Location: Sugarcane Research2011 Annual Report
1a. Objectives (from AD-416)
The long-term goals of this project are to develop sugarcane cultivars that are better adapted and more economical to grow and harvest, to meet current and evolving needs of both a sugar and a biofuels industry, and to gain a greater understanding of sugarcane from genetic and physiological perspectives. The objectives are to utilize: (1) a basic breeding program to broaden the genetic base of parental germplasm and increase the adaptability of sugarcane to more temperate climates through the introgression of genes from wild species (Saccharum spontaneum) and related genera of sugarcane, and (2) parental clones from the basic program to develop sugarcane cultivars that are: higher yielding (gross cane and sugar), require fewer inputs, more tolerant to disease and insect pests, and adapted to a broader range of environments than current cultivars (commercial breeding program). To assist in the selection process, trait-specific molecular markers for early sucrose accumulation, sugarcane borer resistance, and cold tolerance will be developed.
1b. Approach (from AD-416)
Included in the basic program’s breeding strategy to increase the genetic diversity of parental clones are: (1) acquisition and maintenance of germplasm from wild species of Saccharum and related genera; (2) characterization of parents and progeny for traits (cold tolerance, stubbling ability, disease resistance, and sugarcane borer resistance) that will increase the adaptation of sugarcane to Louisiana’s temperate climate; (3) utilization of crossing and molecular marker techniques to produce interspecific and intergeneric hybrids containing new sources of disease and insect resistance and cold tolerance; and (4) recombination of progeny through backcrossing to develop parental material containing a concentration of desirable genes for the commercial breeding program. Screening procedures will be developed to determine relative cold tolerance among clonal material in the basic breeding program. In the development of cultivars for sugar and bioenergy, emphasis will be placed on yield components (stalk number, height, and diameter), quality components (sucrose and fiber accumulation), longevity (stubbling ability), harvestability (root anchorage, stalk erectness, and stalk brittleness), hardiness (winter survival, early spring vigor, and stalk freeze tolerance), stress tolerance (droughts, floods, and heavy clay soils), and resistance to stalk boring insects (sugarcane borer and Mexican rice borer) and diseases (smut, rust, leaf scald, mosaic, yellow leaf virus, and ratoon stunting disease). Recurrent selection techniques will be utilized to accelerate the rate of genetic improvement for important traits. In addition, trait-specific markers closely associated with desirable traits such as sucrose accumulation, cold tolerance, and resistance to the sugarcane borer will be developed to assist breeders in eliminating undesirable plants early in the selection process.
3. Progress Report
Parental lines were placed on crossing carts at the Agricultural Research Service (ARS), Sugarcane Research Unit's (SRU) newly built crossing and photoperiod facilities at Schriever, LA; at the old crossing facilities at Houma, LA; and at Canal Point, FL, in preparation for the fall 2011 crossing season. Last fall, 4,626 candidate commercial sugarcane clones and 380 clones from the recurrent selection for the sugarcane borer program (RSB) were advanced to first clonal stage, 814 candidate commercial clones and 55 candidate RSB clones were advanced to the second clonal stage, and 40 commercial sugar and 3 commercial RSB clones were given permanent alphanumeric designations and advanced into multi-location nurseries for yield testing in 2010. Currently there are 38 clones developed at the SRU from the 2005 to 2009 assignment series that are being evaluated as commercial sugarcane varieties in advanced yield trials. In addition, there are 15 clones from the RSB program representing the 2005 to 2009 assignment series that are also being evaluated in these advanced yield trials. Regional tests involving five high-fiber clones developed at the SRU were harvested in Georgia (2), Louisiana (1), Mississippi (2), and Texas (2) in partial fulfillment of the requirements of a USDA-Department of Energy sponsored grant to coordinate energycane research in the southeast. A total of 4,886 new seedlings from the sugarcane borer resistance (RSB) recurrent selection program were set to the field in spring 2011. In 2011, two parents from the recurrent selection program for sucrose and five parents from the recurrent selection for sugarcane borer resistance were included on crossing carts at Houma, LA, to continue recurrent selection for increasing sucrose content and resistance to the sugarcane borer. In the spring of 2011, 16,109 basic seedlings from the 2010 crossing season were planted to the field, 2,443 from the 2008 crossing season were advanced to the first clonal stage, 282 from the 2007 crossing season were advanced to the second clonal stage, and 53 from the 2006 crossing season were given permanent alphanumeric designations. Sixty-seven basic clones were selected for inclusion in the 2010 parental population on the breeding carts. Characterization of wild clones for traits of interest, in particular, cold tolerance and disease resistance, is continuing. Genetic analysis of several traits (starch and fiber content, plant height, stalk diameter, etc.) and a search for sugar content-related single nucleotide polymorphism (SNP) deoxyribonucleic acid (DNA) markers using a preliminary genetic linkage map for the variety LCP 85-384 is continuing.
