Resistenzeigenschaften im Gersten- und Weizensortiment Gatersleben 7. Prüfung der Frostresistenz von Wintergersten im künstlichen Gefrierversuch

Zusammenfassung Von den Faktoren, die zur Winterfestigkeit der Gersten beitragen, wird die Frostresistenz untersucht. Dazu wird ein Verfahren des künstlichen Gefrierens im Kältegewächshaus ausführlich beschrieben.Mit Hilfe dieses Verfahrens wurden aus dem Material des Gaterslebener Wintergerstensortiments bisher 367 Zucht- und Landsorten untersucht. Nach Vergleich mit fünf aus früheren Untersuchungen zur Verfügung stehenden Standardsorten ließen sich diese Sorten in entsprechende Resistenzgruppen einordnen. Die Sorten mit guter Frostresistenz sind Albert (Frankreich), Almerfelder, Dominator, Hellmann und Teilhaber, Schwarze Wintergerste (Deutschland), Kostek, Kujawiak, lski II (Polen), Mozdokskij Mestnij, Odesskij 17 (Sowjetunion) und eine Herkunft vom Peloponnes. Der Verlauf ihrer Frostresistenz während des Winters wird im einzelnen charakterisiert. Die 103 Sorten mit mittlerer Frostresistenz sind einzeln aufgeführt (Tabelle 4).Die Möglichkeiten dieses Verfahrens für eine umfassende Beurteilung der Frostresistenz werden diskutiert, ebenso das Problem der Züchtung winterfesterer Gersten.

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Summary The frost-hardiness of barley, one of the several factors causing winter-hardiness, has been studied by artificial freezing in a cooled greenhouse. The method is described in detail.Out of the Gatersleben collection 367 varieties and land-races of winter barley were tested. This material was grouped, in comparison to standard varieties, into corresponding classes of frost-resistance according to the degree of plant injury. Varieties with high frost-resistance are Albert (France), Almerfelder, Dominator, Hellmann und Teilhaber, Schwarze Wintergerste (Germany), Kostek, Kujawiak, lski II (Poland), Mozdokskij Mestnij, Odesskij 17 (Sowjet-Union) and one land-race from Peloponnesus. Their reaction to frost-resistance during the winter is described in detail. Further 103 varieties, listed in table 4, showed moderate resistance.Finally the possibilities are discussed, given by this method for a comprehensive estimation of frost-resistance, as well as the problem of breeding winter barley varieties with higher frost resistance.

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Water use efficiency and uptake patterns in a runoff agroforestry system in an arid environment

Water is the most limiting factor for plant production in arid to semiarid regions. In order to overcome this limitation surface runoff water can be used to supplement seasonal rainfall. During 1996 we conducted a runoff irrigated agroforestry field trial in the Turkana district of Northern Kenya. The effects of two different Acacia saligna (Labill.) H. Wendl. tree planting densities (2500 and 833 trees per ha), tree pruning (no pruning vs. pruning) and annual intercrops (no intercrop vs. intercrop: Sorghum bicolor (L.) Moench during the first season and Vigna unguiculata (L.) Walp. during the second season) on water use were investigated. The annual crops were also grown as monocrops. Water consumption ranged from 585 to 840 mm during the first season (only treatments including trees). During the second season, which was shorter and the plants relied solely on stored water in the soil profile, water consumption was less than half of that during the first season. Highest water consumptions were found for non-pruned trees at high density and the lowest were found for the annual crops grown as monocrops. Tree pruning decreased water uptake compared to non-pruned trees but soil moisture depletion pattern showed complementarity in water uptake between pruned trees and annual intercrops. The highest values of water use efficiency for an individual treatment were achieved when the pruned trees at high density were intercropped with sorghum (1.59 kg m^–3) and cowpea (1.21 kg m^–3). Intercropping and high tree density increased water use efficiency in our runoff agroforestry trial. We ascribe the observed improvement in water use efficiency to the reduction of unproductive water loss from the bare soil.This revised version was published online in November 2005 with corrections to the Cover Date.     

Wood as a natural smart material

The dominant feature of artificial smart materials is the “shape memory” effect. This phenomenon is based on frozen strains (FS). They were detected in wood fastened specimens during drying in the early 1960s. The integral law of wood deforming under loading and moisture content and/or temperature changes was subsequently formulated. This law takes into account the forming of FS. It was applied for the calculation of wood drying stresses. Stress memory and strain memory effects for wood were discovered. Wood has the ability to recollect the type of loading (tension or compression) which it had undergone. The difference between the free and restrained shrinkage is named “frozen shrinkage” (FSh). In calculations of drying stresses, it is more justified to use the FSh concept than “mechano-sorptive creep” (MSC). The MSC phenomenon is observed at cyclical change of moisture content in loaded wood. “Hygrofatigue” that reduces wood stiffness plays the main role in this process.     

A functional screen for the type III (Hrp) secretome of the plant pathogen Pseudomonas syringae

Type III secreted "effector" proteins of bacterial pathogens play central roles in virulence, yet are notoriously difficult to identify. We used an in vivo genetic screen to identify 13 effectors secreted by the type III apparatus (called Hrp, for "hypersensitive response and pathogenicity") of the plant pathogen Pseudomonas syringae. Although sharing little overall homology, the amino-terminal regions of these effectors had strikingly similar amino acid compositions. This feature facilitated the bioinformatic prediction of 38 P. syringae effectors, including 15 previously unknown proteins. The secretion of two of these putative effectors was shown to be type III--dependent. Effectors showed high interstrain variation, supporting a role for some effectors in adaptation to different hosts.     

Strong association of de novo copy number mutations with autism

We tested the hypothesis that de novo copy number variation (CNV) is associated with autism spectrum disorders (ASDs). We performed comparative genomic hybridization (CGH) on the genomic DNA of patients and unaffected subjects to detect copy number variants not present in their respective parents. Candidate genomic regions were validated by higher-resolution CGH, paternity testing, cytogenetics, fluorescence in situ hybridization, and microsatellite genotyping. Confirmed de novo CNVs were significantly associated with autism (P = 0.0005). Such CNVs were identified in 12 out of 118 (10%) of patients with sporadic autism, in 2 out of 77 (3%) of patients with an affected first-degree relative, and in 2 out of 196 (1%) of controls. Most de novo CNVs were smaller than microscopic resolution. Affected genomic regions were highly heterogeneous and included mutations of single genes. These findings establish de novo germline mutation as a more significant risk factor for ASD than previously recognized.     

Comment on "Fire-derived charcoal causes loss of forest humus"

Wardle et al. (Brevia, 2 May 2008, p. 629) reported that fire-derived charcoal can promote loss of forest humus and belowground carbon (C). However, C loss from charcoal-humus mixtures can be explained not only by accelerated loss of humus but also by loss of charcoal. It is also unclear whether such loss is related to mineralization to carbon dioxide or to physical export.