|Changes in Characteristics of NSW Wheat Varieties,1965-1997
As part of a broader study of the genetic diversity of the wheat varieties that farmers grow, a study was made of the changes from 1965 to 1997 in wheat varieties grown in selected shires in NSW. The eight shires selected to represent farming systems across NSW were Wagga, Temora, Cowra, Carrathool, Lachlan, Coonabarabran, Gunnedah and Narrabri.
The varieties grown by farmers have continually changed, as growers sought the most appropriate mix of varieties for their environment. This study provides insights into the reasons for those changes and an assessment the impacts on the NSW wheat industry. An average of approximately 8-10 wheat varieties were grown in each shire each year. Generally, three of those varieties were grown on a substantial proportion of the area; the minor varieties were either new varieties in the process of being built up to their peak adoption or older varieties in the stage of being replaced. In southern shires, there has been a tendency to reduce the total number of varieties grown each year, while in the northern shires the number of varieties grown has increased over the past 30 years.
The rate of turnover from old to new varieties has increased in the southern shires since the 1960s, but has slowed in the northern shires. The pattern of adoption and disadoption of varieties shows that, on average, varieties reached a peak share of 15% of the wheat area in the shire in the fifth year after release, but continued to be grown for a further 17 years. The progress of breeders in developing both higher-yielding and higher-quality varieties has been notable over the past 30 years. Wheat yields increased markedly in all shires since 1965, at an average rate of 2.2% per year. When the relative yields from variety trials were weighted by the proportion of the area sown to each variety, the overall average rate of varietal yield improvement was 1.2% per year throughout the period. The rates of yield improvement were broadly the same in the southern shires as in the north. Thus, of the 2.2% per year increase in shire yields since the late 1960s, 1.2% is attributable directly to varietal improvement and 1.0% per year is due to other factors such as management and agronomic practices.
At the same time, the bread-making quality of the varieties grown in southern NSW has also increased markedly since the 1960s. In some northern shires, where Prime Hard wheats were already being produced in the 1960s, there has been little change in the overall bread-making quality of the varieties grown. In other shires, especially in the south and central west of NSW, there has been rapid growth in the bread-making quality of the varieties grown. On average, varietal quality for bread-making has increased at 1.2% per year over the period since 1965, a similar rate to varietal yield increases.
The relevance of NSW Agriculture's role in providing information and advice on varieties to growers is shown by the fact that farmers have generally grown the varieties on NSW Agriculture s list of recommended or approved varieties for each region, with an average of 81% of the area sown to such varieties each year. In addition, the majority of the varieties grown in each shire have been released by breeding programs in the local region.
As well as changing yield and quality of varieties, breeders have brought about a change in the morphological characteristics of the varieties that farmers grow. Over the period since 1965, varieties have generally become shorter, with stronger straw, a lighter coloured grain and more awned. There has also been a significant shift since the 1970s away from growing varieties with a mix of maturity types to a concentration on mid-maturing varieties.
There was little change in the diversity of the mix of varieties grown in most shires up to the 1980s, but there has been some decline in the level of varietal diversity in the southern shires in the 1990s. While the varietal mix has been changing, there has also been a decline in the underlying genetic diversity of those varieties. In some shires, the genetic diversity of the varieties grown has generally declined since the 1980s, raising some concerns about the capacity to manage crop pests and diseases in the future.
In summary, wheat growers in NSW have adopted the higher-yielding and higher-quality varieties from the wheat breeding programs, while relying strongly on Departmental advice on which varieties to grow. Together these changes have led to substantial benefits for NSW wheat growers. If farmers had continued using varieties with yields similar to those grown in 1965, their income would have been, on average across the eight shires analysed, $103 per hectare lower in 1997. However, in some areas, the concentration on a smaller number of varieties in recent years has raised some concerns that the genetic base of the varieties grown is becoming narrower and more vulnerable to pests and diseases.
In conclusion, it is clear from the results of the study that wheat breeders have provided valuable improvements in varieties for NSW farmers since 1965. The future of wheat growing in NSW will depend on maintaining the level of varietal improvements in the coming years.