Cullen Australasicum Research Articles

Productivity and nutritional value of 20 species of perennial legumes in a low‐rainfall Mediterranean‐type environment in southern Australia

AbstractIn the rain‐fed mixed‐farming systems of southern Australia, the consistent supply of high‐value forage is limited by a range of climatic, edaphic and systems constraints. Over 2 years, we compared biomass production and nutritional value of 30 accessions of perennial legumes, and predicted intake, grazing days and growth of ewes and lambs. There was significant variation in nutritional value and biomass production between and within species. Lucerne (Medicago sativa) and sulla (Hedysarum coronarium) produced the greatest amount of biomass and energy. There was variability among accessions in digestibility (DMD), acid detergent fibre (ADF) and crude protein, and the rate of change in these traits as plants matured. Trifolium species had the highest DMD across all growth stages. Hairy canary clover (Dorycnium hirsutum), erect canary clover (Dorycnium rectum), greater birdsfoot trefoil (Lotus uliginosus), Australian trefoil (Lotus australis) and running postman (Kennedia prostrata) had energy levels that would not maintain liveweight of mature sheep. In the second year, species differed in response to harvesting treatments. Lucerne and sainfoin (Onobrychis viciifolia) were more productive under a frequent cutting regime. Accessions of white clover (Trifolium repens), red clover (Trifolium pratense), alsike clover (Trifolium hybridum), cullen (Cullen australasicum), strawberry clover (Trifolium fragiferum), sainfoin and birdsfoot trefoil (Lotus corniculatus) showed some promise, while Tedera (Bituminaria bituminosa) and milkvetch (Astragalus cicer) performed poorly under the experimental conditions. We conclude by discussing additional agronomic and nutritional factors that need consideration when developing novel perennial legumes for mixed‐farming systems in the context of a changing climate.

Inferring Invasion Paths Into Cotton by Creontiades dilutus (Hemiptera: Miridae) From Arid Zone and Agricultural Sources.

Managing agricultural pests that use multiple host plant species is a challenge when individuals move between host plants in natural vegetation and agricultural environments. The green mirid (Creontiades dilutus) Stål (Hemiptera: Miridae) is endemic to Australia and routinely invades cotton from local uncultivated vegetation, but may also originate from remote locations in the arid continental interior. This bug is polyphagous and highly mobile, which contributes to its pest status in cotton L. (Malvaceae) systems as well as its persistence in arid environments with sparsely distributed ephemeral host plants. The aim of this study was to evaluate how C. dilutus individuals use a variety of host species across remote arid regions and highly managed agricultural landscapes. Structured field surveys spanning vast areas across the Simpson Desert in the arid heart of Australia, as well as subcoastal cotton production systems, were designed to evaluate host use across environments that share few plant species. High numbers of C. dilutus were collected from Cullen australasicum (Schltdl.) J.W.Grimes (Fabaceae) (perennial hosts) and Goodenia cycloptera R.Br. (Goodeniaceae) (ephemeral hosts) in the desert following rain. In agricultural environments, C. dilutus bugs were mostly found on irrigated Medicago sativa L. (Fabaceae) (lucerne), and to a lesser extent Melilotus indicus (L.) All. (Fabaceae) near rivers. Significantly, bugs were on these plants prior to the planting of cotton across all environments surveyed. These data allow inferences relating host use, host abundance, and insect migration to one another to understand the connection that C. dilutus bugs have between arid and agricultural environments.

Physiological and morphological adaptations of herbaceous perennial legumes allow differential access to sources of varyingly soluble phosphate.

