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United States Department of Agriculture

Agricultural Research Service

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SRU Research Update
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Sugarcane Varieties L 99-226 and L 99-233 Released in 2006 for Commercial Planting in Louisiana.  Higher yielding and more pest-tolerant sugarcane varieties are needed to insure the sustainability of the U.S. sugarcane farmer.  ARS scientists at the SRU played a pivotal role in the development of all varieties now in commercial production in Louisiana to include the release of two new varieties L 99-226 and L 99-233 in 2006.  ARS scientists are also responsible for identifying desirable traits from wild species and transferring them into breeding lines containing other desirable traits that can then be used as parents to broaden the genetic base upon which the commercial varieties are developed. This long-term "basic" breeding program has made and continues to make a substantial economic impact on the Louisiana sugarcane industry.  ( )


DNA markers identified for use in sugarcane BREEDING AND SELECTION.  The general utility of 221 sugarcane simple satellite repeat (SSR) DNA markers from the International Sugarcane Microsatellite Consortium (ICSB) was evaluated as a means of molecularly differentiating (fingerprinting) sugarcane varieties has never been fully tested on the varieties being used in ARS's sugarcane breeding program.  Using a fluorescence labeling/capillary electrophoresis-based molecular genotyping system, these 221 markers were evaluated for polymerase chain reaction (PCR) robustness, frequency of irregular PCR products, and the ability to reveal the extent of genetic variability among five representative sugarcane clones from Louisiana and Florida.  Sixty-seven SSR markers were found to produce highly robust and distinctive DNA fragments for the varieties being tested.  Sugarcane breeders are using these SSR markers to molecularly identify the varieties being used as parents and to evaluate the success of their crossing efforts in producing hybrid seedlings from these crosses. (


NEW PARENTAL LINES OF SUGARCANE DEVELOPED.  All of the sugarcane varieties commercially grown in the continental United States (U.S.) can trace their ancestry to one female parent. Black Cheribon, a non-thrifty chewing cane from New Guinea that is incapable of surviving most winters in Louisiana.  The weedy species of sugarcane (Saccharum spontaneum) is better adapted to sub-tropical environments.  As part of NP 301's component IIb (Genetic Improvement), we developed several new lines of hybrids with an array of backgrounds using S. spontaneum as the female parent.  The utilization of S. spontaneum as the female parent was made possible because of advances made at the SRU in using molecular markers to identify parents and the offspring resulting from these crosses.  Several of these lines have been shown to have sucrose contents that match those of current commercially grown varieties.  These lines will be used as parents during the 2006 crossing season in the hopes of developing sugarcane varieties with improved cane and sugar yields over a range of environments.  ( )


DIFFERENTIATED PARENTS IN A SEVEN-PARENT POLYCROSS USING DNA MARKERS.  Sugarcane geneticists have long recognized that polycrosses (as opposed to bi-parental crosses) can greatly increase the number of genetic combinations among parents in a crossing season.  There has been a reluctance to make polycrosses because the male parent could not be determined with any degree of certainty, resulting in a rapid loss of pedigree information over time.  As part of NP 301's component II b (Genetic Improvement), we demonstrated that we could positively identify the male parent in over 90% of the progeny originating from a seven-parent polycross, using seven highly specific  microsatellite markers.  We also learned that self pollination occurs more frequently in a polycross than had been heretofore imagined, which brings into question the advisability of applying family selection in polycross progeny in early selection stages.  (


