In this study, the seedlings of two wheat cultivars were used: drought-resistant Chinese Spring (CS) and drought-susceptible (SQ1). Seedlings were subjected to osmotic stress in order to assess the differences in response to drought stress between resistant and susceptible genotype. The aim of the experiment was to evaluate the changes in physiological and biochemical characteristics and to establish the optimum osmotic stress level in which differences in drought resistance between the genotypes could be revealed. Plants were subjected to osmotic stress by supplementing the root medium with three concentrations of PEG 6000. Seedlings were grown for 21 days in control conditions and then the plants were subjected to osmotic stress for 7 days by supplementing the root medium with three concentrations of PEG 6000 (D1, D2, D3) applied in two steps: during the first 3 days of treatment -0.50, -0.75 and -1.00 and next -0.75, -1.25 and -1.5 MPa, respectively. Measurements of gas exchange parameters, chlorophyll content, height of seedlings, length of root, leaf and root water content, leaf osmotic potential, lipid peroxidation, and contents of soluble carbohydrates and proline were taken. The results highlighted statistically significant differences in most traits for treatment D2 and emphasized that these conditions were optimum for expressing differences in the responses to osmotic stress between SQ1 and CS wheat genotypes. The level of osmotic stress defined in this study as most suitable for differentiating drought resistance of wheat genotypes will be used in further research for genetic characterization of this trait in wheat through QTL analysis of mapping population of doubled haploid lines derived from CS and SQ1.

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Relatively little is known of the genetic control of chlorophyll fluorescence (CF) and pigment traits important in determining efficiency of photosynthesis in wheat and its association with biomass productivity. A doubled haploid population of 94 lines from the wheat cross Chinese Spring × SQ1 was trialled under optimum glasshouse conditions for 4 years to identify quantitative trait loci (QTL) for CF traits including, for the first time in wheat, JIP-test parameters per excited cross section (CSm): ABS/CSm, DIo/CSm, TRo/CSm, RC/CSm and ETo/CSm, key parameters determining efficiency of the photosynthetic apparatus, as well as chlorophyll and carotenoid contents to establish associations with biomass and grain yield. The existing genetic map was extended to 920 loci by adding Diversity Arrays Technology markers. Markers and selected genes for photosynthetic light reactions, pigment metabolism and biomass accumulation were located to chromosome deletion bins. Across all CF traits and years, 116 QTL for CF were located on all chromosomes except 7B, and 39 QTL were identified for pigments on the majority of chromosomes, excluding 1A, 2A, 4A, 3B, 5B, 1D, 2D, 5D, 6D and 7D. Thirty QTL for plant productivity traits were mapped on chromosomes 3A, 5A, 6A, 7A, 1B, 2B, 4B, 6B, 7B, 3D and 4D. A region on chromosome 6B was identified where 14 QTL for CF parameters coincided with QTL for chlorophyll content and grain weight per ear. Thirty-five QTL regions were coincident with candidate genes. The environment was shown to dominate in determining expression of genes for those traits.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-013-9862-8) contains supplementary material, which is available to authorized users.

Production of double haploids in oat (Avena sativa L.) by pollination with maize (Zea mays L.) Abbreviations 2,4-D -2,4-dichlorophenosyacetic acid; dicamba -3,6-dichloro-2-methoxybenzoic acid; DH -double haploid. IntroductionModern crop breeding has a number of advantages when using DH plants, such as shortening of the production time of new varieties and the possibility of using them in research. Classical methods of production of new varieties, based on a selection in every generation, take six to ten years. Biotechnological methods allow for a shortening of this time, even to one vegetative season. Breeders can make new cultivars with features from DH lines and be confident about completely homozygous plants. Moreover, DH lines can be used in the production of genetic maps, which help in the search for quantitative traits loci (QTL), conjugated with molecular markers and connected with many physiological processes, such as receptivity to the effectiveness of androgenesis or tolerance to biotic and abiotic stresses [1,2]. Haploids can be obtained using a number of methods, namely: from male gametophyte by androgenesis, using anther cultures or isolated microspores cultures [3][4][5][6][7][8], or from female gametophytes by gynogenesis or wide crossing, usually with maize (a method also known as chromosomes elimination) [1,9,10]. In comparison to anther culture, pollination with maize has an advantage because all regenerated haploid embryos are green, whereas in anther culture many of them are albino. The method of chromosome elimination that has been used in these experiments includes the following stages: after emasculation of cereal flowers the stigma is pollinated by maize, the pollen then germinates, a pollen tube is formed [11,12] and grows into the cereal embryo sac, where the cereal egg is fertilised by the maize sperm nuclei. A hybrid zygote is produced. The hybrid zygotes Keywords: Wide crossing • 2,4-D • Dicamba • Oat haploid embryosAbstract: The aim of the study was to optimize the method of oat haploid production by pollination with maize. Seventeen oat genotypes were used in the experiment. Various factors influencing the growth and development of ovaries and embryo production were investigated: genotype, time of pollination, growth regulators and time of their application. Emasculated before anthesis, oat florets were pollinated with maize pollen after 0, 1 or 2 days. Next, one of two auxins analogues (2,4-D or dicamba) were applied to oat pistils. These auxins had no significant influence on the number of enlarged ovaries and embryos. The time of application of these growth regulators had a significant influence on embryo production. Haploid embryos were obtained from all used genotypes, although the frequency of enlarged ovaries and obtained embryos did not differ markedly between the genotypes. On average, 85% of ovaries were enlarged and 11.7% of them produced haploid embryos. Depending on the regeneration medium, 24-41% of embryos were germinated, of which 12% had developed into green plant...

