Damage assessment for selection of resistance to the spotted stalk borer and genetic correlations for resistance and yield components in sugarcane

We conducted an assessment of the stalk damage of the spotted borer, Chilo sacchariphagus (Bojer), on 65 cultivars and elite clones under natural infestation conditions in Réunion Island, with the objectives (i) of comparing seven damage measures on the basis of their quantitative genetic parameters and (ii) of studying the relationships between borer resistance and sugarcane yield components. The heritabilities of the damage measures related to counts of borer exit holes were low, whereas the heritabilities of the damage measures related to bored stalks or internodes were high and similar amongst them. The percentage of bored stalks exhibited high phenotypic and genotypic correlations with the other damage measures, and appeared as the best cost effective damage measure. Genetic correlations revealed a negative relationship between resistance to borer and cane yield, due to a relationship of stalk damage with stalk length and (in a lesser extent) with stalk number. No significant genetic relationship between resistance and sugar content parameters was observed.