The aim of this study was to investigate the capacity of three perennial legume species to access sources of varyingly soluble phosphorus (P) and their associated morphological and physiological adaptations. Two Australian native legumes with pasture potential (Cullen australasicum and Kennedia prostrata) and Medicago sativa cv. SARDI 10 were grown in sand under two P levels (6 and 40 µg P g(-1) ) supplied as Ca(H2 PO4 )2 ·H2 O (Ca-P, highly soluble, used in many fertilizers) or as one of three sparingly soluble forms: Ca10 (OH)2 (PO4 )6 (apatite-P, found in relatively young soils; major constituent of rock phosphate), C6 H6 O24 P6 Na12 (inositol-P, the most common form of organic P in soil) and FePO4 (Fe-P, a poorly-available inorganic source of P). All species grew well with soluble P. When 6 µg P g(-1) was supplied as sparingly soluble P, plant dry weight (DW) and P uptake were very low for C. australasicum and M. sativa (0.1-0.4 g DW) with the exception of M. sativa supplied with apatite-P (1.5 g). In contrast, K. prostrata grew well with inositol-P (1.0 g) and Fe-P (0.7 g), and even better with apatite-P (1.7 g), similar to that with Ca-P (1.9 g). Phosphorus uptake at 6 µg P g(-1) was highly correlated with total root length, total rhizosphere carboxylate content and total rhizosphere acid phosphatase (EC 3.1.3.2) activity. These findings provide strong indications that there are opportunities to utilize local Australian legumes in low P pasture systems to access sparingly soluble soil P and increase perennial legume productivity, diversity and sustainability.

High levels of diversity for seed and forage production exist in Cullen australasicum, a potential new perennial forage legume for dry environments in southern Australia

The seed and forage production of a diverse group of the perennial forage legume Cullen spp., collected in southern Australia, was assessed with the aim of discovering diversity for exploitation in future breeding programs. Eighty ecotypes were assessed at the Waite Institute in South Australia, using replicated, spaced-plant field trials, between 2008 and 2012. Seed production in collected ecotypes of Cullen (Expt 1) ranged from 0 to 485 kg ha–1 for windrowed seed yield and from 0 to 790 kg ha–1 for total seed yield, which included vacuum-harvested seed from pods that had fallen to the ground. Individual plants were selected for seed production from their original populations, and the seed and fodder production of their progeny was evaluated in a further field experiment (Expt 2). Moderate to high heritability estimates were recorded for seed production traits. Seed production in progeny families ranged from 0 to1 423 kg ha–1 and was highly correlated with the number of seeds per inflorescence (r = 0.85) and forage yield (r = 0.59). Edible biomass, measured using the Adelaide visual appraisal method, ranged from 50 to 906 g dry weight (DW) plant–1 in parent ecotypes and from 404 to 1248 g DW plant–1 in the selected family progenies. Disease infection with anthracnose (Colletotrichum trifolii) caused considerable damage to plants in Expt 1, resulting in the death of all plants of 10 ecotypes, and infection with Alfalfa mosaic virus in Expt 2 was linked to the death of 67 individuals. The results are discussed in relation to breeding C. australasicum for increased seed yield and disease resistance to overcome these deficiencies as barriers to commercial adoption.

Moderating mycorrhizas: arbuscular mycorrhizas modify rhizosphere chemistry and maintain plant phosphorus status within narrow boundaries

Pastures often experience a pulse of phosphorus (P) when fertilized. We examined the role of arbuscular mycorrhizal fungi (AMF) in the uptake of P from a pulse. Five legumes (Kennedia prostrata, Cullen australasicum, Bituminaria bituminosa, Medicago sativa and Trifolium subterraneum) were grown in a moderate P, sterilized field soil, either with (+AMF) or without (-AMF) addition of unsterilized field soil. After 9-10 weeks, half the pots received 15 mg P kg(-1) of soil. One week later, we measured: shoot and root dry weights; percentage of root length colonized by AMF; plant P, nitrogen and manganese (Mn) concentrations; and rhizosphere carboxylates, pH and plant-available P. The P pulse raised root P concentration by a similar amount in uncolonized and colonized plants, but shoot P concentration increased by 143% in uncolonized plants and 53% in colonized plants. Inoculation with AMF decreased the amount of rhizosphere carboxylates by 52%, raised rhizosphere pH by ∼0.2-0.7 pH units and lowered shoot Mn concentration by 38%. We conclude that AMF are not simply a means for plants to enhance P uptake when P is limiting, but also act to maintain shoot P within narrow boundaries and can affect nutrient uptake through their influence on rhizosphere chemistry.

