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Context: The legume shrub/tree leucaena (Leucaena leucocephala (Lam.) de Wit.) is highly regarded as a cattle fodder, although it is considered an environmental weed in many parts of Australia. Aims: We investigated the feasibility of developing a forage variety of triploid leucaena through interspecific hybridisation that is sterile (without seeds) as a strategy to mitigate its weed risk. Methods: A conventional breeding strategy was used to create triploid hybrids from hand-crosses between tetraploid and diploid species of leucaena. Molecular markers were developed to confirm successful crosses and flow cytometry was used to confirm the ploidy level. The plants are being evaluated for flowering behaviour, seed and herbage production across two environmentally diverse sites at Carnarvon and Kununurra in northern Western Australia. Key results: During 2018/19 and 2019/20, 2260 crosses between 45 different combinations of diploid females by tetraploid males and their reciprocals have created over 3000 putative triploid hybrid plants. This is the first time that triploids have successfully been created in Australia and 10 new parental combinations were created as a world-first. Conclusions: A cohort of sterile triploid plants has been identified and selections will be made based on their edible biomass productivity, insect tolerance, capacity for regrowth after cutting, nutritive value and plant chemistry (including anti-methanogenic responses). A sterile leucaena variety will have application not only in Australian grazing systems but also in other tropical regions of the world. Implications: A cost-effective technology for mass vegetative propagation of leucaena will be required for commercialisation of a sterile variety. The legume shrub/tree leucaena is highly regarded as a tropical cattle fodder, although it is considered an environmental weed in many parts of the world. In an Australian first, we report the successful creation of triploid leucaena germplasm through interspecific hybridisation. These give rise to sterile adults (without seeds), mitigating weed risk. Over 2000 hand-crosses between 45 different combinations of diploid and tetraploid leucaena species have created a cohort of sterile plants to evaluate for field performance. [ABSTRACT FROM AUTHOR]

Background: In contrast to trees from northern hemisphere genera, there has been little research into the selection and vegetative propagation of Australian native tree species for use as street trees. Eucalyptus leucoxylon F. Muell. is one of a few eucalypts occurring in south-eastern Australia with bright coloured flowers and is highly regarded as an ornamental tree that flowers readily. It is propagated from seed, but progeny typically show seedling variability and diversity. Eucalyptus leucoxylon was identified as the most widely planted eucalypt in the streets of the city of greater Melbourne, Australia. Methods: This research assessed 300 E. leucoxylon street trees growing across the city of greater Melbourne for their performance against arboricultural criteria relating to canopy structure and density, straightness of the trunk, health (assessed on canopy, trunk, and branch condition, production of exudates, and presence of fungal fruiting bodies), flower colour, and root systems. Results: The results showed that E. leucoxylon was a suitable street tree species with most specimens showing good habit, vigour, and health. Discussion: The trees had traits such as live crown ratio, height, flower colour, and capacity to cope with pruning that are considered appropriate for a street tree. Their dense canopies and high live crown ratios provide shade that can reduce the urban heat island (UHI) effect. Conclusion: This suggests the species has the potential to be a successful street tree not only in Australia, but in other parts of the world where it has been grown successfully in forestry plantations. [ABSTRACT FROM AUTHOR]

Pandanus grayorum Callm., Buerki & Gallaher (Pandanaceae) is newly described from the Wet Tropics of north-eastern Queensland in Australia. It is the second Australian species other than P. gemmifer H.St.John known to reproduce by axillary plantlets on aerial branches. It can be distinguished from P. gemmifer and P. solms-laubachii F.Muell. by the dimensions of its leaves, shape and dimensions of its syncarps, and by the morphology of its phalanges. The placement of P. grayorum in a molecular phylogeny confirmed morphological evidence and showed that the new species clusters with P. gemmifer and P. solms-laubachii in a clade closely related to the P. tectorius Parkinson complex. Pandanus grayorum is known from near the banks of the lower reaches of Mulgrave, Russell, Johnstone and Moresby rivers and associated subcoastal flood plains. Most collection records are from areas outside national parks and a preliminary conservation assessment of Vulnerable is suggested using the IUCN Red List. Finally, a key to north-eastern Queensland Pandanus species is also provided. A new species of screw pine (Pandanaceae) is described from north-eastern Queensland in Australia: Pandanus grayorum Callm., Buerki & Gallaher. The new species occurs mainly in lowland rainforest, along large river banks and associated small creeks and is named in honour of Joy and Bruce Gray. It is the second Australian Pandanus species other than P. gemmifer H.St.John, also occurring in north-eastern Queensland, to show active vegetative propagation producing axillary plantlets on branches. An identification key to the eight species of Pandanus known from north-eastern Queensland is provided. [ABSTRACT FROM AUTHOR]

To assist with rapid screening for rice blast resistance as a precursor in a breeding program, the susceptibility to rice blast of 13 rice genotypes from Australia was evaluated in May to June 2013 using three distinct inoculation methods (spot, filter paper and standard methods) at seedling, vegetative and reproductive stages. The results revealed that the spot and filter paper inoculation methods were successful in discerning susceptibility to the rice blast disease ( P ≤ 0.05). Disease susceptibility declined significantly from the vegetative to reproductive stages. The standard method was conducted at three different stages for pot plants grown inside the mist house. However, low temperatures did not produce disease symptoms except in a few genotypes. Among the 13 rice genotypes screened, AAT9 expressed a highly resistant response, and AAT4, AAT6, AAT10, AAT11, AAT13, AAT17 and AAT18 expressed resistance at various stages. The results will be useful for selecting elite genotypes for disease tolerance where rice blast is prevalent. In addition, the resistant genotypes can serve as a gene pool used in breeding programmes to develop new resistant genotypes. [ABSTRACT FROM AUTHOR]

Abstract: The vegetation communities of the eastern and southern shores of Lake Lefroy, a large salt lake near Kambalda, Western Australia, were studied. The aim of the studies was to explore the relationship between the distribution of vegetation along salt lake shores in relation to soil conditions and the depth to ground-water. Four distinct lake shore types were investigated and two-way indicator species analysis (TWINSPAN) was used to classify the vegetation communities occurring on the lake shores. Seven vegetation communities, with a total of 50 vascular plant species, were identified. More than half of the species recorded were herbs. Those communities occurring on highly saline soils close to the shallow hypersaline ground-water-table included the halophytic genera Halosarcia and Frankenia. Communities on less saline soils and at greater elevations were more diverse. It was concluded that depth to ground-water and soil texture were likely to be key factors in determining the distribution of vegetation communities along the shores. The findings of the study have implications for the design of rehabilitation programmes for shores disturbed by mining activity. [Copyright &y& Elsevier]

1. We used artificial substrata in forested and open streams in South-East Queensland, Australia, to determine the relative importance of shading from riparian vegetation and of nutrients on periphyton growth, and whether nitrogen and/or phosphorus limited algal productivity. 2. Nutrient-diffusing substrata consisting of agar enriched with N, P and N + P, and controls without nutrients, were deployed in duplicate at 15 sites in headwater streams with riparian canopy cover ranging from 0 to 88%. 3. Shading was the over-riding factor controlling periphyton biomass accrual on the artificial substrata, with nutrients playing a relatively minor role. Microscopic examination of periphyton scrapings taken after 7 weeks revealed that diatoms dominated on the artificial substrata in shaded streams, whereas filamentous green algae dominated the algal assemblage in the more open canopy streams. 4. Whilst nutrients had little effect on the accrual of algal biomass compared with riparian shading, there was evidence that nitrogen, and not phosphorus, stimulated periphyton production in streams with sufficient light. [ABSTRACT FROM AUTHOR]