Effect of Methyl Jasmonate on the Biosynthesis of Volatile Compounds Associated with the Ripening of Grape Tomato Fruits.

The present work aims to evaluate the roles of methyl jasmonate (MeJA) in the formation of volatile organic compounds (VOC) from grape tomatoes during ripening. Fruits were treated with MeJA, ethylene, 1-MCP (1-methylcyclopropene), and MeJA+1-MCP, with analyses of the VOC and levels of the gene transcripts for the enzymes lipoxygenase (LOX), alcohol dehydrogenase (ADH), and hydroperoxide lyase (HPL). An intimate relationship between MeJA and ethylene in aroma formation was detected, mainly among the VOC from the carotenoid pathway. Expression of the fatty acid transcripts, LOXC, ADH, and HPL pathway genes, was reduced by 1-MCP, even when associated with MeJA. In ripe tomato, MeJA increased most of the volatile C6 compounds, except 1-hexanol. The MeJA+1-MCP treatment followed most of the increases in volatile C6 compounds that were increased by MeJA alone, which evidenced some ethylene-independent mechanism in the production of the volatile C6 compounds. In ripe tomato, MeJA and MeJA+1-MCP increased the levels of 6-methyl-5-hepten-2-one, which is derived from lycopene, evidencing an ethylene-independent biosynthetic process.

Post-Harvest Treatment with Methyl Jasmonate Impacts Lipid Metabolism in Tomato Pericarp (Solanum lycopersicum L. cv. Grape) at Different Ripening Stages.

The application of exogenous jasmonate can stimulate the production of ethylene, carotenoids, and aroma compounds and accelerate fruit ripening. These alterations improve fruit quality and make fruit desirable for human consumption. However, fruit over-ripening results in large losses of fruit crops. This problem is overcome by applying 1-methylcyclopropene to the fruits, due to its capacity to block the ethylene receptors, suppressing fruit ripening. In this study, treatments with only 1-methylcyclopropene and both 1-methylcyclopropene and methyl jasmonate were administered to observe whether exogenous methyl jasmonate can improve the metabolite levels in fruits with blocked ethylene receptors. Fruit pericarps were analyzed at 4, 10, and 21 days after harvest (DAH) and compared with untreated fruits. The post-harvest treatments affected primary metabolites (sugars, organic acids, amino acids, and fatty acids) and secondary metabolites (carotenoids, tocopherols, and phytosterols). However, the lipid metabolism of the tomatoes was most impacted by the exogenous jasmonate. Fatty acids, carotenoids, tocopherols, and phytosterols showed a delay in their production at 4 and 10 DAH. Conversely, at 21 DAH, these non-polar metabolites exhibited an important improvement in their accumulation.