1. New sugarcane variety promises high yields and tolerance to diseases, insects, and freezing temperatures. ARS researchers at the Sugarcane Research Unit (SRU)at Houma, LA, developed and released to the Louisiana sugarcane industry HoCP 04-838 for commercial sugarcane production. The new variety produces sustained yields through the second-ratoon crop and to date is resistant to the four most important sugarcane diseases found in Louisiana – smut, leaf scald, ratoon stunting disease, and brown rust. It is also resistant to the most important sugarcane insect pest in Louisiana – the sugarcane borer – making it a variety that can be planted in environmentally sensitive areas where insecticide use is restricted. No variety currently grown in Louisiana resists stalk deterioration following a severe freeze during the harvest season better than HoCP 04-838. The positive performance of HoCP 04-838 for so many important traits suggests that it will be a variety that will be embraced by growers and a variety certain to contribute to the economic sustainability of the industry.
2. Construction of a sugarcane molecular identity database. Traditionally, sugarcane breeders identify clones based on appearance and the presence or absence of certain structures. Although this method of identification may serve well for breeders who are directly involved in the evaluation and selection processes, breeders from other locations or researchers in other disciplines may not be familiar with the traits, especially when the environment influences appearance. ARS scientists at the Sugarcane Research Unit, Houma, LA, constructed a molecular identity database of Louisiana clones using 144 DNA fingerprints produced by 21 single satellite report (SSR) markers. The molecular identity database provides molecular descriptors for new variety releases, and aids breeders in accurately determining paternity of cross offspring. For sugarcane growers, the database can be used as a reference to distinguish varieties.
3. The first genetic linkage map for Louisiana’s popular variety LCP 85-384. Unlike other crops, sugarcane varieties have complex genomes with 100 to 130 chromosomes belonging to ten homo(eo)logous groups (HGs) with 10 to 13 chromosomes within each group. Furthermore, the chromosome makeup may differ to a great extent among varieties grown in different geographical areas. ARS scientists at the Sugarcane Research Unit, Houma, LA, constructed a preliminary genetic linkage map of Louisiana’s popular variety LCP 85-384 using a population consisting of 300 self-pollinated offspring and 773 single dose DNA markers. The map contains 108 co-segregation groups (CGs) with a cumulative map length of 5,387 centimorgan (cM) [unit for measuring genetic linkage] and a density of 7.5 cM per marker. In addition, 65 of the 108 CGs were further grouped into eight HGs. With an estimated genome size of 12,313 cM, the map covered approximately 43.7% of the genome. By adding more SSR markers, the map can be enriched so that it will be useful in finding trait-specific markers to facilitate the use of marker-assisted selection by sugarcane breeders.
Pan, Y.-B. 2010. Databasing molecular identities of sugarcane (Saccharum spp.) clones constructed with microsatellite (SSR) DNA markers. American Journal of Plant Sciences. 1(2):87-94. DOI: 10.4236/ajps.2010.12011