OPPORTUNITIES TO INCREASE RATES OF PARENT IMPROVEMENT IN AUSTRALIAN SUGARCANE BREEDING PROGRAMS

BSES plant improvement programs continue to deliver new, improved cultivars to the Australian sugar industry that offer improvements over existing cultivars. However, examination of recently released cultivars reveals many have parents that are quite old, suggesting limited generation-wise gains in parent performance is occurring. If large generation-wise gains in parent performance were evident, it would be expected that the best young parents would be significantly better than the best old parents. Data from the 1993 to 2000 series of routine progeny assessment trials in the plant improvement programs for the Southern, Central and Burdekin districts were analysed to determine the influence of parental age on parent performance. These analyses revealed that younger parental age usually had a positive effect on general combining ability for CCS and sugar yield. Nevertheless, it was possible to find elite parents of any age, with the best old parents often as good as the best new parents, despite extensive use of new parents. This suggests that parents should not be discarded from the breeding program based purely on their age. Explanations for lack of clear generation-wise improvement are presently unclear. However, alternative breeding strategies to those currently used are proposed. These include crossing designs that utilise gene action associated with specific combining ability effects, and approaches to allow better estimation of general combining ability effects.