Drought response in tomato: molecular and physiological analysis

Drought stress in plants is one of the resulting effects of climatic change in the world and itsconsequences cause major yield losses. Most crop plants, including tomato (Solanumlycopersicum), are sensitive to drought stress. Substantial genetic variation for Drought Tolerance(DT) exists within the cultivated tomato, as well as in other related wild species. However, thegenetic variability in the response to drought stress in tomato species is not well understood towarrant its use for developing drought-tolerant cultivars.The aim of this work is to identify polymorphisms within genes involved in DT across tomatocultivars and wild species by re-sequencing. The tomato genotypes were tested, belong to differentSolanum species and to a collection of cultivated varieties and ecotypes. Phenotypiccharacterization of genotypes was performed at the physiological level by determination of relativewater content (RWC) and water loss rate (WLR) after many hours of dehydration. In addition, theeffect of the water deficit was also assessed on the photosynthetic performance in leaves of 3genotypes of tomato grown under a plastic tunnel. Photosynthetic performance of PSII, stomatalconductance, RWC and leaf water potentials in tomato leaf tissues were monitored duringapplication of stress and after recovery watering.In order to identify Single Nucleotide Polymorphisms (SNPs), specific primers were designedfor sequences of 6 putative drought stress-related genes retrieved from GenBank. In particular,sequences annotated as MKP1 (MAP kinase phosphatase), Asr2 (ABA stress ripening), TSW12 (alipid transfer protein gene), dehydrin TAS14, rd22 (dehydration responsive gene) and STO(putative zinc-finger protein) were analyzed. After amplification, SNPs discovery was achieved byre-sequencing PCR products on a ABIPRISM 3130 GENETIC ANALYZER. An average of 16SNP and 2 IN/DEL were identified in these gene sequences. The wild species showed manymutations and this was predictable because the reference sequence reported in GenBank was fromS. lycopersicum.The identification of polymorphisms associated to the DT may lead to the development ofuseful molecular markers helping assisted selection programs.