EVALUATED CANE AND SWEET-SORGHUM VARIETIES AS POTENTIAL BIOENERGY CROPS.  To remain sustainable, sugarcane growers must be able to produce other "saleable products" from the harvested sugarcane stalks.  As part of both NP 301 (Genetic Improvement) and NP 306 (New Uses, Quality, and Marketability of Plant and Animal Products), we are evaluating varieties rejected from our sugarcane program based on unacceptably high fiber contents as possible high biomass producing energy canes for a cellulose to ethanol bio-fuels industry.  We are also evaluating the integration of these energy canes with sugarcane production and the growing of other grass crops such as sweet sorghum to insure a continuous supply of feedstock to a cellulose conversion facility.  Both the high fiber energy cane and the sweet sorghum crops could be harvested outside the timeframe that sugarcane is normally harvested for sugar; sorghum in late summer and energy cane in the winter months of January-March.  Having a viable bioenergy crop complimentary to sugarcane would be a boon to the Southern U.S. sugar industry and would help the U.S. in meeting its renewable energy targets.  ( )


Effect of Sugarcane Yellow Leaf Virus on Sugarcane Yield and Juice Quality DEFINED.  Sugarcane yellow leaf virus (SCYLV) was first detected in Louisiana sugarcane in 1996; however, the effect of the virus on the productivity and processing of sugarcane in Louisiana was unknown.  This research demonstrated that cane and sugar yields were reduced in the third production year of LCP 85-384, the leading commercial variety in Louisiana and that excess starch accumulated in green leaves and the immature portions of the stalk of the SCYLV-infected plants of LCP 85-384 and Ho 95-988, another recently released variety, during all three production years.  Elevated starch levels in the cane delivered to the mill reduces processing efficiency.  The majority of green leaves and immature sections of stalks is normally removed when cane is harvested with chopper harvesters; however, these tissues may not be removed if the harvester is not being operated at full extractor fan efficiency, when the cane is lodged, or when harvesting under rainy conditions.  The results of this research contributed to the decision to establish a maximum level of SCYLV infection that would be tolerated in fields of seed cane certified by the Louisiana Department of Agriculture and Forestry. (


DISEASE RESISTANCE INFORMATION CONTRIBUTES TO THE RELEASE OF SUGARCANE VARIETIES FOR COMMERCIAL SUGAR PRODUCTION.  Disease resistance information developed by the SRU's pathologists contributed to the release of one variety in 2003, HoCP 96-540; two varieties in 2004, Ho 95-988 and L 97-128; and two varieties in 2006, L 99-226 and L 99-233 by the Louisiana Sugarcane Variety Advancement Committee composed of researchers from ARS, and Louisiana State University, and farmers, millers, and staff of the American Sugar Cane League.  In experimental tests, the varieties met or exceeded the yield of the current leading variety, LCP 85-384, and were resistance or moderate resistance to mosaic and leaf scald. Ho 95-988 and HoCP 96-540 had higher levels of RSD resistance than any variety recently grown in Louisiana.  The varieties should provide growers an excellent alternative to the planting of LCP 85-384 and lessen the vulnerability of the industry to the introduction of a new disease or biotype of a disease already present in the industry. The greatest constraint to releasing a sugarcane variety with improved characteristics is the long testing cycle (12-14 years) and the difficulty of incorporating a large number of desirable traits into a single variety. (


DISEASE THREATS MONITORED.  The introduction of new diseases is a threat to the profitability and efficiency of sugarcane growers and processors.  Monitoring the sugarcane industry for exotic pathogens as proposed in Objective 4 which addresses Component 4, Pathogen Biology, Genetics, Population Dynamics, Spread and Relationship with Host and Vectors, of the NP303 Action Plan uncovered a new sugarcane pathogen.  In 1996, a new pathogenic virus, sugarcane yellow leaf virus (SCYLV), was discovered in Louisiana.  Research was initiated to determine the effect of this new pathogen on sugarcane grown in Louisiana and to develop disease management strategies to control the pathogen.  Initially, research was limited because the known aphid (Melanaphis sacchari) vectors required for transmission were not discovered in Louisiana until 1999.  In the course of the current program cycle, a protocol for transmission of SCYLV by M. sacchari in the greenhouse was developed and differences in variety susceptibility to infection were demonstrated.  Field experiments have also revealed differences in susceptibility of varieties to the virus and the effects of the virus on sugar and cane yields as well as changes in juice quality that can affect processing efficiency.  The demonstration of the adverse effects of SCYLV infection on sugarcane contributed to the decision to inspect commercial seed cane fields and to establish a tolerance level of SCYLV infections in fields to be certified by the Louisiana Department of Agriculture and Forestry.  Since most growers used commercially available certified seed cane, this regulatory action will reduce the incidence of the virus disease and its impact on the crop and processing efficiency at the mills.  Information about the susceptibility of varieties is shared with sugarcane breeders for the development of varieties with resistance to the SCYLV. (


