Synthetic hexaploid wheats (SHWs) and their synthetic derivative lines (SDLs) are being used as a means of introducing novel genetic variation into bread wheat (BW). Phenotypic information for days to flowering, height, grain weight and grain yield was collected from multiple environments for three SDL families, each with ∼50 lines, and their elite BW parents. In general, the SDLs were earlier flowering and taller with larger grain size, but similar grain yield to the BWs. The three SDL families and their SHW and BW parents were genotyped using mapped DArT (diversity arrays technology) markers. Within each SDL family, SHW-specific DArT markers were used to identify SHW-derived chromosomal regions that appeared to be preferentially retained in the SDL families, as determined by retention at frequencies >0.25, the expected frequency for Mendelian segregation. Regions on chromosomes 2BS and 7BL appeared to be preferentially retained in all three SDL families, while regions on chromosomes 1AL, 1BS, 3BS, 5AS, 5BL, and 7AS were preferentially retained in two of the three SDL families. Other regions were preferentially retained in single families only, including some regions located on the D genome. Single-marker regression analysis was performed using the preferentially retained markers and identified markers and regions that were significantly associated with one or more of the four traits measured. Comparative mapping also indicates that these preferentially retained markers and chromosome regions may co-locate with previously identified QTLs for anthesis, height, grain weight and/or grain yield. Therefore, SHWs may contain novel alleles at these loci in these regions for these traits, which may provide a selective advantage to the SDLs. This approach could provide a useful method for identifying chromosomal regions of interest with potentially novel alleles for introgression for further BW improvement.

The genus Lotus includes a group of forage legume species including genotypes of agronomic interest and model species. In this work, an experimental hydroponic growth system allowed the discrimination of growth responses to ionic–osmotic stress in a population of recombinant inbred lines (RILs) developed from L. japonicus × L. burttii and the identification of the associated quantitative trait loci (QTLs). The analyses led to the identification of eight QTLs: three for shoot growth localised on chromosome 3, 5 and 6; one for root growth on chromosome 1; three for total growth on chromosome 1, 4 and 5; and one associated with shoot/root ratio on chromosome 3. An interaction of QTL × stress condition was established and the effect of the environment quantified. In summary, it was established that the allele from L. burttii explained most responses to osmotic stress, while the alleles of L. japonicus explained the responses related to ionic stress conditions. Of 49 markers linked to all QTLs identified, 41 expressed superiority of the L. burttii parental allele in the osmotic stress condition, but when an iso-osmotic concentration of NaCl was applied, L. burttii lost superiority in 21 of these markers. This shows the superiority of the L. japonicus parental allele in ionic stress conditions. This study is the first report in which a RIL population of lotus is analysed with the aim of providing molecular markers associated with plant responses to ionic or osmotic stress.

Parastagonospora nodorum is a major fungal pathogen of wheat in Australia, causing septoria nodorum blotch (SNB). Virulence of P. nodorum is quantitative and depends largely on multiple effector–host sensitivity gene interactions. The pathogen utilises a series of proteinaceous, necrotrophic effectors to facilitate disease development on wheat cultivars that possess appropriate dominant sensitivity loci. Thus far, three necrotrophic effector genes have been cloned. Proteins derived from these genes were used to identify wheat cultivars that confer effector sensitivity. The goal of this study was to determine whether effector sensitivity could be used to enhance breeding for SNB resistance. We have demonstrated that SnTox1 effector sensitivity is common in current commercial Western Australian wheat cultivars. Thirty-three of 46 cultivars showed evidence of sensitivity to SnTox1. Of these, 19 showed moderate or strong chlorotic/necrotic responses to SnTox1. Thirteen were completely insensitive to SnTox1. Disease susceptibility was most closely associated with SnTox3 sensitivity. We have also identified biochemical evidence of a novel chlorosis-inducing protein or proteins in P. nodorum culture filtrates unmasked in strains that lack expression of ToxA, SnTox1 and SnTox3 activities.

Allele-specific markers for important genes can improve the efficiency of plant breeding. Their value can be enhanced if effects of the alleles for important traits can be estimated in identifiable types of environment. Provided potential bias can be minimised, large, unbalanced, datasets from previous plant-breeding and agronomic research can be used. Reliable, allele-specific markers are now available for the phenology genes Ppd-D1, Vrn-A1, Vrn-B1 and Vrn-D1, the aluminium-tolerance gene TaALMT1, and the plant-stature genes Rht-B1 and Rht-D1. We used a set of 208 experiments with growing-season rainfall of <347 mm from southern Australia to estimate the effects of seven frequent combinations of the phenology genes, an intolerant and a tolerant allele of TaALMT1, and two semi-dwarf combinations Rht-B1b   Rht-D1a (Rht-ba) and Rht-B1a   Rht-D1b (Rht-ab) on grain yield in lower rainfall, Mediterranean-type environments in southern Australia. There were 775 lines in our analyses and a relationship matrix was used to minimise bias.

Differences among the phenology genes were small, but the spring allele Vrn-B1a might be desirable. The tolerant allele, TaALMT1-V, was advantageous in locations with alkaline soils, possibly because of toxic levels of aluminium ions in subsoils. The advantage of TaALMT1-V is likely to be highest when mean maximum temperatures in spring are high. Rht-ab (Rht2 semi-dwarf) was also advantageous in environments with high mean maximum temperatures in spring, suggesting that for these stress environments, the combination of Vrn-B1a plus TaALMT1-V plus Rht-ab should be desirable. Many successful cultivars carry this combination.

