Involvement of ethylene production and polyamines in rind pitting of ‘Fino’ lemon fruit

Rind disorders in early cultivars of lemon fruits cause serious economic losses at market since these lemons are very sensitive to develop rind pitting during postharvest. Therefore, the aim of this study was to determine the involvement of ethylene and polyamines (PAs) in rind pitting of 'Fino' lemons grown with an intensive fertigation (IF) and standard fertigation (SF). Results after degreening treatment showed that lemons harvested from the IF system had ca. 48 %, 3.5-fold, 2.5-fold and 28 % more respiration rate, ethylene production, free and total 1-aminocyclopropane-1-carboxylic acid (ACC), respectively, than SF lemons. Furthermore, the concentrations of spermidine and spermine were ca. 30 % lower in IF lemons compared to SF ones, without differences in putrescine levels. After 7 days of storage at 8 °C, the highest values of rind pitting incidence and severity of damage were found in IF lemons. It was observed that lemons with rind pitting harvested from the IF system had the highest concentration of free-ACC and total-ACC, whereas the spermine content was ca. 3-fold higher in fruits without rind pitting independently of the fertigation system. Thus, the results showed that ethylene can be considered as a marker for the lemon fruit susceptibility to suffer rind pitting, while PAs have a protective role.