Carbon and nitrogen allocation and partitioning in traditional and modern wheat genotypes under pre-industrial and future CO2 conditions

The results of a simultaneous 13C and 15N labelling experiment with two different durum wheat cultivars, Blanqueta (a traditional wheat) and Sula (modern), are pre- sented. Plants were grown from the seedling stage in three fully controllable plant growth chambers for one growing season and at three different CO2 levels (i.e. 260, 400 and 700 ppm). Short-term isotopic labelling (ca. 3 days) was performed at the anthesis stage using 13CO2 supplied with the chamber air and 15NH4-15NO3 applied with the nutrient solution, thereby making it possible to track the allocation and par- titioning of 13C and 15N in the different plant organs. We found that photosynthesis was up-regulated at pre-industrial CO2 levels, whereas down-regulation occurred under future CO2 conditions. 13C labelling revealed that at pre-industrial CO2 carbon investment by plants was higher in shoots, whereas at future CO2 levels more C was invested in roots. Furthermore, the modern genotype invested more C in spikes than did the traditional genotype, which in turn invested more in non-reproductive shoot tissue. 15N labelling revealed that the modern genotype was better adapted to assimi- lating N at higher CO2 levels, whereas the traditional genotype was able to assimilate N more efficiently at lower CO2 levels

Opportunities and challenges in doubled haploids and haploid inducer-mediated genome-editing systems in cucurbits

Doubled haploids have played a major role in cucurbit breeding for the past four decades. In situ parthenogenesis via irradiated pollen is the preferred technique in order to obtain haploid plantlets further chromosome doubled in Cucurbitaceae like melon, cucumber, pumpkin, squash and winter squash. In contrast to doubled haploid procedures in other species, in situ parthenogenesis in cucurbits present many limiting factors which impede an efficient production of haploids. In addition, is very time-consuming and labor-intense. However, haploid inducer-mediated genome-editing system is a breakthrough technology for doubled haploid production. CRISPR/Cas9 system have been reported several times in cucurbit species and although its application has many bottlenecks the targeting of CENH3 gene for knock-out will allow breeders to obtain haploid inducer lines further used for parthenogenetic embryo obtention. In this review, we have discussed the progress made towards the development of doubled haploids and haploid inducer genotypes by using CRISPR/Cas9 technologies in cucurbit species. The present review provides insights for the application of haploid inducer-mediated genome-editing system in cucurbit species

Parthenogenetic double haploid production in melon 'Piel de Sapo' for breeding purposes

Double haploids in melon breeding are commonly used for hybrid F1 production. Via parthenogenesis, double haploids can be efficiently obtained in melon. Melon fruit traits and pathogen resistances were first appraised to analyse the commercial value of donor genotypes further used in a parthenogenetic process. Parthenogenetic capacity from melon 'Piel de Sapo' germplasm, including six inbred genotypes and Melito cultivar, was evaluated and optimized in this study. Melon fruit set after pollination with irradiated pollen, haploid embryo obtention, in vitro germination and growth of haploid embryos, in vitro and in vivo chromosome doubling with colchicine or oryzalin, and fruit set of double haploid plants were steps deeply assessed in this study. Parthenogenetic efficiencies of 'Piel de Sapo' genotypes showed a high genotypic dependency during the whole process. Pollinated female flowers set fruit after pollination with irradiated pollen (15.78%). Three different methods were assayed for haploid embryo detection of the 178 melon fruits recovered: one-by-one, X-ray and liquid medium. X-ray radiography of seeds was 4-5 times faster than one-by-one method and jeopardized eight times less haploid embryo obtention than liquid medium. One third of those fruits carried haploid embryos, which 50.94% did not developed into plantlets because failed to germinate or plant died at the first stages of development as a consequence of deleterious gene combination in haploid homozygosity. The distribution of the ploidy-level of 26 parthenogenetic plantlets was: 73.08% haploids, 23.08% spontaneous double haploids and 3.84% mixoploids. Two in vitro chromosome doubling methods with colchicine or oryzalin were compared with a third in vivo method. In vivo immersion of apical meristems showed the best results of plant survival, 57.33%, and doubling, 9.30% mixoploids and 20.93% double haploids. Fruit set and seed recovery of double haploids plants was achieved. In this study, double haploid lines were produced from the seven genotypes of melon 'Piel de Sapo', however, further improvements are needed to increase the parthenogenetic efficiency

