Surrogate transformation of perennial ryegrass, Lolium perenne, using genetically modified Acremonium endophyte.

Summary Conditions have been developed for transforming protoplasts of the perennial ryegrass endophyteAcremonium strain 187BB. Unlike most other ryegrass endophytes, this strain does not produce the lolitrem B neurotoxin and is therefore suitable as a host for surrogate introduction of foreign genes into grasses. Transformation frequencies of 700–800 transformants/g DNA were obtained for both linear and circular forms of pAN7-1, a hygromycin (hph) resistant plasmid. Up to 80% of the linear transformants were stable on further culturing but only 25% of the circular transformants retained hygromycin resistance. Integration of pAN7-1 into the genome was confirmed by Southern blotting and probing of genomic digests of transformant DNA. Both single and tandemly repeated copies of the plasmid were found in the genome and both the number and sites of integration varied among the transformants. At least 13 chromosomes were identified in 187BB using contour-clamped homogeneous electric field (CHEF) gel electrophoresis. Probing of Southern blots of these gels confirmed that pAN7-1 had integrated into different chromosomes. The -glucuronidase (GUS) gene,uidA, was also introduced into 187BB by co-transformation of pNOM-2 with pAN7-1. GUS activity was detected by growing the transformants on plates containing 5-bromo-4-chloro-3-indolyl -D-glucuronic acid and by enzyme assays of mycelial extracts. Severalhph- anduidA-containing transformants were reintroduced into ryegrass seedlings and expression of GUS visualized in vivo, demonstrating that 187BB can be used as a surrogate host to introduce foreign genes into perennial ryegrass. Molecular analysis of fungal isolates from the leaf sheath confirmed that the pattern of pAN7-1 and pNOM-2 hybridizing fragments was identical to that observed in the fungus used as inoculum.     

Effect of aluminium on the growth of 34 plant species: A summary of results obtained in low ionic strength solution culture

The results from many experiments conducted over 5 years to determine the tolerance of 34 plant species (87 cultivars) to aluminium (Al) are summarised. All experiments were conducted in a temperature-controlled glasshouse using a low-ionic-strength solution culture technique. The activity of Al³⁺ (M) at which top yields were reduced by 50% (Al_RY50) was determined for each cultivar.The species Bromus wildenowii, Cynosurus cristatus, Hordeum vulgare, Triticum aestivum (cvs Warigal, Scout, Sonora-63), Avena byzantina, Arabidopsis thaliana, Lycopersicon esculentum and Nicotiana plumbaginifolia were all very sensitive to Al (Al_RY50<1). The species Poa pratense, Lolium perenne (NZ-derived cultivars), Lotus corniculatus, Avena sativa (cvs West, Carbeen, Camellia and Coolabah), Triticum aestivum (cvs Cardinal and Waalt), Allium cepa and Asparagus officinalis were sensitive to Al (Al_RY50 1–2).The pasture grass species Lolium perenne (Australian and European and derived cultivars), Lolium hybridum and Lolium multiflorum, Dactylis glomerata (Apanui and Kara), Phalaris aquatica, Festuca arundinacea and the pasture legumes species Trifolium pratense, Trifolium repens and Trifolium subterraneum were all moderately sensitive to Al (Al_RY50 2–5). Other species that were also moderately sensitive included Triticum aestivum (cvs Atlas-66, BH146, and Carazinho), Avena sativa (cvs Swan and Blackbutt), Avena Strigosa, Petunia x and Phaseolus vulgaris (cvs Red Kidney, Black Turtle and Haricot).The most tolerant species (Al_RY50>5) were (in order of increasing tolerance) Phaseolus vulgaris (cvs Tendergreen, The Prince and Yatescrop), Cucurbita maxima, Dactylis glomerata (cv Wana), Paspalum dilatatum, Lotus pedunculatus, Ehrharta calycina, Medicago sativa, Holcus lanatus, Festuca rubra, Phaseolus lunatus and Agrostis tenuis. Agrostis tenuis was at least twice as tolerant as the next most tolerant species (Al_RY50>30 compared to 15.6).     

Organic acids from the anaerobic decomposition of Agropyron repens rhizomes

Phytotoxicity originating from the anaerobic decomposition of couch grass rhizomes has been studied. Short chain aliphatic (acetic, propionic and butyric) acids appear to be mainly responsible but hexanoic, succinic, phenylacetic, cinnamic, p-coumaric, 4-hydroxyphenylpropionic and 3,4-dihydroxyphenylpropionic acids are also present in the phytotoxic solutions formed during the decomposition.     

