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Hydroponic systems are known to provide a platform for uniform growth conditions until the reproductive stage. However, many plant species, including sunflower, show poor growth and survivability under conventional hydroponic systems due to poor nutrient availability, hypoxia and algal contamination. Thus, we tested various hydroponic systems to select a hydroponic system suitable for screening of sunflower germplasm. Sunflower accessions showed better growth and leaf gas exchange in newly-designed over conventional hydroponic systems. Selected hydroponic systems were further engaged in sunflower accession screening under heat and osmotic stress in a two-pan system (210 cm × 60 cm). Heat stress treatment was applied by growing sunflower germplasm at 42 °C and osmotic stress by adding polyethylene glycol 8000 which decreased the osmotic potential to − 0.6 MPa. There was significant variability among the sunflower accessions for their ability to survive under stress. Accessions such as C-2721 (43%), C-291 (46%) and D-14 (43%) had lower cell membrane injury percentage under osmotic stress and high seedling survivability (60‒80%) under heat stress when compared with susceptible accessions. Moreover, resistant accessions exhibited greater cuticular waxes and root length but lower transpiration losses. The newly designed hydroponic platform proved reliable for the selection of resistant sunflower accessions. Selected parental lines were validated by assessing their hybrids under field trials across two seasons under water and temperature stress during the reproductive phase (autumn). Hybrid H3 obtained by crossing drought and heat resistant parents had the highest seed yield and water use efficiency.

Common fig (Ficus carica L.), an economically-important fruit species widely cultivated in the Mediterranean Basin, is gaining increasing interest in the tropical and subtropical regions. A vast genetic diversity of common fig is available; however, systematic studies of cultivar performance in a particular new environment are scarce. The objective of this study was to evaluate the performance of 17 common fig cultivars grown under the Malaysian tropical climate. Evaluation was based on 15 parameters relevant to fruit yield, fruit quality and pest susceptibility. The results showed variable performance among the cultivars tested; 10 cultivars performed well for orchard establishment. Cultivar ‘A134’ produced the highest fruit yield per plant (3410 g) compared to the average yield of the cultivars studied (2500 g). Cultivars ‘Fen Chan Huang’ and ‘Wuhan’ produced the highest number of fruits per plant, 119 and 82 fruits, respectively. Mealybug infestation and ostiole-end splitting are major limitations to fig cultivation in Malaysia. Cultivar ‘Longue d’Aout’ was the most susceptible to mealybug infestation; whereas cultivar ‘B110’ was the most resistant. Above 60% of the fruits of cvs. ‘Brunswick’ and ‘Qing Pi’ had split ostiole; however, this was less than 20% in cvs. ‘Longue d’Aout’ and ‘Alma’. This study facilitates successful farming of figs in Malaysia and provides insights for future development programs.

A common modern cultivation practice is bagging the fruit bunch if date palm (Phoenix dactylifera L.) which may influence fruit maturity and nutraceutical quality. Exposure of fruits to photooxidative stress induces changes in the endogenous concentrations of plant hormones and other metabolites, which may cause accelerated fruit maturity. This study was conducted to examine the effect of exposure to direct and indirect sunlight on date palm fruit development. The indirect sunlight treatment was simulated by fruit bunch bagging, a common practice in modern date production. The exposure of date palm fruits to direct sunlight-induced photooxidative stress causing an increased concentration of ascorbic acid and decreased content of chlorophyll, anthocyanins, carotenoids, and phenols compared to the fruit bagging treatment. Direct sunlight also reduced the concentration of phytohormones, including indoleacetic acid, gibberellin, and zeatin, but increased abscisic acid accumulation. The directly-exposed fruits reached a partially-mature stage (Rutab) in August, whereas the bagged fruits remained at the immature stage (Khalal). This study is the first to describe the biochemical basis of the observed improvement of date palm fruit development in response to reduced light intensity. Besides, it provides insights into controlling date palm fruit maturity and subsequently prolonging the shelf life dates on the tree; thus, extending the marketing period for the benefit of the farmers.

This study addresses the development of unpollinated and pollinated flowers of date palm (Phoenix dactylifera L.). cv. Deglet Noor in three successive seasons (2015–2017), focusing on the physico-c...

The objective of this research was to examine the response of different X-ray doses to two okra genotypes, Hassawi okra and the commercial Clemenson genotype on germination and biochemical analysis...

