Yield, water use and water-use efficiency (WUE) in the high-rainfall zone of Tasmania are highly variable because of environmental and agronomic constraints to grain production that limit yield potential. The expansion of irrigation infrastructure in Tasmanian production systems with access to low-cost, plentiful irrigation sources will also influence these components in some areas. This paper reports on desktop modelling studies that aimed to benchmark wheat WUE and to explore the sensitivity of yield, water use and WUE to changes in management practice in a high-rainfall environment. Here, WUE was defined as: grain yield/(evapotranspiration   drainage   runoff). The crop simulation model APSIM-Wheat was used to quantify key water balance elements and estimate ‘attainable’ and ‘potential’ WUE and grain yield for 27 wheat trials. The upper limit for WUE was ∼30 kg/ha.mm in excess of 180 mm evaporation, which is 16% higher than previous estimates at this southerly latitude for wheat. Attainable WUE ranged from 58% to 100% of potential WUE and was limited by nitrogen supply and water loss through evaporation, drainage and runoff. Model scenarios showed that co-limitation of inputs of nitrogen and irrigation was an important driver of grain yield and WUE. The implications of this research on crop management and production in temperate, high-rainfall environments are discussed.

Phosphorus (P) recovery and P-use efficiency (PUE) by wheat are low, and genetic improvement in PUE is a potential means of improving the effectiveness of P in farming systems. We examined variation in response to P in wheat to identify genotypes that showed consistent responsiveness to P fertiliser in the field and which may be the target of future studies, and examined differences in P uptake and partitioning. The response to P was studied among a diverse set of bread wheat germplasm at three sites in South Australia between 2009 and 2012. Up to 53 varieties and breeding lines were grown at two rates of P, 0 kg/ha and 30 kg/ha. Grain yield at 0 kg P/ha and response to P varied independently among genotypes. There were large effects of site and season on the response to P, but some genotypes showed consistently low and others high response to P. Analysis of a subset of lines revealed large responses in vegetative growth to P but the response diminished as crops matured, and variation in early vegetative growth was unrelated to the responses in biomass at maturity or grain yield. Genotypic variation in grain yield was more strongly related to variation in P utilisation efficiency than to variation in P uptake among wheat genotypes, which was associated with differences in P harvest index (PHI). Although breeding has improved yield, there has been no significant genetic gain in total P uptake; rather, improvements in PUE have been associated with an increase in P utilisation efficiency and PHI.

Starch in wheat is an important component of flour and is related to grain yield and wheat end-products. In this study, a doubled haploid (DH) population with 168 lines derived from a cross of elite Chinese wheat (Triticum aestivum L.) cultivars Huapei 3 and Yumai 57 was used to identify dynamic quantitative trait loci (QTLs) for total starch content (TSC), amylose (AMS) and amylopectin (AMP) in wheat grain. Traits were measured at stages, grown under three treatments in two seasons, and were assessed by unconditional and conditional QTL analyses. Thirty-three additive QTLs and 21 pairs of epistatic QTLs for TSC, AMS and AMP were detected by unconditional mapping, whereas 19 additive QTLs and 15 pairs of epistatic QTLs were identified by conditional mapping. Of these, QTsc4A.1 and QAms4A.1 were detected continuously at five stages under three treatments in two seasons by unconditional mapping, indicating that the accumulated effects of these QTLs were expressed stably from 12 days after flowering (DAF) and were little affected by nitrogen and water agronomic treatment. These two QTLs also showed net expression from 12 to 22 DAF by conditional mapping. The results indicate that the two loci play an important role in starch synthesis. Most of the epistatic QTLs belonged to a minor QTL, but played an important role in the target traits. Therefore, the development of starch is mainly affected by additive effects besides the epistasis effect. The data are useful for potential marker-assisted selection and cloning of the target gene in further fine mapping, and provide a foundation to understand the genetic mechanism underlying the development of starch in wheat and to increase yield.

