摘要：A study was made of the changes from 1965 to 1997 in wheat varieties grown in selected shires representing farming systems across NSW. The eight shires examined were Wagga, Temora, Cowra, Carrathool, Lachlan, Coonabarabran, Gunnedah and Narrabri. In each shire, approximately 8-10 varieties were grown 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 number of varieties grown, while in the northern shires the number of varieties grown has increased since 1965. 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 of 2.2% per year, with the rates of yield improvement broadly the same in the southern shires as in the north. Of the 2.2% per year increase in shire yields since the late 1960s, 1.2% is attributable to varietal change 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 NSW has also increased. 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, there has been rapid growth in the bread-making quality of the varieties grown. 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, most of the varieties grown in each shire have been released by local breeding programs. As well, 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 concentration on mid-maturing varieties since the 1970s. In summary, wheat growers in NSW have adopted the higher-yielding and higher-quality varieties from a range of 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 narrow and more vulnerable to pests and diseases.
