For the foreseeable future, plant breeding methodology will continue to unfold as a practical application of the scaling of quantitative biology. These efforts to increase the effective scale of breeding programs will focus on the immediate and long-term needs of society. The foundations of the quantitative dimension will be integration of quantitative genetics, statistics, gene-to-phenotype knowledge of traits embedded within crop growth and development models. The integration will be enabled by advances in quantitative genetics methodology and computer simulation. The foundations of the biology dimension will be integrated experimental and functional gene-to-phenotype modelling approaches that advance our understanding of functional germplasm diversity, and gene-to-phenotype trait relationships for the native and transgenic variation utilised in agricultural crops. The trait genetic knowledge created will span scales of biology, extending from molecular genetics to multi-trait phenotypes embedded within evolving genotype–environment systems. The outcomes sought and successes achieved by plant breeding will be measured in terms of sustainable improvements in agricultural production of food, feed, fibre, biofuels and other desirable plant products that meet the needs of society. In this review, examples will be drawn primarily from our experience gained through commercial maize breeding. Implications for other crops, in both the private and public sectors, will be discussed.

Experiments conducted over three seasons in southern New South Wales tested the effects of concentrating anhydrous ammonia (AA) and urea fertiliser in bands occupying ∼3.5% of the topsoil volume. Yield responses to applied nitrogen (N) were small or negative in a drought but larger (17 kg grain kg^–1 N fertiliser) in favourable seasons. There was no consistent difference between AA and urea effects on yield, grain protein or efficiency of fertiliser-N recovery, and there were no consistent differences arising from banding depth or application time. Gaseous loss of ammonia to the atmosphere was negligible from urea granules or AA injected into the soil as gas or liquid. Soil ammonium concentration was >700 μg N g^–1 in bands of ∼5 cm diameter when measured 6 days after AA application but halved within 5 weeks due to nitrification. Within 1 day of banding AA or urea at sowing, pH_water in the bands rose from 6 to 8.5, leading to transient changes in microbial activity and populations. Immediately after banding, microbial biomass carbon and numbers of protozoa fell by about half, but numbers of ammonia- and nitrite-oxidisers were unchanged. Five weeks later, microbial biomass carbon and protozoa had partly recovered whereas numbers of ammonia- and nitrite-oxidisers increased 5–10-fold. After 7 months, there was a small reduction in microbial diversity in the bands, shown by analysis of fatty acid methyl esters. Seedling growth was slower where N fertiliser was applied in concentrated bands than when mixed throughout the topsoil, supporting previous research showing that roots avoid bands of highly concentrated ammonium. Banding thus provided a slow-release form of N to wheat crops, thereby reducing excessive seedling growth and the risks of haying-off.

Foxtail millet (Setaria italica (L.) P. Beauv.) is an ideal crop for changing climates and stressed environments due to its short duration, high photosynthetic efficiency and good level of resistance to pest and diseases. Soil salinisation is an increasing problem, with 23% of the global cultivated land already affected. Foxtail millet has potential as a crop for salt-affected soils, with its high tolerance to salinity. The foxtail millet core collection (n = 155) was screened in a soil saturated once with 100 mm NaCl and in a non-saline control in 2008 and a subset (n = 84) in 2009 in a partly controlled environment using Alfisol to identify the best salt-tolerant germplasm. Plants were grown in pots and protected from rain. The salinity response was measured as grain yield per pot. Genotype and salinity × genotype interaction effects were significant for most traits, and there was a large range of yield and biomass variation across accessions. Salinity delayed panicle emergence and maturity, and reduced shoot biomass by 24–41% and grain yield by 7–30%. Salinity did not reduce the harvest index. Among the plant components, stem biomass was reduced most by salinity. There was a large variation in grain yield and other traits among the genotypes in the saline pots. The yield loss by salinity was associated with duration of crop growth, and grain yield loss was highest in the early-maturing accessions. All accessions were grouped into five sets based on grain yield under saline conditions, and the most highly tolerant group had 13 accessions. The salinity-tolerant accessions can be useful parents once their performance is confirmed under saline field conditions.

The diet of millions of people around the world is deficient in selenium (Se). Bread-making wheat has been successfully used in Se biofortification programs under temperate climate to remedy Se deficiency. However, its suitability under Mediterranean conditions and its effect on the grain yield and quality parameters are not well known. In a wheat field in south-western Spain, two foliar Se fertilisers (sodium selenate and sodium selenite) were applied at four application rates (0, 10, 20, 40 g ha^–1) in 2010–11 and 2011–12. Results showed a strong and linear relationship between total Se in grain and Se dose for both fertilisers, although selenate was much more efficient. A dose of 10 g sodium selenate ha^–1 was able to increase significantly the Se in grain to close to the recommended values, although Se loss of 28% during the milling process might be expected. Grain yield was not negatively affected by fertilisation, but grain protein and dry gluten were slightly negatively affected, but only in the dry year. Alveograph parameters were either not affected or slightly favoured by Se fertilisation in any studied year. Bread-making wheat is a good candidate to be included in biofortification programs under semi-arid Mediterranean conditions.

