Strawberry Research Papers - Academia.edu (original) (raw)

Strawberry is one of the most popular fruits due to its delicious flavor and attractive aspect, and the demand for strawberries, as well as its culture, is continuously increasing worldwide. This crop, however, is not absent of problems that compromise yield or fruit quality. Actually, strawberry is considered by the consumers as one of the most inconsistent commodities in the marketplace. The use of highly producer cultivars with large but poorly flavored fruits, incorrect crop management practices such as harvesting the fruits before full ripening, the short postharvest life of strawberry fruits or the extensive use of dangerous fumigants to control pest are among the main problems of this crop. Nowadays, people demand plant biology researchers to focus more efforts on safer and sustainable agriculture, avoiding as much as possible the use of chemicals, and to improve fruit quality traits. The implementation of biotechnological approaches within traditional breeding programs can be helpful to reach this goal. Besides this practical view, strawberry has been adopted as a model crop for some molecular and physiological studies, such as the ripening of non climacteric fruits, increasing their importance in the scientific world. The aim of this volume is to provide updated information about the current stage of genomics, transgenesis and biotechnology in strawberry, through the inclusion of reviews and research papers wrote by leader groups in these areas. Molecular markers have been explored in strawberry from the 80´s but in recent years the development of high throughput sequencing technologies has increased dramatically the amount of genomic data in this species. These advances in structural genomics in the genus Fragaria have been reviewed by Bonet and Monfort, and the release of the first draft of the strawberry genome is expected very soon. Most strawberry cultivars show seasonal flowering, requiring short photoperiod and/or low temperature for the induction of flowering, while the opposite environmental signals are needed for runnering. Hytönen and Elomaa have reviewed our current knowledge about candidate genes involved in flowering induction. This review is complemented by the paper of Massetani et al. who examine the effect of abiotic stresses, nutritional factors and propagation techniques on strawberry plant architecture. These studies can provide efficient tools to extend cropping season and increase berry yields. Besides attractive flavor, strawberries are a rich source of phytochemicals beneficial for human health. Hanhieneva et al. and Schmeda et al. have reviewed recent advances in metabolomics of both, cultivated strawberry and the Chilean strawberry Fragaria chiloensis, respectively. While both papers highlight the chemical composition of fruits, data about metabolomics of vegetative organs are also included. Increasing postharvest shelf life of strawberry fruit is central to strawberry research, which is very short mainly due to its fast softening rate and enhanced pathogen susceptibility usually associated with this process. Cell wall disassembly and loss of cell turgor during fruit ripening are considered the main factors responsible for fruit softening. Posé et al. have reviewed the main features of the disassembly cell wall process, and how the manipulation of some cell wall genes through transgenesis can reduce fruit softening without affecting other fruit quality parameters, while Alleva et al. examine the role of the water channel aquaporins in the loss of cell turgor during fruit ripening. For a limited number of genes, their role on fruit ripening has been assessed by stable genetic transformation. However, the increased knowledge of genes involved in fruit ripening requires efficient and fast systems for gene function analysis. Schawb et al. show how gene down-regulation by RNA interference in agroinfiltration experiments has been successfully used to assess the role of several fruit specific genes, avoiding time-consuming and labor-intensive stable transformation systems. Genetic modification could be a successful approach in improving quality of strawberry crop, as has been demonstrated with several fruit ripening genes. The application of this technology requires robust regeneration and transformation systems for each particular genotype. Currently, Agrobacterium tumefaciens infection in combination with a leaf disk regeneration system is the most popular method to get transgenic strawberry plants. Husaini et al. analyze key factors determining the success of genetic transformation in this species, and describe a general transformation protocol that has been proven useful in several strawberry cultivars. However, the toughest impediment in the development of this technology is the poor consumer perception of transgenic crops. These concerns are examined by Schaart et al. They describe the results of a recent consumer survey indicating that transgenic crops would be better accepted if only genes from the species itself, the so called intragenic or cisgenic plants, were used. This review also describes the attempts to get intragenic strawberry plants resistant to Botrytis cinerea. Intragenic modification requires the use of native promoters to drive gene expression. In their research article Schaart et al. describe the characterization of a promoter sequence of the strawberry fruit expansin FaExp2 gene. One of the main problems of the strawberry industry is the high amount of pesticides required to avoid loss of production, mainly due to fungal infections. Natural resistance against important diseases is scarce within the genus Fragaria, and therefore, alternative approaches to get tolerant cultivars are quite desirable. Garrido et al. summarize recent advances in the methods for detection and identification of strawberry fungal pathogens as well as strategies for their biocontrol using microorganisms. In a research paper, Matsubara et al. show that arbuscular mycorrhizal colonization enhances tolerance to Fusarium wilt and this effect is related to an increased level of antioxidative ability. Finally, Shokaeva et al. describe a method for the obtainment of plants tolerant to Botrytis cinerea or Phytophtora cactorum, and also to salinity stress, through screening and selection of somaclonal variants developed after exposure to these stressors under in vitro conditions. As many people that enjoy consuming strawberries, for us too it has been a pleasure to work in the preparation of this project. We hope that readers of this special issue, biotechnologists, physiologists, breeders or simply strawberry lovers, enjoy the reviews and find them useful. We are thankful to our families for having adjusted with us, while we were busy for long hours during the preparation of this volume. We finally thank all authors for their excellent contributions, and also for their patience during the long time required to complete this hybrid book, and to the GSB Editor-in-Chief Dr. Jaime Teixeira da Silva for his generous support.