Site and Saccharum spontaneum introgression level drive sugarcane yield component traits and their impact on sucrose yield in contrasted radiation and thermal conditions in La Réunion

Multivariate mixed model of log transformed yield components was adjusted to estimate each component's contribution to sucrose yield genetic variance, taking into account interrelationships among components. Each component's contribution to sucrose yield variance was site-dependent. On the low altitude site with high photo-thermal conditions, stalk section was the main contributor to yield variance, while on the high altitude site with low photo-thermal conditions, stalk height was the main contributor. A linear regression showed that the estimated proportion of S. spontaneum genome in the hybrids' genome had significant effects on sucrose yield and its components. These effects also varied with the site: under low altitude conditions, the estimated proportion of S. spontaneum genome in the hybrid's genome exerted a significant negative effect on sucrose yield, whereas no significant effect was found under high altitude conditions. These results suggest that both efforts toward introgression and selection on yield components for sugarcane breeding purposes should depend on the targeted cropping environment.