Fourier transform infra-red (FTIR) spectroscopy based partial least squares regression (PLSR) models were developed to assess multiple accessions of Cenchrus spp (buffel grass). The germplasm tested included accessions collected from different pastoral regions of Australia and an international set of germplasm sourced from the Australian Pasture Genebank. Drawing upon this germplasm collection, the field study described herein aimed to determine the relationships between cell wall composition, neutral detergent fiber (NDF) and indigestible NDF (iNDF) values across different strata levels and between stem and leaf tissues. Predictive models were able to identify and distinguish characteristic traits for each tissue and strata; leaf tissue possessed elevated concentrations of extractives, arabinan, galactan and ash, while stem tissue had elevated concentrations of all other variables measured. Upper strata tissue consistently had greater concentrations of acid-soluble lignin (ASL) and mannan. Of the four tissues, lower stem had the highest NDF but was also the least digestible with the highest iNDF. NDF was strongly associated with the concentration of cell wall (CW) in biomass of all tissues except for upper stem tissue, where the correlation was weaker. iNDF correlated well with higher concentrations of acid-insoluble lignin (AIL) and xylan in stem tissue, while in leaf tissue, only xylan remained closely associated with iNDF. Not only were PLSR models able to characterize the tissue types investigated, they also detected differences between the two years sampled, likely attributable to the impact of abiotic factors during the different growing seasons or the two different methods employed to clear the experimental plots.

The impact of decreased Photosynthetic Photon Flux (PPF) on the biomass and quality of Cynodon turf grasses are of considerable interest to the turf community, however there is little available data regarding its effect upon cell walls. Fourier Transform Infra-Red (FTIR)-based Partial Least Squares Regression (PLSR) models are useful for assessing the cell wall composition of a multitude of samples in a high-throughput manner. Such models were generated to predict cell wall components, water and extractive non-cell wall content of Cynodon grass biomass to determine if different levels of PPF imposed by woven polyester cloth influenced the cell wall composition of six cultivars of C. dactylon and two hybrid cultivars of C. dactylon x C. transvaalensis. The trial ran over seven weeks, and cell wall composition was assessed at three time points, week two (short period), week five (medium period) and week seven (long period). Cultivar had the strongest influence on cell wall composition in the short period, while at the end of the long period, reduced PPF was the more influential factor affecting the composition of the cell wall. At the final experimental time point, turf quality was negatively correlated with reduced PPF (50% and 70% reduction), total lignin and Acid Insoluble Lignin (AIL) and positively correlated with higher PPF (30% and 0% reduction) carbohydrates and Acid Soluble Lignin (ASL). It is proposed that the defense response pathway was preferred over the typical shade avoidance responses due to the weekly clipping regime confounding the response to reductions in PPF, leading to higher percentages of lignin, ash and lower carbohydrate content in the cell wall of Cynodon grasses.

Soil nitrification (microbial oxidation of ammonium to nitrate) can lead to nitrogen leaching and environmental pollution. A number of plant species are able to suppress soil nitrifiers by exuding inhibitors from roots, a process called biological nitrification inhibition (BNI). However, the BNI activity of perennial grasses in the nutrient-poor soils of Australia and the effects of BNI activity on nitrifying microbes in the rhizosphere microbiome have not been well studied. Here we evaluated the BNI capacity of bermudagrass (Cynodon dactylon L.), St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze), saltwater couch (Sporobolus virginicus), seashore paspalum (Paspalum vaginatum Swartz.), and kikuyu grass (Pennisetum clandestinum) compared with the known positive control, koronivia grass (Brachiaria humidicola). The microbial communities were analysed by sequencing 16S rRNA genes. St. Augustinegrass and bermudagrass showed high BNI activity, about 80 to 90% of koronivia grass. All the three grasses with stronger BNI capacities suppressed the populations of Nitrospira in the rhizosphere, a bacteria genus with a nitrite-oxidizing function, but not all of the potential ammonia-oxidizing archaea. The rhizosphere of saltwater couch and seashore paspalum exerted a weak recruitment effect on the soil microbiome. Our results demonstrate that BNI activity of perennial grasses played a vital role in modulating nitrification-associated microbial populations.