Crop growth and developmental rate around the pre-heading phase are important for determining grain yield potential in barley (Hordeum vulgare L.) and other crop cereals. The photothermal quotient, Q (ratio between photosynthetically active radiation (PAR) and temperature) around the flowering period has been found to be a good predictor of grain number per unit area under potential growing conditions when both solar radiation and temperature vary, but not under suboptimal nitrogen (N) conditions. Under suboptimal conditions, Q might not account for differences in grain number due to modifications in radiation-use efficiency (RUE), biomass partitioning between vegetative and reproductive organs, fruiting efficiency, and/or a combination of these factors. This paper aims at providing insights into how grain yield is defined during the pre-heading phase in 2- and 6-row barleys under contrasting N and radiation environments, using a model proposed by RA Fischer for grain number determination.

Nitrogen and radiation treatments affected grain number, and consequently grain yield, through changes in spike biomass at heading, and not by a direct N effect. When low and high N conditions were included, Q poorly explained variations in grain number. Nitrogen increased RUE during the pre-heading phase. When accumulated PAR intercepted between the maximum number of spikelet primordia and heading stages (PAR_ia) was considered together with RUE, the accuracy of the model was increased. Nitrogen slightly increased biomass partitioning between reproductive and vegetative organs, but it was not strong enough to improve the model between PAR_ia and grain number. In the case of fruiting efficiency, genotype × N and shading × N interactions highlighted that this trait was maximised when 6-rowed barleys and shading were imposed under the high N treatment.

Random surveys conducted in the Western Australian (WA) grain belt have shown that herbicide-resistant Lolium rigidum and Raphanus raphanistrum are a widespread problem across the cropping region. In 2010, a random survey was conducted to establish the levels of herbicide resistance for common weed species in crop fields, including the minor but emerging weeds Bromus and Hordeum spp. This is the first random survey in WA to establish the frequency of herbicide resistance in these species. For the annual grass weed Bromus, 91 populations were collected, indicating that this species was present in >20% of fields. Nearly all populations were susceptible to the commonly used herbicides tested in this study; however, a small number of populations (13%) displayed resistance to the acetolactate synthase-inhibiting sulfonylurea herbicides. Only one population displayed resistance to the acetyl-coenzyme A carboxylase-inhibiting herbicides. Forty-seven Hordeum populations were collected from 10% of fields, with most populations being susceptible to all herbicides tested. Of the Hordeum populations, 8% were resistant to the sulfonylurea herbicide sulfosulfuron, some with cross-resistance to the imidazolinone herbicides. No resistance was found to glyphosate or paraquat, although resistance to these herbicides has been documented elsewhere in Australia for Hordeum spp. (Victoria) and Bromus spp. (Victoria, South Australia and WA).

There are no current commercial releases of genetically modified white clover, but several research groups are working on traits such as virus resistance, stress tolerance and bloat safety that are likely to provide large economic benefits for livestock farmers. However, white clover pollen is a common constituent of honey produced by bees foraging white clover flowers. Therefore, there is a need to develop tools to detect the presence of genetically modified pollen in white clover honey. The results presented in this paper describe the development and application of PCR-based techniques to detect the Alfalfa mosaic virus coat protein gene (AMV CP) and the neomycin phosphotransferase 2 selectable marker gene (npt2) in genetically modified white clover pollen, whether this pollen is collected fresh, from honey bees that have been foraging white clover, or from honey. Further research and development will be required to develop ‘field-ready’ tools for the detection and quantification of these transgenes in pollen and honey products. However, this paper demonstrates prospects and principles in pollen and honey from honeybees foraging transgenic white clover.

In this study, 137 canola (Brassica napus L.) accessions were evaluated for germination speed, which is a critical character in the plant life cycle. The accessions were grouped into three categories, fast (F), medium, and slow (S), with nine category F (7%) and 12 category S (9%) germination accessions identified and validated in repeated Petri dish and pot experiments. Although accessions in category F showed significantly faster germination and emergence than those in category S, seedling growth parameters did not differ greatly. Based on germination speed and seedling characteristics, four accessions with high early vigour and four with low early vigour were identified. Seed germination speed was not affected by seed weight and was not simply controlled by gibberellic acid and abscisic acid, but 10% smoke water significantly delayed seed germination. The identified accessions with contrasting early vigour can be used to study the genetic and molecular mechanism of seed germination and seedling development and to breed superior canola cultivars.

