Effects of Fe-Zn-NA chelates priming on the vigour of aged hybrid rice seeds and the maintenance of priming benefits at different storage temperatures

The effects of seed priming with Fe-Zn-NA chelate (FeSO4+ZnSO4+niacinamide) and the longevity of the beneficial priming effects were investigated for aged seeds of hybrid rice cv. Lingyouhuazhan (LYHZ) and cv. Longxiangyou 130 (LXY130). As compared with untreated and hydroprimed seeds, Fe-Zn-NA chelate priming significantly enhanced germination energy (GE), germination percentage (GP), germination index (GI), vigour index (VI) and normal seedling rate (NSR), and increased seedling shoot height (SH) and seedling dry weight (DW) in both cultivars. After priming with Fe-Zn-NA chelates, the GP of LYHZ was 96.0%, which was 12.7 and 12.0% higher than hydroprimed and non-primed seeds, respectively. Similarly, the GP of LXY130 was 89.5%, significantly higher than the hydroprimed and non-primed seeds (by 11.5 and 10.0%, respectively). When stored at 25°C, the benefits of Fe-Zn-NA chelate priming on seed vigour and viability was maintained for three months; while after six months storage, the GP of LYHZ and LXY130 was only 48.0 and 34.0%, respectively, which was significantly lower than the non-primed seeds (84.0 and 71.1%). When stored at 15 or 5°C for six months, the germination potential of Fe-Zn-NA chelate-primed seeds was still high. The GP of LYHZ and LXY130 seeds was 94.4% and 77.8%, respectively, after storage at 15°C, and 97.8% and 85.6% after storage at 5°C. In conclusion, the Fe-Zn-NA chelate priming was an effective method to improve the vigour and viability of hybrid rice aged seeds; however, the duration of beneficial priming effects needs to be determined according to the storage temperature.