Evaluation of production efficiencies at pasture of lactating suckler cows of diverse genetic merit and replacement strategy

Feed costs account for the largest proportion of direct cost within suckler beef production systems. By identifying the cow type with enhanced capability of converting grazed herbage to beef output across lactations, suckler cow systems would become more efficient and sustainable. The objective of this study was to estimate grass DM intake (GDMI) and production efficiency among lactating suckler cows of diverse genetic merit for the national Irish maternal index (Replacement Index) which includes cow efficiency components such as milk yield and feed intake. Data from 131 cows of diverse genetic merit within the Replacement Index, across two different replacement strategies (suckler or dairy sourced), were available over two grazing seasons. Milk yield, GDMI, cow live weight (BW) and body condition score (BCS) were recorded during early, mid and late-lactation, with subsequent measures of production efficiency extrapolated. Genetic merit had no significant effect on any variables investigated, with the exception of low genetic merit (LOW) cows being 22 kg heavier in BW than high genetic merit (HIGH) cows (P < 0.05). Beef cows were 55 kg heavier in BW (P < 0.001), had a 0.31 greater BCS (P < 0.05) and 0.30 Unité Fourragère Lait (UFL) greater energy requirement for maintenance compared to dairy sourced beef × dairy crossbred (BDX) cows (P < 0.001). The BDX had 0.8 kg greater GDMI, produced 1.8 kg more milk (P < 0.001), had a 0.8 UFL greater energy requirement for lactation and produced weanlings that were 17 kg heavier in BW than beef cows (P < 0.05). Subsequent efficiency variables of milk per 100 kg BW (P < 0.001), milk per kg GDMI (P < 0.001) and GDMI per 100 kg BW (P < 0.001) were more favourable for BDX. The correlations examined showed GDMI had moderate positive correlations (P < 0.001) with intake per 100 kg BW, net energy intake per kg milk yield, RFI and intake per 100 kg calf weaning weight but was weakly negatively correlated to milk yield per kg GDMI (P < 0.001). No difference was observed across genetic merit for beef cows for any of the traits investigated. Results from the current study showed that, while contrasting replacement strategies had an effect on GDMI and production efficiency, no main effect was observed on cows diverse in genetic merit for Replacement Index. Nonetheless, utilising genetic indexes in the suckler herd is an important resource for selecting breeding females for the national herd and phenotypic performance generated from this study can be included in future genetic evaluations to improve reliability of genetic values.     

Using consecutive prescribed fires to reduce shrub encroachment in grassland by increasing shrub mortality

Woody plant encroachment into open grasslands occurs worldwide and causes multiple ecological and management impacts. Prescribed fire could be used to conserve grassland habitat but often has limited efficacy because many woody plants resprout after fire and rapidly reestablish abundance. If fire‐induced mortality could be increased, prescribed fire would be a more effective management tool. In California's central coast, shrub encroachment, especially of Baccharis pilularis (coyote brush), is converting coastal prairie into shrub‐dominated communities, with a consequent loss of native herbaceous species and open grassland habitat. B. pilularis has not been successfully controlled with single prescribed fire events because the shrub resprouts and reestablishes cover within a few years. We investigated whether two consecutive annual burns would control B. pilularis by killing resprouting shrubs, without reducing native herbaceous species or encouraging invasive plants. As expected, resprouting did occur; however, 2 years after the second burn, B. pilularis cover on burned plots was only 41% of the cover on unburned plots. Mortality of B. pilularis more than doubled following the second burn, likely maintaining a reduction in B. pilularis cover for longer than a single burn would have. Three native coastal prairie perennial grasses did not appear to be adversely affected by the two burns, nor did the burns result in increased cover of invasive species. Managers wanting to restore coastal prairie following B. pilularis encroachment should consider two consecutive annual burns, especially if moderate fire intensity is achievable.     