Drought is a major constraint to canola production around the world. There is potential for improving crop performance in dry environments by selecting for transpiration efficiency (TE). In this work we investigated TE by studying its genetic association with carbon isotope discrimination (Δ) and other traits, e.g. specific leaf weight (SLW) and leaf chlorophyll content (SPAD). Among the 106 canola genotypes – including open-pollinated, hybrid, inbred types and cytoplasmic variants – tested in the field and glasshouse there was significant genotypic variation for TE, Δ, plant total dry weight, SLW and SPAD. Strong negative correlations were observed between TE and Δ (–0.52 to –0.76). Negative correlations between Δ and SLW or SPAD (–0.43 to –0.78) and smaller but significant positive correlations between TE and SLW or SPAD (0.23 to 0.30) suggested that photosynthetic capacity was, in part, underpinning the variation in TE. A cytoplasmic contribution to genetic variation in TE or Δ in canola was also observed with Triazine tolerant types having low TE and high Δ. This study showed that Δ has great potential for selecting canola germplasm with improved TE.

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia. The perennial legume leucaena (Leucaena leucocephala) is grown across the subtropics for a variety of purposes including livestock fodder. Livestock in Australia emit a significant proportion of the methane produced by the agriculture sector and there is increasing pressure to decrease emissions from beef cattle production systems. In addition to direct productivity gains for livestock, leucaena has been shown to lower enteric methane production, suggesting an opportunity for emissions mitigation and Commonwealth Emissions Reduction Fund (ERF) methodology development, where leucaena browse is adopted for high value beef production. Determining the proportion of leucaena in the diet may be one of the more challenging aspects in attributing mitigation. Current enteric emission relationships for cattle consuming mixed grass-leucaena diets are based on intensive respiration chamber work. Herd-scale methane flux has also been determined using open path laser methodologies and may be used to validate an on-farm herd-scale methodology for leucaena feeding systems. The methodology should also address increased potential for soil organic carbon storage by leucaena grazing systems, and changes in nitrous oxide production. This paper outlines the background, justification, eligibility requirements and potential gaps in research for an emissions quantification protocol that will lead to the adoption of a leucaena methodology by the Australian beef industry. Development of a methodology would be supported by research conducted in Australia.

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia. A research program to develop sterile leucaena has commenced to enhance red-meat production in additional regions of Australia including Western Australia, Northern Territory and New South Wales, where growing seeded leucaena is not currently permitted or encouraged. In this study we report on the development of methodology using a mutagenizing agent, EMS (ethyl methanesulfonate), to cause mutations in the self-fertile commercial leucaena cultivar, Redlands. Several experiments to determine the optimum rate of EMS have been completed and first generation mutagenized plants (M0) established in the field at Redlands Research Station, Cleveland, Queensland, Australia. An EMS concentration of 0.35% applied to germination paper proved the best method to achieve a target emergence percentage of 50%. To date, 27 of 179 mutagenized M0 seedless plants are considered to be putatively sterile. A further 1,200 M0 plants have been established in the field providing an even greater chance of identifying sterile leucaena plants with the desired forage quality and psyllid-resistance attributes.

Silvopastoral systems with the tree legume leucaena (Leucaena leucocephala (Lam.) de Wit) and grass pastures are widely used for ruminant feeding in subtropical and tropical regions. Different densities and planting configurations of leucaena will influence relative yields of both species because of intra- and interspecific competition. With the aim to describe the effects of competition between leucaena and Rhodes grass (Chloris gayana Kunth), a Nelder Wheel trial with 10 different leucaena tree densities (100–80 000 trees ha–1) growing with and without Rhodes grass was established in a subtropical environment at Gatton, south-east Queensland, in November 2013. From 2014 to 2016, the biomass of leucaena (six harvests) and Rhodes grass (seven harvests) was measured by using allometric equations and the BOTANAL sampling procedure over 742 and 721 days, respectively. No complementary or facilitative aboveground interactions were observed between the leucaena and Rhodes grass components of the pasture system. Increasing leucaena tree density resulted in greater aboveground intra- and interspecific competition. Average maximum individual tree yield (38.9 kg DM tree–1 year–1) was reached at 100 trees ha–1 without grass competition and was reduced by 60% with grass competition. Rhodes grass biomass yield was negatively affected by shading from the leucaena canopy, with negligible grass yield at tree densities ≥8618 trees ha–1. Therefore, there was effectively no grass competition on individual tree yield at higher leucaena densities. Accordingly, edible leucaena biomass per unit area was positively related to log10 leucaena density (R2 = 0.99) regardless of grass competition, reaching 21.7 t DM ha–1 year–1 (2014–15) and 27 t DM ha–1 year–1 (2015–16) at the highest leucaena density of 80 000 trees ha–1. By contrast, the yield of Rhodes grass was linearly and inversely correlated with log10 tree density (R2 = 0.99). Practical implications for the design and management of commercial leucaena–grass pastures are discussed.

