Establishing Sugarcane (Saccharum spp.) Genetic Resources in Vitro

Sugarcane (Saccharum spp.) is used to produce sugar, a variety of alcoholic beverages, bagasse and industrial ethanol utilized in making fuel. In production fields, sugarcane is propagated vegetatively and currently, the crop’s genetic resources are also preserved as field plantings. The National Plant Germplasm System, USDA-ARS maintains 18 species of Saccharum with a total of over 2,400 accessions. To secure the collection from stress factors and invertible loss, efforts are made to introduce the germplasm into in vitro culture. Apical cane segments of S. officinarum, S. robustum and S. sinensis were sterilized in 70 % isopropanol, subsequently in 2.5 % sodium hypochlorite and rinsed with sterile water. Excised shoots (ca. 10-15 mm long) were cultured on Murashige Skoog medium at 25+2^oC, at 16 hours photoperiod. Microbial contamination and phenolic compound secretion were the main visible factors preventing shoot development. After 3-4 weeks, contamination-free cultures developed an average of 2 shoots. In the next three subculture intervals (each lasting 4 weeks) and an addition of antioxidants to media (citric acid 100 mgL^-1 or L-cysteine 100 mgL^-1, or polyvinylpyrrolidone 300 mgL^-1, or L-glutathione 50 mgL^-1), the number of shoots increased from 2 to 8-12 shoots. In comparison to the control, some of the antioxidants tested showed a positive effect increasing the number of shoots and their vigor; however, the effectiveness was genotype specific. In our studies only ca. 25 % of explants produced clean and propagating cultures, and the in vitro establishing method requires further improvements. Introducing field-grown sugarcane plants in vitro is daunting; nevertheless, the effort is necessary to secure Saccharum genetic resources for food and industrial supply, research and distribution.