Date palm (Phoenix dactylifera L.) is a fruit tree resilient to adverse climatic conditions predominating in hot arid regions of the Middle East and North Africa. The date fruit contains numerous chemical components that possess high nutritional and medicinal values. Traditional propagation by offshoots is inefficient to satisfy current demands for date palm trees. Alternatively, micropropagation provides an efficient means for large-scale propagation of date palm cultivars. Both somatic embryogenesis and organogenesis, either directly or indirectly though the callus phase, have been demonstrated in date palm in vitro regeneration. Culture initiation commonly utilizes shoot-tip explants isolated from young offshoots. Recently, the immature inflorescences of adult trees were utilized as an alternative nondestructive source of explants. In addition to the nature of the explant used, successful plant regeneration depends on the cultivar, composition of the culture medium and physical status. Challenges of date palm micropropagation include long in vitro cycle, latent contamination, browning, somaclonal variation as well as ex vitro acclimatization and transplanting. A remarkable amount of research investigating these factors has led to optimized protocols for the micropropagation of numerous commercially important cultivars. This has encouraged the development of several international commercial tissue culture laboratories. Molecular characterization provides an assurance of genetic conformity of regenerated plantlets, a key feature for commercial production. This article describes date palm micropropagation protocols and also discusses recent achievements with respect to somaclonal variation, molecular markers, cryopreservation and future prospects.

The formation of new proteins under the influence of harsh environmental conditions is a plant adaptation reaction. Two-year-old date palm tissue culture-derived plants from ‘Barhee’ grown in the field were subjected to salt stress (70 g l-1 NaCl) and dehydration-induced by applying 70 g l-1 polyethylene glycol or without irrigation and withholding irrigation (0 g l-1) for one month. The soluble carbohydrate content increased in response to salinity and polyethylene glycol treatment in leaves compared to the control and drought treatment without irrigation. Proline increased in all treatments. Malondialdehyde and hydrogen peroxide increased under salinity. Salinity treatment increased the activity of ascorbate peroxidase and catalase enzyme. Salinity and polyethylene glycol treatments increased abscisic acid, whereas the indoleacetic acid level decreased. The protein pattern of roots and leaves in one-dimensional polyacrylamide gel electrophoresis showed that the stress conditions led to new protein bands' appearance and other proteins' disappearance. A comparison of protein patterns between the control and stress treatments revealed that the relative intensity of proteins in roots and leaves were more associated with salinity treatment than the drought. The results may be clearing important the molecular mechanism of tolerance under the influence of extreme environmental stress.

Date palm (Phoenix dactylifera L.) is a fruit tree adapted the desert climate. The dates are rich in sugar, minerals, vitamins, and numerous pharmaceutical compounds. Seeds propagating results in heterogeneous offsprings with inferior dates. Therefore propagation of offshoots is the preferred method among farmers. This method, however, is constrained by the limited number of offshoots. Currently, micropropagation is used effectively for large-scale commercial propagation of date palm. This chapter describes a micropropagation protocol based on indirect somatic embryogenesis using apical shoot tip explants. Fully-detailed step-wise procedures are described including explant isolation and disinfection, callus induction and maintenance, development of somatic embryos, rooting and plantlet formation, and finally acclimatization and field establishment.

Date palm (Phoenix dactylifera L.), is a dioecious tropical and subtropical monocot fruit species cultivated mainly in the Middle East. Nowadays, date palm, as a salt and drought tolerant plant, attracts the attention of growers in various countries in Africa, Asia, Europe, and the Americas (Al-Khayri et al. 2015aa, b).

The modern cultivated strawberry (Fragaria × ananassa Duchesne) is one of the world’s most appetizing and delicious fruits. The genotypic diversity, highly heterozygous nature and broad range of environmental adaptation have made this fruit unique. It is a good source of fructose, glucose, vitamin-A, vitamin-C, and minerals like potassium, calcium and phosphorus. The anticancer effects of individual phytochemical constituents of strawberries, as well as whole strawberry extracts, have been demonstrated. Research on the antioxidant content of strawberries is providing us with more and more evidence about decreased lipid peroxidation in blood vessel linings following consumption, and less malondialdehyde formation as well. Breeding and induction of somaclonal variation are useful to create new genetic variability for the improvement of strawberry genotypes. The application of classical breeding and biotechnological approaches are potential tools to improve yield and taste of strawberry. Different diseases like crown rot and Verticillium significantly impede yield. Somaclonal variation was discussed as a breeding tool for future improvement of strawberry varieties. Although the chapter is predominantly written and arranged emphasizing the specific research on biotechnology and genetic improvement of strawberry; nevertheless information on origin, taxonomy, breeding, mutagenesis and parthenocarpy are also presented.

Date palm is one of the major crops growing in regions where abiotic stress conditions are extreme. Abiotic stress affects plant growth, development, physiology, and biochemical processes. This chapter describes a protocol to evaluate the response of date palm cultures to abiotic stresses. Tolerance to salinity stress is assessed using calcium chloride (CaCl2), potassium chloride (KCl), and sodium chloride (NaCl) at 11.96, 12.06, and 9.45 g/L, respectively (equivalent to 0.8 MPa osmotic potential), with different exposure durations (1-12 days). Polyethylene glycol (PEG 8000) is tested at 0-30% (w/v) to assess tolerance to drought stress. Techniques are described to define the effects of these stress agents on the growth of callus and cell suspension cultures, water content, proline accumulation, and Na+ and K+ content ratio, in addition to the technique used for determining the median lethal dose (LD50) for PEG (29.5%) and NaCl (11.54 g/L). This protocol will be useful for future studies of in vitro selection of tolerant cell lines.

