Changes in juice quality and sugarcane yield with recurrent selection for sucrose

Sugarcane (Saccharum spp. hybrids) breeding programs in Louisiana have made improving sucrose content a top priority because a short growing season limits cane yield. Using a recurrent selection strategy, the cultivars with the highest sucrose content are crossed, and a new generation of cultivars is selected from the progeny. This study was designed to determine how selection primarily for sucrose content has modified physiological characters, and impacted sucrose content and yield. Five cultivars were randomly selected from each of seven generations of recurrent selection in Louisiana and planted in two experiments. The plant and first stubble crops were harvested late in the harvest season from each experiment. Cane yield and juice quality were determined. Cultivars from the last three generations were superior to cultivars from the first three generations for Brix % cane, sucrose % cane, purity, theoretically recoverable sugar (TRS), cane yield and sugar yield. Fiber % cane was not different among the generations. Selection primarily for sucrose has increased Brix % cane from 14% to 16%, sucrose % cane from 12% to 14%, purity from 82.5% to 87.3%, and TRS from 98 to 122 kg Mg⁻¹. A plateau in juice quality and sucrose yield in the last three generations may indicate that: (1) Louisiana's short growing season may restrict sucrose accumulation; (2) the genetic potential for late season juice quality has been reached with currently available germplasm; or (3) the inclusion of lower juice quality Saccharum spontaneum germplasm into the breeding program in order to increase disease tolerance, cold tolerance, and ratooning ability has diluted the effect of recurrent selection for sucrose.