Sugarcane Pathology Research

INVESTIGATOR: J. W. Hoy

PERFORMING INSTITUTION:
Plant Pathology & Crop Physiology
Louisiana State University
Baton Rouge, Louisiana 70803

OBJECTIVES: 1. To evaluate disease resistance as part of the sugarcane cultivar selection program. 2. To determine methods for successful billet planting. 3. To reduce the impact of ratoon stunting disease through infection monitoring. 4. To evaluate the potential impact of sugarcane yellow leaf virus. 5. To study changes in soil microbial communities resulting from sugarcane cultivation that are detrimental to growth. 6. To develop improved sugarcane disease management practices.

APPROACH: A blend of applied and basic research using lab, greenhouse and field experimentation will address current disease problems affecting sugarcane in Louisiana.

PROGRESS: 2004/01 TO 2004/12
Two sugarcane cultivars, Ho 95-988 and L 97-128, were released during 2004. These cultivars have good to acceptable resistance to the diseases of importance and will provide an alternative to the current number one cultivar, LCP 85-384, that is susceptible to rust. Screening in the selection program identified clones with resistance to smut, leaf scald, and mosaic. A seedling inoculated test showed promise for evaluation of heritability of resistance to leaf scald. Research to develop methods for successful planting of stalk billets continued. Results were obtained from first and second ratoon crops of experiments evaluating planting date and rate of planting. Very early and late planting dates have produced lower yields. Low planting rates also have produced lower yields, while very high rates have not increased yield. Ratoon stunting disease testing contributed to an on-going survey of infection levels in the Louisiana sugarcane industry. The incidence of farms, fields, and stalks per field were 14.3%, 6.7% and 1.2%, respectively. Factors associated with decreased RSD were widespread cultivation of a cultivar with resistance to disease spread, LCP 85-384, and planting of healthy seedcane produced through micropropagation and certification by the La. Dept. of Agriculture and Forestry. RSD was not detected in sources of commercial micropropagated seedcane. A local quarantine was conducted to provide healthy plant material to establish foundation stock plants that provide the source for micropropagation. A four-year study comparing the rate of RSD spread by chopper and whole-stalk harvesters and in different cultivars was completed. The chopper harvester did not spread RSD more rapidly than the whole-stalk harvester. Differences were detected among cultivars in rate of RSD spread. Spatial distribution of Sugarcane yellow leaf virus (SCYLV) infection and aphid vectors was analyzed with data from contiguous quadrat plots in four fields over two seasons. Initial distributions were random, and patterns remained random with occasional aggregation detected. Certification of commercial seedcane for SCYLV infection was conducted for the first time. A decrease in yield was detected in infected LCP 85-384 in second ratoon. Virus infection did not decrease yield of Ho 95-988 in plant cane. The effect of rust on yield in Louisiana was determined for the first time. Cane tonnage increased 21% when rust was controlled by multiple fungicide applications at one location. Rhizosphere soil samples were collected from adjacent fields with and without a recent sugarcane cropping history, and the prokaryotic communities were different when compared with sole carbon source utilization profiles.

IMPACT: 2004/01 TO 2004/12
Continued development of disease resistant cultivars is essential. Two new cultivars should have a positive impact. Billet harvesting has become predominant in Louisiana; therefore, developing methods for successful billet planting is imperative. Practices have been identified that will maximize the chances of success. Historically, ratoon stunting disease, RSD, has been the most important disease in Louisiana. Significant yield losses will not result from the disease levels now occurring. The reductions in RSD result from a partnership of the LSU Agricultural Center, the La. Dept. of Agriculture and Forestry, and a commercial seedcane company that makes certified, healthy seedcane available and by the cooperative breeding program that produced the widely planted, RSD resistant cultivar, LCP 85-384. Availability of certified seedcane produced through micropropagation also contributes to the management of other systemic diseases, including mosaic, smut, leaf scald and yellow leaf. Research on spread and increase of Sugarcane yellow leaf virus suggests it can be managed by a healthy seedcane program utilizing micropropagated seedcane, and this disease was added to the seedcane certification standards for 2004. Demonstration of the impact of rust on LCP 85-384 will speed the shift to new culivars. Improving understanding of detrimental changes in soil microbial communities associated with sugarcane monoculture and evaluation of alternative control measures could lead to reductions in losses caused by soilborne disease.

PUBLICATIONS: 2004/01 TO 2004/12
1. Hoy, J., Grelen, L., and Paccamonti, J. 2004. RSD testing time again. Sugar Bull. 83(1):19-20.
2. Hoy, J. W., Richard, C. A., Jackson, W. R., Waguespack, H. L., Jr. 2004. Effects of cultivars, fungicides, and fertilization at planting on yields obtained from whole stalk and billet planting in Louisiana. J. Amer. Soc. Sugar Cane Technol. 24:70-80.
3. Salassi, M. E., Breaux, J. B., and Hoy, J. W. 2004. Estimated cost differences between whole stalk and billet sugarcane planting methods in Louisiana. J. Amer. Soc. Sugar Cane Technol. 24:250-257.


PROJECT CONTACT:
Name: Hoy, J. W.
Phone: 225-388-1392
Fax: 225-388-1415
E-mail: jhoy@agcenter.lsu.edu  

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