Somatic embryogenesis is considered the most effective method for commercial propagation of date palm. However, the limitation of obtaining synchronized development of somatic embryos remains an impediment. The synchronization of somatic embryo development is ideal for the applications to produce artificial seeds. Abscisic acid (ABA) is associated with stress response and influences in vitro growth and development. This chapter describes an effective method to achieve synchronized development of somatic embryos in date palm cell suspension culture. Among the ABA concentrations tested (0, 1, 10, 50, 100 μM), the best synchronized growth was obtained in response to 50-100 μM. Here we provide a comprehensive protocol for in vitro plant regeneration of date palm starting with shoot-tip explant, callus initiation and growth, cell suspension establishment, embryogenesis synchronization with ABA treatment, somatic embryo germination, and rooting as well as acclimatized plantlet establishment.

Genetic diversity plays a major role in varietal improvement of crops. The genus Ziziphus (jujube or ber) is an important fruit crop of arid zones consisting of above 100 species of deciduous or evergreen plants and shrubs widely scattered in the desert, tropical and subtropical areas. In Pakistan, several local and exotic accessions are being cultivated for fruit production. Jujube is neglected fruit crop in Pakistan with diminutive assessment of fruit morphological characters. In this study, 22 selected accessions were characterized based on various physico-morphological traits. The results proved broad genetic base in all 22 genotypes for various commercial traits. Fruits from the selected genotypes were assessed based on fruit weight, fruit length, seed weight, seed length, seed diameter, fruit pulp weight and total soluble solids (TSS). Highest variation (7.22%) was recorded in fruit weight which ranged from 6.08 to 37.64 g among the tested genotypes; however, least variation was recorded in seed weight. Strongest correlation of r = 0.99 was measured between fruit and pulp weight with all 22 genotypes were clustered into three main classes with maximum variation of 163% within class c followed by classes a and b with variation of 73.35 and 64.18% within the classes, respectively. Studied genotypes had broad genetic base with a high flow of characters among them, could be used in advanced breeding for varietal improvement programs. Keywords: Physico-morphological characters; Cultivars; PC analysis; Correlation and cluster analysis http://dx.doi.org/10.19045/bspab.2016.50116

Complex organic additives are known to improve growth and differentiation of in vitro plant cultures. The present investigation was conducted to determine the effect of various concentrations of yeast extract (YE) and casein hydrolysate (CH) on callus growth and somatic embryogenesis in date palm cultivar Nabout Saif. Callus induced from shoot tip explants was grown on callus multiplication medium supplemented with either YE or CH at 0.0, 0.1, 0.25, 0.5, and 1 g l−1. To induce somatic embryogenesis, callus was transferred to a hormone-free medium containing the corresponding concentration of additives. The results have shown that callus weight and the number of somatic embryos were directly proportional to increases in the concentration of organic additives tested. Callus growth was best achieved when 1 g l−1 of either YE or CH was added to the culture medium. At this concentration of YE, callus growth was double that of the control medium. On CH-containing media growth was 2.3 times that of the control. This indicates that CH is more effective in enhancing callus growth. However, YE was more effective in enhancing somatic embryogenesis. The data show that the best somatic embryo formation was obtained on either 1 g l−1 YE or 0.5 g l−1 CH which produced 45 and 30 embryos per culture, respectively, as compared to 20 embryos produced in the control treatment. Resultant somatic embryos successfully rooted and regenerated plantlets which exhibited normal growth in the greenhouse. Enhanced plant regeneration, an essential criterion for commercial micropropagation, was achieved.

Proline accumulation is a common biochemical indicator for assessing environmental stress in plants. The ob- jective of this study was to determine the effect of various doses of two types of magnetic fields on date palm (Phoenix dactylifera L. (cv. Khalas) seedlings based on proline accumulation. The first type involved static magnetic field (SMF) generated by an electromagnetic circuit set at 10, 50, and 100 mT for 30, 60, 120, 180, 240 and 360 min. The second type involved alternating magnetic field (AMF) generated by a magnetic resonance imaging (MRI) device set at 1.5 T for 1, 5, 10, and 15 min. Following exposure to radiation, the seedlings were grown in potting soil for 4 weeks after which proline analysis was conducted. The results showed a significant two-way interaction between SMF intensity and exposure dura- tion. At the lowest intensity, 10 mT, proline concentration increased in response to longer exposure durations reaching a maximum at 240 min. Beyond this duration, reduction in proline concentration occurred. In contrast, at 50 and 100 mT, proline concentration decreased as the exposure duration was increased. AMF significantly reduced proline concentration after as short as a 1-min exposure. This study would facilitate investigations related to stress physiology and in vitro selec- tion of date palm tissue culture.

