Browsing by Subject "Pflanzenmorphologie"

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Diversity in the tropical multipurpose shrub legumes Cratylia argentea (Desv.) O. Kuntze and Flemingia macrophylla (Willd.) Merrill.
(2006) Andersson, Meike S.; Schultze-Kraft, Rainer
Cratylia argentea (Desv.) O. Kuntze and Flemingia macrophylla (Willd.) Merrill are promising tropical multipurpose shrub legumes. Both are drought-tolerant, well adapted to low-fertility, acid soils, and especially suited for low-input smallholder production systems in the sub-humid and humid tropics. They can be used e.g. as dry season forage supplementation, live soil cover or mulch, erosion barrier hedges, and shade-providing shrubs in young coffee and cocoa plantations. Germplasm collections were assembled from the wild-legume flora in Brazil (C. argentea) and Southeast Asia (F. macrophylla), but research and development are so far based on only a few accessions. Knowledge about the extent of genetic diversity within these collections is very limited. In addition, the potential utilization of F. macrophylla is so far limited by poor forage quality and acceptability of the few evaluated accessions. The objective of the present study, conducted in a research cooperation with the International Centre for Tropical Agriculture (CIAT), Cali, Colombia, was to assess the diversity in the germplasm collections of C. argentea (38 accessions) and F. macrophylla (69 accessions) in terms of morphological and phenological traits, agronomic and forage quality traits, and molecular markers, and to identify superior genotyes. Based on these different characterization approaches, the objective was furthermore to establish core collections for F. macrophylla, and to compare and validate the different strategies, giving particular consideration to their practical implications (time and cost efficiency) for the application to small collections of perennial wild tropical legumes. Cratylia argentea High diversity in terms of phenological and agronomic as well as forage quality traits was detected in the collection, with scope for plant improvement in terms of higher dry season DM production. Accessions CIAT 18674 and 22406 were identified as promising for further evaluation since they were similar to the commercial cultivar "Veraniega" in terms of forage quality, and superior in terms of DM production, particularly in the dry season. Molecular marker analysis with RAPDs showed that the genetic diversity in the collection was relatively low and fairly homogeneously distributed. Accessions CIAT 22373, 22378, 22380, 22381 and 22411 were identified as possible duplicates. Flemingia macrophylla High diversity in terms of morphological and agronomic as well as forage quality traits was detected among the 69 accessions. The identification of four morphotypes in the collection probably has taxonomic implications. Scope for plant improvement was identified with respect to forage quality - one of the species´ main limitations. Accessions CIAT 18437, 21083 and 21090 had similar DM production and higher digestibility than the control accession, and were virtually free of extractable condensed tannins. Problems with low palatability and low seed production of these promising accessions need to be further studied. Genetic diversity in F. macrophylla was higher than in C. argentea, and corresponded closely to the four morphotypes revealed by conventional characterization. Various duplicate accessions were identified, and evidence was provided that the non-Asian accessions are not native to their collection site regions, but rather introduced from Southeast Asia. The results have direct applications for plant improvement of these promising multipurpose legumes. The superior genotypes selected in this study will be used in work with farmers in CIAT-research sites in Central America and distributed to partners. It must be recognized, however, that the diversity assessed is influenced by the climatic and edaphic conditions at the site where the studies were conducted. Therefore, multilocational trials should be considered with a selected subset (including the promising accessions) of C. argentea and F. macrophylla i) to assess the extent of genotype x environment interaction, and ii) to identify genotypes with consistently high performance in a range of distinct environments. Research on the reproduction system of both species is urgently required to determine the potential extent and impact of outcrossing. Beyond the immediate application of these species for farmer utilization, the results of the use and comparison of different approaches to assess diversity and to establish core collections can help to improve germplasm management and characterization of wild tropical legume species in general. Random sampling has been identified as a valuable and resource-efficient strategy for the creation of core collections when no additional information about accessions is available, and in the absence of adequate funds. The validation of the findings of this study with a broader range of perennial tropical wild legumes is necessary to assess their applicability to other species.
