Extreme climatic events, including drought, are predicted to increase in intensity, frequency, and geographic extent as a consequence of global climate change. In general, to grow crops successfully in the future, growers will need to adapt to less available water and to take better advantage of the positive effects of drought. Fortunately, there are positive effects associated with drought. Drought stimulates the secondary metabolism, thereby potentially increasing plant defences and the concentrations of compounds involved in plant quality, particularly taste and health benefits. The role of drought on the production of secondary metabolites is of paramount importance for fruit crops. However, to manage crops effectively under conditions of limited water supply, for example by applying deficit irrigation, growers must consider not only the impact of drought on productivity but also on how plants manage the primary and secondary metabolisms. This question is obviously complex because during water deficit, trade-offs among productivity, defence, and quality depend upon the intensity, duration, and repetition of events of water deficit. The stage of plant development during the period of water deficit is also crucial, as are the effects of other stressors. In addition, growers must rely on relevant indicators of water status, i.e. parameters involved in the relevant metabolic processes, including those affecting quality. Although many reports on the effects of drought on plant function and crop productivity have been published, these issues have not been reviewed thus far. Here, we provide an up-to-date review of current knowledge of the effects of different forms of drought on fruit quality relative to the primary and secondary metabolisms and their interactions. We also review conventional and less conventional indicators of water status that could be used for monitoring purposes, such as volatile compounds. We focus on fruit crops owing to the importance of secondary metabolism in fruit quality and the importance of fruits in the human diet. The issue of defence is also briefly discussed.

Here, we present an optimization of colorimetric determination of hydrogen peroxide content in plants using potassium iodide. Our method is based on a one step buffer (extraction and reaction) for the determination of H 2 O 2 in different plant tissues and overcomes interference of soluble antioxidant and color background. A particular attention is paid to buffer pH shown to be tissue dependent. With this inexpensive microplate method, it is possible to analyze 12 experimental samples in about 45 min all in triplicates, with blanks, controls and standard curve.

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Postharvest degradation of minimally processed mangoes limits the marketability of fruit. The effect of heat treatments applied to whole 'Keitt' mango fruit on physical, physiological and biochemical quality of minimally processed mangoes was studied. Whole mangoes were subjected to hot water dipping (HWD) at 46 or 50 • C for 30 or 75 min, cooled for 15 min, minimally processed and stored at 6 • C for 9 d. Sensory analysis, firmness, color, acidity, pH, total soluble solids (TSS), ascorbic acid, total carotenoids, malondialdehyde (MDA) and respiration rate (RR) were investigated. A global beneficial effect of HWD 50 • C/30 min was observed. This treatment was the only one to maintain the acceptability of fresh-cut mangoes for 6 d, the yellow color, expressed by b* value, for 9 d and the firmness for 3 d compared to the control. Moreover, HWD 50 • C/30 min increased the total carotenoids content after 3 d compared to the control. Although the ascorbic acid content decreased during storage, HWD 50 • C/30 min is the less degrading condition of the heat treatments. Lipid peroxidation, estimated by MDA content, was less important for HWD 50 • C/30 min. Finally, the RR of whole mangoes treated by HWD 50 • C/30 min was lower than in the other treatments and could be used as an indicator of product shelf-life. This study selected the HWD 50 • C/30 min as the optimal heat treatment to improve the quality of fresh-cut 'Keitt' mangoes.

Background and aims Plant soluble sugars, as main components of primary metabolism, are thought to be implicated in defence against pathogenic fungi. However, the function of sucrose and hexoses remains unclear. This study aimed to identify robust patterns in the dynamics of soluble sugars in sink tissues of tomato plants during the course of infection by the necrotrophic fungus Botrytis cinerea. Distinct roles for glucose and fructose in defence against B. cinerea were hypothesized. Methods We examined sugar contents and defence hormonal markers in tomato stem tissues before and after infection by B. cinerea, in a range of abiotic environments created by various nitrogen and water supplies. Key Results Limited nitrogen or water supplies increased tomato stem susceptibility to B. cinerea. Glucose and fructose contents of tissues surrounding infection sites evolved differently after inoculation. The fructose content never decreased after inoculation with B. cinerea, while that of glucose showed either positive or negative variation, depending on the abiotic environment. An increase in the relative fructose content (defined as the proportion of fructose in the soluble sugar pool) was observed in the absence of glucose accumulation and was associated with lower susceptibility. A lower expression of the salicylic acid marker PR1a, and a lower repression of a jasmonate marker COI1 were associated with reduced susceptibility. Accordingly, COI1 expression was positively correlated with the relative fructose contents 7 d after infection. Conclusions Small variations of fructose content among the sugar pool are unlikely to affect intrinsic pathogen growth. Our results highlight distinct use of host glucose and fructose after infection by B. cinerea and suggest strongly that adjustment of the relative fructose content is required for enhanced plant defence.

The effects of different levels of water stress on oxidative parameters (H 2 O 2 and MDA), the total pool sizes of ascorbate, the activities of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), as well as the activities and relative transcript levels of the enzymes of ascorbate-glutathione cycle ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were studied in the fruit of tomato (Solanum lycopersicum L. cv. Micro-Tom). Plants were subjected to three levels of water stress (S50, S25 and S0) and fruits at different development stages were harvested after 3, 6 and 10 days of stress. Changes in H 2 O 2 and MDA contents indicated that water stress induced oxidative stress in fruits. The concentrations of ascorbate (AsA) and dehydroascorbate (DHA) generally modified with water stress treatments. Moreover, changes in SOD and CAT activities and DHAR, MDHAR, APX and GR activities and relative transcript levels were dependent on the fruit development stage and the intensity and the duration of water stress. These results suggest that the response of antioxidant systems of tomato fruits to oxidative stress induced by water stress treatments was different depending on the fruit development stage.

The effects of different levels of salt stress on the oxidative parameters (H2O2 and MDA), the total pool sizes of ascorbate, the activities of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), as well as the activities and relative transcript levels of the enzymes of ascorbate-glutathione cycle; ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were studied in fruits of tomato. Plants were treated by three concentrations of NaCl (50, 100 and 150 mM) and fruits at different development stages were harvested after 3 and 6 days of stress. The concentrations of ascorbate (AsA) and dehydroascorbate (DHA) generally changed with salt stress treatments. Moreover, changes in SOD and CAT activities and DHAR, MDHAR, APX and GR activities and relative transcript levels were dependent on the fruit development stage and the intensity and duration of salt stress. These results suggest that the response of antioxidant systems of tomato fruits to oxidative stress induced by salt stress treatments was different depending on the fruit development stage.

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