As part of work to optimize the regeneration processes of winter wheat callus culture the effects of two auxins (2,4-D, IAA), two cytokinins (kinetin, zeatin), and the fungal mycotoxin zearalenone, were tested individually in vitro using embryo-, and inflorescence-derived callus.To determine the role of oxidative stress in cell regeneration, changes in the basic antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidases (PODs) were investigated. In general, zearalenone (ZEN) was found to be more effective than cytokinin treatments for inducing shoot production, whereas auxins suppressed the regeneration process. Regenerating callus showed higher induction of these antioxidant enzymes in comparison with non-regenerating callus. SOD, CAT and POD activities were higher in callus derived from inflorescence than in callus derived from immature embryo. Activities of SOD, CAT and POD in culture derived from immature embryos were depending on type of growth regulator in medium. The highest enzyme activities were observed in nonregenerating tissues after auxins treatment and in regenerating tissues after cytokinins treatment. The effect of ZEN was similar to that of cytokinins. One MnSOD band and two Cu/ZnSOD bands were detected in all cultures. Changes in SOD izoform patterns occurred in callus culture on media with auxins and ZEN, but not on media with cytokinins. Our results suggest that callus regeneration is associated with reactive oxygen species production induced by specific growth regulators. Reactive oxygen species under the control of cellular antioxidant machinery can mediate signalling pathways between exogenously applied growth regulators and the induction and/or creation of the direction of morphogenesis.

Production of doubled haploid (DH) cereals is becoming increasingly important in crop breeding programs, but the methods currently applied still remain inefficient. In this study, we present the procedure for obtaining haploid and DH oat plants by pollination with maize. Thirty-three oat genotypes were used in the experiments. Oat plants (14,543 florets) were pollinated with maize pollen 2 days after emasculation and treated with auxin analogues: 2,4-dichlorophenoxyacetic acid (2,4-D) or 3,6-dichloro-2-methoxybenzoic acid (dicamba), at a concentration of 100 mg dm -3 . These auxins had no significant influence on the number of haploid embryos developed, but they significantly affected their germination ability, and thus haploid and DH plant production. After application of 2,4-D, 5.06 % of haploid embryos developed per emasculated florets, 1.37 % of haploid plants and 0.54 % of DH lines, whereas after dicamba treatment, 4.3 % of haploid embryos, 0.64 % of haploid plants and 0.25 % of DH lines. Haploid embryos were obtained from all genotypes tested, however, their frequency differed between individual genotypes. The highest number of embryos per emasculated florets (9.0 %) was obtained from the DC09040 genotype after dicamba treatment, and from STH123 9 Skorpion (8.9 %) after 2,4-D treatment. The genotype did not significantly affect the development of haploid plants, nevertheless the highest number of DH lines was obtained from the Arab 9 Typhon genotype. There were 52 DH lines acquired from 28 genotypes, which produced a total of 5227 seeds. The number of seeds varied between the DH lines from 2 to 595. Seeds of all the DH lines produced fertile next generation. DH lines are currently included in breeding programs. Keywords 2,4-D, dicamba Á Oat haploids Á Wide crossing Á DH lines Á F 1 progeny & Edyta Skrzypek

Drought is one of the major factors limiting wheat yield in many developing countries worldwide. Parameters of chlorophyll a fluorescence kinetics under drought stress conditions have been used to characterize dehydration tolerance in wheat. In the present study, a set of 94 doubled haploid lines obtained from Chinese Spring £ SQ1 (CSDH), mapped with 450 markers, was evaluated for yield (grain dry weight/main stem ear), number of grains/main stem ear (NG) and chlorophyll a fluorescence parameters (FC) under moderate and severe drought stress, and compared with results for well-watered plants. quantitative trait loci (QTLs) were identified using Windows QTLCartographer version 2.5 software and the results were analysed using single-marker analysis (SMA) and composite interval mapping (CIM). Analysis using SMA and CIM showed mostly similar QTLs for all traits, though more QTLs were identified by SMA than by CIM. The genetic control of yield, NG and FC varied considerably between drought-stressed and non-stressed plants. Although no major QTL co-locations were found for yield and FC using CIM, the co-location of QTLs for NG, yield and F v /F m in drought-stressed plants was observed on chromosome 5A using SMA.

BackgroundMelatonin (MEL) is a signaling molecule in plants that affects developmental processes during vegetative and reproductive growth. Investigations have proved that exogenously applied MEL also has the potential to improve seed germination and plant development.MethodsIn the present study, seeds of stevia, a species with a very low germination rate, were germinated on an agar gel (AG) containing MEL at various concentrations (5, 20, 100, and 500 µM) in light. Seeds germinated on AG without MEL were used as controls. For the first 24 or 48 h of germination, the seeds were maintained in darkness as a pre-incubation step. Some seeds were not exposed to this pre-incubation step.ResultsAt concentrations of 20 and 5 µM, MEL significantly improved germination, but only in seeds pre-incubated in darkness for 24 h (p < 0.001). At concentrations of 100 and 500 µM, MEL had an inhibitory effect on germination, regardless of the pre-incubation time. Melatonin also affected plantlet properties. At a concentration of 20 µM, MEL increased plantlet fresh weight and leaf numbers. At a concentration of 5 µM, it promoted plantlet height. Regarding root development, the most favorable MEL concentration was 500 µM. Biochemical analysis revealed that MEL promoted higher pigment concentrations but hampered superoxide dismutase activity. On the other hand, the concentrations of sugars and phenolics, as well as the activities of catalase and peroxidase, increased at a MEL concentration of 500 µM.DiscussionThe results suggest that MEL can improve germination of positively photoblastic stevia seeds and that it can play a role in plantlet development. However, the effects observed in the present study depended on the quantity of MEL that was applied.