Soil constraints are a major limitation to grain production on waterlogging-prone sodic soils in the medium-rainfall zone of southern Australia, and several options have been proposed to overcome these constraints. A field experiment commenced in 1999 to compare the effectiveness of different management strategies, including improved crop nutrition, soil amelioration by using gypsum with or without deep ripping, applying organic matter, using raised beds or delayed sowing on improving the growth and grain yields of four consecutive crops including wheat (Triticum aestivum) in 1999 and 2002, barley (Hordeum vulgare) in 2000, and faba beans (Vicia faba) in 2001.

Improving crop nutrition alone generally did not significantly improve grain yields, whereas adding ameliorants such as composted pig bedding–litter or deep ripping   gypsum produced grain yield increases in all crops by up to 48% compared with the control. Similar increases in grain yields were produced when crops were grown on raised beds, even in seasons when growing-season rainfall was well below average. Greatest yield increases were recorded when both raised beds and ameliorants were used (up to 2 t/ha, or 63%). Spring-sown crops consistently produced lower grain yields than the (autumn-sown) control. For the three cereal crops (two wheat and one barley), increases in grain yields resulting from soil amelioration generally were not associated with increased harvest index or kernel size but were associated with greater tiller number and number of grains per m². For the pulse crop, faba beans, yield increases were associated with greater dry matter production and increased number of grains per m². All management strategies significantly increased crop nitrogen (N) uptake, although this did not necessarily translate to increased grain protein because of a dilution effect in the highest yielding treatments. Increases in grain yield coincided with improved root growth throughout the profile (up to 140 cm depth). All physical amelioration treatments either reduced the degree of temporary waterlogging, as indicated by shallow piezometers, or improved soil structure, as indicated by reduced cone penetrometer resistance, compared with the control. Reduction in soil exchangeable sodium percentage on this highly sodic clay soil, measured within the first season after implementation, was less clear-cut. Increases in grain yield, however, appeared related to improved N supply rather than greater water use. Large increases in grain yields across a range of seasonal conditions appear possible on these soil types in medium-rainfall environments provided both soil structure and nutrition are improved.

Fusarium wilt, caused by several formae speciales of Fusarium oxysporum, is an important disease of most crop and pasture legumes, including field pea (Pisum sativum), chickpea (Cicer arietinum), lucerne (alfalfa, Medicago sativa) and barrel medic (M. truncatula). Medicago truncatula is an important pasture legume and a model legume species. Hence, it can be used to increase our knowledge of resistance mechanisms efficient to block F. oxysporum infection if its response to the disease is characterised. We evaluated the physiological and susceptibility responses to the disease of two contrasting M. truncatula genotypes, and the effect of several cultural conditions known to affect the disease incidence, such as plant age at infection time, growth substrate and the method of inoculation. Our results indicated that the A17 accession harbours a moderate level of resistance to the disease. We also showed that the method of inoculation strongly affected development of fusarium wilt disease in this model species, whereas it was not significantly altered by plant age or the inorganic growth substrate tested. In addition, we describe a rapid change in leaf temperature after infection, which can be used as an indirect parameter to confirm fungal infection at a very early stage of the interaction.

Atmospheric nitrogen (N) deposition is an important issue of global climate change and it will significantly affect plant growth and reproduction, resulting in damage to ecological systems. However, little attention has been given to the effects of this factor on plant reproductive strategies. We investigated how variation in atmospheric N deposition affects the reproductive strategy of Chloris virgata (feathertop Rhodes grass). We simulated atmospheric N deposition to evaluate the trade-off between seed size and seed number, as well as its effects on offspring vigour. We found significant negative correlations between seed size and seed number per spike in the control and 20.0 g N m^–2 treatments, as well as between seed size and seed number per plant in the control treatment. Seed number and seed weight per spike behaved similarly and were significantly lower in the control and 20.0 g N m^–2 treatments than in the other N supply treatments. Spike number and seed yield behaved similarly, and the greatest gains in these values occurred from 2.5 to 20.0 g N m^–2. Seed size reached its maximum values at low and high N levels, whereas seed N concentrations increased with N level. Although the germination percentage remained stable under different N levels, the highest germination rate occurred in the control treatment. Our findings showed that simulated atmospheric N deposition affected the reproductive pattern and seed vigour of C. virgata.