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.
Barton L.,UWA Institute of Agriculture |
Hoyle F.C.,UWA Institute of Agriculture |
Stefanova K.T.,University of Western Australia |
Murphy D.V.,UWA Institute of Agriculture
Agriculture, Ecosystems and Environment | Year: 2016
Increasing soil organic matter (OM) is promoted as a strategy for improving the resilience of coarse-textured cropping soils in semi-arid climates. While increasing soil OM can benefit crop productivity, it can also enhance nitrous oxide (N2O) emissions in temperate climates. Our objective was to investigate if increasing soil OM affected soil greenhouse gas (GHG) fluxes and grain production in a semi-arid region in south-western Australia. We firstly measured N2O and methane (CH4) fluxes from a free-draining sandy soil with contrasting soil OM content for 2.5 years using automated soil chambers. The randomized block design included two OM additions (no OM, plus OM) by two nitrogen (N) fertilizer rates (0, 0N; 100 kg N ha−1 yr−1, +N) by three replicate plots. Organic matter (chaff) had been applied to the plus OM treatments every three years since 2003, with 80 t OM ha−1 applied in total. Secondly, we investigated the interaction between soil OM content and N fertilizer addition on grain yield for two growing seasons. The randomized split-plot design included two OM treatments by five N fertilizer rates (0, 25, 50, 75 and 100 kg N ha−1), by three replicates. Increasing soil OM increased grain yields and soil mineral N, but also enhanced soil N2O emissions. Nitrous oxide emissions were low by international standards (<0.12% of the N fertilizer applied), with total N2O emissions after two years ranked: plus OM (+N; 427 g N2O-N ha−1) > plus OM (0N; 194 g N2O-N ha−1) > no OM (+N; 41 g N2O-N ha−1) = no OM (0N; 14 g N2O-N ha−1). Increasing soil OM also decreased CH4 uptake by 30%. Management practices that increase soil OM in sandy-textured rainfed, cropping soils in semi-arid regions should be encouraged as they can improve grain yield without substantial increases in soil N2O or CH4 emissions. © 2016 The Authors
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.
Teakle N.L.,UWA Institute of Agriculture |
Teakle N.L.,University of Western Australia |
Colmer T.D.,UWA Institute of Agriculture |
Pedersen O.,UWA Institute of Agriculture |
And 2 more authors.
Plant, Cell and Environment | Year: 2014
A combination of flooding and salinity is detrimental to most plants. We studied tolerance of complete submergence in saline water for Melilotus siculus, an annual legume with superhydrophobic leaf surfaces that retain gas films when under water. M.siculus survived complete submergence of 1 week at low salinity (up to 50molm-3 NaCl), but did not recover following de-submergence from 100molm-3 NaCl. The leaf gas films protected against direct salt ingress into the leaves when submerged in saline water, enabling underwater photosynthesis even after 3d of complete submergence. By contrast, leaves with the gas films experimentally removed suffered from substantial Na+ and Cl- intrusion and lost the capacity for underwater photosynthesis. Similarly, plants in saline water and without gas films lost more K+ than those with intact gas films. This study has demonstrated that leaf gas films reduce Na+ and Cl- ingress into leaves when submerged by saline water - the thin gas layer physically separates the floodwater from the leaf surface. This feature aids survival of plants exposed to short-term saline submergence, as well as the previously recognized beneficial effects of gas exchange under water. © 2014 John Wiley & Sons Ltd.