Drought is one of the major abiotic stresses limiting rice (Oryza sativa L.) production. Quantitative trait loci (QTLs) for drought tolerance (DT) at the reproductive stage were identified with two sets of reciprocal introgression lines derived from Lemont × Teqing. In total, 29 and 23 QTLs were identified in the Teqing and Lemont backgrounds, respectively, during the reproductive stage under drought and irrigated conditions for spikelet number per panicle, seed fertility, filled grain weight per panicle, plant height, and grain yield per plant. Most of these QTLs showed obvious differential expressions in response to drought stress. Another 21 QTLs were detected by the ratio of trait values under drought stress relative to the normal irrigation conditions in the two backgrounds. For 28 DT QTLs, the Teqing alleles at 23 loci had increased trait values and could improve DT under drought stress. Only five (17.9%) DT QTLs (QSnp1b, QSnp3a, QSnp11, QSf8, and QGyp2a) were consistently detected in the two backgrounds, clearly suggesting overwhelming genetic background effects on QTL detection for DT. Seven of the DT QTL regions identified were found to share the same genomic regions with previously reported DT-related genes. Introgressing or pyramiding of favourable alleles from Teqing at the validated QTLs (QSnp3a, QSnp11 and QGyp2a) into Lemont background may improve DT level of Lemont.

Late foliar diseases (especially leaf rust) reduce assimilate supply during post-anthesis, determining fewer assimilates per grain and thereby inducing grain weight reductions. Although the assimilate reduction hypothesis is the most accepted to explain decreases in grain weight due to late foliar diseases, it has not been clearly established whether those reductions could be completely ascribed to source limitations or whether diminished grain weight could be the consequence of reductions in grain weight potential. The objective of this work was to determine whether grain weight reductions due to leaf rust during grain filling could be associated with source–sink limitations. Two experiments (during 2007 and 2008 growing seasons) including healthy and diseased wheat crops were conducted under field conditions. Source–sink manipulation treatments and grain water content measurements were made to test the source- and sink- limitation hypotheses due to the appearance of late foliar diseases during grain filling. Leaf rust was induced to appear exclusively during grain filling, and in both years, it reduced grain yield and grain weight in both experiments. However, except for distal grains, there were no significant differences between healthy and diseased plots in maximum grain water content, indicating that late foliar diseases did not affect the potential size of the grains. The reserves stored in stems were remobilised to the growing grains in both healthy and diseased crops. However, the reserves remaining at physiological maturity were significantly reduced in diseased crops. Reduction in grain number by trimming the spikes increased the grain weight in diseased but not in healthy crops. Grain weight of trimmed spikes in diseased crops reached similar values to those of healthy crops. These results support the hypothesis that foliar diseases could cause source limitation for grain filling beyond differences in grain weight potential when the crops are severely affected by late foliar diseases such as leaf rust.

Although geographically small, Tasmania has a diverse range of regional climates that are affected by different synoptic influences. Consequently, changes in climate variables and climate-change impacts will likely vary in different regions of the state. This study aims to quantify the regional effects of projected climate change on the productivity of rainfed pastoral and wheat crop systems at five sites across Tasmania. Projected climate data for each site were obtained from the Climate Futures for Tasmania project (CFT). Six General Circulation Models were dynamically downscaled to ∼10-km grid cells using the CSIRO Conformal Cubic Atmospheric Model under the A2 emissions scenario for the period 1961–2100. Mean daily maximum and minimum temperatures at each site are projected to increase from a baseline period (1981–2010) to 2085 (2071–2100) by 2.3–2.7°C. Mean annual rainfall is projected to increase slightly at all sites. Impacts on pasture and wheat production were simulated for each site using the projected CFT climate data. Mean annual pasture yields are projected to increase from the baseline to 2085 largely due to an increase in spring pasture growth. However, summer growth of temperate pasture species may become limited by 2085 due to greater soil moisture deficits. Wheat yields are also projected to increase, particularly at sites presently temperature-limited. This study suggests that increased temperatures and elevated atmospheric CO₂ concentrations are likely to increase regional rainfed pasture and wheat production in the absence of any significant changes in rainfall patterns.

Sulla is a biennial forage legume native to the central-western Mediterranean Basin and has increasing interest for regions with Mediterranean-climate. The Italian germplasm is a reservoir of variation for important agronomic traits. This study aimed to support breeding programs by investigating patterns of agronomic, adaptive and morpho-physiological variation among ecotypes collected from the three main Italian regions of species cultivation: central Italy, and the two islands of Sicily and Sardinia. Forage yield and morpho-physiological traits were evaluated at a site with Mediterranean climate in Sicily. Forage yield and cold tolerance in a cold-prone site of northern Italy were also assessed, to locate useful germplasm for widening crop resilience and climatic adaptability. Collection regions, and ecotypes within regions, differed for total forage yield and final plant survival, but their responses were subjected to interactions with test location. Specific adaptation dominated the adaptive responses of ecotypes and elite commercial varieties. Ecotype adaptation to cold winter was associated with latitude and, more specifically, the extent of cold stress in collecting sites. The ecotype collection region had a bearing also on morpho-physiological characteristics. A few ecotypes from central Italy performed outstandingly with respect to elite varieties, displaying wide adaptation across cold-prone and drought-prone environments.