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Nedlands, Australia

Shanmugam S.,UWA Institute of Agriculture | Abbott L.K.,UWA Institute of Agriculture
Applied and Environmental Soil Science | Year: 2015

This study investigated whether there was residual effect of application of lime- and clay-amended biosolids (LaBC®) on ryegrass growth and soil microbial biomass in a coarse-textured, acid pasture soil. Reapplied LaBC® increased fertiliser-use efficiency and plant growth in this glasshouse experiment. Soil management history was established with a single application of LaBC® (50 t ha-1 wet weight equivalent) with or without inorganic fertiliser (NPK) prior to growing annual ryegrass for 5 cycles. In cycle 6 there was no residual nutrient effect of the original application of LaBC® but there was a residual liming effect of the previously applied LaBC®. A nutrient effect of reapplied LaBC® in plant growth cycle 6, had little residual benefit in cycle 7. The residual concentration of inorganic N remaining in this coarse-textured acid soil after a single application of LaBC® was negligible and did not appear to be a risk to the environment when applied at 50 t ha-1 wet weight equivalent. Copyright © 2015 S. Shanmugam and L. K. Abbott.

Ma X.,UWA Institute of Agriculture | Yan G.,UWA Institute of Agriculture
Acta Horticulturae | Year: 2014

Since the development of a reliable DNA extraction method on ten genera of Proteaceae in 1994 by Maguire et al., considerable progress has been made in the application of DNA technology in breeding proteaceous plants. The research and application can be divided into the following areas: 1) DNA diversity studies for parent selection in breeding programmes, for systematics and for ecological characterisation. The research spins from the evaluation of different marker systems such as RAPD, ISSR, AFLP, SSR and sequences to the fingerprinting of species and cultivars, and identification of true hybrids; 2) characterisation of specific traits/genes for marker assisted selection in breeding. The specific traits studied include sex determination in Leucadendron, drought tolerance in Banksia, allergens, and antibacterial and antifungal traits/genes; 3) development of linkage maps for map-based marker identification and map-based cloning. The first such map in Proteaceae was developed in 2003 in macadamia by Peace et al. and we have recently developed a map in Grevillea with the aim to identify Phytophthora tolerance. Genetic modification has not been used widely in Proteaceae possibly because of limitations of a reliable regeneration system and availability of useful genes.

Purnamasari M.,University of Western Australia | Cawthray G.R.,University of Western Australia | Barbetti M.J.,University of Western Australia | Erskine W.,UWA Institute of Agriculture | Croser J.S.,UWA Institute of Agriculture
Plant Disease | Year: 2015

Camelina sativa (L.) Crantz. has been proposed as a novel source of oilseed resistance to Sclerotinia rot (SR; causal agent Sclerotinia sclerotiorum (Lib.) de Bary). To assess factors likely important in determining the level of resistance to this pathogen, 30 diverse C. sativa genotypes were evaluated using a cotyledon test under controlled environmental conditions. Confirmed cotyledon SR-resistant (CS370) and SR-susceptible (CS2305) genotypes were assessed for camalexin production across time following inoculation at the 1-month vegetative stage of growth. There were significant differences among C. sativa genotypes in response to inoculation with S. sclerotiorum in terms of percent cotyledon disease index (%CDI), with the mean %CDI ranging from 30.9 to 69.4% across germplasm and confirmation screening, respectively. Genotype CS370 consistently showed low %CDI indicating high level of resistance to S. sclerotiorum, whereas CS2305 showed the highest %CDI value. These findings highlight the potential to develop highly SR-resistant cultivars of C. sativa by selection. Furthermore, liquid chromatographic analysis of leaves for both SR-resistant and SR-susceptible genotypes demonstrated that camalexin was produced when inoculated with S. sclerotiorum. However, camalexin production was not linked with disease severity in either genotype, indicating that SR resistance in C. sativa is independent of the level of camalexin production. © 2015 The American Phytopathological Society.

Chen S.,UWA Institute of Agriculture | Wan Z.,University of Western Australia | Wan Z.,Huazhong Agricultural University | Nelson M.N.,UWA Institute of Agriculture | And 9 more authors.
Journal of Heredity | Year: 2013

The oilseed Brassica juncea is an important crop with a long history of cultivation in India and China. Previous studies have suggested a polyphyletic origin of B. juncea and more than one migration from the primary to secondary centers of diversity. We investigated molecular genetic diversity based on 99 simple sequence repeat markers in 119 oilseed B. juncea varieties from China, India, Europe, and Australia to test whether molecular differentiation follows Vavilov's proposal of secondary centers of diversity in India and China. Two distinct groups were identified by markers in the A genome, and the same two groups were confirmed by markers in the B genome. Group 1 included accessions from central and western India, in addition to those from eastern China. Group 2 included accessions from central and western China, as well as those from northern and eastern India. European and Australian accessions were found only in Group 2. Chinese accessions had higher allelic diversity per accession (Group 1) and more private alleles per accession (Groups 1 and 2) than those from India. The marker data and geographic distribution of Groups 1 and 2 were consistent with two independent migrations of B. juncea from its center of origin in the Middle East and neighboring regions along trade routes to western China and northern India, followed by regional adaptation. Group 1 migrated further south and west in India, and further east in China, than Group 2. Group 2 showed diverse agroecological adaptation, with yellow-seeded spring-sown types in central and western China and brown-seeded autumn-sown types in India. © 2013 The American Genetic Association.

Dwivedi S.L.,Indian International Crops Research Institute for the Semi Arid Tropics | Sahrawat K.L.,Indian International Crops Research Institute for the Semi Arid Tropics | Upadhyaya H.D.,Indian International Crops Research Institute for the Semi Arid Tropics | Upadhyaya H.D.,Kansas State University | And 9 more authors.
Advances in Agronomy | Year: 2015

Legumes form symbiotic relationship with root-nodule, rhizobia. The nitrogen (N2) fixed by legumes is a renewable source and of great importance to agriculture. Symbiotic nitrogen fixation (SNF) is constrained by multiple stresses and alleviating them would improve SNF contribution to agroecosystems. Genetic differences in adaptation tolerance to various stresses are known in both host plant and rhizobium. The discovery and use of promiscuous germplasm in soybean led to the release of high-yielding cultivars in Africa. High N2-fixing soybean cultivars are commercially grown in Australia and some countries in Africa and South America and those of pea in Russia. SNF is a complex trait, governed by multigenes with varying effects. Few major quantitative trait loci (QTL) and candidate genes underlying QTL are reported in grain and model legumes. Nodulating genes in model legumes are cloned and orthologs determined in grain legumes. Single nucleotide polymorphism (SNP) markers from nodulation genes are available in common bean and soybean. Genomes of chickpea, pigeonpea, and soybean; and genomes of several rhizobium species are decoded. Expression studies revealed few genes associated with SNF in model and grain legumes. Advances in host plant and rhizobium genomics are helping identify DNA markers to aid breeding of legume cultivars with high symbiotic efficiency. A paradigm shift is needed by breeding programs to simultaneously improve host plant and rhizobium to harness the strength of positive symbiotic interactions in cultivar development. Computation models based on metabolic reconstruction pathways are providing greater insights to explore genotype-phenotype relationships in SNF. Models to simulate the response of N2 fixation to a range of environmental variables and crop growth are assisting researchers to quantify SNF for efficient and sustainable agricultural production systems. Such knowledge helps identifying bottlenecks in specific legume-rhizobia systems that could be overcome by legume breeding to enhance SNF. This review discusses the recent developments to improve SNF and productivity of grain legumes. © 2015 Elsevier Inc.

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