RESUMO
Oat (Avena sativa) is an annual cereal grown for forage, fodder and grain. Seasonal flowering behaviour, or phenology, is a key contributor to the success of oat as a crop. As a species, oat is a vernalization-responsive long-day plant that flowers after winter as days lengthen in spring. Variation in both vernalization and daylength requirements broadens adaptation of oat and has been used to breed modern cultivars with seasonal flowering behaviours suited to different regions, sowing dates and farming practices. This review examines the importance of variation in oat phenology for crop adaptation. Strategies to advance understanding of the genetic basis of oat phenology are then outlined. These include the potential to transfer knowledge from related temperate cereals, particularly wheat (Triticum aestivum) and barley (Hordeum vulgare), to provide insights into the potential molecular basis of variation in oat phenology. Approaches that use emerging genomic resources to directly investigate the molecular basis of oat phenology are also described, including application of high-resolution genome-wide diversity surveys to map genes linked to variation in flowering behaviour. The need to resolve the contribution of individual phenology genes to crop performance by developing oat genetic resources, such as near-isogenic lines, is emphasised. Finally, ways that deeper knowledge of oat phenology can be applied to breed improved varieties and to inform on-farm decision-making are outlined.
RESUMO
Wheat (Triticum aestivum L.) is the most widely-grown crop in the Mediterranean semi-arid (150-400 mm) cropping zones of both southern Australia and the inland Pacific Northwest (PNW) of the United States of America (United States). Low precipitation, low winter temperatures and heat and drought conditions during late spring and summer limit wheat yields in both regions. Due to rising temperatures, reduced autumn rainfall and increased frost risk in southern Australia since 1990, cropping conditions in these two environments have grown increasingly similar. This presents the opportunity for southern Australian growers to learn from the experiences of their PNW counterparts. Wheat cultivars with an obligate vernalization requirement (winter wheat), are an integral part of semi-arid PNW cropping systems, but in Australia are most frequently grown in cool or cold temperate cropping zones that receive high rainfall (>500 mm p.a.). It has recently been shown that early-sown winter wheat cultivars can increase water-limited potential yield in semi-arid southern Australia, in the face of decreasing autumn rainfall. Despite this research, there has to date been little breeding effort invested in winter wheat for growers in semi-arid southern Australia, and agronomic research into the management of early-sown winter wheat has only occurred in recent years. This paper explores the current and emerging environmental constraints of cropping in semi-arid southern Australia and, using the genotype × management strategies developed over 120 years of winter wheat agronomy in the PNW, highlights the potential advantages early-sown winter wheat offers growers in low-rainfall environments. The increased biomass, stable flowering time and late-summer establishment opportunities offered by winter wheat genotypes ensure they achieve higher yields in the PNW compared to later-sown spring wheat. Traits that make winter wheat advantageous in the PNW may also contribute to increased yield when grown in semi-arid southern Australia. This paper investigates which specific traits present in winter wheat genotypes give them an advantage in semi-arid cropping environments, which management practices best exploit this advantage, and what potential improvements can be made to cultivars for semi-arid southern Australia based on the history of winter wheat crop growth in the semi-arid Pacific Northwest.
