Zheng Kong^{1, 2}, Degang Zhao^{1, 3,}

The Asian cultivated rice (Oryza sativa L.) is a major type of cultivated rice in Asia [1]. The Kam sweet rice reported on Science have been able to preserve their varieties against genetic contamination from Indica strains [2]. Gou Cengao is an indigenous aromatic Kam sweet rice variety of China. This study aimed to characterize the effect of abscisic acid(ABA) on volatile compounds in grains of Gou Cengao. Using GC-O and SPME-GC-MS, nonanal displayed the highest odor activity value (OAV) in the grains and decreased after applicaton of ABA in the rice seedlings. The relative expression of rice OsLOX3 (rice lipoxygenase 3) and OsHPL1 (rice hydroperoxide lyase 1) was assessed by RT-PCR in grains of Gou Cengao and the non-aromatic Lailong rice after pollination. Our data showed that OsLOX3 was elevated in Gou Cengao compared with the non-aromatic rice. In agreement, lipoxygenase (OsLOX3 gene product) levels and activity were elevated in aromatic rice samples. Interestingly, a significant negative Pearson correlation (-0.945) was found between the concentrations of endogenous ABA and the relative expression of rice OsLOX3 (p < 0.01). The results suggest that the inhibiting effect of ABA on the biosynthetic pathway of nonanal.

Kam sweet rice, nonanal, 2-Acetyl-1-pyrroline, lipoxygenase activity, abscisic acid, OsLOX3