This article reviews knowledge of 23 plant viruses infecting pasture grasses and legumes in New Zealand. The incidence, ecology and impact of each virus and prospects for control using natural or artificial resistance genes or by vector control is discussed. The most prevalent viruses are Alfalfa mosaic virus and White clover mosaic virus in pasture legumes and Cocksfoot mottle virus, Ryegrass mosaic virus and Barley yellow dwarf virus in pasture grasses. Lucerne Australian latent virus is restricted to the North Island and Red clover necrotic mosaic virus is largely restricted to the South Island. These patterns are likely to be dynamic with ongoing changes in weather patterns, land use, the spread of insect vectors and the continuing introduction of viruses and vectors. The existing and potential threats to 12 pasture species are tabulated and the knowledge gaps for each species highlighted. Control of vectors including aphids, eriophyid mites and soil-borne fungi is probably not economic per se but could be an additional benefit of integrated pest management in pasture and cropping systems. The most cost-effective and practical preventative measures are likely to be the use of virus-tested seed to establish new pastures and the incorporation of resistance genes by conventional breeding or by genetic engineering. Finally, recommendations are made for future research for New Zealand, which is also relevant to other temperate regions of the world.

The Gpc-B1 gene from wild emmer has been proposed as a potential mechanism for improving grain protein in bread wheat without reducing grain yield. Near-isolines with and without the Gpc-B1 gene in three Australian-adapted genetic backgrounds, Gladius, Wyalkatchem and VR1128, were compared in 14 experiments across the south and west of Australia for grain yield, grain protein content and grain weight. The donor parents of Gpc-B1 were the Canadian cultivars Burnside and Somerset. One of the 14 experiments was discarded because of inadequate rust control and confounding effects of Yr36, a gene closely linked to Gpc-B1. Heading date and test weight were measured in five experiments.

Across all comparisons, Gpc-B1 increased grain protein content and reduced grain weight, with a negligible effect on grain yield. Selected lines containing Gpc-B1 in a Wyalkatchem background had comparable grain yields to the elite cultivar Mace, but with significantly higher grain protein contents, slightly higher grain weights, similar heading dates and acceptable test weights. The development of agronomically acceptable lines containing Gpc-B1 was partially attributed to the removal of undesirable genes from wild emmer during the breeding of the Canadian donor parents and the use of Australian recurrent parents with high test weights.

The ion toxicities of aluminium (Al), manganese (Mn) and iron (Fe) induced in transiently waterlogged acid soils decrease root and shoot growth and grain yield more in intolerant than tolerant wheat genotypes. Whether these tolerances might also enhance grain yield in moisture-limited acid soils is not known. Wheat genotypes contrasting in ion toxicity tolerances (differing 6-fold for Al, 14-fold for Mn and 2.7-fold for Fe tolerance, quantified via relative root length (Al) or relative root dry weight (Mn and Fe)), but otherwise having a similar yield potential and maturity, were evaluated in plots with and without lime in multi-location field experiments (including two dry and one non-moisture-limiting site) in the Western Australian wheatbelt. Liming reduced surface soil acidity, and increased grain yield more in ion-toxicity tolerant than intolerant genotypes. The combined adverse effect of soil acidity and drought reduced relative grain yield less in Al- and Mn-tolerant genotypes (68%, 2347 kg ha^–1) than intolerant genotypes (76%, 2861 kg ha^–1) in drought-stressed environments. It appears that a deep root system to allow uptake of water from deep horizons in acidic soils with a dry surface layer is contingent on tolerance to multiple ion toxicities.

This study used semi-thin sectioning and cytochemistry to investigate the relationship between pollen nutrient metabolism and pollen abortion in male sterile lines of wheat induced by SQ-1 (a chemical hybridising agent). Anthers were collected from the tetrad to trinucleate stages, and 4′ ,6-diamidino-2-phenylindole staining was used to visualise nuclei and confirm the development stage. Sudan Black B, periodic acid–Schiff, Coomassie Brilliant Blue, and toluidine blue were used to detect lipids, starch, proteins, and acidic polyanions, respectively. Semi-thin sectioning indicated that nutrient accumulation was much higher in the fertile line 1376 than in the sterile line 1376-PHYMS. Further, no lipids were found in the free microspore stage in the sterile line; however, at the late microspore stage, more proteins and acidic polyanions were found in the sterile line 1376-PHYMS pollen than in the fertile line 1376 pollen. From the binucleate to trinucleate pollen stages, the starch content was low and the intine considerably thinner in the pollen of the 1376-PHYMS line. SQ-1 probably hampered nutrient metabolism in the anthers, leading to decreased nutrient supply and abnormal intine formation, ultimately resulting in pollen abortion. A new mechanism for nutrient absorption, i.e. endocytosis of Ubisch bodies or orbicules by the intine through the germinal aperture, was revealed.

