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Broadhurst L.M.,ACSIRO Plant Industry | Murray B.G.,University of Auckland | Forrester R.,Australian National University | Young A.G.,ACSIRO Plant Industry
Australian Journal of Botany | Year: 2012

Grassland communities worldwide have been extensively modified or lost following broadscale agricultural expansion. In south-eastern Australia few natural grasslands remain, with most now being small, isolated and degraded. Conservation and restoration of grassland communities requires an understanding of the impacts of fragmentation on genetic and demographic processes. Swainsona sericea is a perennial grassland herb with conservation listing in New South Wales, Victoria and South Australia. Reproductive output, progeny fitness and genetic diversity were assessed in nine S. sericea populations occupying fragmented grasslands across the southern tablelands of New South Wales. Unexpectedly, four chromosome classes were observed among the populations (2n=4x=32, 2n=10x=80, 2n=14x=112, 2n=16x=128), suggesting a more complex taxonomy than is currently recognised. There was no association between reproductive output and population size or ploidy level whereas population size influenced the number of alleles and percentage of polymorphic loci while ploidy influenced effective alleles and expected heterozygosity. Restricted maximum likelihood analyses of progeny growth indicated that ploidy had a significant influence on height, shoot weight, shoot to root ratio and days to germination. The cytological complexity in S. sericea requires clarification, including delineating the cytological boundaries to enable land managers to include this in their conservation and management plans. © 2012 CSIRO. Source


Cottee N.S.,ACSIRO Plant Industry | Cottee N.S.,University of Sydney | Bange M.P.,ACSIRO Plant Industry | Wilson I.W.,Black Mountain Laboratories | Tan D.K.Y.,University of Sydney
Functional Plant Biology | Year: 2012

In this study we investigated the heat tolerance of high yielding Australian cotton (Gossypium hirsutum L.) cultivars using a multi-level approach encompassing physiological assays and measurements of performance. Two cultivars with known field performance were evaluated for heat tolerance under optimal (32°C) and high (42°C) temperatures in a growth cabinet with a cell membrane integrity assay. Impacts of temperature on growth were evaluated with leaf level measurements of gas exchange and chlorophyll fluorescence. To extend the multi-level approach, the expression of a Rubisco activase regulating gene (GhRCα2) was also determined. Consistent with previously determined differences in the field, cultivar Sicot 53 outperformed Sicala 45 for the cell membrane integrity assay; this finding was reflective of cultivar differences in gas exchange and chlorophyll fluorescence. Cultivar differences were also consistent for expression of GhRCA2, which may also help explain differences in physiological performance, particularly photosynthesis. This study reaffirmed that physiological and molecular assays were sufficiently sensitive to resolve genotypic differences in heat tolerance and that these differences translate to physiological performance. By comparing performance under high temperatures in the growth cabinet and field, this approach validates the use of rapid screening tools in conjunction with a multi-level approach for heat tolerance detection. © 2012 CSIRO. Source


Rebetzke G.J.,ACSIRO Plant Industry | Chenu K.,Queensland Alliance for Agriculture and Food Innovation | Biddulph B.,Western Australia Locked Bag | Moeller C.,University of Tasmania | And 5 more authors.
Functional Plant Biology | Year: 2013

Field evaluation of germplasm for performance under water and heat stress is challenging. Field environments are variable and unpredictable, and genotypeenvironment interactions are difficult to interpret if environments are not well characterised. Numerous traits, genes and quantitative trait loci have been proposed for improving performance but few have been used in variety development. This reflects the limited capacity of commercial breeding companies to screen for these traits and the absence of validation in field environments relevant to breeding companies, and because little is known about the economic benefit of selecting one particular trait over another. The value of the proposed traits or genes is commonly not demonstrated in genetic backgrounds of value to breeding companies. To overcome this disconnection between physiological trait breeding and uptake by breeding companies, three field sites representing the main environment types encountered across the Australian wheatbelt were selected to form a set of managed environment facilities (MEFs). Each MEF manages soil moisture stress through irrigation, and the effects of heat stress through variable sowing dates. Field trials are monitored continuously for weather variables and changes in soil water and canopy temperature in selected probe genotypes, which aids in decisions guiding irrigation scheduling and sampling times. Protocols have been standardised for an essential core set of measurements so that phenotyping yield and other traits are consistent across sites and seasons. MEFs enable assessment of a large number of traits across multiple genetic backgrounds in relevant environments, determine relative trait value, and facilitate delivery of promising germplasm and high value traits into commercial breeding programs. © 2013 CSIRO. Source


