified and soaked for three days in water from Akouho (20%, 42.08 d), CRAPP (36.67%, 18.82 d), Agrimey (33.33%, 18.30 d), Ilikimou (26.67%, 19.94 d) and Woroko (26.67%, 19.25 d) and then lime scarified seeds from Massi (80%, 14.46 d), Itchede (80%, 21.29 d) and Lobaye (60%, 19.11 d). Seedlings from seeds that were scarified and soaked for three days in water showed optimal growth for all traits; Lobaye and CRAPP provenances showed the best height growth (33.22±1.45 and 31.96±1.15 cm) while Massi and Illikimou provenances showed the best growth in collar diameter (1.08±0.06 and 1.11±0.09 cm). Provenances and pre-treatments revealed a discrete variation in germination and growth of R. heudelotii. Scarification on the one hand and scarification coupled with soaking into the water for three days on the other hand, are the best pre-treatments to increase seedling production while the best provenances are Lobaye, Massi and Itchede. These provenances are potential seed sources for Forestation Program in Benin.