Negative potassium (K) balances on farmlands globally are widespread because fertiliser K input is often less than losses (leaching) and removal of K in hay, straw and grain, which leads to a rundown of plant-available K. When soil K reserves are not large and the plant-available K pools are not well buffered, the risk of K rundown in soils is high. In the south-west of Western Australia, soil K rundown, particularly by continuous cropping or in systems where a large portion of crop biomass is removed, is increasing the prevalence of crop K deficiency even on soils where K was not previously a limiting factor for crop yields. While fertiliser K is required for adequate supply of plant-available K, maximising K use efficiency is also important for cropping profitability and sustainability in dryland agriculture. Plant K uptake and use efficiency can be affected by soil types, crop species and sequences, seasonal conditions, and K management. In water-limited environments, crop K nutrition, especially root access to subsoil K, plays a crucial role in promoting root growth, regulating plant water relations and alleviating biotic and abiotic stresses. Optimised use of both soil and fertiliser K is increasingly necessary to sustain crop yields under stressed conditions in the context of K rundown in soils.

Context. Cytokinin response regulators (RRs) are important components of the two component signal systems that are involved in the regulation of plant growth and development, and in the response to abiotic stresses. Plant cytokinin response regulators (RR) were divided into type A and type B. A-type RR proteins act as negative feedback to regulate cytokinin signals, while B-type RRs could regulate A-type RR gene expression, and B-type RR genes have proved to play important roles in regulating cytokinin signal transduction in various biological processes.

Aims. We aimed to explore and analyse B-type RR genes in wheat in a preliminary fashion.

Methods. Using bioinformatics methods, wheat type B RR genes were identified, and type B Triticum aestivum RR (TaRR) genes were analysed using quantitative real-time polymerase chain reaction. In order to further analyse the function of TaRR, staining experiments were performed.

Key results. Twenty-nine B-type TaRR genes were identified in the wheat genome, divided into three groups according to their phylogenetic relationships. Chromosome mapping showed that 29 TaRRs were evenly distributed on 12 chromosomes, while there were no genes located on the other nine chromosomes, which may have experienced gene loss during evolution. The polymerase chain reaction results showed that TaRRs were significantly up-regulated under polyethylene glycol treatments. Under sodium chloride stress, TaRRs were up-regulated to varying degrees, reaching the maximum at 24 h. The study also found that the expression pattern of TaRRs was different in the root and leaf under different abiotic stresses. In addition, staining experiments also showed that TaRR5.1-6A could induce the self-defence function of leaves.

Conclusions. These results form the basis for further exploring the role of B-type TaRR genes in plant response to drought stress and salt stress.

Implications. This study lays the molecular biology foundation for the functional study of the B-type TaRR genes.

Context and aims. Due to the effect of seed priming on abiotic stress-induced tolerance in plants, this study has been performed to identify the key genes responding to the seed osmo-priming process in a sensitive barley variety under drought stress.

Methods. The microarray data regarding barley expression analysis under drought stress (expression profile of GSE56437) was used to determine differentially expressed probes in time-series data with the BETR package in R. 1388 differentially expressed probes were ranked by 10 attribute weighting approaches in RapidMiner. Also, decision tree models were applied to provide insight into the combination of important probes in a ranked structure.

Key results. Following attribute weighting approaches analysis, 328 differentially probes were identified by at least one attribute weighting approach. The top-ranked genes were HORVU6Hr1G089600 (sugar transporter), HORVU7Hr1G060130 (superoxide dismutase [CU-ZN] 2, Chloroplastic), HORVU4Hr1G076520 (non-specific serine/threonine protein kinase/threonine-specific protein kinase) and HORVU3Hr1G082260 (3-phosphoinositide dependent protein kinase-1).

Conclusions. According to the promoter analysis of key genes, important transcription factor binding sites related to developmental processes, biotic and abiotic stress responses were identified. The most frequent consensus binding sites were related to the vernalisation1 transcription factor. Enriched gene ontology term analysis pointed out processes with a distinguished role in drought tolerance like oxidation–reduction.

