The influence of cultivar, environment and nutrition management onwheat quality in the high rainfall zone of south west, Western Australia

Abstract

The high rainfall zone (HRZ) of south west Western Australian (WA) has traditionally been dominated by livestock industries. However, a reduction in wool price throughout the 1990’s has stimulated a transition to farm systems that contain an increasing proportion of annual cropping enterprises. The HRZ, compared to traditional wheat belt areas of WA, has higher rainfall and a longer, cooler growing season. Potential grain yields as determined by seasonal rainfall are not often achieved because of inadequate nutrition and other constraints such as water-logging and disease. Substantial research has been conducted in the HRZ focusing on increasing grain yield to limits set by seasonal rainfall. Research on wheat grain quality characteristics, however, has been limited. The aim of this research was to examine the influence of cultivar, environment and nutrition management on wheat quality characteristics in the HRZ of south west WA and to examine the stability of cultivar performance in relation to site and season.A series of experiments was grown at Moora and Williams in 2005, 2006 and 2007. Sites were chosen to represent contrasting environments within the HRZ. Moora, the more northern site typically has higher temperatures and lower rainfall compared to Williams. Eight cultivars were selected, two that are accepted into each of the commercial quality grades (Australian Prime Hard APH, Australian Hard AH, Australian Premium White APW and Durum). Three levels of nutrition management were applied ‘control’, ‘grower’ and ‘researcher’ and were chosen to simulate low, medium and high fertiliser rates likely to be used by growers in the HRZ. Treatments effects were measured for grain yield, physical grain quality characteristics and grain protein quality charactertics as determined by a mixograph.Environment was responsible for almost 90% of the variation for grain yield, screenings, Hagberg falling number and milling yield. Management of crop nutrition was the principal source of variation for grain protein quantity (48%), dough strength as measured by mixograph area below the curve (52%) and water absorption (46%-52%). It was often the second greatest source of variation for other characteristics measured in this study. Cultivar was the predominant source of variation for dough strength as measured by mixograph initial build-up (46%) and dough stability (47%), but it had only a small affect on grain yield and grain protein quantity (2%).The increase in nutrition resulted in a significant increase in water absorption and dough strength and a trend towards increasing dough stability. An increase in gliadin and glutenin proteins is thought to be responsible for this result. The low nutritional status of soils in the HRZ not only restricts grain yield but grain protein quantity and quality. The impact of nutrition management on grain yield and quality characteristics as shown in these experiments should be considered by breeders, agronomists and marketers when interpreting experimental results. Furthermore, the results indicate that the nutritional management of breeding experiments should be based on a sound methodical approach, incorporating a combination of soil test results, grain yield potential and seasonal monitoring for the environment in question and not be simply based on levels that are either ‘district practice’ or ‘non-limiting’.This study has also identified statistically significant differences between cultivars for stability of grain yield and grain protein quality. Four cultivars (three bread wheat and one durum wheat) were characterised as having dynamic stability, which is described as the ability to respond to an environment in a predictable way. In addition, three cultivars were assessed as having static stability, unchanged performance regardless of any variation in environment for water absorption. This information indicates that assessment of stability of cultivars during the early stages of testing can assist commercial buyers in sourcing suitable grain quality and even that there may be potential to breed cultivars with improved static or dynamic stability.If it is assumed that the Australian wheat industry cannot compete in a global wheat market based on the relatively small level of production. Then the future of the industry lies in producing the qualities required by specific markets. Realizing the impact of nutrition management on quality characteristics in the HRZ of WA will be a positive step towards a sustainable industry.