Although Setaria has been proposed as a model to investigate C-4 photosynthesis, it may also be considered a suitable representative for biofuel feedstock species that are predominantly closely related panicoid grasses. In order to extend our understanding of the fundamental molecular and physiological mechanisms underpinning cell wall deposition as they occur during plant development, we have investigated an elongating stem internode of S. viridis. The chosen internode progressed from an active meristem and region of cell expansion at the base of the internode towards maturing fully expanded cells at the top of the internode. Along this developmental gradient, RNAseq of the mRNA fraction of the transcriptome was undertaken. A holistic understanding of the synthesis, composition and structure of the cell wall and the molecular mechanisms that signal the transition from primary to secondary cell wall synthesis will be integral to engineering crops with a structure that lends itself to more efficient deconstruction.

Despite the popularity of bermudagrass (Cynodon dactylon L.) around the world, there are few studies that report genotypic and seasonal variation for sprouting of stolons used in pasture establishment or revegetation of disturbed land. This study investigated the genotypic/seasonal variation and the physiological basis of sprouting from nodes of aboveground stolons among 12 bermudagrasses. Sprouting percentage, total nodes per m(2) (Nds), stolon diameter (SD), total aboveground biomass (TaB), and concentration of water soluble carbohydrate [WSC], concentration of starch [starch], concentration of non-structural carbohydrate [NSC], and concentration of crude protein [CP] were determined in different seasons including winter 2013, winter 2014, spring 2014, summer 2015, and fall 2015. Sprouting percentage for stolons sampled in spring and summer was higher than that for winter and fall. Large genotypic variation for sprouting was observed ranging from 44.1 to 80.2% of all nodes when averaged across seasons. Sprouting percentage among genotypes was strongly associated with SD, TaB, and Nds; and weakly associated with concentrations of photoassimilates such as [WSC], [starch], and [CP] in the aboveground biomass. However, when these photoassimilates were calculated as an amount per node, sprouting percentage was highly correlated with water soluble carbohydrate (WSC) (r = 0.80), crude protein (CP) (r = 0.82), and WSC + CP (r = 0.88). These data suggested that the size and/or maturity of the axillary buds at nodes and the available assimilate supply was underlying the sprouting potential of the bermudagrasses, however, more research under field conditions is required to validate this claim.

The increasing demand on potable water has resulted in a greater reliance on poorer quality water, including saline sources, for maintaining forage and turfgrasses in agricultural and urban landscapes. Consequently, it will be crucial to identify grasses that can tolerate saline irrigation water. This study aimed to determine salinity tolerance among a large range of bermudagrasses relative to other perennial C-4 grasses and test the relationship between salt tolerance and drought resistance. We report the salinity tolerance of 70 genotypes of mostly Australian bermudagrass ecotypes that were compared to halophytic cultivars of seashore paspalum (Paspalum vaginatum Swartz) and a non-halophytic cultivar of Queensland blue couch (Digitaria didactyla Willd) using a flood and drain sand culture system with salt treatments 1-40 dS m(-1). For the first time for C-4 grasses, salt tolerance was determined by comparing total biomass of the grasses with and without salt treatment. Large genetic variation in salinity tolerance was identified and six bermudagrasses collected from saline habitats had salinity tolerance equal to that of seashore paspalum under the salinity treatments used in this study. There was no correlation between salt tolerance and drought resistance phenotypes determined from our previous research. Canopy temperature differential during salt stress was negatively correlated (r = -0.71 to -0.91, P < 0.001) to salt tolerance and has potential to be used for screening bermudagrasses for salt tolerance using flood and drain sand culture. Salinity levels above 20 dS m(-1) for 8 weeks appeared to be effective for detecting large variation for salt tolerance in bermudagrass.

Water use and depth of water extraction of leucaena (Leucaena leucocephala) and Rhodes grass (Chloris gayana) pasture, irrigated with desalinated coal seam water (a by-product of the coal seam gas industry), were monitored to provide background information on root activity, spatial and temporal water use and deep drainage over a 757-day period from August 2011 to August 2013. Methodology comprised measurement of soil water from surface to 4 m depth using 8 EnviroSCAN probes connected to dataloggers positioned within leucaena twin rows and within the Rhodes grass interrow. Just over 581,000 individual moisture measurements were collated and are reported here. Water extraction (and by inference root activity) of leucaena and Rhodes grass showed marked seasonal fluctuation with deepest and highest water extraction occurring during the first growing season; water extraction was greatly diminished during the following drier and cooler seasons due to the negative influences of lower soil moisture contents, lower temperatures and increased defoliation on pasture growth. The highest values of deep drainage below 4 m depth occurred when high rainfall events corresponded with high soil water storage in the entire profile (0-4 m depth). Given that water usage by both leucaena and Rhodes grass was greatest in the upper layers of soil (<1.5 m), future research should focus on how the level of competitive interaction might be managed by choice of row spacing and frequency of irrigation. Further studies are needed, including: (a) physical sampling to determine the depth of active roots; (b) how defoliation affects rooting behaviors and water use of leucaena; and (c) modelling of the water and salt balances of leucaena and grass inter-row systems using data from this study, with various levels of irrigation, to investigate the risks of deep drainage over an extended climate sequence.

