In cereals, a common salinity tolerance mechanism is to limit accumulation of Na(+) in the shoot. In a cross between the barley variety Barque-73 (Hordeum vulgare ssp. vulgare) and the accession CPI-71284 of wild barley (H. vulgare ssp. spontaneum), the HvNax3 locus on chromosome 7H was found to determine a ~10-25 % difference in leaf Na(+) accumulation in seedlings grown in saline hydroponics, with the beneficial exclusion trait originating from the wild parent. The Na(+) exclusion allele was also associated with a 13-21 % increase in shoot fresh weight. The HvNax3 locus was delimited to a 0.4 cM genetic interval, where it cosegregated with the HVP10 gene for vacuolar H(+)-pyrophosphatase (V-PPase). Sequencing revealed that the mapping parents encoded identical HVP10 proteins, but salinity-induced mRNA expression of HVP10 was higher in CPI-71284 than in Barque-73, in both roots and shoots. By contrast, the expression of several other genes predicted by comparative mapping to be located in the HvNax3 interval was similar in the two parent lines. Previous work demonstrated roles for V-PPase in ion transport and salinity tolerance. We therefore considered transcription levels of HVP10 to be a possible basis for variation in shoot Na(+) accumulation and biomass production controlled by the HvNax3 locus under saline conditions. Potential mechanisms linking HVP10 expression patterns to the observed phenotypes are discussed.
Alpine plant–pollinator communities play an important role in the functioning of alpine ecosystems, which are highly threatened by climate change. However, we still have a poor understanding of how environmental factors and spatiotemporal variability shape these communities. Here, we investigate what drives structure and beta diversity in a plant–pollinator metacommunity from the Australian alpine region using two approaches: pollen DNA metabarcoding (MB) and observations. Individual pollinators often carry pollen from multiple plant species, and therefore we expected MB to reveal a more diverse and complex network structure. We used two gene regions (ITS2 and trnL) to identify plant species present in the pollen loads of 154 insect pollinator specimens from three alpine habitats and construct MB networks, and compared them to networks based on observations alone. We compared species and interaction turnover across space for both types of networks, and evaluated their differences for plant phylogenetic diversity and beta diversity. We found significant structural differences between the two types of networks; notably, MB networks were much less specialized but more diverse than observation networks, with MB detecting many cryptic plant species. Both approaches revealed that alpine pollination networks are very generalized, but we estimated a high spatial turnover of plant species (0.79) and interaction rewiring (0.6) as well as high plant phylogenetic diversity (0.68) driven by habitat differences based on the larger diversity of plant species and species interactions detected with MB. Overall, our findings show that habitat and microclimatic heterogeneity drives diversity and fine‐scale spatial turnover of alpine plant–pollinator networks.
Monitoring biodiversity is a growing and pressing challenge, particularly as climate change threatens species with extinction and leads to widespread shifts in plant distribution and phenology. Tracking changes via ground vegetation surveys is costly and time‐consuming, hence monitoring of complex and heterogenous communities remains an ongoing challenge. Molecular DNA methods are rapidly being developed to provide fast and reproducible results for environmental monitoring, including diet and ecosystem assessments. Here, we used DNA metabarcoding of pollen foraged by European honey bees (Apis mellifera) to investigate their floral resource use in an urban reserve. We collected three different pollen samples from hives: individual bees, raw honey and pollen traps, and identified plants using two metabarcoding markers (ITS2 and trnL). We then compared the results to a ground vegetation survey of surrounding flowering taxa. Pollen DNA metabarcoding detected 74 taxa (48.6% identified to species) across all pollen sources, compared to 44 taxa recorded by the survey (93% identified to species). Within the metabarcoding results, we identified 25% of the genera and 9% of the species found during the survey, with three of the top 10 flowering genera represented. While honey was the most taxon‐rich pollen source (mean = 8.5, SD = 3.5), followed by honey bees (mean = 5.8, SD = 6.1) and pollen traps (mean = 4.2, SD = 1.7), combining the results of six individual bees could detect similar taxa numbers to honey, while 20 bees were required to detect as many taxa as the survey. We demonstrate how DNA metabarcoding of the pollen foraged by honey bees can detect more flowering taxa than traditional survey methods, and how different pollen sources and genetic markers affect the level of detection of plant taxa. The foraging choices of honey bees matched few species detected by the vegetation survey, therefore pollen metabarcoding is recommended as a complementary approach to ground surveys. Rigorous validation and stringent filtering of metabarcoding results were also required to exclude potential false positives. Altogether, this molecular approach can be used to augment vegetation surveys, while tracking the floral resources used by bees.
