Nya genkällor för ogräskonkurrerande förmåga i höstvete

En allt större areal med höstvete, ökad problem med herbicidresistenta ogräs samt minskad tillgång på tillåtna herbicider gör det svårare att kontrollera ogräsen. Olika system med integrerad ogräsbekämpning har därför fått stort intresse. En komponent i denna är sorternas ogräskonkurrerade förmåga. Denna brukar i stora drag förklaras av skillnader i växtsätt men senare rön tyder även på att allelopati, dvs utsöndring av tillväxthämmande ämnen från rötter och blad, kan vara en viktig faktor. Råg och rågvete har hög ogräskonkurrerande förmåga främst genom en snabb och tidig tillväxt på våren, men speciellt hos råg har allelopatiska egenskaper framförts som viktiga i sammanhanget. Genom att korsa vete med rågvete är det möjligt att ersätta delar av vetets genom med delar av rågens genom och därmed överföra egenskaper från råg till vete. Vetelinjer med inslag av råg har tillsammans med andra urvalslinjer för hög allelopatisk aktivitet provats i fält avseende ogräskonkurrerans under två år. Flertalet av linjerna uppvisade en halverad ogräsbiomassa jämfört med mätarsorten Harnesk. Mer än 50 % av skillnaderna i ogräsbiomassa förklardes av en regressionsmodell med strålängd och allelopatisk aktivitet som signifikanta variabler. Endast dessa variabler var signifikanta även om tidig skottlängd i det närmaste var signifikant. Resultatet visar därmed att inte enbart tillväxt utan även allelopati spelat en stor roll i detta material för ogräskonkurrensen. Flertalet av linjerna och framför allt linjer med råginblandning hade dock en lägre avkastning. Anledningen till detta är troligtvis att utbytet av en vetekromosom eller delar av en med liknande från råg kan få negativa konsekvenser. Det är egentligen endast 1R som har visat sig stabil och resulterat i högavkastande vetesorter. En anledning kan vara att vetebakgrunden härrör från en äldre vetesort. I projektet har därför även nya urval gjorts av linjer med en bakgrund från två moderna vetesorte

QTL for chlorophyll fluorescence of barley plants grown at low oxygen concentration in hydroponics to simulate waterlogging

Waterlogging is a major factor limiting barley grain yield worldwide. Climate change will likely increase this water stress in Northern Europe. Breeding for waterlogging tolerance (WLT), as for other abiotic stresses, is difficult, but identification of genetic markers linked to genes affecting WLT could facilitate the breeding process. To identify a suitable marker population, parents of 14 double-haploid (DH) barley populations were tested for segregation of biomass growth reduction in waterlogged soil. The most interesting was found in the offspring from crossing cv. Psaknon and breeding line (SLUdt1398 from this cross were phenotyped for the chlorophyll fluorescence parameter quantum yield (QY) of electron transport of PSII from leaves of hypoxia-stressed plants and further genotyped with 384-SNP Illumina GoldenGate Bead Array. Five quantitative trait loci (QTL) for QY, with a narrow sense heritability of 0.879 Mona4). Hence, 120 DH-lines derive

Evolutionary changes of weed competitive traits in winter wheat composite cross populations in organic and conventional farming systems.

Seedling root and shoot growth in hydroponics and allelopathic activity using a bioassay have been studied in very diverse populations of winter wheat grown under either organic or conventional conditions for a number of generations and subjected only to natural selection. The study was conducted on seeds from generation 6 (F6) and 11 (F11) from three composite cross populations (CCPs) produced by the Organic Research Centre in the UK. Since the F5 the populations were maintained under organic and conventional conditions in Germany. Two parallel populations were created from each CC, resulting in a total of six organic and six conventional CCPs. The sets of parallel populations showed similar evolutionary trends indicating that the observed changes are related to differences in management rather than chance. Seedling root length and seedling root and shoot weight in the F11 of the organically-managed CCPs were significantly greater than in the organic F6 CCPs. In the conventionally-managed CCPs no such differences were observed. Both organic and conventional CCPs produced for quality showed higher early root and shoot growth than those produced for yield pointing to genetic differences among population types and highlighting the importance of early vigour for NUE. There were no significant differences in the allelopathic activity of the populations and between generations. The Shannon-Weaver diversity indices were similar for the studied traits in organic and conventional CCPs and hence no major changes in diversity had occurred between F6 to F11. As changes in plant height were small and weed pressure in the fields low it is concluded that the observed differences are more related to NUE, rather than intra-specific competition for light or the direct effect of increased weed pressure in the organic system