OLD DISEASE HAS MANY FACES.  Mosaic, has caused significant losses in yield for sugarcane farmers in the past and, even though currently grown varieties are resistant to the disease, the possibility of new strains of the virus that can overcome the resistance remains a concern.  An ongoing impact of the disease is that many promising varieties in the breeding program continue to be eliminated because of susceptibility to mosaic.  We continue to monitor the sugarcane industry for new biotypes of mosaic and other pathogens as proposed in Objective 4 also addresses Component 4, Pathogen Biology, Genetics, Population Dynamics, Spread and Relationship with Host and Vectors, of the NP303 Action Plan.  A study of virus isolates collected from sugarcane exhibiting mosaic symptoms revealed that some isolates appear to be different from previously described strains and that some isolates may represent a virus not reported to cause mosaic in Louisiana sugarcane.  The potentially new virus or virus strains are currently being characterized with molecular techniques and for their ability to attack different sugarcane varieties.  The study also indicated that different strains of the viruses may become predominant at different times.  As a result of this observation, a mixture of strains is used to screen new germplasm for mosaic resistance. (


DNA FINGERPRINTS USED TO IDENTIFY PATHOGENS.  The development of diagnostic procedures based on the unique nucleic acid (either DNA or RNA) sequences of bacterial and viral pathogens in infected sugarcane tissue helps ensure disease-free seed cane for the sugarcane industry.  Polymerase chain reaction (PCR) assays and improved immunoassay techniques for the major bacterial and virus diseases of sugarcane in Louisiana that were developed in the preceding program cycle and validated during this program cycle are used in quarantine facilities to prevent diseased foreign sugarcane stalks from coming into the U.S.A. mainland and in local laboratories to safely permit interstate germplasm exchange.   Accurate and quantitative diagnostic procedures are also critical to the evaluation of research being conducted in each of the four objectives of this project.  During the current program cycle, a real-time RT-PCR protocol was developed for the detection and quantification of the sugarcane yellow leaf virus (SCYLV).  These protocols are providing breeders and pathologists with better tools for monitoring disease epidemics and for evaluating breeding lines and experimental varieties for susceptibility to these diseases.  (


New herbicides for sugarcane evaluated.  Weed control at planting and in the spring during crop establishment is vital in order to attain yields profitable to sugarcane growers.  Herbicidal weed control options within sugarcane crops are limited with many acting through the same mode of action, the inhibition of photosynthesis.  Scientists at the SRU have continued to evaluate several herbicides applied alone and in mixtures for the control of bermudagrass, itchgrass, morningglory, and johnsongrass (seedling and rhizome) when applied as single and sequential applications.  Introducing new herbicides for use in sugarcane will broaden the effective modes of action being utilized which has implications for herbicide resistance management and will reduce effective application rates, reducing environmental impact, as these new herbicides are effective at much lower use rates than herbicides traditionally used in sugarcane.  In a continuing study, the new herbicide trifloxysulfuron-sodium (Envoke?), in combination with the herbicide asulam (Asulox?), has been shown to improve control of rhizome johnsongrass compared to asulam alone, and for the first time in 2006, the herbicide mesotrione (Callisto?) was evaluated for crop safety of broadleaf weed control in sugarcane.  The research conducted by SRU scientists was used by the Louisiana Cooperative Extension Service in the development of weed control recommendations contained in its 2006 Sugarcane Production Handbook.  (


