Evaluation of androgenic competence through anther culture in common eggplant and related species

Anther culture is a convenient technique to obtain androgenic haploid and doubled haploid (DH) plants. In common eggplant (Solanum melongena), this technique has been used to develop DH pure lines for producing uniform F1 hybrid seed of some commercial varieties. However, a comprehensive study of the variation of this useful trait among different materials of common eggplant and related species is still lacking. In this work, we studied the androgenic response of 12 accessions of common eggplant and related materials from the primary (eggplant complex) and secondary genepools. We cultured anthers of all the accessions under the same experimental conditions, and studied their competence to produce calli, embryos and plants, as well as the quality and origin of the embryos produced. In our conditions, anthers of 11 out of the 12 accessions produced somatic calli, whereas only 5 also produced microspore-derived embryos, with variable results in terms of embryo quality and of frequency of embryo induction and plant germination. Embryos of responding accessions were initially haploid, and reached the DH status, verified with SSR markers, after a defined period of culture. In addition to other aspects common to many androgenesis-responsive species, our results allowed us to extract conclusions particular to common eggplant and relatives, including the difficulty for finding sources of androgenic competence out of S. melongena, the reduced impact of calli in the production of non-DH individuals, and the need to avoid the occurrence of severe anatomical and functional problems in the apex of most embryos, which seriously reduces their germinative success.     

Competitive and allelopathic interference between soybean crop and annual wormwood (Artemisia annua L.) under field conditions

Annual wormwood interference on soybean crop growth and yield may result from competition and allelopathy, which are modulated by crop management. Allelochemicals released by annual wormwood (e.g. artemisinin) may affect the crop directly or indirectly through the effect on the nitrogen fixing symbiont, Bradyrhizobium japonicum. The objectives were (i) to quantify the crop response (i.e. biomass production, nodulation and yield) to weed interference and (ii) to determinate the relative change of competition and allelopathy interferences, when a sublethal dose of herbicide is applied. Two split plot field experiments with three replications were used. The experiment involved a factorial combination of five weed–crop density (soybean/annual wormwood, plants m^?2) levels: D1, pure soybean, 40/0 plants m^?2; D2, 40/2 plants m^?2; D3, 40/4 plants m^?2 and D4, 40/8 plants m^?2, and D5, pure annual wormwood, 0/8 plants m^?2, two activated carbon (allelopathy) levels: C?, with activated carbon (reduced allelopathy) and C+, non activated carbon applied (with allelopathy) and two herbicide levels: H?, untreated and H+, treated with a sub-lethal dose of glyphosate. Activated carbon to adsorb allelochemicals (with and without activated carbon) and glyphosate application (with and no herbicide) were assigned to sub-plots. Increasing weed density did not affect crop biomass at flowering, but changed nodule number and soybean yield with a different pattern depending on carbon and herbicide treatment. Relative crop yield decreased with increasing relative weed biomass. This decrease was particularly drastic when allelopathy was reduced by activated carbon and without herbicide application. The maximum yield losses of 33% in 2006 and 17% in 2007 were observed with the highest weed density (8 plants m^?2). In contrast, without carbon (high allelopathy level), soybean yield remained stable within the explored range of annual wormwood biomass, despite the fact that weed biomass at high densities (D4) was high enough to generate competition. The lack of response to increasing weed density could be related to the indirect effect of allelochemicals interacting with soil microorganisms (i.e. B. japonicum) that positively affected the nodulation (e.g. larger nodules in 2006 and increased nodules biomass due to higher number of roots in 2007 at high densities). With herbicide application, soybean yield of both carbon treatments remained stable when biomass of annual wormwood increased. This research provided strong evidence in support of the existence of positive effect of allelopathic and competitive interactions between annual wormwood and soybean crop under field conditions that may be overridden under herbicide application.     

High frequency plantlet regeneration from nodal segment culture of female <Emphasis Type="Italic">Momordica dioica</Emphasis> (Roxb.)

