Water Stress Hinders In Vitro Regeneration of Plants
Plants could be propagated vegetatively via small parts of living tissue called as ‘explant’ on growth mediums under sterile conditions. Plant cell has the ability of forming whole fertile plant which is called 'totipotency', under in vitro culture conditions. High-frequency shoot regeneration is one of the main aims of in vitro culture and it is a prerequisite to guarantee the success in transformation studies and in clonal propagation of plants. It is well known that growth regulators in culture medium and the type of explant affect in vitro regeneration frequency significantly. In this chapter, the importance of tissue water content on in vitro culture response is discussed. Increasing water content of the explant before culture initiation gives rise to increased regeneration capacity. On the other hand, increasing the tissue’s osmotic pressure enables the explant to intake water, all solutes and growth regulators from the growth medium which results in high-frequency shoot regeneration. However, tissues with lack of water are usually not successful in regenerating a satisfactory amount of shoots. The effect of water deficiency on explant’s regeneration capacity and the methods to overcome this problem are discussed in this chapter.
Part of the book: Water Stress in Plants
New Approaches to Agrobacterium tumefaciens-Mediated Gene Transfer to Plants
Agrobacterium tumefaciens, a plant pathogen, is commonly used as a vector for the introduction of foreign genes into plants and consequent regeneration of transgenic plants. A. tumefaciens naturally infects the wound sites in dicotyledonous plants and induces diseases known as crown gall. The bacterium has a large plasmid that induces tumor induction, and for this reason, it was named tumor-inducing (Ti) plasmid. The expression of T-DNA genes of Ti-plasmid in plant cells causes the formation of tumors at the infection site. The molecular basis of Agrobacterium-mediated transformation is the stable integration of a DNA sequence (T-DNA) from Ti (tumor-inducing) plasmid of A. tumefaciens into the plant genome. A. tumefaciens-mediated transformation has some advantages compared with direct gene transfer methods such as integration of low copy number of T-DNA into plant genome, stable gene expression, and transformation of large size DNA segments. That is why manipulations of the plant, bacteria and physical conditions have been applied to increase the virulence of bacteria and to increase the transformation efficiency. Preculturing explants before inoculation, modification of temperature and medium pH, addition chemicals to inoculation medium such as acetosyringone, changing bacterial density, and co-cultivation period, and vacuum infiltration have been reported to increase transformation. In this chapter, four new transformation protocols that can be used to increase the transformation efficiency via A. tumefaciens in most plant species are described.
Part of the book: Genetic Engineering
Dormancy is when there is a lack of germination in seeds or tubers even though the required conditions (temperature, humidity, oxygen, and light) are provided. Dormancy is based on hard seed coat impermeability or the lack of supply and activity of enzymes (internal dormancy) necessary for germination. Dormancy is an important factor limiting production in many field crops. Several physical and chemical pretreatments are applied to the organic material (seeds/tubers) to overcome dormancy. Physical and physiological dormancy can be found together in some plants, and this makes it difficult to provide high-frequency, healthy seedling growth, since the formation of healthy seedlings from the organic material (seeds/tubers) sown is a prerequisite for plant production. This chapter will focus on the description of four different methods we have not seen reported elsewhere for overcoming dormancy.
Part of the book: Seed Biology
The Effect of Leaf Removal–Based Physical Injury on High Seed and Crude Oil Yields in Sunflower (Helianthus annuus L.)
Yield in agricultural production decreases due to biotic (diseases and pests) and abiotic (salinity, drought, high temperature, etc.) stress factors. Chemical methods have been widely used to fight against biotic stress factors. However, the use of chemicals in agriculture causes extra financial cost and environmental pollution. Improvement of high yielded cultivars via plant breeding methods does not seem to be adequate for meeting food demand of increasing population. That is why, the improvement of environmentally friendly new methods for high yield is obligatory. Leaves in plants form an active surface for photosynthesis. High photosynthetic activity affects yield directly by increasing matter production. The aim of this study was to increase seed and oil yields in sunflower via leaf defoliation. Oil-type sunflower cultivars used in the study, “08-TR-003,” “TR-3080,” and “TARSAN-1018,” were obtained from the “Trakya Agricultural Research Institute.” When plants reached to “star-shaped head stage,” which is the beginning of the reproductive period, four different defoliation treatments were performed. They were control (no leaves removed), two leaves removed, four leaves removed, and six leaves removed. Half of the leaves were removed from just below the head, while the other half was removed from the middle part of the plant. After harvest, seed yield per plant, seed yield per decare, crude protein percentage, crude oil percentage, crude protein yield per decare, and crude oil yield per decare were determined. At the end of the study, it was observed that the application of defoliation, compared to the control, affected all characteristics positively.