New Sugarcane Ripeners Evaluated.  Harvesting of sugarcane in Louisiana begins before the natural ripening of the sugarcane is complete.  In order to increase sugar yields, much of the sugarcane is treated with low rates of the herbicide, glyphosate. Glyphosate has been recently shown to negatively impact gross yields in the treated crop and may negatively impact the regrowth of the crop the following year (ratoon crop), especially if harvest is delayed too long following treatment.  Currently glyphosate is the only chemical ripener registered for use in Louisiana sugarcane.  Several potential sugarcane ripeners were evaluated for their potential use in Louisiana sugarcane, including trinexapac-ethyl (Palisade?), nicosulfuron (Accent?), and imazapyr (Arsenal?), which were all shown to be promising alternatives to glyphosate.  This research will be continued and expanded in order to provide new alternatives for sugarcane ripening with greater safety to sugarcane crops.  (


YIELD REDUCTIONS ASSOCIATED WITH BERMUDAGRASS COMPETITION ASSESSED.  Sugarcane growers in Louisiana usually spend well over $100/ha annually on herbicides for weed control with additional money being spent on mechanical control of weeds (cultivation).  Recent studies by Sugarcane Research Unit (SRU) scientists have shown bermudagrass, not controlled at planting, can reduce sugar yields in the subsequent first production year (plant-cane crop) by as much as 32% even if the bermudagrass is completely removed in March at the start of the growing season. Yield losses in second and third production years (ratoon crops) were less and often insignificant and total sugar yield losses for the three-year crop cycle were as high as 15%.  This study shows the importance of eliminating bermudagrass from sugarcane fields prior to planting, as the majority of yield losses occurred during the plant-cane establishment period.   The results of these studies will help in formulating recommendations to growers in order to improve management of these problem weeds while showing the impacts of crop residue management and tillage on sugarcane production.  (


INSECT RESISTANCE INFORMATION CONTRIBUTES TO THE RELEASE OF SUGARCANE VARIETIES FOR COMMERCIAL SUGAR PRODUCTION.  The sugarcane borer is the most important insect pest of sugarcane in Louisiana and is also an important pest of sugarcane in Florida and Texas. Growing sugarcane varieties with natural resistance to the borer is a viable attribute in an integrated pest management program.  Unfortunately, resistance to sugarcane borer is not a primary selection trait in the Louisiana commercial variety development program. Therefore, the resistant category (resistance, intermediate, susceptible) of new varieties must be determined prior to their release to farmers. Scientists at the SRU determined the resistance category of the two most recent varieties released in 2006. One variety, L 99-233, was classified as susceptible and the second, L 99-226, was classified as resistant. Such classification provides farmers and their consultants with information necessary to effectively manage borer control and thus reduce the amounts of insecticides sprayed into the environment. This information is also critical to plant breeders as they make decisions on what bi-parental crosses to make. Crossing resistant varieties to susceptible varieties increases the frequency of borer resistance in progeny and thus increases the probability of ultimately releasing new sugarcane varieties with resistance to this insect.  (


UTILIZATION OF INSECT PREDIATORS CAN REDUCE THE NEED FOR INSECTICIDE APPLICATIONS IN SUGARCANE.  An additional attribute of a successful integrated pest management system for the control of the sugarcane borer is the presence of natural predators that attach the sugarcane borer especially when it is in the damaging larval stage. Research by SRU scientists and cooperators identified the weak-links in establishing a parasitic wasp (Cotesia flavipes) into Louisiana. The weak-link identified was the absence of overwintering sites followed by an inappropriate searching area when parasites emerge following overwintering. Sugarcane in Louisiana fails to provide either of these two necessary components. However, greenhouse experimentation has shown that native grass species may provide both of these components, plus a third potentially useful component - an alternative host. Ultimately these findings will be of great importance to growers as they will be able to alter their on-farm management practices in a manner that will allow them to establish another beneficial insect with the resulting increase in benefits of biological control. (