Grazing and productivity alter individual grass size dynamics in semi-arid woodlands

The spatial arrangement of perennial vegetation is critical for ecosystem function in drylands. While much is known about how vegetation patches respond to grazing and abiotic conditions, the size dynamics of individual plants is mostly limited to theoretical studies. We measured the size distribution (mean, variance, skewness) and density of individual grasses, and grass species composition at 451 sites spanning a range of grazing intensities across three broad vegetation communities in semi-arid eastern Australia. We assessed the relative role of grazing by livestock (cattle and sheep), native (kangaroos) and introduced (rabbits) free ranging herbivores, and several environmental measures (productivity, diversity, composition and groundstorey plant cover) on the size distribution and density of individual grasses. We found mean grass size and density were more sensitive to shifts in grazing intensity and environmental conditions than size variance or the frequency of the smallest individuals (skewness), and shifts were mostly driven by site productivity and cattle and kangaroo grazing. Sheep grazing only reduced mean grass size, and rabbit grazing had no consistent effects. Importantly, we found that site productivity and species composition altered the impacts of grazing on grass density and size distribution. For example, increasing cattle grazing led to larger grasses in low productivity sites. It also led to larger, denser, more variable-sized grasses among grass species from sites with finer soil texture. Increasing kangaroo grazing led to smaller, denser individuals among grass species from sites with coarse soil texture. At high diversity sites kangaroo grazing led to denser, more homogenised grass sizes with a lower frequency of small individuals. Understanding the in situ response of individual plant sizes gives us insights into the processes driving shifts in perennial vegetation patchiness, improving our ability to predict how the spatial arrangement of ecosystems might change under global change scenarios.     

Roles of BdUNICULME4 and BdLAXATUM‐A in the non‐domesticated grass Brachypodium distachyon

In cultivated grasses, tillering, spike architecture and seed shattering represent major agronomical traits. In barley, maize and rice, the NOOT‐BOP‐COCH‐LIKE (NBCL) genes play important roles in development, especially in ligule development, tillering and flower identity. However, compared with dicots, the role of grass NBCL genes is underinvestigated. To better understand the role of grass NBCLs and to overcome any effects of domestication that might conceal their original functions, we studied TILLING nbcl mutants in the non‐domesticated grass Brachypodium distachyon. In B. distachyon, the NBCL genes BdUNICULME4 (CUL4) and BdLAXATUM‐A (LAXA) are orthologous, respectively, to the barley HvUniculme4 and HvLaxatum‐a, to the maize Zmtassels replace upper ears1 and Zmtassels replace upper ears2 and to the rice OsBLADE‐ON‐PETIOLE1 and OsBLADE‐ON‐PETIOLE2/3. In B. distachyon, our reverse genetics study shows that CUL4 is not essential for the establishment of the blade–sheath boundary but is necessary for the development of the ligule and auricles. We report that CUL4 also exerts a positive role in tillering and a negative role in spikelet meristem activity. On the other hand, we demonstrate that LAXA plays a negative role in tillering, positively participates in spikelet development and contributes to the control of floral organ number and identity. In this work, we functionally characterized two new NBCL genes in a context of non‐domesticated grass and highlighted original roles for grass NBCL genes that are related to important agronomical traits.     

Ranking buffel: Comparative risk and mitigation costs of key environmental and socio‐cultural threats in central Australia

Changed fire regimes and the introduction of rabbits, cats, foxes, and large exotic herbivores have driven widespread ecological catastrophe in Australian arid and semi‐arid zones, which encompass over two‐thirds of the continent. These threats have caused the highest global mammal extinction rates in the last 200 years, as well as significantly undermining social, economic, and cultural practices of Aboriginal peoples of this region. However, a new and potentially more serious threat is emerging. Buffel grass (Cenchrus ciliaris L.) is a globally significant invader now widespread across central Australia, but the threat this ecological transformer species poses to biodiversity, ecosystem function, and culture has received relatively little attention. Our analyses suggest threats from buffel grass in arid and semi‐arid areas of Australia are at least equivalent in magnitude to those posed by invasive animals and possibly higher, because unlike these more recognized threats, buffel has yet to occupy its potential distribution. Buffel infestation also increases the intensity and frequency of wildfires that affect biodiversity, cultural pursuits, and productivity. We compare the logistical and financial challenges of creating and maintaining areas free of buffel for the protection of biodiversity and cultural values, with the creation and maintenance of refuges from introduced mammals or from large‐scale fire in natural habitats. The scale and expense of projected buffel management costs highlight the urgent policy, research, and financing initiatives essential to safeguard threatened species, ecosystems, and cultural values of Aboriginal people in central Australia.