Glödbrandens effekter på trädrötter

Skogsbrand var tidigare ett allmänt inslag i de svenska skogarna och idag används elden i naturvårdsarbetet. För att förstå dess effekter på trädmortalitet har ett flertal studier genomförts där man har tittat på trädens försvar mot brand. Mycket är känt om hur stam och krona påverkas, men brandens inverkan på rötter som ligger skyddade under marken är förhållandevis okänt. Det är inte den flammande elden som når rötterna utan glödbranden som rör sig i markens humusskikt. Vi utförde försök där vi brände trädgrenar placerade i kommersiell torv, detta för att simulera rötter under marken. Grenarnas fuktkvot och torrvikt mättes innan och efter brand och temperaturutvecklingen mättes med termoelement på olika positioner i torven. I försöken gick att urskilja ett tydligt samband mellan rötternas tjocklek och deras motståndskraft mot brand. Ved i de grövre diameterklasserna konsumerades till mindre grad än de med mindre diameter. Torvtjocklekens påverkan var mindre tydlig. En marginellt ökad konsumtion av veden gick att urskilja i de försök där torvdjupet var större. Temperaturen i torven under glödbranden hade en maxtemperatur mellan +400 och +500℃ , och temperaturer > 250℃ ca 1-2 timmar, vilket resulterade i att grenarnas fuktkvot sjönk markant under branden och i många fall till att veden förkolnades helt eller delvis. Resultaten visar att grövre rötter står emot avbränningen i en högre grad än de tunna. Ett mäktigare humuslager bidrar eventuellt till högre åverkan på trädens rötter.Forest fires once a regular occurrence in Sweden is today mainly used in nature preservation purposes. To understand its effects on forests regarding mortality there has been several studies about trees defence against fires. The effects on bole and crown are fairly well known, but the impact on roots, protected by the soil is relatively unknown. It is not the flaming fire reaching the roots but the smouldering fire that moves through the humus. We carried out trials where we burned branches placed in commercial peat to simulate roots in the humus layer. The branches moisture content and dry weight was measured before and after fire and the temperature development was measured with thermocouples placed in different positions in the peat. In the trials there was a clear connection between the thickness of roots and their resistance against fire. Wood with larger diameter had a smaller share consumed material than the smaller ones. The impact of peat thickness was less clear, although there was a marginally increased consumption with greater peat depths. The temperature of the peat during smouldering fire had a maximum of about +400 to + 500℃ , and temperatures > 250C for approximately 1-2 hours, resulting in a significant lower moisture content in the branches and in some cases branches becoming char during fire. Thicker roots will not be as severed as easily as the thin ones. A thicker humus layer may contribute to a higher degree of damage on tree roots

Root morphology and seed and leaf ionomic traits in a Brassica napus L. diversity panel show wide phenotypic variation and are characteristic of crop habit

Background: Mineral nutrient uptake and utilisation by plants are controlled by many traits relating to root morphology, ion transport, sequestration and translocation. The aims of this study were to determine the phenotypic diversity in root morphology and leaf and seed mineral composition of a polyploid crop species, Brassica napus L., and how these traits relate to crop habit. Traits were quantified in a diversity panel of up to 387 genotypes: 163 winter, 127 spring, and seven semiwinter oilseed rape (OSR) habits, 35 swede, 15 winter fodder, and 40 exotic/unspecified habits. Root traits of 14 d old seedlings were measured in a ‘pouch and wick’ system (n = ~24 replicates per genotype). The mineral composition of 3–6 rosette-stage leaves, and mature seeds, was determined on compost-grown plants from a designed experiment (n = 5) by inductively coupled plasma-mass spectrometry (ICP-MS). Results: Seed size explained a large proportion of the variation in root length. Winter OSR and fodder habits had longer primary and lateral roots than spring OSR habits, with generally lower mineral concentrations. A comparison of the ratios of elements in leaf and seed parts revealed differences in translocation processes between crop habits, including those likely to be associated with crop-selection for OSR seeds with lower sulphur-containing glucosinolates. Combining root, leaf and seed traits in a discriminant analysis provided the most accurate characterisation of crop habit, illustrating the interdependence of plant tissues. Conclusions: High-throughput morphological and composition phenotyping reveals complex interrelationships between mineral acquisition and accumulation linked to genetic control within and between crop types (habits) in B. napus. Despite its recent genetic ancestry (<10 ky), root morphology, and leaf and seed composition traits could potentially be used in crop improvement, if suitable markers can be identified and if these correspond with suitable agronomy and quality traits

An ecological future for weed science to sustain crop production and the environment. A review

Sustainable strategies for managing weeds are critical to meeting agriculture's potential to feed the world's population while conserving the ecosystems and biodiversity on which we depend. The dominant paradigm of weed management in developed countries is currently founded on the two principal tools of herbicides and tillage to remove weeds. However, evidence of negative environmental impacts from both tools is growing, and herbicide resistance is increasingly prevalent. These challenges emerge from a lack of attention to how weeds interact with and are regulated by the agroecosystem as a whole. Novel technological tools proposed for weed control, such as new herbicides, gene editing, and seed destructors, do not address these systemic challenges and thus are unlikely to provide truly sustainable solutions. Combining multiple tools and techniques in an Integrated Weed Management strategy is a step forward, but many integrated strategies still remain overly reliant on too few tools. In contrast, advances in weed ecology are revealing a wealth of options to manage weedsat the agroecosystem levelthat, rather than aiming to eradicate weeds, act to regulate populations to limit their negative impacts while conserving diversity. Here, we review the current state of knowledge in weed ecology and identify how this can be translated into practical weed management. The major points are the following: (1) the diversity and type of crops, management actions and limiting resources can be manipulated to limit weed competitiveness while promoting weed diversity; (2) in contrast to technological tools, ecological approaches to weed management tend to be synergistic with other agroecosystem functions; and (3) there are many existing practices compatible with this approach that could be integrated into current systems, alongside new options to explore. Overall, this review demonstrates that integrating systems-level ecological thinking into agronomic decision-making offers the best route to achieving sustainable weed management