Brown rust of sugarcane was not considered to be of major importance in Louisiana until 2000 when an epidemic occurred throughout the sugarcane industry.  The outbreak and its continued presence is of concern because the most severely affected variety is LCP 85-384, a variety that occupies the majority of the sugarcane acreage in Louisiana.  Five sugarcane fields were sectioned into smaller sections (grids).   Soil samples were collected and then rust severity was monitored at weekly intervals for a period of six to seven weeks at each grid point to determine if a relation could be found between soil properties and sugarcane rust levels.  The soil properties at each location showed significant variability (9 to 70%) over all locations.  In addition, soil properties were spatially correlated in 39 of 40 cases and rust ratings were spatially correlated in 32 of 33 cases.  In other words, samples that were spaced at a distance less than the range of spatial correlation were more similar than those at distances greater than this range.  The range of spatial correlation for soil properties varied from 39 to 201-meters and from 29 to 241-meters for rust ratings.  Rust ratings were correlated with several soil properties, most notably soil phosphorus and soil sulfur.  Other soil properties correlated with rust occurrence include: pH, potassium, calcium, magnesium, organic matter, and cation exchange capacity.  When all locations were combined the best correlations were obtained with soil sulfur and phosphorus levels and soil pH.  Taken together, these relations indicate that rust severity increased with soil fertility levels.  This also suggests that sugarcane growers that apply fertilizer in excess of plant requirements will increase the incidence and severity of rust infestations in their fields.  (


LEAF REFLECTANCE MEASUREMENTS PREDICT SUGARCANE VARIETY, DISEASE PRESENCE AND SUCROSE LEVEL.  Louisiana's sugarcane producers and millers have been under increased economic pressure for the past several years.  If the industry is to survive, new technologies that maximize productivity and profitability must be identified and adopted.  Several tests were initiated in 2005 to ascertain if leaf reflectance measurements at specific wavelengths could be used to determine disease presence, identify varieties, and predict sucrose levels.  Leaf samples were collected at several dates from sugarcane yellow leaf disease (SCYLD) and mosaic test plots before and after the appearance of visual symptoms. Samples exhibiting either mild or severe mosaic symptoms could be correctly identified with leaf reflectance in 75 and 68% of the cases, respectively.  Disease-free controls could be identified in 77% of the cases. Leaf reflectance measurements also identified samples infected with sugarcane yellow leaf virus (SCYLV) in 77% of the cases.  The SCYLV-infected leaves also had lower levels of most plant pigments compared to non-infected controls. In a second study, leaf samples were collected from plots in a historical sugarcane nursery containing seven generations of varieties selected for sucrose accumulation over a time period of more than eighty years.  Reflectance measurements were effective in correctly identifying 80% of the varieties present in the study.  In the final test, which involved the sampling of leaves from the Sugarcane Research Unit's 2005 maturity study, leaf reflectance was effective at predicting theoretically recoverable sugar levels in 77% of the cases in the combined data set.  The successful development of remote sensing techniques will help growers identify yield limiting crop disease outbreaks at earlier stages so that corrective actions could be taken in a timely and efficient manner.  These techniques could also have a potential benefit to varietal development programs by allowing for increased accuracy and efficiency in varietal selection.  Finally, growers and mill personnel could potentially use a simple leaf sample taken in the field to develop ripener treatment and harvest schedules that could aid in maximizing sugar yields. (


GREEN CANE HARVESTING PROCEDURES OPTIMIZED.  Operational settings on sugarcane harvesters are extremely important in green-cane harvesting since one is relying solely on the harvester to remove leafy material instead of the traditional pre-harvest burn method.  The objective of this research was to determine the effects of harvester ground speed and cleaning fan speed on sugar yield, cane quality, and field losses. Under the optimal conditions of low leaf and soil moisture (dry harvesting conditions), the high fan speed increased sugar content by 10% but decreased cane yield by 15% compared to the two lower fan speeds resulting in similar sugar yields for all fan settings. Under wet  conditions (high leaf and soil moisture), this high fan speed decreased cane yield by 13% without an increase in sugar content, resulting in lower sugar yields than the low or medium fan settings.  Harvester ground speed, under both conditions, did not affect cane yield or quality.   This study demonstrated the operational settings to optimize harvester efficiency under both ideal and poor harvesting conditions.  (