A large collection of over 1000 naturalised Australian bermudagrasses (Cynodon dactylon) was assembled. Previous research indicated that a subset of the grasses collected from Australian Mediterranean environments were drought resistant and characterised by large rhizomes that could be a potential source of nutrients, water and carbohydrates when these grasses grow under saline conditions. The objective of this research was to test the salinity tolerance of 12 bermudagrass genotypes with different levels of drought resistance using a flood and drain, sand-solution hydroponic system. Eight salt treatments were imposed ranging from 1.3 to 21 dS m(-1) (corresponding 0 to 175 mM NaCl) for up to 17 weeks. Salinity tolerance among genotypes was categorised on the basis of 50% reduction in cumulative clipping yields, verdure and root biomass, and green cover, relative to the control treatment. There was no correlation between salt tolerance and drought resistance (r = -0.079 to 0.572), although some drought-resistant grasses did have excellent salt tolerance, such as entries MED1 and MED3. At 21 dS m(-1), most grasses not only maintained over 50% total biomass but also retained over 70% green cover, relative to the control treatment, and were considered as highly salt tolerant. These salt-tolerant grasses have great potential for stabilising and revegetating saline and/or sodic soils.

Soil erosion and stabilisation are huge problems facing Australian land users, including those working in agriculture, mining, road construction and urban sports and community landscapes. There is a large opportunity for the Australian turfgrass industry to play a role in providing solutions to Australia's land stabilisation issues. If 10% of these denuded landscapes can be vegetated by turfgrasses, the turfgrass industry as a whole can benefit greatly, particularly in the current economic climate, where the hangover from the global financial crisis has persisted. Collectively, the areas to be stabilised are enormous and to date the methods used to revegetate these land masses are limited. Hydrosprigging (HS) is an inexpensive, automated method of delivering grass sprigs (stolons) with a hydraulic pump to large areas of bare soil. In this study, we present our latest research on developing state-of-the-art HS methods. Significant differences for stolon sprouting of up to about 30% were identified among 12 bermudagrass genotypes harvested from the field. We hypothesise that the sprouting potential and vigour of shoots may be a function of the levels of nonstructural carbohydrate (NSC) present in the stolons at the time of planting. We also suggest that photothermal quotient, the ratio of solar radiation to temperature during the growing period, may provide the theoretical basis for predicting when levels of NSC may be optimum through the growing season.

Climate change has brought a sharp and renewed focus on plant breeding programs to develop cultivars with improved performance in dry environments. The pleiotropic effects of selection for drought resistance are not well understood in perennial C-4 grasses. The objective of this study was to determine the commercial production characteristics including sod strength and post-harvest regrowth of bermudagrass ecotypes selected for drought resistance. These attributes were studied in a set of bermudagrasses (Cynodon dactylon), a species used extensively around the world for forage and turfgrass. Three field experiments using 12 genotypes contrasting for drought resistance were evaluated, on bermudagrass turf production facilities, for quality and regrowth after the canopy (sod) was mechanically removed. Among the genotypes tested, there was large genotypic variation for rhizome dry matter (RhDM) (0.01-0.81 kg m(-2)), aboveground dry matter (ADM) (0.59-0.17 kg m(-2)) and root dry matter (RDM) (0.04-0.12 kg m(-2)). Regrowth of the canopy was positively correlated to RhDM (r = 0.79-0.80) and negatively correlated to ADM (r = -0.69 similar to-0.74) but there was no association with RDM. Biomass partitioning determined at the time of the second harvest revealed that genotypes with more rapid regrowth had larger proportional DM distributed to rhizome (63.5% vs 7.1%) than to aboveground (27.2% vs 86.5%) and root (8.5% vs 8.1%). Our previous research with these genotypes showed a strong correlation between drought resistance and RhDM prior to the drought period. Consequently, an analysis of the relationship between drought resistance measured previously and post-harvest regrowth in the experiments described here revealed a strong positive correlation (r > 0.64). Genotypic variation for sod strength, an important turf quality attribute, was large ranging from 1281 kg m(-2) to 5671 kg m(-2). However, sod strength was neither correlated to drought resistance, nor the traits measured from harvested sod such as stolon diameter, internode length, number of branches and single stolon strength, nor to dry matter distribution. These results may reflect the existence of a range of different mechanisms for sod strength present in the material tested. Nevertheless, there were genotypes e.g., MEDI that combined the favorable traits of drought resistance, faster regrowth rate and higher sod strength and could be used as an important genetic resource for future breeding. MED1 was one of several highly rhizomatous genotypes in the study that originated from the Mediterranean climatic zone of Australia. (C) 2015 Elsevier B.V. All rights reserved.