Interspecific hybridisation is being utilised in white clover (Trifolium repens L.) breeding programs to overcome factors currently restricting productivity and persistence. Valuable new traits that may be introduced from the wild relative T. uniflorum include root characteristics and other adaptations to its natural, Mediterranean habitat. This study examined the effect of hybridisation on growth and macronutrient composition of white clover compared with T. uniflorum and T. repens × T. uniflorum backcross 1 (BC₁) hybrids in two glasshouse sand culture experiments. Shoot and root dry weights of BC₁ hybrids were greater than of white clover in low-concentration nutrient treatments but not in a more concentrated treatment. Decreases in dry weight with decreasing nutrient treatment strength were also smaller for some BC₁ hybrids compared with white clover and other hybrid families. Most foliar macronutrient levels were adequate for white clover growth, but mean shoot or leaf phosphorus (P) concentrations were below published critical levels. Higher dry matter production under these low internal P concentrations suggests that some T. repens × T. uniflorum BC₁ hybrids may be more tolerant of lower soil P levels than white clover. Such adaptations are likely to have been inherited from T. uniflorum. However, transgressive segregation may also be occurring, as T. uniflorum was larger than white clover in some, but not all, cases of low nutrient supply.

Previous studies in sand culture suggested that some white clover (Trifolium repens) × T. uniflorum interspecific hybrids were more tolerant than white clover of low external phosphate (P) supply. Here, P acquisition and growth responses were determined in soil for two T. repens × T. uniflorum backcross hybrids and their parental white clover cultivar, grown in a glasshouse pot experiment at Olsen P of 6, 7, 9, 14, or 20 mg P kg^–1 soil. Growth of all of the clover entries responded strongly to increasing soil P levels, and one hybrid clover grew, on average, 17% better than the white clover control cultivar at Olsen soil P 9–20 mg kg^–1. Internal P concentrations and shoot growth per unit P absorbed did not differ among the clovers. Instead, improved growth of the hybrid resulted from a greater ability to acquire soil P. This hybrid had the longest, most frequently branched roots. Frequent branching and growth of root tips into fresh soil would reduce the limitations to P uptake imposed by slow diffusion of P to the root surface. The results confirm previous observations that interspecific hybridisation is a useful strategy for increasing the range of P responsiveness in breeding populations for white clover.

A series of field experiments aimed to quantify reproductive development of four clover species, arrowleaf (Trifolium vesiculosum), balansa (T. michelianum), gland (T. glanduliferum) and Persian (T. resupinatum), for introduction to New Zealand dryland pastures. The duration from emergence to flowering was related to the length of, and direction of change in, photoperiod at the time of first trifoliate leaf appearance. Autumn-sown crops that emerged into a decreasing photoperiod had a longer vegetative growth before they turned reproductive. The time to flower became shorter with increasing photoperiod until the longest day of the year, before it began to slow down as photoperiod decreased towards late summer. Prima gland clover flowered earlier (500–1216 degree-days) than Bolta balansa (600–1733 degree-days), Cefalu arrowleaf (940–1834 degree-days) and Mihi Persian (1047–2610 degree-days) clovers. The duration from pollination to physiological maturity was 274–689 degree-days for Cefalu, 185 degree-days for Bolta, 256 degree-days for Prima, and 425 degree-days for Mihi. The differences in flowering time suggests the suitability of Prima gland clover for areas that dry out quickly in late spring, Bolta balansa clover for areas of wet winter and dry summer, and Cefalu arrowleaf and Mihi Persian clovers for areas that receive higher spring rainfall.

Monitoring pasture growth rate is an important component of managing grazing livestock production systems. In this study, we demonstrate that a pasture growth rate (PGR) model, initially designed for NOAA AVHRR normalised difference vegetation index (NDVI) and since adapted to MODIS NDVI, can provide PGR at spatial resolution of ∼2 m with an accuracy of ∼2 kg DM/ha.day when incorporating in-situ sensor data. A PGR model based on light-use efficiency (LUE) was combined with in-situ measurements from proximal weather (temperature), plant (fraction of absorbed photosynthetically active radiation, fAPAR) and soil (relative moisture) sensors to calculate the growth rate of a tall fescue pasture. Based on an initial estimate of LUE_max for the candidate pasture, followed by a process of iterating LUE_max to reduce prediction errors, the model was capable of estimating PGR with a root mean square error of 1.68 kg/ha.day (R² = 0.96, P-value ≈ 0). The iterative process proved to be a convenient means of estimating LUE of this pasture (1.59 g DM/MJ APAR) under local conditions. The application of the LUE-PGR approach to developing an in-situ pasture growth rate monitoring system is discussed.