Implications. To our awareness, this is the first study for identifying genes involved in priming-induced tolerance via integrating time-series data analysis, various attribute weighting approaches and decision tree models.

Drought stress is detrimental to male reproduction in maize (Zea mays L.), largely through reducing the quantity and quality of pollen grains. However, transcriptional response of maize pollen grains to drought stress has not been well documented. We compared pollen gene expression for a maize hybrid (ZhongDan909) under well-watered and drought-stress conditions, based on RNA-Seq validated by quantitative real-time PCR analysis. Expression of 6424 genes and 1302 transcripts was altered in pollen grains of maize subjected to 7 days of drought during flowering. Gene Ontology annotations showed 308 differentially expressed genes, annotated and classified into 50 primary functional categories. Kyoto Encyclopedia of Genes and Genomes analyses revealed 44 differentially expressed genes in nine metabolic pathways. In relation to carbohydrate metabolism pathways, there was downregulation of a polygalacturonase gene, which could reduce cell wall lysis in early pollen germination, and an increase in callose synthase transcripts along with reduced cellulase transcripts. These altered gene expressions responsible for cell wall integrity may inhibit the initiation of pollen tube growth. The onset of tube growth could be further impeded by observed changes in gene expression that potentially influence hormone metabolism (including downregulation of AUXIN RESPONSE FACTOR 18 and EIN3-BINDING F-BOX), reduce mitochondrial function, and alter protein translation. Genes with potential roles in adaptation were also altered in their transcript levels. These included genes encoding the upregulated transcription factor ZmNF-YC2, and the downregulated ZmbHLH13, a negative regulator of jasmonic acid responses. The upregulated flavin enzyme gene DIHYDROLIPOYL DEHYDROGENASE 1, associated with increased levels of reactive oxygen species, is of interest in relating redox homeostasis to stress adaptation. Overall, the analyses identified a suite of genes involved in the development of pollen grains and tubes and responsive to drought stress. The findings enhance understanding of the gene networks underlying compromised pollen viability under drought stress.

Context. Germination and emergence are key to successful annual crop establishment. Emergence rate depends on germination rate, sowing depth, and rate of pre-emergent shoot elongation. The rate at which a shoot grows prior to emerging from the soil becomes significant when crops such as chickpea (Cicer arietinum L.) and lentil (Lens culinaris Medik.) are deep sown to utilise moisture below the conventional sowing zone.

Aims. In seeds of contrasting size, we aimed to compare the ability of chickpera and lentil varieties to emerge from deep sowing. Here we describe genetic variation for epicotyl growth rate, and phenotypic variation for epicotyl and root growth rates and biomass partitioning, of chickpea and lentil, as they relate to seed size. We further assess the impact of deep sowing and soil type on emergence, establishment and yield of the two species.

Methods. Epicotyl elongation rates, root growth and seedling biomass partitioning were determined in controlled environment studies, using soil tubes. Field trials were conducted on two different soil types at two sowing depths.

Key results. Most of the variance in epicotyl growth rate could be attributed to species rather than variety. Although epicotyl emergence was faster in lentil, chickpea epicotyl growth rates were higher than those in lentils and unrelated to seed size, whereas growth rates in lentils were weakly correlated to seed size (r = 0.31). Root development and epicotyl diameter appeared to be traded for maintenance of growth in smaller seeds of both species. In the field, sowing depth did not affect emergence, establishment or yield of chickpeas at either site. Deeper sowing resulted in minor reductions in emergence of lentil at one site, although biomass and yield were not affected.

Conclusions. Emergence of both crops was unaffected by deep sowing (to at least 200 mm) under controlled environment and sandy field conditions. There was minimal genetic variation for the measured parameters within a species. Seed size was of little importance for emergence rate; however, shoot growth rate from small seeds was maintained by reducing seedling vigour.

