Traits for canopy development and light interception by twenty-seven Brazilian sugarcane varieties

Since new varieties are released continuously in the Brazilian sugarcane agro-industry, the understanding of their growth, development and yields are necessary. In Brazil, there is a lack of studies on sugarcane variety traits for canopy development and yields, especially those employed by the sugarcane modelling community. This paper assessed the canopy development and light interception by 27 sugarcane varieties grown at two tropical sites (Sao Romao, MG, and Guadalupe, PI) under non-limiting (potential) conditions in Brazil and tested the capability of the well-known APSIM-Sugar model to distinguish these varieties. Parameters for APSIM-Sugar canopy traits (leaf size, green leaf number, tillering and stalk emergence) and the light extinction coefficient were derived for each variety from field experiments and by calibration for the plant cane cycle. Trait parameters were then validated satisfactorily against independent datasets from the same two sites (first racoon cycle of 27 varieties) and a row spacing experiment at Sao Romao (plant and racoon for six varieties). A validation was also done using published experiments in other five sites across Brazil (four varieties). After APSIM-Sugar parameters were calibrated and validated, long-term simulations were run for each variety at the two sites. APSIM-Sugar outputs of thermal time to reach 50% of canopy closure were employed to group the varieties in terms of canopy formation by clustering analysis. The four major clusters corresponded well with promotional information from breeding companies in Brazil about canopy formation. These findings suggest it is reasonable to hypothesise that the APSIM-Sugar parameters are plausible and are an important step for unravelling genetic x environment x management interactions to improve yields and quality in the Brazilian sugarcane agro-industry