Bipolaris sorokiniana (teleomorph: Cochliobolus sativus) is the fungal pathogen responsible for spot blotch in barley (Hordeum vulgare L.) and occurs worldwide in warmer, humid growing conditions. Current Australian barley varieties are largely susceptible to this disease and attempts are being made to introduce sources of resistance from North America. In this study we have compared chromosomal locations of spot blotch resistance reactions in four North American two-rowed barley lines; the North Dakota lines ND11231-12 and ND11231-11 and the Canadian lines TR251 and WPG8412-9-2-1. Diversity Arrays Technology (DArT)-based PCR, expressed sequence tag (EST) and SSR markers have been mapped across four populations derived from crosses between susceptible parental lines and these four resistant parents to determine the location of resistance loci. Quantitative trait loci (QTL) conferring resistance to spot blotch in adult plants (APR) were detected on chromosomes 3HS and 7HS. In contrast, seedling resistance (SLR) was controlled solely by a locus on chromosome 7HS. The phenotypic variance explained by the APR QTL on 3HS was between 16 and 25% and the phenotypic variance explained by the 7HS APR QTL was between 8 and 42% across the four populations. The SLR QTL on 7HS explained between 52 to 64% of the phenotypic variance. An examination of the pedigrees of these resistance sources supports the 1 Authors' accespted version of Bovill, Jessica and Lehmensiek, Anke and Sutherland, Mark and Platz, Greg and Usher, Terry and Franckowiak, Jerome and Mace, Emma (2010) Mapping spot blotch resistance genes in four barley populations. Molecular Breeding: new strategies in plant improvement, 26 (4). pp. 653-666. ISSN 1380653-666. ISSN -3743 doi: 10.1007 2 common identity of resistance in these lines and indicates that only a limited number of major resistance loci are available in current two-rowed germplasm.
Hybridization has an important and often positive role in plant evolution. However, it can also have negative consequences for species. Two closely related species of Ornduffia are endemic to the Porongurup Range in the South West Australian Global Biodiversity Hotspot. The rare Ornduffia calthifolia is found exclusively on the summits, while O. marchantii is more widely dispersed across a greater range of elevation and is not considered threatened. Hybridisation in suitable overlapping habitat has been suspected between them for decades. Here we combine genotyping by sequencing to verify hybridisation genetically, and fine scale (2 m resolution) species distribution modelling (SDM) to test if hybrids occur in suitable intersecting habitat. From a study area of c. 4700 ha, SDM identified c. 275 ha and c. 322 ha of suitable habitat for O. calthifolia and O. marchantii, respectively. We identified range overlap between species of c. 59 ha), which enveloped 32 individuals confirmed to be hybrids. While the hybrids were at the margin of suitable habitat for O. marchantii, their preference for elevated habitat was closer to the more narrowly distributed O. calthifolia. The combination of genetic data and fine scale spatial modelling approaches enabled a better understanding of hybridisation among taxa of conservation significance. However, the level to which hybrid proliferation and competition for habitat presents as a threat to O. calthifolia is currently unknown and requires priority in conservation management given the threats from global warming and disturbance by tourism.
