Location: Sugarcane Field Station2012 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 129,757 seeds from 531 crosses sent to Louisiana; 45,723 seeds from 85 crosses sent to Texas; and 708,611 seeds from 726 crosses remained in Florida. Cultivars developed by ARS occupy more than 86% 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 cultivar selection for sand soils. In 2012, for the second consecutive year, all stages of the selection program were planted on sand soils, beginning with the seedling stage. In addition, all stages of the selection program were conducted on muck soils. Four recently released varieties CPCL 97-2730, CP 03-1912, CP 00-1101, and CP 01-1372 are being expanded rapidly by growers with sand soils. In addition, in 2012, there were five new varieties released. One of these five was specifically for sand soils, two were for muck and sand soils, and two were 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 all five releases were fully resistant to brown rust and three of the five were fully resistant to orange rust. One of the five was susceptible to orange rust. Researchers in France identified a gene in sugarcane that confers resistance to brown rust. It was demonstrated that this gene has had an increasing presence in selected material in the Canal Point breeding program since brown rust arrived in Florida in 1978. This indicates that this breeding program had been unknowingly selecting for the presence of this gene. Further, the group at Canal Point started selecting for this marker (Bru1) beginning with Stage 2 of their selection program this year. This was the first report of an application of marker assisted selection in sugarcane. It was found that genotypes with high sucrose content tolerate freeze better than low sucrose genotypes and that temperatures =-4oC are detrimental to all sugarcane genotypes. Proteins relevant to freeze tolerance in other crops were identified in sugarcane and can be used as biomarkers. Microsatellite markers were also developed for screening. 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 stomatal conductance, chlorophyll fluorescence and leaf photosynthesis could be useful for early detection of sugarcane water-deficit stress. Field studies are underway to test if theses physiological traits can be used to screen and evaluate sugarcane genotypes for stress tolerance.
1. Marker assisted selection in sugarcane for disease resistance. Brown rust causes severe yield losses of sugarcane in Florida and also severely impacts the sugarcane breeding program that provides new varieties for growers. In collaboration with private researchers in Florida, and one of the researchers who discovered the Bru1 gene for resistance to brown rust in France, ARS researchers at the Sugarcane Field Station in Canal Point, FL applied the use of this molecular marker (Bru1) to their sugarcane breeding program. This was the first reported application of marker assisted selection in sugarcane. They learned that the Bru1 gene is prominent in their selected varieties and that while it will be helpful for making progress for brown rust resistance, they also need to be cautious and be sure that all of their resistance to brown rust is not due to the Bru1 gene.
Zhao, D., Comstock, J.C., Glaz, B.S., Edme, S.J., Glynn, N.C., Del Blanco, I.A., Gilbert, R., Davidson, W., Chen, C.Y. 2012. Vigor rating and brix for first clonal selection stage of the Canal Point Cultivar Development Program. Journal of Crop Improvement. 26:60-75.