Influence of hot water treatment on brown rot of peach and rapid fruit response to heat stress

Recent results on hot water as an alternative treatment open a new perspective in disease incidencereduction. In the present work peach fruit were wounded, inoculated with conidia of Monilinia laxa and15 min, 3, 6, 12, 24 and 48 h after inoculation treated by dipping in hot water (HT) at 60◦C for 20 s. Theeffect of heat treatment on some cell wall genes involved in ripening such as -galactosidase (-GAL),pectin lyase (PL), polygalacturonase (PG) and pectin methyl esterase (PME), was analyzed by qRT-PCR.The expression levels of defense related genes, phenylalanine ammonia lyase (PAL) and chitinase (CHI),heat stress-related genes such as heat shock proteins 70 and 90 (HSP70, HSP90), and reactive oxygenspecies (ROS) scavenging genes were also evaluated by qRT-PCR. A 100% disease incidence reduction, ascompared to untreated fruit, was obtained by treating 6 and 12 h after inoculation. Moreover, brown rotwas inhibited by 85.7% when fruit were heat-treated 48 h after inoculation. The expression levels of cellwall genes (-GAL, PL, PG and PME) showed a general decrease in HT fruit as compared to the control,whereas PAL, CHI, HSP70 and ROS-scavenging genes increased their expression level in HT samples withrespect to the untreated ones. Our results show a curative activity of heat on peach inoculated withM. laxa 48 h before treatment. Each analyzed gene proved to be differentially expressed following heattreatment