This study was conducted to examine the response of date palm (Phoenix dactylifera L., cvs. Barhee and Hillali) calli to water stress. Callus derived from shoot tip explants was inoculated in liquid Murashige and Skoog medium containing 10 mg dm−3α-naphthaleneacetic acid, 1.5 mg dm−3 2-isopentenyladenine, and 0 to 30 % (m/v) polyethylene glycol (PEG 8000) to examine the effect of water stress. After 2 weeks, callus growth, water content, and proline accumulation were assessed. Increasing water stress caused a progressive reduction in growth as expressed in callus fresh mass, relative growth rate, and index of tolerance. Both genotypes tested followed this general trend, however, cv. Barhee was more tolerant to drought stress than cv. Hillali. Increasing PEG concentration was also associated with a progressive reduction in water content and increased content of endogenous free proline.

Variability in callus growth and somatic embryogenesis in response to silver nitrate (AgNO3) among genotypes of date palm (Phoenix dactylifera L.) was investigated. Callus was cultured on MS medium containing 53.7 μM naphthaleneacetic acid (NAA) and 7.4 μM 2-isopentenyladenine (2iP) and supplemented with AgNO3 at 0, 12.5, 25, 37.5, 50, 62.5, 75, 87.5, or 100 μM. Subsequently, somatic embryogenesis was induced by transferring callus to hormone-free MS medium containing corresponding AgNO3 concentrations. Callus growth of cvs. Barhee, Naboot Saif, Ruzaiz, and Hillali was significantly promoted in response to 37.5 μM AgNO3 but optimum growth occurred at 50 μM in the former three cultivars, whereas cv. Hillali grew best at 62.5 μM. In contrast, cv. Khusab exhibited significant increase in callus weight at 12.5 μM but maximum growth occurred at 62.5 μM. Callus proliferation, expressed in increased callus fresh weight, which precedes the formation of somatic embryos during the regeneration stage, also varied depending upon AgNO3 concentration and cultivars. Regeneration percentage was significantly enhanced in all genotypes except cv. Hillali that was unaffected. Optimum AgNO3 concentrations were 62.5, 50, 37.5 μM for cvs. Barhee, Hillali, and Ruzaiz, respectively, whereas 12.5 μM was optimum for cvs. Naboot Saif and Khusab. Significant increase in number of somatic embryos was observed in cvs. Barhee, Naboot Saif, and Ruzaiz in response to 75, 12.5, and 37.5 μM AgNO3 but 75, 87.5, and 75 μM, respectively, were optimum. Embryo numbers in cvs. Hillali and Khusab were unchanged by AgNO3 and at concentrations higher than 50 μM numbers decreased. This study identified optimum AgNO3 levels for somatic embryo production of some commercial date palm cultivars.

This study was conducted to develop a micropropagation protocol for grey mangrove, Avicennia marina (Forsk.)

Growth and physiological responses of date palm. Phoenix dactylifera L. cv. Barhee, callus to salinity stress were examined. Callus induced from shoot tips of offshoots was cultured on Murashige and Skoog medium supplemented with NaCl at concentrations ranging from 0 to 225 mM, in consective increments of 25 mM. Data obtained after 6 wk of exposure to salt have shown a significant increase in callus proliferation in response to 25 mM NaCl the lowest level tested, beyond which callus weight decreased. At 125 mM NaCl and higher, callus growth was nearly completely inhibited. Physiological studies on callus exposed to salt stress have shown an increase in proline accumulation in response to increased salinity. Proline accumulation was correlated to callus growth inhibition. Furthermore, increasing the concentration of NaCl in the culture medium generally resulted in a steady increase in Na+ and reduction in K+ concentrations. However, at 25 mM NaCl, the only level at which callus growth was significantly enhanced, an increase in K+ content was noted, in comparison to the NaCl free control. In response to increasing external NaCl level, the Na+/K+ ratio increased The Na+/K+ ratio was positively correlated to proline accumulation and hence callus growth inhibition. This study provides, an understanding of the response of date palm callus to salinity, which is important for future studies aimed at developing strategies for selecting and characterizing somaclonal variants tolerant to salt stress.

This study was conducted to examine the effect of biotin and thiamine concentrations on callus growth and somatic embryogenesis of date palm (Phoenix dactylifera L.). Embryogenic callus derived from offshoot tip explants was cultured on hormone-free MS medium containing biotin at 0, 0.1, 1, or 2 mg l−1 combined with thiamine at 0.1, 0.5, 2, or 5 mg l−1. Embryogenic callus weight, number of resultant embryos, and embryo length were significantly influenced by thiamine and biotin concentration. The optimum callus growth treatment consisted of 0.5 mg l−1 thiamine and 2 mg l−1 biotin. This treatment also gave the highest number of embryos. Embryo elongation was greatest at 0.5 or 2 mg l−1 thiamine combined with 1 mg l−1 biotin. Embryos from all treatments germinated and regenerants exhibited normal growth in soil. This study provides an insight into the importance of optimizing various culture medium components to overcome in vitro recalcitrace of date palm.