The need for continual improvement in water productivity of rice farming has led to the development of delayed permanent (continuous) water (DPW) irrigation practice for drill-sown rice in south-eastern Australia. Current rice-growing practices have the crop flooded for most, or all, of its growing period, whereas DPW has reduced the period of flooding during the vegetative phase, resulting in significant water savings. The changed water-management practice required nitrogen (N) management practices to be investigated, because traditional N application timings and rates may no longer be suitable. Six experiments were conducted over three rice-growing seasons, 2010–11, 2011–12 and 2012–13, on two soil types in south-eastern Australia. Nitrogen applications at sowing, early tillering, mid-tillering and pre-PW were investigated at different rates and split-timing combinations. In the third season, three current commercial semi-dwarf rice varieties, Reiziq, Sherpa and Langi, were investigated for their growth and grain yield using different N treatments under DPW management.

Nitrogen applied with the seed at sowing increased vegetative plant growth but did not increase grain yield, whereas N applied at early tillering had no significant impact on plant growth or grain yield. Nitrogen applied at mid-tillering often increased plant growth but did not lead to increased grain yield over treatments that received all N before PW application at 18–22 days before panicle initiation. When rice is managed under DPW, all N should be applied in one application, before the application of PW. The results from this research show that applying 100 kg N ha^–1 before PW for rice grown under DPW was the best N-management option for the experimental fields. All three varieties grew and yielded well under the practice of DPW and responded similarly to N application rates and timings.

We assessed the feasibility of determining the nitrogen (N) and potassium (K) content of fresh, greenhouse-grown tomato leaves by using a new polarisation reflectance spectrum spectro-goniophotometer system developed by our research group and coupled with appropriate multivariate calibration methods. The main factors that affect the polarised reflectance characteristics of tomato leaves are discussed, including incident zenith angle, azimuth, detection zenith angle, and polariser angle. Orthogonal experiments and range analyses were performed to verify the optimum angle combination from the polarised reflectance parameters. Optimum angle combination experiments were then conducted to fine-tune the optimal parameters, which resulted in the following conditions: incident zenith angle, 60°; viewing zenith angle, 45°; polariser on light source, 0°; polariser on detector, 45°; and azimuth, 180°. On this basis, 122 fresh leaves of greenhouse-grown tomato were used to establish models of N and K content. Results showed that the performance of the iPLS-GA model under incident zenith angle 60° was superior to that of the other models. The optimal model for N was achieved with R = 0.9418 and root mean square error of prediction (RMSEP) = 0.519 in the prediction set; the optimal model for K was achieved with R = 0.8645 and RMSEP = 0.700 in the prediction set. The results show that it is feasible to measure the nutrient content of fresh, greenhouse-grown tomato leaves by polarisation reflectance spectroscopy with an appropriate multivariate calibration model under angle selection. This method allows for in-depth study of plant nutrient status and rapid detection at the single-leaf scale and has theoretical and practical significance.