Anisotropic pinned/biased magnetization in SrRuO3/SrMnO3SrRuO_3/SrMnO_3 superlattices

The exchange coupling at the interfaces of magnetic superlattices consisting of ferromagnetic $SrRuO_3$ and antiferromagnetic $SrMnO_3$ grown on (001) oriented $SrTiO_3$ is studied with in-plane and out-of-plane orientations, with respect to the substrate plane, of the cooling magnetic field. The magnetization of the in-plane, field cooled hysteresis loop is lower than the corresponding in-plane zero-field-cooled hysteresis loop. The out-of-plane field cooled hysteresis loop is shifted, from the origin, along the graphical magnetization axis. We attribute this irreversible rotation of the moment to the pinning/biasing of spin in the $SrRuO_3$ layer in the vicinity of interfaces by the antiferromagnetic $SrMnO_3$ layer.Comment: To be published in Eur. Jour. Phys. B for a topical issue on "new trends in magnetic exchange bias phenomena

Characterization of different Arundo donax L. Clones from the Mediterranean region

The present study assessed the behaviour of a tour ecotypes of Arundo donax L. (giant reed) as a perennial rhizomatous grass with an increasing interest due to its high biomass production and great s adaptability to stress conditions. In this study we perform a molecular, physiological and biomass characterization in greenhouse conditions on four mediterranean ecotypes. Not large significant differences were found in physiological and biomass parameters. However, it was possible to observe large differences in the chromosome count for the four ecotypes. In this way, we detected different number of chromosomes for each ecotype (98 to 122), but surprisingly, no correlation was observad between their chromosomes number and their physiological and biomass responses

Limited carbon inputs from plants into soils in arid ecosystems: a study of changes in the d13C in the soil-root interface

Background and aims. The tracing of C assimilation and the subsequent partitioning among plant organs has been a central focus of studies utilising Free Air CO2 Enrichment (FACE) facilities. The approach makes use of the fossil origin of this carbon, which is depleted in 13C. However, there is little data for desert environments. The Nevada Desert FACE Facility (NDFF), located in the Mojave Desert, has been one of the main facilities for the study of C dynamics in arid ecosystems and how they respond to rising atmospheric CO2 concentrations. In this experiment, we studied the incorporation of fixed CO2 during the previous two years (detectable by its lower 13C) in the soil fraction surrounding roots. Methods. The soil was collected monthly in direct vicinity to the roots during a complete growth season, at two depths (5 and 15 cm). Soil samples were dried and fractionated by size (> 50 μm and 50 μm), 13C values ranged between -1 and -2¿ for carbonates and between -23 and -25¿ for soil organic matter. These values did not significantly change throughout the experiment and were not affected by depth (5 or 15 cm). In contrast, 13C values for both organic and inorganic carbon in the fine fraction ( 50 μm). The 13C values for organic C ranged mostly between -20¿ and -27¿, and were roughly maintained throughout the sampling period. For inorganic C, the 13C values were mostly between 0¿ and -15¿, and tended to become less negative during the course of the sampling period. Overall the effect of [CO2] on 13C values of either organic or inorganic carbon was not significant for any experimental condition (plant species, depth, fraction). Conclusion. Little or no signs of recently fixed CO2 (13C-depleted) were detected in the soils close to the roots, in the coarse fraction (> 50 μm), the fine fraction (< 50 μm), the organic matter, or in carbonates. This indicates a slow C turnover 45 in the studied soils, which can result from a highly conservative use of photoassimilates by plants, including a very low release of organic matter into the soil in the form of dead roots or root exudates, and from a conservative use of available C reserves