Phenotypic variation for productivity and drought tolerance is widespread in germplasm collections of Australian Cullen species

Cullen australasicum is a legume species from Australia that holds promise for development as a drought-tolerant perennial pasture species, yet only a few accessions have been evaluated for agronomic traits. Several Cullen species aside from C. australasicum may also have potential for use as perennial pastures. We compared the field survival and aboveground biomass production of 100 germplasm accessions from 9 Cullen species, 2 lucerne (Medicago sativa) cultivars and 2 perennial Lotus species over 18 months in a low-rainfall region of the wheatbelt of Western Australia. Nutritive value of selected Cullen accessions was also compared with lucerne and L. australis. Several accessions of C. australasicum demonstrated good survival, productivity and nutritional value, and some accessions of C. discolor, C. lachnostachys, C. pallidum and C. pustulatum also showed promise in some or all of these traits. Significant phenotypic variation was seen among accessions of C. australasicum, C. pallidum, C. cinereum and C. tenax for some agronomic traits. We discuss the implications of this variation for further experiments or development of Cullen species. While survival and productivity of many Cullen accessions was similar to lucerne, only a few C. australasicum accessions were more productive than lucerne. We conclude that C. australasicum is currently the best prospect among Cullen species for cultivar development as a perennial pasture legume, and our analysis has highlighted accessions of particular interest. In addition, further work on C. discolor, C. lachnostachys, C. pallidum and C. pustulatum may also, in the longer term, provide useful pasture species.

Evaluation of Perennial Forage Legumes and Herbs in Six Mediterranean Environments

There is an absence of drought tolerant herbaceous perennial forage legume and herb options other than lucerne (Medicago sativa L.) for environments with Mediterranean-like climates common in extensive areas of Southern Australia, the Mediterranean basin, and Chile. Therefore, a collection of 174 forage perennial legume and herb entries from 103 species and 32 genera was evaluated for adaptation in a diverse range of Mediterranean climatic environments in Southern Australia. The seasonal rainfall distribution varied from moderately to highly winter dominant with long term average annual rainfall ranging from 318 to 655 mm. The entries were rated for productivity and persistence over 3 yr. The 12 entries identified as the most promising for winter, summer, or all-year round production included Bituminaria bituminosa (L.) C.H. Stirt. var. albomarginata; Cichorium intybus L.; Cullen australasicum (Schltdl.) J.W. Grimes; Dorycnium hirsutum (L.) Ser.; Kennedia prostrata R. Br.; Lotononis bainesii Baker, Lotus pedunculatus Cav.; L. corniculatus L.; L. cytisoides L.; Medicago sativa subsp. sativa L.; Medicago sativa subsp. caerulea (Less. ex Ledeb.) Schmalh., and M. sativa subsp. falcata (L.) Arcang. These entries maintained production and persisted for the period of the evaluation, with the exception of C. intybus and L. corniculatus that declined in persistence over time. The potential role of these species in extensive grazing systems in Mediterranean climatic zones, their attributes and limitations, and current progress in developing them as useful forage plants was discussed.

Seasonal production of lucerne and other perennial legumes and herbs in a summer dominant rainfall zone

Thirty one perennial legume and three herb cultivars/lines sown near Manilla on the North West Slopes in northern New South Wales, Australia, were assessed for seasonal herbage mass for 2 years after establishment. Medicago sativa subsp. sativa (lucerne) cv. ‘Sceptre’ had predicted herbage production that was higher than all of the cultivars/lines evaluated in seven of the eight seasons that it was tested, ranging from 557 kg DM/ha in autumn 2005 to 3803 kg DM/ha in summer 2005. Cullen australasicum and Dorycnium hirsutum generally had consistently good performance, followed by Cichorium intybus cv. ‘Puna’ and Astragalus suberosus, but did not match that of ‘Sceptre’. The clear superiority of ‘Sceptre’ lucerne in most seasons indicated that research should be targeted to overcome issues of bloat risk and low ground cover that restrict the use of lucerne in the region. Comparisons of two M. sativa subspecies highlighted variation that warrants further investigation.

