Abstract
Within the tomato clade, Solanum chilense is considered one of the most promising sources of genes for tomato (S. lycopersicum) selection to biotic and abiotic stresses. In this study, we compared the effects of drought, high temperature, and their combination in two cultivars of S. lycopersicum and six populations of S. chilense, differing in their local habitat. Plants were grown at 21/19 °C or 28/26 °C under well-watered and water-stressed conditions. Plant growth, physiological responses, and expression of stress-responsive genes were investigated. Our results demonstrated strong variability among accessions. Differences in plant growth parameters were even higher among S. chilense populations than between species. The effects of water stress, high temperature, and their combination also differed according to the accession, suggesting differences in stress resistance between species and populations. Overall, water stress affected plants more negatively than temperature from a morpho-physiological point of view, while the expression of stress-responsive genes was more affected by temperature than by water stress. Accessions clustered in two groups regarding resistance to water stress and high temperature. The sensitive group included the S. lycopersicum cultivars and the S. chilense populations LA2931 and LA1930, and the resistant group included the S. chilense populations LA1958, LA2880, LA2765, and LA4107. Our results suggested that resistance traits were not particularly related to the environmental conditions in the natural habitat of the populations. The expression of stress-responsive genes was more stable in resistant accessions than in sensitive ones in response to water stress and high temperature. Altogether, our results suggest that water stress and high temperature resistance in S. chilense did not depend on single traits but on a combination of morphological, physiological, and genetic traits.
Highlights
Tomato (Solanum lycopersicum L.) is one of the most important vegetable crops in the world
Our results demonstrated strong variability among accessions even under control conditions (21-WW)
At 21 ◦C under well-watered (21-WW), accessions mainly differed with respect to plant growth parameters, while photosynthesis and water status-related parameters were similar, with the exception of leaf and stem water content (WC), chlorophyll concentration, and MDA concentration; these last three parameters were higher in S. lycopersicum than in S. chilense
Summary
Tomato (Solanum lycopersicum L.) is one of the most important vegetable crops in the world. Numerous studies have investigated the physiological and morphological impact of drought and heat applied individually on tomato, while the impact of combined stress has only recently been addressed [2,7,8,9,10]. The most relevant method to improve the tomato and make it more resistant to abiotic stresses (drought, high temperatures, salinity, etc.) is the introgression of resistant genes from wild relatives species [11,12]. The cultivated tomato is phylogenetically related to 13 wild tomato species native to South America that demonstrate considerable morphological and ecological diversity [13]. Compared with the large genetic variability found in wild tomato species, the genetic diversity of the cultivated tomato varieties is very limited due to their recent domestication from a small number of individuals [14,15]. It was found that annual precipitations and temperature are significant factors in determining the distribution of wild tomato species [16]
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