RELATIVE ECONOMIC GENETIC VALUE (rEGV)—AN IMPROVED SELECTION INDEX TO REPLACE NET MERIT GRADE (NMG) IN THE AUSTRALIAN SUGARCANE VARIETY IMPROVEMENT PROGRAM

NET MERIT Grade (NMG), a selection index developed more than 40 years ago, has been used exclusively by breeders to rank and select clones in the Australian sugarcane breeding programs. However, due to substantial changes in production systems, there are now important weaknesses with NMG, and an improved index is highly desirable. For example, NMG underestimated the economic value of commercial cane sugar (CCS) relative to cane yield in selection trials. Sugarcane breeders have been arbitrarily awarding an extra bonus for higher CCS varieties when making decisions on which varieties should be promoted for further testing. In addition NMG only considers measurements on four crop traits (CCS, cane yield, fibre content, and appearance grade). Other important traits, such as disease resistance, are not included. Therefore a new selection index addressing these issues was developed for use in the BSES-CSIRO Variety Improvement Program. In this paper we will introduce this newly developed selection index, relative Economic Genetic Value (rEGV). rEGV combines economic and biological/genetic information to evaluate the economic merit of clones to the whole industry. Its implementation and impact on the BSES-CSIRO breeding program are discussed.