Above- and below-ground interactions of grass and pasture legume species when grown together under drought and low phosphorus availability

Interactions between annual grass and perennial legume species when they are grown together under drought and limited phosphorus (P) availability are likely to be very important for pasture productivity, but are not well understood. Therefore, the objective of this study was to compare the interactions of drought and species combination on growth, nutrition, hydraulic lift and photosynthesis of the Australian native legume Cullen australasicum and the exotic legume Medicago sativa when grown with the exotic annual ryegrass (Lolium rigidum) with poorly soluble FePO4 as the source of P. Plants were grown for 22 weeks in monoculture and in legume-grass mixtures in 1-m tall pots filled with river sand. Two moisture treatments were applied, drought (top 70 cm of soil allowed to dry after 16 weeks of establishment) and control (field capacity). In monoculture, shoot dry weight (DW) pot-1 of L. rigidum was higher than that of C. australasicum and M. sativa. In the mixtures, compared with the monocultures, an increase in shoot DW pot-1 for L. rigidum and a decrease for both C. australasicum and M. sativa resulted in a relative yield total >1. Citrate was the main carboxylate in the rhizosphere of all species, except for the drought-treated L. rigidum in monoculture and mixtures, for which malate was the main constituent. Both C. australasicum and M. sativa had higher concentrations of Ca, Mg, S, Cu, Zn, Mn and Mo in their leaves than did L. rigidum. Hydraulic lift was not detected in M. sativa and C. australasicum; likely reasons are discussed. Photosynthetic rate was similar for all species, but L. rigidum had tighter stomatal control. C. australasicum survived longer under drought than did M. sativa. In conclusion, L. rigidum out-competed the legumes. The legumes provided benefits to the growth of L. rigidum through solubilising P, but not through hydraulic lift. In addition, L. rigidum conserved moisture through tight stomatal control and produced an extensive root system to take up water and nutrients efficiently.

From controlled environments to field simulations: Developing a growth model for the novel perennial pasture legume Cullen australasicum

To allow development of a dynamic plant growth model for the simulation of dry matter (DM) production in the field based on meteorological data, in the absence of detailed information on phenology and growth, a model was developed solely using data from plants grown in large pots under glasshouse conditions. The little studied Australian native perennial legume Cullen australasicum, which has potential as a pasture species, was used. Phenological development (e.g. rooting depth, leaf appearance, leaf growth and shedding) and physiological characteristics (e.g. photosynthetic capacity) were measured in the glasshouse for model development and parameterisation. Whenever possible and appropriate, established models were used to explain individual processes (e.g. canopy photosynthesis and evapotranspiration); if unavailable, models were developed. A diverse independent data set was used to validate the model, including published and unpublished results from the Western Australian wheatbelt under non-irrigated conditions and different plant densities (1, 2, 4, 8 and 16 plants m −2), and from other locations as well. Main stem node appearance was simulated fairly well, with a root mean square of deviations (RMSD) of 1.86 nodes day −1 ( r = 0.996, n = 11). The model predicts the DM production well for non-irrigated conditions in the Western Australian wheatbelt under densities of 1, 2, 4 and 8 plants m −2, and at Wagga Wagga and Barmedman, New South Wales, but not for a density of 16 plants m −2 in the Western Australian wheatbelt and not under irrigated, fertilised conditions. Overall, the model explained over 78% of the observed variation in DM with a RMSD of 54 g m −2 ( r = 0.89, n = 31). The high prediction accuracy suggests that this generic approach to model development offers promise for the simulation of the growth of C. australasicum for the tested locations, particularly under non-fertilised and non-irrigated conditions. This approach should prove valuable for quick evaluation of the diverse array of novel crop and pasture species now under evaluation for low-rainfall areas, as it requires only limited information and minimal parameterisation.

Multiple adaptive responses of Australian native perennial legumes with pasture potential to grow in phosphorus- and moisture-limited environments.

