Salinity is a widespread problem caused by an imbalance between rainfall and transpiration in the dryland cropping systems of southern Australia. The need to use more perennials has been identified and this paper examines the possibility of replacing annual with perennial pasture legumes and the germplasm available to do so. While lucerne is already used widely in eastern Australia it has only recently been adopted in the wheat belt of Western Australia. There are doubts about its adaptation to acid soils and to climates where summer rainfall is low and ambient temperatures are high. There is also a need to diversify the species available to reduce the likelihood of invasion by exotic diseases and insects. Several genera are likely to be of value in this respect, although few will be as widely adapted as lucerne. Perennial legumes are found in environments ranging from alpine to desert. Targeted collections of genera from the dry areas, especially where soils are acid, are likely to yield species of value. These may include perennial species of Astragalus, Hedysarum, Lotus, Onobrychis, Psoralea, and Trifolium. Some Australian genera, for example Swainsona, Glycine, and Cullen may also be of value. Most of these genera are from alkaline soils, and the need to cope with acid soils that are often high in free aluminium is seen to limit their use in southern Australia. However, since virtually nothing is known of the ecology and ecophysiology of species from the dry areas, it is possible that through selection and the use of adapted rhizobia, some at least may be of value in Australian conditions. Cropping in rotation with perennial legumes is likely to involve several changes in farming systems. It is impossible to predict their nature but it is essential that we understand what these changes are before the species are widely introduced. Account must also be taken of their ability to use water. It is entirely possible that perennials from dry areas are dormant in summer despite the fact that there is no evidence in the literature to this effect. It was concluded that although lucerne is suitable for phase farming, alternatives to lucerne are needed. They will have to match the water-using and nitrogen-fixing capacities of lucerne, and farming systems will be required that make full use of the new germplasm. Collaboration with institutions in the Mediterranean basin and elsewhere is needed and a beginning has been made in this direction. Additional keywords: lucerne, Trifolium, Astragalus, phase farming.

Ecology of herbaceous perennial legumes: a review of characteristics that may provide management options for the control of salinity and waterlogging in dryland cropping systems

Perennial plants such as lucerne are now widely acknowledged as one means of controlling the expansion of dryland salinity in southern Australia. However, their inclusion in farming systems is limited by poor seedling vigour, thought to be associated with greater allocation of biomass to perennating organs in roots, and poor adaptation to some soils and climatic conditions in south-western Australia. For this reason, interest in other perennial options such as perennial wheat is increasing. In this research we compared early (29-day) seedling growth and root : shoot ratios for annual and perennial medics (Medicago truncatula and M. sativa), and for annual and perennial wheat (Triticum aestivum and Triticum × Agropyron cross). For the medics, the annual reached the 6-leaf stage after 29 days and produced more root and shoot biomass than lucerne (4-leaf stage after 29 days), but there was no difference in root : shoot ratio or depth of root growth. For wheat, there were no differences in root growth, shoot growth, or root : shoot ratio between the annual and perennial lines (Zadoks growth stages 23 and 21, respectively, after 29 days). The poor competitive performance of M. sativa seedlings relative to M. truncatula was not due to changed allocation of biomass to shoots, but was related more to seed size (2.7 and 5.0 mg, respectively). This does not seem to occur to the same extent in perennial wheat lines, suggesting that their seedling performance may be more competitive.

Root and shoot growth by seedlings of annual and perennial medic, and annual and perennial wheat

BACKGROUND Glyphosate is routinely used in Australia to control the Arctotheca species Arctotheca calendula (L.) Levyns (referred hereinafter as capeweed). This study identifies the first global case of field-evolved glyphosate-resistant capeweed, collected from the grainbelt of Western Australia. RESULTS In 2020, a capeweed biotype that was collected from Borden in the southern Western Australian grainbelt was confirmed to be glyphosate-resistant (referred hereinafter as Spence population). When compared to the pooled mortality of six field-collected, glyphosate susceptible capeweed populations (S1, S2, S3, S4, S5 and S6), the Spence population was found > 11-fold more resistant to glyphosate than the pooled results of the susceptible populations (S1-S6) at the lethal dose of 50% (LD50 ) level. The growth of the Spence population was also less affected, requiring > 13-fold more glyphosate to reduce growth than the pooled susceptible populations at the growth reduction of 50% (GR50 ) level. Sequencing of the plastidic 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene indicated no known single gene mutation imparting glyphosate resistance. This study, however, did not investigate any other known mechanisms that impart glyphosate resistance. When screened at the field-applied rate, this Spence population was also found to survive an inhibitor of acetolactate synthase (ALS) (metosulam) and an inhibitor of phytoene desaturase (diflufenican). CONCLUSIONS This is the first confirmation of glyphosate resistance evolution in a capeweed population globally. With capeweed resistance already confirmed to photosystem-I inhibiting herbicides (paraquat and diquat), this study emphasizes the importance of using integrated measures that do not depend only on the use of non-selective herbicides for controlling herbicide resistance-prone capeweed populations. © 2021 Society of Chemical Industry.

Identification of the first glyphosate-resistant capeweed (Arctotheca calendula) population.

......................................................................................................................5 INTRODUCTION ...............................................................................................................7 AIM..................................................................................................................................12 METHODOLOGY ............................................................................................................13 RESULTS: TREES ..........................................................................................................19 RESULTS: SHRUBS .......................................................................................................70 RESULTS: GRASSES...................................................................................................109 DISCUSSION ................................................................................................................136 CONCLUSIONS & RECOMMENDATIONS ...................................................................143 ACKNOWLEDGEMENTS ..............................................................................................152 GLOSSARY...................................................................................................................154 REFERENCES ..............................................................................................................155 APPENDIX A .................................................................................................................170

The environmental weed risk of revegetation and forestry plants

A field experiment in autumn-sown lucerne was conducted at Tatura to quantify the growth of winter weeds and the effects of weeds on lucerne seedling establishment, plant densities and hay production over the first year of cutting. In addition, mowing treatments and a range of herbicides were evaluated with respect to weed control. Weed growth rates in spring of up to 114 kg ha-l day-1 DM and high yields of annual winter weeds excluded lucerne (Medicago sativa L. cv. Delkalb 167) almost entirely from the first hay cut and significantly reduced seedling vigour and plant densities. The unsprayed control plots yielded 9.3 t ha-1 at the first hay cut and comprised 52% capeweed, 41% ryegrass and less than 1% lucerne. In other treatments where either capeweed or ryegrass remained uncontrolled, the proportion of lucerne in the hay was low. Weeds significantly reduced lucerne yields (P < 0.01) at the first and second hay cuts of 5 cuts taken in the first season. Combinations of herbicides gave the best weed control and highest lucerne yield at the first and second cuts and significantly higher total lucerne yield. The best herbicide combination was trifluralin and bromoxynil, which controlled all weed species on the site, reduced the weed yield at the first cut by 87% below that of the control and produced the highest total lucerne yield of 14 t ha-l. The hay composition of this treatment at the first cut comprised 59% lucerne, 27% ryegrass and 14% other weed species, while at the second hay cut lucerne comprised 95% of the DM. Lucerne was the highest yielding species in all treatments at the second cut. Lucerne plant densities were lowest on the unsprayed control plots, with 56% fewer plants than for the herbicide combination treatments. Mowing in August was effective in preventing the decline in lucerne plant density that occurred on the unsprayed control plots.

Influence of weed competition on autumn-sown lucerne in south-eastern Australia and the field comparison of herbicides and mowing for weed control

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Influence of weed competition on autumn-sown lucerne in south-eastern Australia and the field comparison of herbicides and mowing for weed control