Exploring and modelling the influence of spectral light composition on soybean (Glycine max (L.) Merr.)
(2019) Hitz, Tina; Graeff-Hönninger, Simone
The development of soybean cultivars for the climatic conditions in Europe is an urgent need in order to increase the European production and to decrease the dependence of imported soybean. A speed breeding system can accelerate the process of developing new cultivars by growing more generations per season in climate chambers. The project MoLED-Plant aimed towards the development of a speed breeding system for soybean under LED lighting. The major objectives of this thesis were to: (i) construct a three dimensional model of an LED chamber to simulate micro-light climate, (ii) develop a functional-structural plant (FSP) model of soybean and derive a blue photon flux density (BPFD) response curve from simulations, (iii) apply the FSP model with the integrated response curve for spectral optimization, (iv) explore the influence of BPFD under constant photosynthetic photon flux density (PPFD), and (v) disentangle the influence of red to far-red ratio (R:FR) and PPFD on the shade avoidance response (SAR). The objectives were fulfilled with a combination of FSP modelling in the Growth Grammar-related Interactive Modelling Platform (GroIMP) and plant experiments under multiple spectra in LED chambers. The presented LED chamber model was the first three dimensional environment, which was developed for spectral optimizations in indoor farming using FSP modeling. Measurements performed with a spectrometer in multiple heights and orientations were compared to simulations recorded with a virtual sensor at the same locations. The model was evaluated as a tool for assessment of spectral light heterogeneity under an alternative placement of the LED modules. Applying the model can assist in choosing the best chamber design and placements of LEDs to assure homogeneous light conditions. Subsequently, static soybean plants were incorporated into the chamber model. Comparison of light simulations and measurements from below the soybean canopy in four reconstructed scenarios assured a good simulation of micro-light climate. The model was applied to simulate the effect of an increased plant density in an experiment in the chamber. The simulations of light homogeneity in the experimental setup can assist in choosing the optimal design. The developed dynamic FSP model of soybean within the chamber model represents the first FSP model with an integrated response to BPFD. The soybean model was calibrated with data from BPFD experiments. From simulations, a common response curve of internode elongation to the perceived BPFD was derived for the second and third internode. The response curve was integrated in the model and was applied for spectral optimization in a chamber scenario with an alternative high reflective bottom material. The soybean response to BPFD under constant PPFD and the influence of R:FR and PPFD on SAR was explored by designing specific spectra from LEDs. Soybean experiments were performed under six levels of BPFD (60-310 µmol m-2 s-1) and constant PPFD (400 µmol m-2 s-1). Plant height and biomass decreased, leaf mass ratio increased and the ratio of stem biomass (internode plus petiole) translocated to the internode decreased under high BPFD. Three soybean cultivars were grown under nine light treatments to disentangle the effect of R:FR and PPFD. Internode elongation responded mainly to low PPFD with an additive effect from low R:FR, whereas petiole elongation was influenced to a great extent by low R:FR. In the context of SAR, petiole elongation can be seen as the main response to the threat of shade (high PPFD and low R:FR) and both petiole and internode elongation as the response to true shade (low PPFD and low R:FR). This thesis showed how PPFD, BPFD and R:FR work both independently, antagonistically and synergistically on the physiology and morphology of soybean. The increased insight in these responses can e.g. support crop breeding and spectral optimization in indoor farming. Furthermore, interesting and important objectives for future research were identified. These experiments should include physiological measurements for a deeper understanding of interactions and underlying mechanisms. Spectral optimization of indoor farming depends on the purpose of the production. For instance, a high BPFD of 260 µmol m-2 s-1 was optimal for speed breeding, whereas an intermediate BPFD would be preferable to increase biomass. Comprehensive investigation of spectral influence on plant physiology and morphology is necessary to fully utilize the spectral flexibility of LED lighting. The developed FSP model of soybean in a virtual LED chamber represents an important step towards utilizing the advantages of FSP modelling by simulation of a wide variety of scenarios. The model can be adjusted or extended depending on the purpose of the model. It can be calibrated for other crop species and the setting of the chamber dimensions can be changed.