Many Australian legumes have evolved in low-phosphorus (P) soils and low-rainfall areas. Therefore a study was made of the interaction of soil [P] and water availability on growth, photosynthesis, water-use efficiency (WUE) and P nutrition of two Australian native legumes with pasture potential, Cullen australasicum and C. pallidum, and the widely grown exotic pasture legume, lucerne (Medicago sativa). Plants were grown in a glasshouse at 3, 10 and 30 mg P kg(-1) dry soil for 5 months. At week 10, two drought treatments were imposed, total pot dried (all-dry) and only top soil dried (top-dry), while control pots were maintained at field capacity. Shoot dry weight produced by lucerne was never higher than that of C. australasicum. For C. pallidum only, shoot dry weight was reduced at 30 mg P kg(-1) dry soil. The small root system of the Cullen species was quite plastic, allowing plants to access P and moisture efficiently. Lucerne always had a higher proportion of its large root system in the top soil layer compared with Cullen species. All species showed decreased photosynthesis, leaf water potential and stomatal conductance when exposed to drought, but the reductions were less for Cullen species, due to tighter stomatal control, and consequently they achieved a higher WUE. All species showed highest rhizosphere carboxylate concentrations in the all-dry treatment. For lucerne only, carboxylates decreased as P supply increased. Citrate was the main carboxylate in the control and top-dry treatments, and malate in the all-dry treatment. Multiple adaptive responses of Cullen species and lucerne favoured exploitation of low-P soils under drought. The performance of undomesticated Cullen species, relative to that of lucerne, shows their promise as pasture species for environments such as in south-western Australia where water and P are limiting, especially in view of a predicted drying and warming climate.

Effects of leaf development and phosphorus supply on the photosynthetic characteristics of perennial legume species with pasture potential: modelling photosynthesis with leaf development

Age-dependent changes in leaf photosynthetic characteristics (i.e. parameters of the light response curve (maximum photosynthetic rate (Pmax), quantum yield (Φ) and the convexity parameter (θ)), stomatal conductance (gs) and dark respiration rate (Rd)) of an exotic perennial legume, Medicago sativa L. (lucerne), and two potential pasture legumes native to Australia, Cullen australasicum (Schltdl.) J.W. Grime and Cullen pallidum A. Lee, grown in a glasshouse for 5 months at two phosphorus (P) levels (3 (P3) and 30 (P30) mg P kg–1 dry soil) were tested. Leaf appearance rate and leaf area were lower at P3 than at P30 in all species, with M. sativa being the most sensitive to P3. At any leaf age, photosynthetic characteristics did not differ between P treatments. However, Pmax and gs for all the species and Φ for Cullen species increased until full leaf expansion and then decreased. The convexity parameter, θ, did not change with leaf age, whereas Rd decreased. The estimates of leaf net photosynthetic rate (Pleaf) obtained through simulations at variable Pmax and Φ were lower during early and late leaf developmental stages and at lower light intensities than those obtained when Φ was assumed to be constant (e.g. for a horizontally placed leaf, during the 1500°C days developmental period, 3 and 19% reduction of Pleaf at light intensities of 1500 and 500 µmol m–2 s–1, respectively). Therefore, developmental changes in leaf photosynthetic characteristics should be considered when estimating and simulating Pleaf of these pasture species.

First report of anthracnose (Colletotrichum trifolii) onCullen australasicum(syn.Psoralea australasica)

We report the incidence of anthracnose caused by Colletotrichum trifolii on Cullen australasicum, a native Australian legume. Natural infection was observed on plants grown in a genetic resources characterisation experiment at Waite Research Precinct, Adelaide. The affected plants showed wilting of the branches and light brown lesions on the leaves. The characteristic symptom was a bluish black discolouration on the infected leaves and stems. In some plants, the infection spread from the leaves and stems across the entire plant leading to the death of the plant.

Floral morphology and pollination system in the native Australian perennial pasture legume Cullen australasicum (syn. Psoralea australasica)

Cullen australasicum (syn. Psoralea australasica) is a native perennial legume with potential in the low-rainfall wheatbelt of southern Australia. The objective of this study was to investigate the reproductive biology of C. australasicum utilising five accessions. Glasshouse and field pollination experiments were conducted in Adelaide, South Australia. Floral morphology, stigma receptivity and pollen : ovule ratios were determined. Pollen tube growth and stigma morphology were examined using fluorescence and scanning electron microscopes. Glasshouse pollination studies indicated that four of the accessions showed the need for an external tripping agent to bring about pollination and that hand-tripping was the most efficient method. A scanning electron microscopy study revealed there are two types of stigmas in this species. Stigma receptivity was significantly lower at the early bud stage before anther dehiscence. The results show that C. australasicum is a self-compatible species comprising accessions with a wide range of outcrossing potential.