Embryogenic callus derived from offshoot tip of date palm ( Phoenix dactylifera L.) was transferred to MS medium containing 0, 25, 50, 75, or 100 μM AgNO 3 combined with 0 or 0.5 μM 2iP. Embryogenic callus weight, number of embryos developed and embryo elongation were significantly influenced by the interaction between silver nitrate (AgNO 3 ) and 2iP. In the absence of 2iP, callus weight was greatest with 75 μM AgNO 3 , but in the presence of 2iP omitting silver nitrate resulted in the highest callus proliferation. The number of embryos increased in response to increasing silver nitrate concentration in the absence of 2iP, but in the presence of 2iP increasing the concentration of silver nitrate gave the opposite trend. The number of resultant embryos was the highest on 25 μM AgNO 3 in the presence of 0.5 μM 2iP. This treatment also caused maximum embryo elongation. The results have shown that silver nitrate promoted callus proliferation and enhanced the formation and elongation of somatic embryos of date palm. Furthermore, the action of silver nitrate was clearly modified by the addition of 2iP. Depending on the response, 2iP modification ranged from slight alteration to complete inversion of the general trend associated with increasing silver nitrate concentration. The observed stimulatory action of AgNO 3 on date palm somatic embryogenesis may contribute to improve existing regeneration systems particularly for recalcitrant date palm genotypes.

Ethylene is a plant growth regulator that is known to influence in vitro morphogenesis. This study investigated the effects of three ethylene inhibitors, silver nitrate (AgNO3), 2,5-norbornadiene, and cobalt chloride (CoCl2), on the regeneration of cowpea from cotyledon explants. Significant increases in the percentage of regeneration occurred as a result of adding either 50 µM AgNO3 or 100 µM 2,5-norbornadiene. The number of shoots produced per explant was enhanced by adding 25 µM CoCl2 or 100 µM norbornadiene. Maximum shoot elongation was obtained with 25 µM of either CoCl2 or norbornadiene. The effect of the duration of exposure to AgNO3 was also determined. The greatest percent regeneration was obtained with the addition of 60 µM AgNO3 either to both the initiation and regeneration stages, or to only the regeneration stage. The promotive effects on organogenesis in response to ethylene inhibitors suggests an important role for ethylene in the process of in vitro morphogenesis of cowpea and may contribute to its normally low regeneration frequency.

A system for micropropagation of Epimedium grandiflorum Morr. from rachis explants was developed. Explants were cultured onto Murashige and Skoog (MS) basal salts medium supplemented with (per L) 100 mg myo-inositol, 2 mg pyridoxine-HCl, 2 mg nicotinic acid, 0.40 mg thiamine-HCl, 30 g sucrose, and 2 g Phytagel. The medium also contained 2,4-dichlorophenoxyacetic acid (2,4-D) at 0.1, 0.2, or 0.25 mg/L (0.5, 0.9, or 1.1 µM) combined with either N6-benzyladenine (BA) or 2-isopentenyl adenine (2ip) at 2.5, 5, or 10 mg/L (11.1, 22.2, or 44.4 µM BA or 12.3, 24.6, or 49.2 µM 2iP). Cultures were maintained at a 16-h photoperiod (40 µmol/m2/s) and 23±2° C. Callogenesis preceded shoot regeneration. Callus formation increased with higher 2,4-D concentrations. The highest percent regeneration, 83% of explants, was obtained on 10 mg BA per L (44.4 µM) combined with 0.25 mg 2,4-D per L (1.1 µM). The maximum number of shoots, 15 per explant, was obtained from explants cultured on a medium containing 0.1 mg 2,4-D per L (0.45 µM) combined with 2.5 mg BA per L (11.1 µM). Maximum shoot length, 0.4 cm, was obtained on 5 mg BA per L (22.2 µM) combined with 0.2 mg 2,4-D per L (0.9 µM). To produce whole plants, shoots were separated and rooted on hormone-free medium containing 1 g activated charcoal per L. Rachises provided an excellent source of explants for Epimedium micropropagation and proved suitable for callus production.

