Ethylene

It is a gas at ambient temperature and it plays important roles as phytohormone in most plants [35]. Lin et al. [35] review all aspects of ethylene metabolisms in plant biology, including production and perception (Fig. 3.6).

Regarding the ethylene role in grape defence, there has been a series of recent papers by the team of Prof. J. M. Merillon, University of Bordeaux 2, France showing that 2-chloroethylphosphonic acid, an ethylene precursor also called ethephon, led to a decrease of fungus growth when sprayed onto grapevines, through elicitation of natural defences [36]. More details are available in the Chap. 5 in this book.

Additionally, a recent series of microarray analyses, using mRNAs extracted from berry tissues after exogenous application of ethylene on grape clusters, has been partly published by Chervin et al. [37]: the expression of some genes involved in plant defence was shown to be modulated by such a phytohormone.

Fig. 3.6 Ethylene (MW: 28 g; gas at ambient temperature)

Fig. 3.7 Methyl jasmonate (MW: 224 g; BP: 89°C, 192°F)

3.8 Jasmonic Acid and Methyl Jasmonate

Jasmonic acid is present naturally in grape berries, particularly in seeds [38] up to 50 pmol/seed, and methyl jasmonate is also present to a lesser extent (about ten times less) (Fig. 3.7). Data are lacking to check the variability over various cultivars.

Methyl jasmonate has been shown to promote stilbene accumulation [39] and natural defenses of grape. There will be more details developed in the Chap. 5 in this book.

3.9 Salicylic Acid and Methyl Salicylate

The salicylic acid is well-known to be part of the SAR: Systemic Acquired Resistance [40]. Park et al. [41] showed that both conversions of salicylic acid to methyl salicylate and methyl salicylate to salicylic acid were essential for SAR in tobacco, and they concluded that methyl salicylate is a SAR signal in this plant (Fig. 3.8).

However, there is still some controversy about the direct involvement of salicylic acid and methyl salicylate in SAR [40, 42].

Fig. 3.8 Methyl salicylate (MW: 152 g; BP: 222°C, 432°F)

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