Abstract:

Two different fleshed watermelon cultivars，orange-yellow fleshed‘WM-Clr-2’and red fleshed‘PI 179881’were used in this study. Lycopene and β-carotene accumulation were analysised using HPLC at 7 growth stages through the whole fruit-set period for totally 56 days. The relative expression of eight genes（PSY1，PSY2，PDS，ZDS，CRTISO，LCYB，NCED1，NCED7）involved in the lycopene and β-carotene biosynthesis and biodegradation were analysised by qRT-PCR. According to the results，the accumulation of both lycopene and β-carotene were higher in‘PI 179881’than in‘WM-Clr-2’at each growth stage based on the phenotype of HPLC analysis. PSY1 gene were higher expressed in‘PI 179881’than in‘WM-Clr-2’，on the contrary，NCED1 and LCYB genes showed lower expression levels in‘PI 179881’than in‘WM-Clr-2’.The analysis of lycopene and β-carotene accumulation and the transcriptional expression of eight genes confirmed that a large quality of lycopene accumulated in red-fleshed‘PI 179881’，reflecting the elevated expression of the PSY1 gene，the down-regulation of the LCYB gene and the low transcriptional levels of the NCED1 gene. The reduced transcriptional expression of PSY1 gene and the increased expression of NCED1 gene and LCYB gene were the main factors contributing to low accumulation of lycopene and β-carotene in‘WM-Clr-2’.

Key words: watermelon, lycopene, β-carotene, fruit development, gene expression