Shoot multiplication was induced in cowpea, cv. Georgia-21, from shoot tip explants. Shoot tips, 5 mm long, were isolated from in vitro-grown seedlings and cultured on MS medium containing N6-benzyladenine (BA) at 1, 2.5, or 5 mg/liter (4.4, 11.1, or 22.2 µM) or 6-furfurylaminopurine (kinetin) at 1, 2.5, or 5 mg/liter (4.6, 11.6, or 23.2 µM) combined with 2,4-dichlorophenoxyacetic acid (2,4-D) at 0.01, 0.1, or 0.5 mg/liter (0.05, 0.5, or 2.3 µM) or naphthaleneacetic acid (NAA) at 0.01, 0.1, or 0.5 mg/liter (0.05, 0.5, or 2.7 µM). Cultures were maintained at a 12-h photoperiod (40 µmol·m−2·s−1) and 23 ± 2° C. Treatments with BA induced greater shoot proliferation than those with kinetin. The highest number of shoots was produced on 5 mg (22.2 µM) BA per liter in combination with NAA or 2,4-D at 0.01 mg/liter (0.05 µM). Callus proliferated from the basal ends of shoot pieces in all treatments. The cultures also formed roots in the presence of kinetin, but not on BA-containing medium. To produce whole plants, the shoots were separated and rooted on 0.1 mg (0.5 µM) NAA per liter. Resulting plants grew normally under greenhouse conditions. Shoot tips provide an excellent explant source for cowpea micropropagation and can be used for callus induction.

This study was conducted to establish and optimize a regeneration system for adapted U.S. rice genotypes including three commercial rice cultivars (LaGrue, Katy, and Alan) and two Arkansas breeding lines. Factors evaluated in the study were genotype, sugar type, and phytohormone concentration. The system consisted of two phases, callus induction and plant regeneration. In the callus induction phase, mature caryopses were cultured on MS medium containing either 1% sucrose combined with 3% sorbitol or 4% sucrose alone, and 0.5 to 4 mg·L−1 (2.26 to 18.10 μM) 2,4-D with or without 0.5mg·L−1) (2.32 μM) kinetin. In the plant regeneration phase, callus was transferred to 2,4-D-free MS medium containing 0 or 2 mg·L−1 (9.29 μM) kinetin combined with 0 or 0.1 mg·L−1 (0.54 μM) NAA. Callus induction commenced within a week, independent of the treatments. Callus growth and plant regeneration, however, were significantly influenced by interactions among experimental factors. Generally, the greatest callus growth and plant regeneration were obtained with 0.5 mg·L−1 (2.26 μM) 2,4-D and decreased with increasing 2,4-D concentrations. Kinetin enhanced callus growth only when combined with 0.5 mg·L−1 (2.26 μM) 2,4-D, and 4% sucrose. Inducing callus on kinetin-containing medium generally enhanced regeneration capacity in the presence of sucrose but not with a sucrose/sorbitol combination. Media containing sucrose alone generally supported more callus proliferation, but the sucrose/sorbitol combination improved regeneration of some cultivars. NAA and kinetin had little effect on regeneration.

A micropropagation system was developed forAcacia mearnsii De Wild., which is the principal source of the world’s tanbark and an excellent firewood. Shoot tips 5-mm long from 3-wk-old seedlings germinated in vitro served as explants. The seeds were germinated on hormone-free MS medium and the shoot tips were cultured on three-fourth-strength MS medium supplemented with combinations of auxins [indole-3-butyric acid (IBA) andα-naphthaleneacetic acid (NAA)] and cytokinins [kinetin and benzylaminopurine (BAP)]. Cultures were maintained at 25° ± 5° C and exposed to 12-h photoperiods of cool-white fluorescent light (70 µEm−2·s−1). Multiple shoot formation was promoted by BAP at 2 mg · liter−1 (8.87µM) and higher combined with or without 0.01 mg · liter−1 (0.049µM) IBA. Cytokinins at concentrations of less than 1 mg · liter−1 combined with 0.01 to 0.1 mg · liter−1 auxin inhibited multiple shoot formation and promoted rooting of the shoot tip explants. Shoot multiplication cultures were maintained by transferring segments of multiple-shoot clusters onto a medium containing 2 mg · liter−1 BAP and 0.01 mg · liter−1 IBA. Although higher levels of BAP promoted more multiple shoot formation, this BAP level allowed shoot elongation as well as multiplication. In-vitro-produced shoots were induced to root on a range of NAA concentrations (0.0 to 0.8 mg · liter−1[4.3µM]) supplemented to half- or full-strength MS medium. The highest frequency of root proliferation was on half-strength MS medium supplemented with 0.6 mg · liter−1 (3.22µM) NAA. Plantlets survived in potting soil and exhibited normal growth under greenhouse conditions.

This study investigated the influence of osmotic stress, induced by sorbitol and sucrose combinations, on growth and proline accumulation in callus cultures of rice (Oryza sativa L.). Dehusked mature seeds, cv. Hassawi, were induced to callus on MS medium supplemented with 4.52 µM 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.32 µM 6-furfurylaminopurine (kinetin). The medium also contained 29.2, 58.4, 87.6, and 116.8 mM sucrose combined with 0, 54.9, 109.8, and 164.7 mM sorbitol. Callus formation was observed in about 35 % of the cultured seeds irrespective of the sugar treatment. An increase in callus mass was observed as sucrose concentration increased reaching a maximum growth at 87.6 mM. Callus growth was enhanced in response to 54.9 mM sorbitol but at higher concentration it was inhibitory. Best callus growth was obtained on a medium containing 54.9 mM sorbitol combined with 87.6 mM sucrose. Increasing osmotic stress, as a consequence of increasing sucrose and sorbitol concentrations, induced proline accumulation and the highest concentration of proline, 5.8 µmol g−1(f.m.), was obtained on 164.7 mM sorbitol combined with 116.8 mM sucrose.

