Early stage selection for commercial cane sugar (CCS) in sugarcane clones: effects of time of sampling and irrigation

Commercially recoverable sugar content in sugarcane (CCS, expressed as a percentage) is a key selection criterion in sugarcane breeding programs. In some sugarcane breeding programs there may be significant operational advantages in measuring CCS early in the crop growth cycle, well before commercial harvesting would normally commence, and in restricting growth by withholding irrigation to reduce cane yield and lodging. Two field experiments were conducted to investigate these effects. The experiments included clones representative of genotypes routinely assessed in the earliest stages of clonal selection in breeding programs. Differences among genotypes for CCS were expressed early when cane had very low CCS (in February or March), and then rates of increase in CCS following that time were similar in most genotypes. Therefore, time of sampling had little effect on ranking of genotypes for CCS, and selection for high CCS could be effective early in the year. Irrigation regime also had little effect on ranking of the clones for CCS, indicating that mild water stress could be imposed with no adverse effect on selection results. The results are discussed in relation to optimising selection procedures and systems in early stage selection trials in sugarcane breeding programs, and better understanding the physiological basis of genetic variation in CCS.