Common root rot (CRR) caused by Bipolaris sorokiniana is a serious disease constraint in the dry temperate cereal growing regions of the world. Currently little is known about the genetic control of resistance to CRR in cereals. In this study based on a Delta/Lindwall barley population we have undertaken a bulked segregant analysis (BSA) and whole genome mapping approach utilising Diversity Arrays Technology (DArT) to identified quantitative trait loci (QTL) associated with CRR expression.One QTL each was identified on chromosomes 4HL and 5HL explaining 12 and 11% of the phenotypic variance, respectively. IntroductionThe fungal pathogen Bipolaris sorokiniana (teleomorph: Cochliobolus sativus (Ito & Kuribayashi) Drechs. ex Dastur), is the causal agent of the foliar disease spot blotch and the root disease common root rot (CRR) in winter cereals. Common root rot infected seedlings develop dark brown necrotic lesions on the roots, crown and lower leaf sheaths (Kumar et al. 2002). The disease impairs the functioning of roots and crown, resulting in fewer tillers and heads, which causes a reduction in grain yield and quality (Wildermuth et al. 1992). As high soil temperatures and low soil moisture appear to contribute to the severity of the disease, damage due to CRR can vary widely from year to year in a given location (Van Leur et al. 1997;Kumar et al. 2002;Mathre et al. 2003). This disease is a significant constraint in the dryer temperate cereal growing regions of the world, and has been particularly damaging in Syria, Canada, USA and Australia (Wildermuth 1986;Conner et al. 1996;Van Leur et al. 1997;Kumar et al. 2002;Tobias et al. 2009). In Australia, CRR has been reported in wheat and barley cropping fields in every mainland state, with estimated yield losses of up to 24% reported in Queensland (Wildermuth et al. 1992).Integrated strategies for controlling B. sorokiniana on barley include soil and residue management, chemical control, crop rotation and resistance breeding (Mehta 1988; Steffenson 1997). Wildermuth and McNamara (1991) demonstrated that rotational strategies involving a range of other crops, in particular lucerne, resulted in the reduction of soil populations of B. sorokiniana and thus a reduction in the severity of CRR. However, after a Phenotypic screening for CRR resistance generally relies on assessment of visual discolouration along the sub-crown internode and on the roots (Tobias et al. 2009) of advanced plant materials sampled from the field. These methods are subjective, time consuming, expensive and prone to significant environmental interactions. Due to these limitations, molecular marker technologies combined with conventional breeding methods may provide a faster and more robust means of identifying resistant progeny, thus increasing the efficiency of selection in cereal breeding programs.This study examined a population of recombinant inbred barley lines (RILs) developed from a cross between the moderately resistant parent variety Delta and the susceptible variety Lindwall, with the...
Within tribe Gnaphalieae (Asteraceae), the Australasian clade is one of the four major clades. In Australia, the Gnaphalieae account for 488 species or approximately half of the native Asteraceae, encompassing wide ecological and morphological diversity including shrubs, everlasting paper daisies, cudweeds, alpine cushion plants, and ephemeral herbs in the arid zone. The evolution of the Australasian clade is still poorly understood. The most detailed previous infratribal classification of Gnaphalieae has recently been revised, resulting in the recognition of two subtribes, with all Australian species placed in subtribe Gnaphaliinae. The most comprehensive previous phylogeny of Australian Gnaphalieae used high-copy ribosomal and chloroplast markers but showed limited resolution and branch support. We used conserved ortholog set data produced with sequence capture and 53 chloroplast genes to infer nuclear and chloroplast likelihood phylogenies for Australian Gnaphalieae, generating data for at least one species each from 80 of the 86 native genera. Four major clades were resolved: the Euchiton clade of cudweed-like and alpine perennial species; the shrubby Cassinia clade; the predominantly perennial and eastern Australian Waitzia clade; and the predominantly ephemeral and western Australian to Eremaean Angianthus clade. The Cassinia, Waitzia, and Angianthus clades are largely congruent with "groups" in a previous morphological analysis and classification of Gnaphalieae. Analysis of ancestral ranges implied the temperate Southeast of Australia as the most likely area of origin for the Australian Gnaphalieae as a whole and for three of the four major clades. The Angianthus clade was implied to be ancestrally Eremaean, with a major secondary radiation originating in southwestern Australia. Our broadly sampled phylogeny provides a framework to inform sampling and design of future studies to test the circumscription of genera.
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