An in vitro propagation method for female plants of Momordica dioica (Roxb.) has been established. The nodal segments were harvested and the cut ends of the explants were sealed with wax and then surface sterilized and cultured. Bud breaking occurred on Murashige and Skoog’s (MS) agar-gelled medium + 2.0 mg L⁻¹ 6-Benzylaminopurine (BAP) + 0.1 mg L⁻¹ Indole-3 acetic acid (IAA). The cultures were amplified by passages on MS medium supplemented with 1.0 mg L⁻¹ BAP + 0.1 mg L⁻¹ IAA. Further, shoot amplification (29.2 shoots per vessel) was achieved by subculturing of in vitro regenerated shoot clump on MS medium + 0.5 mg L⁻¹ BAP + 0.1 mg L⁻¹ IAA. The micropropagated shoots were subsequently transferred for root formation on half-strength MS medium + 2.0 mg L⁻¹ Indole-3 butyric acid (IBA) with 89% success rate. The in vitro-regenerated shoots were also rooted ex vitro with 34% success. These plantlets were hardened in the greenhouse and transferred to the field. The established protocol is suitable for true to type cloning of mature female plant of M. dioica.     

Interactive responses to water deficits and crop load in olive (Olea europaea L., cv. Morisca). II: Water use, fruit and oil yield

To understand the relations between water use and yield in response to crop load, two experiments were conducted in olive (cv. Morisca), during six consecutive years (2002-2007) in an experimental orchard located in Badajoz, Southwest Spain. Experiment 1, assessed the responses during the early years of the orchard (2002-2004) using four irrigation treatments that applied fractions of the estimated crop evapotranspiration (ET_c) (125%, 100%, 75% and 0%) and three crop load levels (100%, 50% and 0% of fruit removal, termed Off, Medium and On treatments). Experiment 2 assessed the response of more mature trees (2005-2007) to three irrigation treatments (115%, 100%, and 60% of ET_c) and the natural crop load which were Off, On, and Medium in 2005, 2006 and 2007, respectively. Yield was reduced by water deficits and so did the estimated tree transpiration which was linearly related to yield (y = 1.2302x − 21.15, R² = 0.8864), showing the high sensitivity of cultivar Morisca to water deficits. The relations between fruit number and fruit weight showed that high crop loads had lower fruit weights and oil yield, a decrease that was more pronounced as water deficits increased. The yield response to water supply in the control and excess treatments, and the observations on the water relations of these two treatments suggest that the calculations made using the FAO method (Doorenbos and Pruit, 1974) with the crop coefficient proposed by Pastor et al. (1998) and the reduction coefficient (Fereres et al., 1982) to apply 100% of ET_c in the control treatment, underestimated the ET_c of the orchard. The results indicate that, although the absence of fruits lead to reduced water use as compared to situations of medium and high crop loads, canopy size was much more determinant of orchard water requirements than crop load.     

Mutations in a human ROBO gene disrupt hindbrain axon pathway crossing and morphogenesis

The mechanisms controlling axon guidance are of fundamental importance in understanding brain development. Growing corticospinal and somatosensory axons cross the midline in the medulla to reach their targets and thus form the basis of contralateral motor control and sensory input. The motor and sensory projections appeared uncrossed in patients with horizontal gaze palsy with progressive scoliosis (HGPPS). In patients affected with HGPPS, we identified mutations in the ROBO3 gene, which shares homology with roundabout genes important in axon guidance in developing Drosophila, zebrafish, and mouse. Like its murine homolog Rig1/Robo3, but unlike other Robo proteins, ROBO3 is required for hindbrain axon midline crossing.     

The Physcomitrella genome reveals evolutionary insights into the conquest of land by plants

We report the draft genome sequence of the model moss Physcomitrella patens and compare its features with those of flowering plants, from which it is separated by more than 400 million years, and unicellular aquatic algae. This comparison reveals genomic changes concomitant with the evolutionary movement to land, including a general increase in gene family complexity; loss of genes associated with aquatic environments (e.g., flagellar arms); acquisition of genes for tolerating terrestrial stresses (e.g., variation in temperature and water availability); and the development of the auxin and abscisic acid signaling pathways for coordinating multicellular growth and dehydration response. The Physcomitrella genome provides a resource for phylogenetic inferences about gene function and for experimental analysis of plant processes through this plant's unique facility for reverse genetics.