YIELD VARIABILITY IN SUGARCANE FIELDS DOCUMENTED.  Precision agriculture techniques were utilized to document the extent of variability present in commercial sugarcane fields in Louisiana.  Cane and sugar yields were monitored in 9 to 10 acre fields that had been divided into 0.04 acre quadrants (grids). Cane yields were found to vary from 15 to 60 tons per acre within fields.  Sugar yields and TRS levels in the same field varied from 3,000 to 13,000 pounds per acre and from 130 to 250 pounds per ton, respectively.  When the yield data was analyzed with geostatistical methods the sugar yields were found to be spatially correlated with a range of 278 feet. To explore the possibility that some of these differences may be associated with differences in nutrient availability, experiments were conducted to investigate the utility of VR lime application in comparison to a conventional (uniform rate) lime application and no liming.  Prior to lime application, soil samples (0-8 in) were taken from each site on a 1-acre grid. A composite soil sample from each field was used to determine the field liming rate, based on current extension recommendations.  In all experiments, both conventional and VR applications of lime increased cane and ultimately sugar yields at the end of each production year of a 3-year crop cycle.  Differences in cane and sugar yields were obtained in only one experiment and only in the first production year (plant-cane crop).   Results suggest that growers utilizing the VR application of lime method can achieve yields that are similar to the conventional uniform method of lime application.  If similar yields can be obtained with the VR system, while actually applying fewer inputs, then growers will realize an overall increase in profitability while minimizing any potentially adverse impacts of the crop's culture on the environment.  (


BURNING AS A TOOL TO IMPROVE SUGARCANE PRODUCTION EFFICIENCY THREATENED.  The Louisiana Sugarcane industry's continued use of burning as a tool to remove extraneous leaf material to increase harvesting efficiency and sugar recovery and to reduce the impact of the post-harvest residues on the subsequent ratoon crop is in jeopardy due to environmental concerns.  ARS scientists at the SRU assessed the impact of these residues on yields of sugarcane in the production years following green cane harvesting in field experiments throughout the Louisiana industry.  They demonstrated that the presence of the blanket of residue at the start of the subsequent production year slowed the development of the crop from underground buds and that the slowdown was exacerbated by cold soil temperatures and high rainfall during the winter months. The results of our studies indicate that a 2 to 3 degree (F) decrease in spring soil temperature occurs in those plots where the residue was not removed compared to plots where the residue was removed by burning.  The plots with residue also had soil moisture levels that were 3-5% greater than the complete removal treatment.  The combined effects of a lower temperature and higher moisture may slow germination of sugarcane below-ground buds in the late-winter to a sufficient extent that yield is adversely effected.  Recent results have also demonstrated that sugarcane post-harvest residues possess compounds that adversely affect the germination and growth of sugarcane (autotoxicity) or other plants (allelopathy).  These effects may also contribute to the observed yield depressions.  The results continue to suggest that the residue must be removed at least from the row top as soon after harvest as possible to insure optimum yields the following year in these fields.  Results indicate that the method of removal from the row top is of less importance with essentially equal yields obtained with a variety of mechanical removal techniques.  However, in poorly drained fields mechanical placement of leaf litter from the row top into the wheel furrow produced lower yields than burning because the residue prevented proper drainage.  If the residue is to be removed from a field by burning, this should be done soon after harvest to prevent damage to the re-emerging crop.  The combined results of these studies have allowed SRU personnel to provide residue removal guidelines to Louisiana sugarcane producers to avoid these negative effects. (

Last Modified: 8/13/2016
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