Suckering: a facet of ideotype selection and declining CCS in the wet tropics

Declining CCS in the northern sugar industry in the past six years largely can be ascribed to dilution of mature-stalk CCS by increased sucker-culm content in the crop resulting from climatic change. This research collected culm composition and quality component data from two trials containing a broad range of clonal variation. Subjective and objective estimates of sucker-culm contribution and full quality component analyses were obtained for mature stalks and sucker culms. There was wide clonal variation for sucker-culm content. Ranges for sucker-culm and mature-stalk component values were discrete for all components except fibre. Genetic variation was restricted more for all mature-stalk components than for most sucker-related measures. Despite subjective and objective sucker-culm estimates being moderately correlated, exploration of net merit grade options using these showed the concept was well applied in practice. Net merit grade was highly predicted by the independent variables used, but a modification proposed adjusts the relative contributions of these to more equitable levels. There is ample genetic variation for propensity to sucker and selection for clones of low suckering propensity will be successful. The proposed net merit grade change equalises the relative contribution of appearance, or ideotype, assessment and CCS difference at about 56% of the level of relative economic value.