Variation in morphological and physiological parameters in herbaceous perennial legumes in response to phosphorus supply

Change in morphological and physiological parameters in response to phosphorus (P) supply was studied in 11 perennial herbaceous legume species, six Australian native (Lotus australis, Cullen australasicum, Kennedia prorepens, K. prostrata, Glycine canescens, C. tenax) and five exotic species (Medicago sativa, Lotononis bainesii, Bituminaria bituminosa var albomarginata, Lotus corniculatus, Macroptilium bracteatum). We aimed to identify mechanisms for P acquisition from soil. Plants were grown in sterilised washed river sand; eight levels of P as KH2PO4 ranging from 0 to 384 μg P g−1 soil were applied. Plant growth under low-P conditions strongly correlated with physiological P-use efficiency and/or P-uptake efficiency. Taking all species together, at 6 μg P g−1 soil there was a good correlation between P uptake and both root surface area and total root length. All species had higher amounts of carboxylates in the rhizosphere under a low level of P application. Six of the 11 species increased the fraction of rhizosphere citrate in response to low P, which was accompanied by a reduction in malonate, except L. corniculatus. In addition, species showed different plasticity in response to P-application levels and different strategies in response to P deficiency. Our results show that many of the 11 species have prospects for low-input agroecosystems based on their high P-uptake and P-use efficiency.

Infection of Cullen australasicum (syn. Psoralea australasica) with Alfalfa mosaic virus

Severe yellow mosaic and leaf distortion symptoms have been observed on Cullen australasicum (cullen) plants growing in experimental plots at Urrbrae, South Australia. The incidence of the affected plants in a 2-year-old stand was ∼80%. Symptom distribution on plants was uneven and symptom intensity appeared to vary between seasons. Alfalfa mosaic virus (AMV) was identified in 6/10 symptomatic and 1/10 asymptomatic field plants by reverse transcription-polymerase chain reaction (RT—PCR). Transmission of mosaic symptoms from cullen to cullen by mechanical inoculation was unsuccessful, but a cullen AMV isolate passaged through herbaceous indicators induced systemic mosaic in 1/4 of inoculated cullen seedlings. No seed transmission of AMV was observed in 50 seedlings raised from symptomatic parents. These results show that cullen is a host of AMV, but further studies are needed to determine whether AMV is the sole cause of the mosaic disease.

Development, characterization and transferability of microsatellite markers for Cullen australasicum (Leguminosae)

The development of eight polymorphic microsatellite markers for use in the Australian native legume Cullen australasicum is described. The number of alleles per locus ranged from 3 to 8. Observed heterozygosity ranged from 0.208 to 0.667. The cross-species amplification of these eight markers and a ninth marker, which is monomorphic in the populations examined, but may be used to distinguish between species, was also tested in five other species. These microsatellite markers will be useful for investigating the population structure of natural populations of C. australasicum and other Cullen species which may be susceptible to genetic contamination via pollen mediated gene flow from planted pastures of C. australasicum.

Persistence, productivity, nutrient composition, and aphid tolerance of Cullen spp.

The persistence, productivity, and nutrient content of accessions of Cullen australasicum, C. cinereum, C. tenax, and C. parvum were compared with lucerne (Medicago sativa) in grazed swards for 3 years on an acid soil in southern New South Wales. All Cullen spp. established satisfactorily from seed sown into a cultivated seed bed, but C. australasicum accessions were more persistent than C. cinereum, C. parvum, and C. tenax, which declined to a frequency of <5% by the start of the fourth year under rotational grazing. Cullen australasicum was the most productive of the 4 Cullen spp. with herbage yields similar to the lucerne cv. Sceptre. Leaves and stems of the Cullen spp. had significantly lower S, K, B, and Na contents than lucerne. The herbage P content of all Cullen spp., except C. tenax, was lower than in lucerne. Calcium and Mn levels were higher in C. australasicum than in all other species. Sheep often avoided grazing all Cullen spp. when other herbage was available, suggesting that these species had lower palatability. The dry matter digestibility (DMD) of lucerne herbage (76%) in September was higher than in C. australasicum (74.3%), C. cinereum (71.3%), and C. tenax (69.7%) (P < 0.001). The metabolisable energy content of the herbage of C. australasicum was similar to lucerne (10.7–10.9 MJ/kg DM) but was lower in C. cinereum and C. tenax (9.9–10.3 MJ/kg DM). The crude protein content of the 4 Cullen spp. was similar (21.4–22.3%) but significantly lower than for lucerne (33.6%). Glasshouse studies found C. australasicum, C. cinereum, C. pallidum, C. parvum, and C. tenax to be moderately to highly susceptible to bluegreen aphids (BGA) (Acyrthosiphon kondoi Shinji), but one C. australasicum accession was highly tolerant, suggesting that aphid susceptibility can be overcome by selection. All 5 Cullen species proved highly resistant to spotted alfalfa aphids (Therioaphis trifolii Monell). Cullen australasicum was found to be susceptible to Alfalfa mosaic virus, which resulted in stunting of growth of some plants in the field experiment. Of the 4 Cullen spp. examined in the field experiment, C. australasicum demonstrated the most potential as a forage plant for low-rainfall regions with superior persistence and productivity under grazing and the highest resistance to BGA.

