Field Response of Sugarcane Genotypes to Freeze Stress with Genotype x Environment Effects on Quality Traits

Freeze stress negatively affects sucrose yield in sugarcane (Saccharum spp. hybrids), particularly during the harvest season. To understand its impact on the performance of genotypes in the Canal Point (CP) breeding program, the genotype-environment (GxE) interaction was appraised via additive main effects and multiplicative interactions (AMMI) analysis and group-based trajectory modeling (GTM). Forty-five selections of the CP01, CP02, and CP03 series and three cultivars were examined in replicated field tests at Hague and Canal Point, Florida, in the plant-cane (CP01-CP02 in 2006-07) or through the first ratoon (CP03 in 2007-09). Profile analyses of Brix, pol, and sucrose content (SC) were developed from stalks sampled at different times of year to follow their deterioration. Hague experienced more intense freeze nights (17–22 d yr−1 with temperatures [TC] from −0.4 °C to −8 °C) than CP (2 nights, rarely down to −2 °C). Temperatures ≥−2 °C increased SC in a majority of the genotypes and TC ≤ −4 °C hastened juice deterioration. The response was nonlinear when TC gradually declined from 0 ° to −4 °C, but linear after early freeze of ≤−4 °C. The AMMI analysis was appropriate for interpreting the GxE interaction variation, indicating a greater contribution from environments (location-year-sampling combinations) than from G or GxE interaction. The AMMI and GTM identified two to four reaction norms as differential performance under freeze: a susceptible group in the minority with SC declining constantly with TC; the other groups typifying the common profile had an increase in SC with TC ≥ −2 °C and a decline with TC ≤ −4 °C. Genotypes with the highest SC at the onset of freeze tended to hold this level longer than those with the lowest content. The identification of different reaction norms suggests that a genetic component may underpin freeze adaptation in modern sugarcane cultivars relative to the old tropical hybrids. However, breeding efforts to increase the tolerance of sugarcane cultivars to temperatures