The long life cycle of date palm (Phoenix dactylifera L.) makes genetic improvement through traditional breeding methods a tedious endeavor. Biotech­nology offers advanced tools to augment genetic improvement efforts. In vitro selection technique, a major application of plant biotechnology, allows the isolation of mutant cells and the regeneration of plants exhibiting desired new traits. Mutations can be induced chemically and physically through the exposure to various forms of radiation at appropriate levels. Studies indicate that magnetic fields have the ability to induce biochemical and physiological changes including enhanced plant growth and nutritional value. Although the use of magnetic fields in genetic improvement of date palm is in its infancy, necessary relevant information is beginning to accumulate. This chapter reviews research achievements in this area and addresses biological effects resulting from magnetic field exposure in date palm, in anticipation of future application in mutation studies. The impact of both static and alternating magnetic fields on the content of proline, DNA, photosynthetic pigments and elements are discussed. In addition, magnetic field-induced changes in growth para­meters like weight and water content of both shoot and root systems are described. Exploration of magnetic field in in vitro studies of date palm is yet to be realized but encouraged by the regeneration improvements achieved in other plant species. Considering the effectiveness of magnetic field to modify plant systems, the appli­cation of magnetic field to genetically improve date palm merits further investigation.

Shoots regenerated from leaf-derived callus of spinach (Spinacia oleracea L. cultivar ‘High Pack’) were induced to flower by exposure to 14-h photoperiods (50 μmol m−2 s−1) and day/night temperatures of 20° C 16° C . Leaves from male and female plants served as sources for explants. Shoots regenerated from callus were induced to flower on a hormone-free medium. The majority of regenerated plants exhibited sex corresponding to their respective explant donors; a proportion of regenerants of male origin, however, shifted to monoecious. These sex-modified plantlets developed viable seeds in vitro. This phenomenon can be useful in producing seeds from elite selected male plants.

The advent of agricultural biotechnology offers new approaches for the genetic improvement of date palm (Phoenix dactylifera L.), an important economic fruit crop in arid regions. In vitro studies were conducted to recover date palm plants exhibiting enhanced tolerance to salinity and drought stress, two major agricultural problems in arid areas. The response of date palm callus cultures to salt stress was investigated by exposing cell suspension and callus cultures to varying concentrations of sodium chloride (NaCl). The reaction of callus to the duration of exposure to NaCl, potassium chloride (KCl) and calcium chloride (CaCl2) was evaluated. Similarly, drought tolerance was assessed in response to varying concentrations of polyethylene glycol (PEG-8000). Significant differences were reported in various parameters measured including callus growth, somatic embryogenesis, proline content and ion distribution. Calli with enhanced tolerance to these selection agents were obtained; however, plant regeneration from these cell lines was not realized. Although the available data provide an insight of the behavior of date palm callus in the presence of salt and drought stress, further research work is required to refine the selection procedures and plant regeneration from the selected tolerant cell lines.

Spinach (Spinacia oleracea L.; Fig. 1) is a hardy cool-season annual crop classified as a potherb vegetable. It produces a rosette of fleshy edible leaves during the vegetative stage of its life cycle. The reproductive stage, triggered by long-day photoperiods, is marked by stem elongation and branching to form flower stalks. Spinach is mostly a dioecious plant but monoecious plants with varying proportions of male (staminate) and female (pistillate) flowers may also exist (Ryder 1979). Spinach is a diploid with chromosome number 2n = 2x = 12. Its sex determination is hypothesized to be controlled by a monogenic system in which a single gene with three alleles (Y, Xm, and X) appear to explain the existence of monoecious plants in this dioecious species (Janick and Stevenson 1954, 1955).

Spinach (Spinacia oleracea L.), classified as a potherb vegetable, is a member of the family Chenopodiaceae (Jones and Luchsinger 1979). Fresh spinach is becoming more popular due to the rising demand for fresh green salads in diets. It is the most important vegetable green grown in the USA, and it ranks second only to broccoli in total nutrient concentration (Swiader et al. 1992). In 100 g of spinach are 8100 IU vitamin A, 51 mg vitamin C, and 93 mg of calcium. Spinach is also a good source of iron, phosphorus, sodium, and potassium (Ryder 1979).