Commercial products derived from lignite (brown coal), sold mainly as humate preparations, are widely promoted as plant growth stimulants leading to higher crop yields. These products are also claimed to improve key indicators of soil health including soil pH and microbial biomass. In a glasshouse setting, we investigated the effect of six lignite-derived amendments applied at the manufacturer’s recommended rate on the early-stage growth of two pasture species, lucerne (Medicago sativa L.) and ryegrass (Lolium multiflorum Lam.). We used two soil types common to south-eastern Australia, and following an 8-week growing period, assessed soil pH, microbial biomass carbon and mycorrhizal colonisation as key indicators of soil health. We hypothesised that humic acid (HA) and macronutrients derived from the products would positively influence pasture growth and soil health indicators. Although significant growth effects were observed in response to some products, the effects were inconsistent across pasture and soil types. Treatment effects on tissue nutrient accumulation were rare, with the exception of increased potassium in ryegrass in one soil amended with raw brown coal, and decreased nitrogen in lucerne in the same soil amended with a granulated, slow-release humate product. Further, we found no consistent trends in mycorrhizal colonisation or microbial biomass carbon in response to individual treatments. Given the variable responses of the plant species and soil types to the amendments used here, we emphasise the need for further mechanistic studies to help understand how these amendments can be used to greatest effect.

White clover (Trifolium repens L.) is a widely used and highly valued temperate legume; however, its productivity and survival are restricted under dryland and drought conditions. This study investigated whether drought resistance of white clover could be improved by interspecific hybridisation with Trifolium uniflorum L. After almost 4 months without irrigation in a rain-shelter facility, shoot dry weight (DW) decreased significantly less in first-generation backcross (BC₁) hybrids (–47%) than second-generation backcross (BC₂) hybrids (–68%) and white clover (–69%). Stolon morphological parameters such as internode length and leaf lamina area also decreased less under water stress in the BC₁ hybrids than in BC₂ and white clover. There was also lower senescence in BC₁ under water stress than in the other clover types. Genotypes with smaller changes in leaf lamina area, internode length, senescence and lateral spread had smaller changes in shoot DW, and there were significant correlations between constitutive levels of some characteristics and the effect of water stress on shoot DW. Under water stress, the growth form of the BC₁ hybrids was compact, dense and prostrate, whereas white clover was more spreading and open. Increased allocation of dry matter to roots under drought, and greater root diameter, may also have influenced the ability of BC₁ hybrids to maintain water uptake and key physiological processes. Overall, the data confirm that the drought resistance of white clover can be improved through hybridisation with T. uniflorum.

Crop production in the high-rainfall zone of Western Australia (>450 mm average annual rainfall) is an increasing proportion of the state’s total farming system since the 1990s, when the profitability of animal production based on improved pastures was threatened. However, the yields of the dominant crops barley, canola and oats have often been insufficient to maintain whole-farm productivity in the changed system.

The aim of this study was to test the diagnostic approach to agronomic research as a means of increasing crop yields. Experiments were conducted at two farm sites over 5 years with treatments applied according to an initial diagnosis of the factors that may have been limiting production. The diagnosis of limiting factors was based on soil physical and chemical tests, plant tissue analyses and the observations of the farmers. The diagnostic tests were assessed against agreed standards. The highest yields in each year were compared with an estimate of the rainfall-limited potential yields. In both experiments, more than one factor was considered likely to be limiting crop and pasture production; therefore, factorial combinations of treatments were used, including deep-placed lime, deep-placed potassium and claying at one site, and deep ripping, raised beds and gypsum at the other. Split doses of nitrogen were applied to half of the plots after waterlogging events in some years.

The yield responses to the treatments changed each year but the highest yields were close to the calculated potential yield after taking account of estimated losses of water. Interactions between the factors were not often significant. That is, the responses were additive and independent, so they can be applied sequentially. No single factor could be identified as the most limiting at either site over the 5 years. However, the results suggested a hierarchy of measures that could be taken according to the least cost or the most profit principle, or according to farmer preference and convenience.

Bituminaria bituminosa (common name tedera) is a drought-tolerant perennial pasture species of agronomic and pharmaceutical interest for Mediterranean climates. Considering the importance of this legume, in vitro experiments were conducted to develop protocols for plant regeneration from embryogenic calli of leaves, petioles and anthers to efficiently exploit and maintain selected important clones from the tedera breeding program. The type of explant was a key factor in the frequency of embryogenesis and the number of embryos per callus. For plant regeneration from cultured anthers, appropriate anther physiological state (uninucleate stage of microsporogenesis), stress treatments (electroporation, 25 Ω, 25 µF, 1500 V) and culture conditions were determined. A robust flow-cytometry method was developed to analyse the ploidy status of callus, in vitro shoots and in vivo acclimatised plants derived from anther and leaf explants.