The Potential of the MAGIC TOM Parental Accessions to Explore the Genetic Variability in Tomato Acclimation to Repeated Cycles of Water Deficit and Recovery

Abstract

Episodes of water deficit (WD) during the crop cycle of tomato may negatively impact plant growth and fruit yield, but they may also improve fruit quality. Moreover, a moderate WD may induce a plant “memory effect” which is known to stimulate plant acclimation and defenses for upcoming stress episodes. The objective of this study was to analyze the positive and negative impacts of repeated episodes of WD at the plant and fruit levels. Three episodes of WD (–38, –45, and –55% of water supply) followed by three periods of recovery (“WD treatments”), were applied to the eight parents of the Multi-Parent Advanced Generation Inter-Cross population which offers the largest allelic variability observed in tomato. Predawn and midday water potentials, chlorophyll a fluorescence, growth and fruit quality traits [contents in sugars, acids, carotenoids, and ascorbic acid (AsA)] were measured throughout the experiment. Important genotypic variations were observed both at the plant and fruit levels and variations in fruit and leaf traits were found not to be correlated. Overall, the WD treatments were at the origin of important osmotic regulations, reduction of leaf growth, acclimation of photosynthetic functioning, notably through an increase in the chlorophyll content and in the quantum yield of the electron transport flux until PSI acceptors (J0RE1/JABS). The effects on fruit sugar, acid, carotenoid and AsA contents on a dry matter basis ranged from negative to positive to nil depending on genotypes and stress intensity. Three small fruit size accessions were richer in AsA on a fresh matter basis, due to concentration effects. So, fruit quality was improved under WD mainly through concentration effects. On the whole, two accessions, LA1420 and Criollo appeared as interesting genetic resources, cumulating adaptive traits both at the leaf and fruit levels. Our observations show that the complexity involved in plant responses, when considering a broad range of physiological traits and the variability of genotypic effects, represent a true challenge for upcoming studies aiming at taking advantage of, not just dealing with WD.

Impact of water quality and irrigation management on organic greenhouse horticulture

“…For example, fruit phytochemical responses (ascorbic acid and carotenoids) of tomato to water deficit varied between genotypes and stress severity (intensity duration) from negative to positive. Water deficit during fruit ripening also reduced the accumulation of some carotenoids after several water shortage events (Ripoll et al 2016).…”

“…For a range of different tomato genotypes, a soil water deficit resulted in plant osmotic adjustments, leaf growth reduction, and photosynthetic acclimatisation, in particular an increase in chlorophyll leaf content and cyclic electron flow (Ripoll et al 2016). It was also reported that plants might have a "memory" of a water stress period resulting in a reduction of its negative impact during the following water stress period; the response mechanisms are being associated with increased gene expression.…”

“…Suboptimal water scheduling affects crops differently according to their genotype. For example, large fruit tomato genotypes are more sensitive to water stress than cherry in terms of fruits growth, probably due to differences in water flux on fruit expansion, and in carbon supply by leaves and carbon demand by fruits (Ripoll et al 2016). Nevertheless, crop responses to soil water stress are highly variable and depend on many factors among which are species sensitivity and genotypes; physiological developmental stages at which the stress occurs; the intensity, duration and frequency of the stress; and the environmental growing conditions.…”

“…The main responses of plant/fruit composition to water deficit have been attributed to concentration effects, active solute accumulation or the breakdown of storage carbohydrate (Ripoll et al 2016), contributing to their osmotic adjustment. The effects of water deficit on cell size and cell turgor may also impact quality attributes.…”

Model-Assisted Estimation of the Genetic Variability in Physiological Parameters Related to Tomato Fruit Growth under Contrasted Water Conditions

“…Trade-offs between quality and yield seem realistic, but depend strongly on stress intensity and genotypes (Ripoll et al, 2016). Indeed, recent studies on tomato revealed a strong genetic variability in the response to drought from negative to nil to positive impact on fruit size and quality (Ripoll et al, 2015). A large number of genes and molecular mechanisms involved in survival under drought have been identified, in particular in Arabidopsis thaliana (L.) Heynh.…”