A preliminary study has shown that the addition of 15% (v/v) coconut water (CW) to the culture medium significantly improved callus growth, shoot-regenerative capacity, and shoot growth in leaf disk cultures of spinach (Spinacia oleracea L.). Subsequently, the influence of a range of CW concentrations, 0%, 5%, 10%, 15%, or 20% (v/v), was examined. Callus weight obtained after 5 weeks showed direct relationship to the concentration of CW. This stimulator action was observed in both cultivars tested in this study, `High Pack' and `Baker'. On CW-containing medium, shoot regeneration was expedited to 4 to 5 weeks compared with 8 to 12 weeks on a CW-free medium. Callus of `Baker' induced on a CW-free medium exhibited a significant increase in shoot regeneration frequency when transferred to a regeneration medium enriched with CW, suggesting that the addition of CW to the regeneration medium only is sufficient to achieve improved regeneration.

Callus, induced in the dark from leaf tissue of spinach (Spinacia oleracea L. cv. Fall Green) on Murashige and Skoog (MS) medium supplemented with (in mg·liter -1) 2 kinetin and 0.5 2,4-D regenerated shoots upon transfer to a medium containing 2 kinetin, 0.01 2,4-D, and 1 GA3. Complete plants were established by stimulating rooting of the shoots with 1 mg IBA/liter and transferring them to potting soil; survival was 60%. Chemical names used: N-(2-furanylmethyl)-1H-purin-6-amine (kinetin); 2;4-dichlorophenoxy acetic acid (2,4-D); gibberellic acid (GA3); 1H-indole-3-butanoic acid (IBA).

A plant regeneration system applicable to 17 cowpea genotypes was developed. Cotyledons were initiated on 1/3 MS medium containing 15 to 35 mg N6-benzyladenine (BA) per 1 (66.6 to 155.3 µM) for 5 to 15 d. For shoot regeneration, the explants were transferred to a medium containing 1 mg BA per 1 (4.4 µM). Within 1 wk, shoot formation was visible at the proximal end of the cotyledons. Regeneration percentages (1% to 11%) and the numbers of shoots (4 to 12 per explant) were significantly influenced by genotype. Culture duration and BA concentration in the initiation stage significantly affected regeneration capacity. Explants initiated on media containing 15 mg BA per 1 for 5 d resulted in the highest percentage of explants capable of regeneration. Conversely, the highest number of shoots was obtained from explants initiated on media supplemented with 35 mg BA per 1. Whole plants were obtained on a plant growth regulator-free medium. To our knowledge, this is the first report of plant regeneration from U.S. commercial cowpea cultivars and breeding lines. This system is adaptable to diverse cowpea genotypes and will facilitate cowpea genetic transformation.

Cowpea, or southernpea, is an important food legume that provides a source of high-quality protein, especially in the mature seeds. In the United States, industries exist to supply dry and processed seeds. Our aim is to develop a regeneration system for cowpea as a prerequisite for genetic engineering. Our objective was to examine the in vitro responses of shoot tips to growth regulators. Shoot tips isolated from in vitro-germinated seedlings (`Coronet') were cultured on MS medium containing 2,4-D at 0, 0.01, 0.1, or 1 mg·liter–1 and kinetin at 2.5, 5, 10, or 20 mg·liter–1. Cultures were maintained at 12-hour photoperiods and 24C. Callus, shoots, and roots or combinations thereof developed depending on the treatment. Callus formed on 1 mg 2,4-D/liter, regardless of the kinetin level, but at 0.1 mg 2,4-D/liter and 5 or 10 mg kinetin/liter, shoots also grew. Callus, shoots, and roots developed on 2,4-D lower than 0.1 mg·liter–1. Callus induced on 5 mg kinetin/liter and 0.01 mg 2,4-D/liter regenerated shoots on transfer to 5 mg kinetin/liter and 0.1 mg NAA/liter. This work may assist in the development of a micropropagation system for cowpea.

Regenerated spinach (Spinacia oleracea L.) maintained under a 10-h photoperiod (65 uE m-2 s-1) after an incubation period on a GA-containing medium were induced to flower in vitro. The plantlets were regenerated from callus initiated on MS medium with 2.0 mg L-1 kinetin and 0.5 mg L-1 2,4-D and were subsequently transferred to a medium containing 2.0 mg L-1 kinetin, 1.0 mg L-1 GA, and 0.01 mg L-1 2-4,D. While on the regeneration medium, the cultures were exposed to a long-day photoperiod. Regenerants were transferred to an IBA-containing medium for rooting, after which flowering was observed. In vitro flowering plantlets exhibited male and female flowers depending on the sex of the explant donor. Female plantlets developed seeds in the culture vessels. This method of seed production from regenerants can eliminate time-consuming steps in acclimation, transplanting to soil, and plant maintenance.

A 2.4-D concentration of 1.0 mg L −1 resulted in greater callus production than higher concentrations. A 16-h photoperiod of fluorescent light (65 μmol photon m −2 s −1 ) increased callus production over dark conditions. Direct elimination of 2.4-D and dark callus induction resulted in greater regeneration frequency and a higher number of plantlets per callus than gradual elimination and light callus induction. Normal plantlets were transplanted to soil and grown to maturity in the field, where overwinter survival was exhibited