Location: Sugarcane Field Station2011 Annual Report
1a. Objectives (from AD-416)
1. Develop more efficient breeding and selection methodologies for cultivar development and to produce seed of selected sugarcane germplasm for use in Florida, Louisiana, and Texas. 2. Develop better agronomic practices for the Florida sugarcane industry. 3. Identify alleles or genes that can be used in molecular marker-assisted selection to complement the conventional approach of sugarcane cultivar development. 4. Identify agronomic and physiological relationships of sugarcane with stress tolerance to improve sugarcane cultivar development.
1b. Approach (from AD-416)
Development of new cultivars with disease resistance, freeze tolerance, and high sucrose content will be advanced through genetic and genomics approaches. These will involve the utilization of a sugarcane genetic map with quantitative trait loci (QTL) and the identification of variation in candidate genes through gene expression profiling, and in some cases through developing markers for gene insertions. To improve cultivar development on sand soils, genetic studies will compare selection efficiencies on organic and sand soils and repeatability between selection stages, and agronomic research will seek useful traits for identifying high-yielding genotypes on sand soils. Agronomic research will also seek useful traits for identifying tolerance to shallow water tables on organic soils, and will examine sampling procedures for estimating fiber content.
3. Progress Report
As new diseases and new races of current diseases infect previously resistant cultivars, the yields of these cultivars are reduced. The most recent challenge facing Florida sugarcane growers is the introduction of orange rust. True seeds, developed from crosses at Canal Point, Florida, were sent to the ARS cultivar development program in Louisiana, and Texas A&M University program, Texas. It is estimated that there were 77,609 seeds from 278 crosses sent to Louisiana; 53,602 seeds from 95 crosses sent to Texas; and 716,257 seeds from 998 crosses remained in Florida. Cultivars developed by ARS occupy more than 97% of the sugarcane acreage in Florida. This breeding and selection program develops sugarcane cultivars for sand and organic (muck) soils in Florida. Improvements are needed in for cultivar selection for sand soils. In 2011, all stages of the selection program were planted on sand soils, beginning with the seedling stage (but bypassing Stage 1 and going directly to Stage 2). In addition, all stages of the selection program were conducted on muck soils. Three recently released varieties CP 03-1912, CP 00-1101, and CP 01-1372 are being expanded rapidly by growers with sand soils. In addition, in 2011, there were six new varieties released. Three of these six were specifically for sand soils, two were for muck and sand soils, and one was for muck soils. Indications are positive that changes made in selecting for resistance to the brown and orange rust diseases are resulting in the ability of this program to release varieties with resistance to these diseases as four of the six newly released cultivars were resistant to both rusts and two cultivars were moderately susceptible to orange rust. In research to conserve muck soils on which sugarcane in Florida is grown, to help growers meet Best Management Practices for reduction of phosphorus export, a lysimeter and two pot experiments were conducted to learn how shallow water tables and periodic flooding affect the roots and growth of recently planted sugarcane. A DNA sequence polymorphism that separates pathogenic isolates originating from the Western and Eastern Hemispheres was discovered in the orange rust pathogen Puccinia kuehnii a future breeding challenge of the Canal Point program is to develop sugarcane cultivars resistant to both strains. Developing varieties that tolerate freeze conditions is an important aspect of our breeding research. To understanding how sugarcane responds to freeze, the timecourse deterioration in the sucrose profile of elite sugarcane genotypes was studied under field conditions and the physiological underpinning of freeze tolerance was investigated by screening several sugarcane germplasm under controlled conditions. Water deficit during the early growing season is a key abiotic stress which limits sugarcane yields on sand soils in Florida. Pot studies indicated that nondestructive measurements of chlorophyll fluorescence and leaf photosynthesis could be useful for early detection of sugarcane water-deficit stress. Field studies are underway to test if these physiological traits can be used to screen and evaluate sugarcane genotypes.
1. Improving control of brown and orange rusts of sugarcane. Orange rust of sugarcane, a new disease in the western hemisphere, has caused substantial yield losses in Florida and Central America and recently arrived in Brazil. Brown rust of sugarcane has been a major problem in many sugarcane regions for decades. After using traps to collect rust spores, ARS researchers at Canal Point, Florida, developed methods to determine atmospheric concentrations of orange and brown rust spores in Florida and Louisiana. In 2010, spores of orange rust were detected in Louisiana, suggesting that orange rust may soon infect sugarcane in Louisiana. Fluctuations in orange rust spore concentrations over time coincided with changes in environmental conditions and preceded increases in disease severity in Florida. Results from these spore traps are helping determine when Florida sugarcane growers should apply fungicides for disease control of both rust diseases and to develop models that will help sugarcane growers around the world predict heavy brown and orange rust infection periods based on weather data.
2. Release of six high yielding sugarcane cultivars in Florida. New sugarcane cultivars in Florida are continuously needed for sustained or improved yields, resistance to intense disease pressures, and for improved adaptability to freezes. Also, higher yields are needed on sand soils which comprise about 20% of Florida’s sugarcane; muck soils comprise the remaining 80%. ARS researchers at Canal Point, Florida, cooperated with scientists from the University of Florida, Institute of Food and Agricultural Sciences, Everglades Research and Education Center at Belle Glade, Florida, and the Florida Sugar Cane League, Inc. at Clewiston, Florida, to recommend the release of six new sugarcane cultivars (CP 04-1566, CP 04-1844, CP 04-1935, CPCL 95-2287, CPCL 02-0926, and CPCL 02-1295) in Florida. The new cultivars will provide Florida sugarcane growers high yields and additional variability for disease resistance. Florida is the state in the U.S. with the highest sugar production; 19% of all sugar produced in the U.S. CP 04-1566, CP 04-1844, and CP 04-1935 are expected to improve yields for Florida growers with sand soils; CPCL 95-2287 is expected to improve yields for growers with muck soils; and CPCL 02-0926 and CPCL 02-1295 are expected to improve yields for all sugarcane growers in Florida (growers with sand or muck soils).
Zhao, D., Glaz, B.S., Comstock, J.C. 2010. Sugarcane Response to Water-Deficit Stress during Early Growth on Organic and Sand Soils. Amer. J. of Agr. and Biological Science. 5(3):403-414.