Part of the book: Physical Methods for Stimulation of Plant and Mushroom Development
Possible Impacts of Climate Change on Sunflower Yield in Turkey
Sunflower (Helianthus annuus L.) is the main raw material used to produce oil for consumption and oilseed in Turkey; however, its production is not sufficient, even for only domestic consumption. Therefore, studies were needed to determine how to increase both the production area and yield in Turkey. The aim of the study was to evaluate the possible effects of climate changes on future sunflower yield. A total of 29 provinces with intense sunflower cultivation during years of 1985–2014 were evaluated. Sunflower production values and meteorological data, which belong to years of 1985–2014, on climate projections, based on HadGEM2-ES Global Climate Model and RCP8.5 scenario that cover period of 2016–2099, were used as material. In the first part of the study, linear regression analyses were conducted between the observation and production data using the least squares method. In the second part, the possible effects of climate changes on sunflower yield for 2016–2040, 2041–2070, and 2071–2099 were determined using regression equations and climate projection data. Projections indicate that decreases in yield are expected, especially in the second half of this century. In Tekirdag and Konya provinces, where there is intensive sunflower cultivation, severe decreases in yield are expected for all studied periods.
Part of the book: Agronomy
Plant Responses to Salt Stress
Salt stress is one of the harmful abiotic stress factors. It makes agricultural lands especially in arid and semi-arid regions useless despite the efforts. More than six percent of total world agricultural lands are on the edge of vanishing due to salt stress. Salinity in soil occurs as a result of the factors such as lack of drainage, improper irrigation, excessive accumulation of soluble salts. Salinity limits the growth of plants. Despite the main results, some results of plants due to these limitations vary from species to species. The negative effects get morphological, biochemical and physiological reactions from plants. Slowed or stopped growth of roots and shoots, closuring of stomata, germination slowing, decreased or stopped development of seedling, deterioration of photosynthetic activity are the main reactions of plants to stress. On the other hand, plants also develop tolerance mechanisms as a result of some auxiliaries for surviving under adverse conditions. Plants have tendency to protect themselves from salinity with osmotic protectants synthesized by them such as sugars, proline, amino acids, glycine betaine. In this review, the responses of plants to salt stress were investigated and gathered.
Part of the book: Plant Breeding
Gamma Radiation Effect on Agrobacterium tumefaciens-Mediated Gene Transfer in Potato (Solanum tuberosum L.)View all chapters
Potato (Solanum tuberosum L.) is one of the major crops of the world. Significant improvements can be achieved in terms of yield and quality by the determination of efficient transformation methods. On the other hand, low transformation frequency seriously limits the application of molecular techniques in obtaining transgenic crops. In the present study, the effect of gamma radiation on Agrobacterium tumefaciens-mediated transformation to the potato was firstly investigated. Sterile seedlings of potato cv. ‘Marabel’, which was grown on Gamborg’s B5 medium in Magenta vessels, were irradiated with different gamma radiation doses (0-control, 40, 80, 120 Gy 60Co). Stem parts having axillary meristems were excised from irradiated seedlings and inoculated by A. tumefaciens (GV2260), which harbors the binary plasmid p35S GUS-INT contains and GUS (β-glucuronidase) gene controlled by 35S promoter (CaMV) and nptII (neomycin phosphotransferase II) gene driven by NOS (nopaline synthase) promoter). Inoculated stem parts having axillary meristems explants were then directly transported to a selection medium containing duocid (500 mg l−1), and kanamycin (100 mg l−1), 4 mg l−1 gibberellic acid, 1 mg l−1 BAP and 0.1 mg l−1 NAA. The adult transgenic plants were detected by polymerase chain reaction (PCR) analysis. According to the number of transgenic plants determined by PCR analysis, results obtained from explants treated with 40 Gy gamma gave the best results compared to the control (0 Gy) application. The doses over 40 Gy were also found statistically significant compared to the control (0 Gy). It is expected that the protocol described in this study make the transformation studies easier by skipping the stages of ‘co-cultivation’, ‘culturing explants on selection medium’ and ‘recovery of transgenic shoots on selection medium’ not only for potato but also for other crop plants. This study was supported by a grant from the Scientific and Technological Research Council of Turkey (TUBİTAK) (Grant number 113O280 to Prof. Dr. Mustafa YILDIZ).
Part of the book: Solanum tuberosum