Promotion of seed germination and subsequent seedling growth of loquat ( Eriobotrya japonica, Lindl) by moist-chilling and GA 3 applications

Abstract

The germination of loquat seeds faces certain problems. The present research was designed to study the promotion of the germination of loquat seeds by moist-chilling and GA 3 applications. The results showed that loquat seeds display an endogenous dormancy that can be released by moist-chilling treatment for a certain period. In this respect, the best treatment was moist-chilling for 3 weeks at 5 ± 1 °C or 1 week of moist-chilling followed by soaking in 250 ppm GA 3 solution for 20 h. These treatments significantly increased germination percentage (88 and 85%, respectively) and decreased time to 50% germination (T50) (31.5 and 40.7 days, respectively) compared to control (51% and 56 days, respectively). Also, the characteristics of the obtained seedlings were much better than the control seedlings. In addition, the 3-week moist-chilled seeds contained the highest soluble protein concentration and were characterized by the synthesis of new protein band of 161.7 kDa that was absent in all other treatments. This treatment lead to the absence of five polypeptides bands (222.5, 201.5, 109.5, 71.1 and 49.3 kDa), which were synthesized in GA 3 treatment, and the presence of a higher number of polypeptide bands compared with those of other moist-chilling periods and the control treatments. However, increasing the moist-chilling period over 3 weeks significantly decreased both germination percentage and T50. The combination between GA3 and moist-chilling treatments produced differential effects on seed germination, soluble protein and the number of protein bands depending on the length of the moist-chilling period. Although GA3 application on un-chilled seeds resulted in more synthesis of protein bands than other tested treatments, it did not improve the germination process. The concentration of soluble inorganic phosphorus of the tested seeds was negatively ( r = −0.57 *) and the concentration of soluble organic phosphorus positively ( r = +0.49 *) correlated with the germination percentage. It was concluded that treatment of moist-chilling for 3 weeks or 1 week moist-chilling followed by 250 ppm GA 3 is recommended for promoting the germination process of loquat seeds and improving growth characteristics of the subsequent seedlings.