Effect of Seed Quality on Field Emergence and Seedling Performance of Rubber (Hevea brasiliensis)

Abstract

The effect of seed quality on the emergence and seedling growth performance of rubber (Hevea brasiliensis) was studied. Seven seed samples of various initial quality levels of the RRIM 600 clone were collected from various rubber plantations in Nakhon Si Thammarat, Phatthalung and Songkhla provinces, southern Thailand in 2012 and 2013. The seeds were tested for quality and filed sown to investigate the emergence and growth potential of seedlings using the seedling stem diameter, seedling height and leaf number at 6 mth after germination. The results showed that rubber seeds with germination of 85.50% gave a field emergence of 60.50%, whereas the lower quality seeds (50.50–72.50% germination) had field emergence levels of only 27.00–40.00%. The high quality seeds provided the best growth potential under field conditions based on the seedling stem diameter, seedling height and leaf number at 6 mth after planting with values of 1.17 cm, 118.90 cm and 13.10 leaves, respectively. A comparison among the different quality seeds revealed significant reductions in the performance of seedling characteristics such as seedling stem diameter, seedling height and leaf number, respectively. Therefore, high quality seeds with over 85% germination were recommended for rootstock production and to ensure high seedling performance under field conditions. However, using lower 70% germination rubber seeds resulted in a lower plant population by 20–30% and slower growth than from the high quality seeds.