Implications. Seed size should be considered when deep sowing lentils in order to maintain high seedling vigour. Further work is needed to understand how environmental factors influence seedling emergence from depth.

Context. Farmers and consultants are faced with selecting from amongst competing liming materials.

Aim. We sought to establish guidelines for the efficient use of competing liming materials.

Method. The effectiveness of 12 commercial liming materials from around Australia in increasing soil pH, their rate of movement below the depth of incorporation and their residual value to grain yield were measured in our field study.

Key results. Chemical composition (equivalent CaCO₃ content) was a major determinant of effectiveness over the longer term. There appeared to be no value to grain yield in the provision of additional Mg above what was already in the soil at this site. Finer commercial products were more effective in the short term and no less effective in the longer term, indicating that fineness also remains a major determinant of effectiveness. The effect of the source of the liming product was a minor determinant of effectiveness. As previously found, there was a tardiness in the reaction rate of dolomites and a slight advantage in the reaction rate of softer limestones but as with fineness, the data for different sources tended to converge over 6–7 years.

Conclusion. All liming materials provided a benefit to grain yield over the 7 years and that benefit was proportional to the material’s chemical purity and fineness.

Implication. Growers and advisers can select the best value for cost amongst the commercially available products at a given geographical location. The quantitative assessment of chemical composition and particle size remains the best means of assessment over both the short and longer terms.

Single nucleotide polymorphisms (SNPs) are the most abundant form of genetic variation in eukaryote genomes and may be useful for selection of genetically distant parents for crossing in breeding programs. In this study, genome-wide SNPs of tall fescue (Festuca arundinacea Schreb.) were genotyped by using double-digest restriction-site-associated DNA sequencing to determine the genetic variation and differentiation among and within forage, turf and hybrid populations. After filtering, 16 036 SNPs were used to investigate genetic diversity and for structure analysis. SNP markers clearly differentiated the populations from each other. However, the hybrid population had a higher genetic similarity with the turf population than with the forage population. The results were confirmed by genetic differentiation (fixation index, Fst) and gene flow (Nm) statistics, so that low Fst and high Nm were observed between turf and hybrid groups, indicating less genetic distance and a high similarity between them. Based on the results of the weighted pair group method with arithmetic mean clustering, discriminant analysis of principal components and analysis of molecular variance, greater genetic differentiations were found among diverse turf, forage and hybrid populations, especially between turf and forage ones. In conclusion, numerous informative SNPs, natural allelic diversity-led domestication patterns, basic genetic variation statistics (e.g. Fst and heterozygosity) and population structures have multidimensional applicability for tall fescue genomics-assisted breeding.

Context. Tall fescue (Schedonorus arundinaceus) is one of the most important cultivated forage grasses in temperate regions but its association with some Epichloë fungal endophytes usually makes it unsuitable for livestock feeding due to toxic alkaloids. However, re-inoculation of plants with non-toxic endophytes can result in positive effects for livestock feeding.

Aims. Assess the effects of the non-toxic AR584 endophyte on seed viability and germination in two tall fescue cultivars.

Methods. The effects of AR584 endophyte (presence/absence) and tall fescue cultivar (INIA Aurora/Taita) were evaluated on seed viability and germination responses across a range of temperature and water availability regimes. Response to constant temperature and water availability was characterised by the thermal-time and hydro-time models, respectively.

Key results. Under accelerated aging conditions, endophyte presence reduced seed viability in cultivar Taita. For both cultivars, endophyte-infected seeds showed a lower germination rate than endophyte-free seeds, except for INIA Aurora under low incubation temperatures. Also, endophyte-infected seeds in both cultivars displayed lower germination rates and final germination as the water potential was lowered.

Conclusions. A strong cultivar-by-endophyte interaction for seed germination indicates the need to understand how specific cultivar-endophyte combinations best fit a given environmental condition, as defined by temperature and water availability.

Implications. The information we present can be valuable not only for farmers who have to decide what to cultivate but also for seed companies that have to preserve seed quality.