As a warm-season grass, bermudagrass (Cynodon spp.) has been widely used as turf and/or pasture in most parts of the world, however, frost is one of the most important factors to reduce growth and performance. Frost tolerance of 466 bermudagrass ecotypes collected from four climatic zones of Australia was assessed in a single field experiment in Southeast Queensland, Australia. In a second field experiment 12/466 ecotypes were assessed in a separate Southeast Queensland, location. Leaf death was scored after 7 frosts had occurred in each location over a 15-day period. For the evaluation of 466 entries, the ecotypes collected from regions with 30-40 and 40-50 potential frost days (PFD) based on 30-year climate data had over 50% lower leaf death than the ones from 0-10, 10-20 and 20-30 PFD. Ecotypes from the tropical rainy climatic zone had over 26% higher leaf death than the other climatic zones sampled in this study. In addition, there was a significant positive correlation between leaf death and plant height (r=0.84) and leaf death and clipping yield (r=0.96). The frost tolerance rating of 12/466 was validated at the second location. These results indicated that ecotypes from the geographic areas with longer period of PFD had superior frost tolerance. We suggest that the frost tolerant ecotypes were able to enter cold acclimation earlier than susceptible ones.

Wear damage is one of the biggest problems associated with continuous use on sports and recreational turfgrass fields. Wear tolerance of 8 bermudagrass (Cynodon spp.) genotypes including 6 ecotypes collected from regional Australia and two commercial cultivars were evaluated in the field. Green cover after wear treatment of ecotypes 394 and MED3 was over 50% higher than the lowest genotypes. The wear tolerant genotypes also had significantly higher acid detergent fibre content, cellulose, lignin and total cell wall content than wear susceptible genotypes. Optical and scanning electron microscopies were used to study stolon and leaf transverse sections and leaf surface characteristics, respectively. Transverse sections of stolons and leaves, suggested that the fibre area surrounding vascular bundles of the wear tolerant genotypes was about 50% higher than the wear susceptible ones. Scanning electron micrographs of the leaf surface suggested that the arrangement of epidermal cells formed a ridged pattern. The gaps between the ridges of wear tolerant genotypes were shorter than those of the wear susceptible genotypes. Collectively, these results suggested that the mechanism of wear tolerance was associated with high fibre content in stolons and leaves. In addition, we suggest that the wear tolerant genotypes have a denser ridge pattern of epidermal cells probably giving the leaves greater tensile strength.

There is currently a growing coal seam gas (CSG) industry in Queensland, Australia. The industry requires beneficialuse strategies to consume the significant volumes of water released during CSG extraction. Irrigation of tropical and subtropical forage species for beef production is one option; however, quality of coal seam (CS) water varies due to moderate–high salinity and alkalinity. The application of chemically amended CS water over time could potentially increase soil salinity, which is known to reduce plant biomass production (Shabala and Munns 2012). While the salinity tolerance of many tropical and subtropical forage species has been investigated over the last 30 years (Russell 1976; Keating et al. 1986; Kitamura 1986; Hansen and Munns 1988; Deifel et al. 2006), there is a need to examine the tolerance of more recently released species and cultivars, which are suitable for planting in the Queensland CSG area.

We have assembled a large collection of over 1000 naturalised Australian bermudagrasses (Cynodon spp.). Our previous research indicated that a group of the grasses collected from Australian Mediterranean environments were drought resistant and characterized by large rhizomes that could be a potential source of nutrients, water and carbohydrates when these grasses grow under saline conditions. The objective of this research was to test the salinity tolerance of 12 bermudagrass genotypes with different levels of drought resistance using a flood and drain sand solution culture. Eight salt treatments were imposed ranging from 1.3 to 21 dS/M (0 to 175 mM NaCl). There was no correlation between drought resistance and salt tolerance (r = 0.21~0.37ns) although some drought resistant grasses did have excellent salt tolerance. The grass with the best salt tolerance was not highly rhizomatous. At 21 dS/m some grasses maintained over 60% total biomass, relative to the control treatment, and can be considered as highly salt tolerant. Based on these results we are currently screening about 70 genotypes collected from salt scalds, maritime environments, and saline/sodic soils.