The constitutions of terpenoids and hormones of leaves in red-flesh citrus mutants and their wild types

Abstract

To study the profiles and relationships of terpenoids and phytohormones in leaves of red-flesh citrus, we examined four red-flesh mutants that accumulate lycopene in the fruit and their corresponding wild types. We compared their contents of monoterpenoid and sesquiterpenoid volatiles, triterpenoid limonoid aglycones, and tetraterpenoid carotenoids. The types and concentrations of these terpenoids in the leaves varied among genotypes, and the leaf terpenoid profiles differed between red-flesh mutants and their wild types. However, lycopene was not detected in citrus leaves of all eight varieties, including the four mutants. According to phytohormone accumulation in the leaves, the citrus varieties could be classified into a low-phytohormone group (‘Red Anliu’ sweet orange, ‘Anliu’ sweet orange, and ‘Cara Cara’ navel orange), a high-phytohormone group (‘Seike’ navel orange), and a high-jasmonic acid group (‘Red-flesh Guanxi’ pummelo, ‘Guanxi’ pummelo, ‘Chuhong’ pummelo, and ‘Feicui’ pummelo). The contents of terpenoid volatiles were very low in leaves of ‘Red-flesh Guanxi’ and ‘Guanxi’ pummelo; therefore, they are ideal materials for verifying the functions of genes related to terpenoid volatiles in overexpression analyses. Sesquiterpenoid volatiles were positively correlated with phytohormones of abscisic acid, jasmonic acid, and salicylic acid. Taken together, lycopene was undetected in the leaves of red-flesh citrus mutants with abundant lycopene in their juice sacs, which suggested a tissue-specific accumulation pattern of lycopene in citrus red-flesh mutants. Furthermore, leaf volatile profiles could be suitable to develop fingerprint chromatograms of citrus resources, since leaf volatile profiles were dominated by several compounds that varied among genotypes in their combinations and concentrations.

Keywords

• Citrus
• Carotenoid
• Terpenoid volatile
• Limonoid aglycone
• Hormone
• Leaf