Search

Adverse conditions and biotic strain can lead to significant losses and impose limitations on plant yield. Polyamines (PAs) serve as regulatory molecules for both abiotic/biotic stress responses and cell protection in unfavourable environments. In this work, the transcription pattern of 24 genes orchestrating PA metabolism was investigated in Cucumber Mosaic Virus or Potato Virus Y infected and cold stressed tomato plants. Expression analysis revealed a differential/pleiotropic pattern of gene regulation in PA homeostasis upon biotic, abiotic or combined stress stimuli, thus revealing a discrete response specific to diverse stimuli: (i) biotic stress-influenced genes, (ii) abiotic stress-influenced genes, and (iii) concurrent biotic/abiotic stress-regulated genes. The results support different roles for PAs against abiotic and biotic stress. The expression of several genes, significantly induced under cold stress conditions, is mitigated by a previous viral infection, indicating a possible priming-like mechanism in tomato plants pointing to crosstalk among stress signalling. Several genes and resulting enzymes of PA catabolism were stimulated upon viral infection. Hence, we suggest that PA catabolism resulting in elevated H2O2 levels could mediate defence against viral infection. However, after chilling, the activities of enzymes implicated in PA catabolism remained relatively stable or slightly reduced. This correlates to an increase in free PA content, designating a per se protective role of these compounds against abiotic stress.

The aim of this work was to investigate the effects of ReTain (4.15%, w/w, amino ethoxyvinyl glycine, AVG), an ethylene synthesis inhibitor, sprayed at concentrations up to 250 mg L −1 before the green maturation of ‘Konservolia’ olives ( Olea europea L.) on colouring in fruit harvested up to 20 d later and on ripening variables in fruit selected green at harvest and exposed at 20 °C for up to 7 d. Earlier applications and higher ReTain concentrations were more effective in preventing colouring at harvest, and softening and green losses at 20 °C. Ethylene production was non-measurable or very low. Increased respiration was observed only in early treated fruit with ReTain on day 1 at 20 °C, but respiration reduced in all fruit during exposure time. Oleuropein (OE), the major phenolic, hydroxytyrosol, tyrosol, luteolin 7- O -glucoside, luteolin 4- O -glucoside, rutin, and ferulic and p-coumaric acids were measured in all samples. OE, confirmed by HPLC–ESI-MS, and total antioxidant activity were lower in ReTain treated fruit than in controls and remained so after the increases at 20 °C in all fruit. Conclusively, ReTain could be used to extend the harvest period and/or improve the quality of fresh green olives for table use, and particularly those destined for Spanish-style processing.