ENHANCEMENT OF SUGARCANE GERMPLASM FOR DEVELOPMENT OF CULTIVARS AND SUSTAINABLE PRODUCTION
Location: Sugarcane Production Research
Title: Field Response of Sugarcane Genotypes to Freeze Stress with Genotype x Environment Effects on Quality Traits
Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 9, 2012
Publication Date: December 11, 2012
Citation: Edme, S.J., Glaz, B.S. 2012. Field Response of Sugarcane Genotypes to Freeze Stress with Genotype x Environment Effects on Quality Traits. Journal of Crop Improvement. 27:1-30.
Interpretive Summary: The occurrence of a damaging freeze represents a serious economic risk to both young and mature sugarcane in Florida in spite of its sporadic nature. Freeze temperatures of -4oC (25oF) substantially reduce sucrose yield in the three mainland US states (Florida, Louisiana, and Texas) where sugarcane is grown. The cooperative (USDA-ARS, University of Florida, and Florida Sugar Cane League, Inc.) sugarcane breeding program located at Canal Point routinely tests genotypes in the last stage of selection at the Agronomy farm of the University of Florida, located at Hague, FL, which every year experiences freeze events down to -8oC (18oF). This study investigated the ‘keeping quality’ or deterioration of juice traits (Brix, pol, and sucrose content) in genotypes from three different Series (CP 01, CP 02, and CP 03) at Hague and at Canal Point along with three cultivars (CP 78-1628, CP 72-2086, and CP 89-2143) as checks. The profiles were examined in the plant cane for the CP 01 and CP 02 Series during the 2006-07 season and through the first-ratoon crop for the CP 03 Series during the 2007-09 seasons. Hague experienced more intense freeze nights (17-22 d yr-1 with temperatures ranging from -0.4oC to -8oC) than Canal Point (2 nights, rarely down to -2oC/24.8 oF). The genotypes reached their peak sucrose levels at about the same time at both locations. All three traits were affected by the freezes at Hague, and Brix was affected less than pol and sucrose. Temperatures around -2oC increased the sucrose content in the majority of genotypes whereas temperatures =-4oC hastened juice deterioration. Four groups of genotypes were identified in the CP 01 and CP 02 Series: a susceptible group in the minority that showed a decline of 0.21% per day in sucrose content with temperatures around -2oC, the other groups being more or less tolerant as they increased in sucrose content by 0.002-0.024% per day at temperatures between -2oC and -3oC followed by a decline of 0.15-0.18% per day when temperatures dropped to =-4oC. Genotypes with the highest sucrose content at the onset of the freeze events maintained the highest levels throughout the season. However, early (Nov-Dec) freeze events in the -4oC, as experienced by the CP 03 Series genotypes at Hague, produced two groups of genotypes, one with sucrose content decreasing by 0.25% per day and the other by 0.32% per day. The majority of the genotypes tested, along with CP 78-1628 and CP 89-2143 as benchmarks of cold tolerance in the industry, belonged to the most tolerant groups, whereas CP 72-2086 and similar genotypes belonged to an intermediate tolerance group. At Canal Point where the temperatures were milder, the rates of increase in sucrose content were higher than at Hague and the rates of decrease lower. This study provided a clear understanding of the level of tolerance to freeze available in the CP varieties and the information is used by cane growers and researchers to make practical decision on cultivar release and harvest scheduling of released varieties when a hard freeze hits Florida.
Freeze stress is a constraint to sugarcane (Saccharum sp.) with negative effect on sucrose yield, particularly during the harvest season. To understand its impact on the performance of genotypes developed by the Canal Point (CP) breeding program, the genotype by environment (GxE) interaction was appraised via additive main effects and multiplicative interactions (AMMI) and group-based trajectory modeling (GTM). Forty-five selections of the CP 01, CP 02, and CP 03 Series and three cultivars were examined in separate replicated field tests at Hague and at CP, FL in the plant cane (CP 01-CP 02 in 2006-07) or through the first ratoon (CP 03 in 2007-09). Profile analyses of Brix, pol, and sucrose content (SC) were developed from stalk samples taken at three time points yr-1 to follow their time-course deterioration. Hague experienced more intense freeze nights (17-22 d yr-1 with temperatures (TC) from -0.4oC to -8oC) than CP (2 nights, rarely down to -2oC). All three traits were affected, and Brix was affected less than pol and SC. Temperatures = -2oC increased SC in the majority of the genotypes and TC=-4oC hastened juice deterioration in all genotypes. The response was generally nonlinear when TC gradually declined from 0 to -4oC, but linear after early freeze events =-4oC. AMMI was an appropriate modeling approach for interpreting the GxE variation. The contribution from environments (location-year-samplings combinations) was more important than that attributed to G or GxE. AMMI1 and GTM identified two to four reaction norms as differential performance under freeze events: a susceptible group in the minority with SC declining constantly with TC; the other groups typifying the modal profile with an increase in SC with 0=TC =-2oC and a decline with TC=-4oC, but differentiated by the initial SC level and/or its rates of increase or decrease. Genotypes with the highest SC at the onset of freeze tended to hold this level longer than those with the lowest content.