Seed Collection Time Effect on the Germination Rate and Growth of Rubber Tree Rootstock

The bud-grafting method is the most economical technique of Hevea brasiliensis propagation. This technique requires rootstock and scion. The high rootstock demand for the replanting program drives the seeds’ suppliers to collect assorted seeds from cultivated fields, lead to a high variation in the germination rate. The time from seed dehiscent to seeding was hypothesized to be crucial inflicting an inconsistency in the germination rate and seedling rootstock growth. This present study used rubber seeds of the GT1 clone which were laid under trees’ shading to mimic the natural environment. Five laying periods were applied i.e., P0 (directly germinated, control), P1 (laid for one week), P2 (laid for two weeks), P3 (laid for three weeks), and P4 (laid for four weeks). Our study implied that the direct sowing after dehiscent was the best way to attain a high germination rate (GR) (51.67%) while delaying seed sowing for one week reduced the GR up to 22.04%. The longer delaying in P2, P3, and P4 did not show significant differences among them which were 13.33%, 1.19%, and 4.35% respectively. However, the seedling showed a similar growth rate including root/shoot ratio regardless of the laying period treatment. The necessity of establishing seed gardens for rootstock was highlighted in which the harvesting of the seeds could be controlled.