Rebetzke G.J.,ACSIRO Plant Industry | Rattey A.R.,ACSIRO Plant Industry | Farquhar G.D.,Australian National University | Richards R.A.,ACSIRO Plant Industry | Condon A.T.G.,ACSIRO Plant Industry
Functional Plant Biology | Year: 2013

Stomata are the site of CO2 exchange for water in a leaf. Variation in stomatal control offers promise in genetic improvement of transpiration and photosynthetic rates to improve wheat performance. However, techniques for estimating stomatal conductance (SC) are slow, limiting potential for efficient measurement and genetic modification of this trait. Genotypic variation in canopy temperature (CT) and leaf porosity (LP), as surrogates for SC, were assessed in three wheat mapping populations grown under well-watered conditions. The range and resulting genetic variance were large but not always repeatable across days and years for CT and LP alike. Leaf-to-leaf variation was large for LP, reducing heritability to near zero on a single-leaf basis. Replication across dates and years increased line-mean heritability to ∼75% for both CT and LP. Across sampling dates and populations, CT showed a large, additive genetic correlation with LP (=-0.67 to-0.83) as expected. Genetic increases in pre-flowering CT were associated with reduced final plant height and both increased harvest index and grain yield but were uncorrelated with aerial biomass. In contrast, post-flowering, cooler canopies were associated with greater aerial biomass and increased grain number and yield. A multi-environment QTL analysis identified up to 16 and 15 genomic regions for CT and LP, respectively, across all three populations. Several of the LP and CT QTL co-located with known QTL for plant height and phenological development and intervals for many of the CT and LP quantitative trait loci (QTL) overlapped, supporting a common genetic basis for the two traits. Notably, both Rht-B1b and Rht-D1b dwarfing alleles were paradoxically positive for LP and CT (i.e. semi-dwarfs had higher stomatal conductance but warmer canopies) highlighting the issue of translation from leaf to canopy in screening for greater transpiration. The strong requirement for repeated assessment of SC suggests the more rapid CT assessment may be of greater value for indirect screening of high or low SC among large numbers of early-generation breeding lines. However, account must be taken of variation in development and canopy architecture when interpreting performance and selecting breeding lines on the basis of CT. © 2013 CSIRO. Source


Kamphuis L.G.,ACSIRO Plant Industry | Kamphuis L.G.,University of Western Australia | Zulak K.,ACSIRO Plant Industry | Gao L.-L.,ACSIRO Plant Industry | And 4 more authors.
Functional Plant Biology | Year: 2013

Sap-sucking insects such as aphids cause substantial yield losses in agriculture by draining plant nutrients as well as vectoring viruses. The main method of control in agriculture is through the application of insecticides. However, aphids rapidly evolve mechanisms to detoxify these, so there is a need to develop durable plant resistance to these damaging insect pests. The focus of this review is on aphid interactions with legumes, but work on aphid interactions with other plants, particularly Arabidopsis and tomato is also discussed. This review covers advances on the plant side of the interaction, including the identification of major resistance genes and quantitative trait loci conferring aphid resistance in legumes, basal and resistance gene mediated defence signalling following aphid infestation and the role of specialised metabolites. On the aphid side of the interaction, this review covers what is known about aphid effector proteins and aphid detoxification enzymes. Recent advances in these areas have provided insight into mechanisms underlying resistance to aphids and the strategies used by aphids for successful infestations and have significant impacts for the delivery of durable resistance to aphids in legume crops. © 2013 CSIRO. Source

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