Response of Rowan Berry (Sorbus redliana) Shoot Culture to Slow Growth Storage Conditions

Slow growth storage can preserve the genetic resources of endangered species such as those of genus Sorbus. Our aim was to study the storability of rowan berry in vitro cultures, their morpho-physiological changes, and regeneration ability after different storage conditions (4 ± 0.5 °C, dark; and 22 ± 2 °C, 16/8 h light/dark). The cold storage lasted for 52 weeks, and observations were made every four weeks. Cultures showed 100% survival under cold storage, and those taken from the storage showed 100% regeneration capacity after the passages. A dormancy period lasting about 20 weeks was observed, followed by intensive shoot growth until the 48th week, which led to the exhaustion of the cultures. The changes could be traced to the reduction of the chlorophyll content and the F_v/F_m value, as well as in the discoloration of the lower leaves and the appearance of necrotic tissues. Long, etiolated shoots (89.3 mm) were obtained at the end of cold storage. Shoot cultures stored in a growth chamber as control (22 ± 2 °C, 16/8 h light/dark) senesced and died after 16 weeks. Explants from stored shoots were subcultured for four weeks. The number and length of newly developed shoots were significantly higher on explants from cold storage compared to those from control cultures if the storage was longer than one week.

Phytotoxicity and Other Adverse Effects on the In Vitro Shoot Cultures Caused by Virus Elimination Treatments: Reasons and Solutions

In general, in vitro virus elimination is based on the culture of isolated meristem, and in addition thermotherapy, chemotherapy, electrotherapy, and cryotherapy can also be applied. During these processes, plantlets suffer several stresses, which can result in low rate of survival, inhibited growth, incomplete development, or abnormal morphology. Even though the in vitro cultures survive the treatment, further development can be inhibited; thus, regeneration capacity of treated in vitro shoots or explants play also an important role in successful virus elimination. Sensitivity of genotypes to treatments is very different, and the rate of destruction largely depends on the physiological condition of plants as well. Exposure time of treatments affects the rate of damage in almost every therapy. Other factors such as temperature, illumination (thermotherapy), type and concentration of applied chemicals (chemo- and cryotherapy), and electric current intensity (electrotherapy) also may have a great impact on the rate of damage. However, there are several ways to decrease the harmful effect of treatments. This review summarizes the harmful effects of virus elimination treatments applied on tissue cultures reported in the literature. The aim of this review is to expound the solutions that can be used to mitigate phytotoxic and other adverse effects in practice.

Catalytic properties of lipoxygenase extracted from different varieties of Pisum sativum and Lens culinaris

Lipoxygenase (LOX, E.C. 1.13.11.12), among its various roles, catalyzes the degradation of polyunsaturated fatty acids and it is considered to be one of the main causes of undesirable off-flavor developments in legumes. The role of LOX in postharvest physiology is particularly significant in seeds with high values of lipoxygenase and linoleic acid levels. This research aimed to study the biochemical properties of the LOX extracted from green pea (Pisum sativum L. var. Léda, Zeusz, Zsuzsi), dry pea (Pisum sativum L. var. Hanka, Irina, Lutra), and lentil (Lens culinaris L., var. Pinklevi, Rézi, Castelluccio), using linoleic acid as a substrate. The raw extracts showed different catalytic properties, with dry pea (var. Irina) that expressed the highest LOX activity, while lentil (var. Pinklevi) expressed the lowest activity. To complete the biochemical characterization of the crude LOX extracts, their optimal pH and temperature were also examined. The highest value of lipoxygenase activity in the pH range 6-7 was measured in all legumes. The optimal temperature for all extracts fell within the range of 30-60°C given the nutritional importance of legumes. This study will serve as a basis for further detailed investigation of the legumes LOX activity and its roles in food products related to legumes. PRACTICAL APPLICATIONS: This study investigated the biochemical properties of lipoxygenase (LOX) extracted from different varieties of lentil and pea, the two important leguminous crops serving as the main protein source for the population of humans worldwide. The biochemical properties of LOX extracted from legumes showed large differences in terms of kinetic properties. The results of this study revealed that the use of lipoxygenase can be a suitable index for managing stabilization techniques of lentil and pea, in order to inhibit the lipid oxidation in grain legume without compromising its nutritional value.

Shoot tip necrosis of in vitro plant cultures: a reappraisal of possible causes and solutions