The diversity of arbuscular mycorrhizas of selected Australian Fabaceae

Members of the Australian native perennial Fabaceae have been little explored with regard to their root biology and the role played by arbuscular mycorrhizal (AM) fungi in their establishment, nutrition and long-term health. The ultimate goal of our research is to determine the dependency of native perennial legumes on their co-evolved AM fungi and conversely, the impact of AM fungal species in agricultural fields on the productivity of sown native perennial legume pastures. In this paper we investigate the colonisation morphology in roots and the AMF, identified by spores extracted from rhizosphere soil, from three replicate plots of each of the native legumes, Cullen australasicum, C. tenax and Lotus australis and the exotic legumes L. pedunculatus and Medicago sativa. The plants were grown in an agricultural field. The level and density of colonisation by AM fungi, and the frequency of intraradical and extraradical hyphae, arbuscules, intraradical spores and hyphal coils all differed between host plants and did not consistently differ between native and exotic species. However, there were strong similarities between species in the same genus. The three dominant species of AM fungi in rhizosphere soil also differed with host plant, but one fungus (Glomus mosseae) was always the most dominant. Sub-dominant AM species were the same between species in the same genus. No consistent differences in dominant spores were observed between the exotic and native Fabaceae species. Our results suggest that plant host influences the mycorrhizal community in the rhizosphere soil and that structural and functional differences in the symbiosis may occur at the plant genus level, not the species level or due to provenance.

Evaluation of perennial pasture legumes and herbs to identify species with high herbage production and persistence in mixed farming zones in southern Australia

Ninety-one perennial legumes and herbs (entries) from 47 species in 21 genera were evaluated at sites in New South Wales, South Australia and Western Australia over 3 years from 2002 to 2005 to identify plants with superior herbage production, persistence and the potential to reduce ground water recharge. Evaluation was undertaken in three nurseries (general, waterlogged soil and acid soil). Medicago sativa L. subsp. sativa (lucerne) cv. Sceptre was the best performing species across all sites. In the general and acid soil nurseries, Cichorium intybus L. (chicory) cv. Grasslands Puna was the only species comparable with Sceptre lucerne in terms of persistence and herbage production. Trifolium fragiferum L. cv. Palestine and Lotus corniculatus L. SA833 were the best performing species on heavy clay soils prone to waterlogging. Three Dorycnium hirsutum (L.) Ser. accessions persisted well on acid soils, but were slow to establish. Short-lived perennial forage legumes, such as Onobrychis viciifolia Scop. cv. Othello, and three Hedysarum coronarium L. entries, including cv. Grasslands Aokou, had high herbage production in the first 2 years and may be suitable for short-term pastures in phased pasture-crop farming systems. T. uniflorum L. and M. sativa subsp. caerulea SA38052 were highly persistent and could play a role as companion species in mixtures or ground cover species for undulating landscapes. Cullen australasicum (Schltdl.) G.W. Grimes SA4966 and Lotononis bainesii Baker cv. Miles had poor establishment, but were persistent. Chicory, T. fragiferum and L. corniculatus were identified as species, other than lucerne, with the most immediate potential for further selection to increase the diversity of perennial legumes and herbs adapted to southern Australian environments.