Influence of hot water on breaking dormancy, incubation temperature and rhizobial inoculation on germination of Acacia mearnsii seeds

Acacia mearnsii is a tree species commercially cultivated in Africa and South America. This species requires physical or chemical treatments to overcome physical seed dormancy. In this report, we assessed the effect of different treatments with hot water (40 degrees C for 24 h; 60 degrees C for 5 min; 80 degrees C for 5 min; 90 degrees C for 5 min and 100 degrees C for 5 min) on seed dormancy, rhizobial inoculation (Bradyrhizobium sp. SEMIA 6164 = BR 3608) and two different incubation temperature (20 degrees C and 25 degrees C) on germination of A. mearnsii. The results indicated that the immersion of seeds in hot water at 80 degrees C was the most optimum treatment as indicated by total germination (83.0%), germination index (187.5), germination speed (19.5) and accumulated germination speed (24.5). The elevation of incubation temperature from 20 degrees C to 25 degrees C enhanced the germination index by 7.4%. Inoculation of SEMIA 6164 also increased the speed and accumulated speed of germination by 8.7% and 10.1%, respectively. The present study revealed that the immersion of seeds in hot water at 80 degrees C for 5 min, incubation at 25 degrees C and inoculation with SEMIA 6164 offered the most favourable conditions for the maximum and quick recovery of uniform seedlings and can be recommended for raising the forestry nurseries of A. mearnsii.