PRODUCTIVITY INCREASES FROM NEW VARIETIES IN THE QUEENSLAND SUGAR INDUSTRY

MEASURES of the contribution of new varieties to improving sugarcane productivity are important but have been difficult to obtain. Large seasonal variation, expansion on to more marginal soils, and the contribution of improved agronomic practices are some of the problems associated with isolating varietal effects on productivity in the broad sense. Commercial productivity data of individual varieties (tonnes, hectares, cane yield, CCS and sugar yield) are available to varying degrees across the Australian industry. However, these data have remained fragmented across mills and regions. Recently, a database was created with available information on varietal performance in the period 1980 to 2003, as well as the release dates of all varieties in each region. While the dataset has some missing information, it does allow robust analyses of the impact of new varieties on productivity. Restricted maximum likelihood methods were used to analyse this highly unbalanced dataset. Weightings were applied to productivity data based on the percentage of the crop of each variety in each mill area and season. Best Linear Unbiased Predictors were used to estimate varietal effects for cane yield, CCS and sugar yield and to determine commercially realised genetic gain over various periods in different regions. Significant and substantial genetic gains for cane yield, sugar yield and, to a lesser extent CCS, were found in all regions over the past 30 years. Average sugar yield increases of 0.13–0.31 tonnes of sugar per hectare per year indicate that new varieties have made and are continuing to make a major contribution to the viability and profitability of the Australian sugar industry. These data will be updated annually and analyses will be performed on an on-going basis to benchmark future rates of genetic gain. Estimates of the return on the sugar industry investment in plant breeding are also possible from these data. Currently, this equates to an additional gross income of over $20 million each year.