Shoot tip necrosis is a physiological condition that negatively impacts the growth and development of in vitro plant shoot cultures across a wide range of species. Shoot tip necrosis is a physiological condition and disorder that can arise in plantlets or shoots in vitro that results in death of the shoot tip. This condition, which can spread basipetally and affect the emergence of axillary shoots from buds lower down the stem, is due to the cessation of apical dominance. STN can occur at both shoot multiplication and rooting stages. One of the most common factors that cause STN is nutrient deficiency or imbalance. Moreover, the presence or absence of plant growth regulators (auxins or cytokinins) at specific developmental stages may impact STN. The cytokinin to auxin ratio within an in vitro plant can be modified by varying the concentration of cytokinins used in the culture medium. The supply of nutrients to in vitro shoots or plantlets might also affect their hormonal balance, thus modifying the occurrence of STN. High relative humidity within culture vessels and hyperhydricity are associated with STN. An adequate supply of calcium as the divalent cation (Ca²⁺) can hinder STN by inhibiting the accumulation of phenolic compounds and thus programmed cell death. Moreover, the level of Ca²⁺ affects auxin transport and ethylene production, and higher ethylene production, which can occur as a result of high relative humidity in or poor ventilation of the in vitro culture vessel, induces STN. High relative humidity can decrease the mobility of Ca²⁺ within a plant, resulting in Ca²⁺ deficiency and STN. STN of in vitro shoots or plantlets can be halted or reversed by altering the basal medium, mainly the concentration of Ca²⁺, adjusting the levels of auxins or cytokinins, or modifying culture conditions. This review examines the literature related to STN, seeks to discover the associated factors and relations between them, proposes practical solutions, and attempts to better understand the mechanism(s) underlying this condition in vitro.

Cytokinin-induced changes in the chlorophyll content and fluorescence of in vitro apple leaves

Cytokinins (CKs) are one of the main regulators of in vitro growth and development and might affect the developmental state and function of the photosynthetic apparatus of in vitro shoots. Effects of different cytokinin regimes including different types of aromatic cytokinins, such as benzyl-adenine, benzyl-adenine riboside and 3-hydroxy-benzyladenine alone or in combination were studied on the capacity of the photosynthetic apparatus and the pigment content of in vitro apple leaves after 3 weeks of culture. We found that the type of cytokinins affected both chlorophyll a and b contents and its ratio. Chlorophyll content of in vitro apple leaves was the highest when benzyl-adenine was applied as a single source of cytokinin in the medium (1846-2176 μg/1g fresh weight (FW) of the leaf). Increasing the concentration of benzyl-adenine riboside significantly decreased the chlorophyll content of the leaves (from 1923 to 1183 μg/1g FW). The highest chl a/chl b ratio was detected after application of meta-topolin (TOP) at concentrations of 2.0 and 6.0 μM (2.706 and 2.804). Chlorophyll fluorescence was measured both in dark-adapted (Fv/Fm test) and in light-adapted leaf samples (Yield test; Y(II)). The maximum quantum yield and efficiency of leaves depended on the cytokinin source of the medium varied between 0.683 and 0.861 (Fv/Fm) indicating a well-developed and functional photosynthetic apparatus. Our results indicate that the type and concentration of aromatic cytokinins applied in the medium affect the chlorophyll content of the leaves in in vitro apple shoots. Performance of the photosynthetic apparatus measured by chlorophyll fluorescence in the leaves was also modified by the cytokinin supply. This is the first ever study on the relationship between the cytokinin supply and the functionability of photosystem II in plant tissue culture and our findings might help to increase plantlet survival after transfer to ex vitro conditions.

Progress and prospects for interspecific hybridization in buckwheat and the genus Fagopyrum

Cultivated buckwheat, such as common (Fagopyrum esculentum Moench.) and tartary (Fagopyrum tataricum (L.) Gaertn.) buckwheat, is one of the most versatile crops for forage and food and has several benefits for human health. Interspecific hybridization between Fagopyrum species is of great importance to improvement of buckwheat. Hybridization would allow the transfer of agronomical beneficial characteristics from wild Fagopyrum species, including self-pollination and increased fertility, frost tolerance, and higher content of beneficial compounds. However, conventional breeding methods are only partially applicable because of the self-incompatibility and incompatibility barriers between different species. Present review summarizes the morphology of self-incompatibility, the genetic and cellular basis of incompatibility between different Fagopyrum species. In many interspecific crosses hybrid embryos are aborted after successful pollination due to post-zygotic incompatibility. The use of in vitro embryo rescue after interspecific hybridization has been successful in circumventing breeding barriers between Fagopyrum species. Methods applied successfully for the construction of interspecific hybrids are discussed in detail.

Models and tools for studying drought stress responses in peas

The pea (Pisum sativum L.) is an important pulse crop but the growing area is limited because of its relatively low yield stability. In many parts of the world the most important abiotic factor limiting the survival and yield of plants is the restricted water supply, and the crop productivity can only be increased by improving drought tolerance. Development of pea cultivars well adapted to dry conditions has been one of the major tasks in breeding programs. Conventional breeding of new cultivars for dry conditions required extensive selection and testing for yield performance over diverse environments using various biometrical approaches. Several morphological and biochemical traits have been proven to be related to drought resistance, and methods based on physiological attributes can also be used in development of better varieties. Osmoregulation plays a role in the maintenance of turgor pressure under water stress conditions, and information on the behaviour of genotypes under osmotic stress can help selection for drought resistance. Biotechnological approaches including in vitro test, genetic transformation, and the use of molecular markers and mutants could be useful tools in breeding of pea. In this minireview we summarized the present status of different approaches related to drought stress improvement in the pea.