Saccharum spontaneum, wild sugarcane,  is a highly polymorphic species growing in the tropical and subtropical regions of Asia, Africa, and the Pacific islands (8°S to 40°N). It belongs to the Poaceae family (grass family) and is one of the ancestral species of sugarcane. S. spontaneum is highly adaptable to various environments under drought stress in deserts, waterlogged conditions in marshes, and saline conditions near the sea. In addition, it survives under a range of temperatures from tropical heat to winter snow in the temperate area and is found from sea level up to 2700m in the Himalayas [1]. 

Chromosome number: The chromosome number of S. spontaneum (wild sugarcane) varies significantly due to its polyploid nature with a base chromosome number of 8, typically ranging from 2n = 40 to 128, depending on the specific accession and geographic region. This variability contributes to its genetic diversity and its importance in sugarcane breeding programs [1].

• Eastern group (2n=40-80): India, Nepal, Bangladesh, Pakistan and Ceylon. Principal numbers 2n=54, 60, 64, 72, 80. 
• Central group (2n=80-112): An Asia-Pacific region including Myanmar, Thailand, China, Indonesia, Taiwan and Japan. Principal numbers 2n=80, 96, 112.
• Western group (2n=104-128): Includes the African-Mediterranean region and Afghanistan. Principal numbers 2n=112, 120, 128.

Growth Habit: Plants vary in appearance from short, bushy types with no stalk to large-stemmed clones over 5m in height. Stalk diameter varies from 3 to 15 mm. Leaves vary in width from a naked mid-rib to 4 cm. These stalks grow from stools with frequently aggressive rhizomatous tillering [1].

Sugar content: The sugar content of S. spontaneum is generally lower than that of cultivated sugarcane species, such as Saccharum officinarum. The Brix value, which measures total soluble solids, ranges from 5% to 15% for S. spontaneum, depending on the variety and environmental conditions. In contrast, cultivated sugarcane varieties typically have Brix values ranging from 15% to 24%. Additionally, the sucrose content in S. spontaneum juice usually ranges from 3% to 7%, which is significantly lower than that of commercial sugarcane, where sucrose content can exceed 10% to 14%. This lower sugar content makes S. spontaneum unsuitable for direct sugar production [1].

S. spontaneum has played a critical role in the development and establishment of modern sugarcane varieties in improving yield, disease resistance, and adaptability to abiotic stresses. Approximately 15-20% of the genome of modern sugarcane varieties is believed to be contributed from S. spontaneum [2, 3]. Despite the great genetic diversity of S. spontaneum, only a few accessions have been used in sugarcane breeding [4].

The sugarcane industry has recently transitioned from a focus on sugar to a biorefinery model that produces sugar, bioenergy, and biochemicals. To ensure the future success of the industry, it is vital to increase yields of sugar and fiber (Bagasse) while adapting to climate change and promoting sustainable and environmentally friendly production. However, sugarcane breeding has faced stagnation in improvement due to low genetic diversity resulting from only a limited number of parental materials used in developing modern sugarcane varieties [5, 6]. Under these circumstances, the importance of breeding use of S. spontaneum has been increasing to broaden the genetic diversity of breeding for realizing further improvement of sugar and fiber yields, tolerance of biotic and abiotic stress, and the characteristics of sustainable production [7]. Incorporating its traits into cultivated sugarcane ensures the development of varieties that meet the demands of future sugarcane industry.

The sugarcane industry in Thailand is increasingly utilizing bagasse-based bioenergy production to reduce CO₂ emissions. However, Northeast Thailand, the largest sugarcane-producing region, is experiencing low yields in ratoon cultivation due to severe dry seasons. To tackle these challenges, JIRCAS and KKFCRC have focused on S. spontaneum, a sugarcane wild germplasm native to Thailand, and have engaged in international collaborative research on its breeding use since 1997. In our project, we have collected over 300 accessions from all over Thailand [8] and utilized this germplasm to improve sugarcane through interspecific hybridization with cultivated sugarcane.

As a result of this research, a new sugarcane variety called TPJ04-768 has been developed, which is characterized by high bagasse productivity [9]. The Thai government has officially adopted this innovative variety as a recommended variety known as DOA Khon Kaen 4 (KK4) [10]. Compared to the common variety KK3, KK4 exhibits superior productivity in ratoon crops and produces approximately 1.5 times more bagasse due to its higher fiber content while maintaining a similar sugar yield. The introduction of KK4 promises to enhance productivity in regions with historically low yields in ratoon crops, allowing for the expansion of bioenergy production without competing with sugar production.

In addition, the new sugarcane variety, Harunoogi, was developed in Japan through interspecific hybridization [11, 12]. This variety has a high fiber content and a sugar level comparable to that of conventional varieties. Harunoogi exhibits excellent ratooning ability, resulting in superior productivity in ratoon crops.  It produces approximately 1.5 times more bagasse while maintaining a similar sugar yield compared to existing varieties, particularly in high-latitude areas of the Nansei islands in Japan, where low temperatures pose significant challenges to sugarcane production. The varieties with high sugar and fiber productivity developed using interspecific hybridization are expected to contribute significantly to the future success of the sugarcane industry.

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4. Price, S. (1965). Interspecific hybridization in sugarcane breeding. Proc. Int. Soc. Sugar Cane Technol. 12:1021–1026.
5. Roach, B.T. (1989a). A programme for sugarcane improvementfrom genetic diversity: Background and preliminary results.Proc. Int. Soc. Sugar Cane Technol. 11:900–909.
6. Roach, B.T. (1989b). Origin and improvement of the genetic baseof sugarcane. Proc. Aust. Soc. Sugar Cane Technol. 11:34–47.
7. Sugimoto, A. et al. 2011. Developing new types of sugarcane by hybridization between commercial sugarcane cultivars and wild relatives. Proc. Int. Symp. FAO RAP-NIAS. 11-24.
8. Ponragdee, W. et al. (2013). New type of high yielding sugarcane with lower sugar and higher fibre content suitable for stable co-production of sugar and ethanol in Northeast Thailand. Proc. Int. Soc. Sugar Cane Technol. 28:BB17.
9. JIRCAS research highlight. (2015). New sugarcane varieties using wild sugarcane and collaboratively bred in Thailand. https://www.jircas.go.jp/en/publication/research_results/2015_b10
10. JIRCAS press release. (2023). Thailand approves cultivation of sugarcane variety developed by JIRCAS ― Expectations on increased bioenergy production from bagasse―. https://www.jircas.go.jp/en/release/2023/press202315
11. Hattori, et al. (2019). High ratoon yield sugarcane cultivar “Harunoogi” developed for kumage region by using an interspecific hybrid between a commercial cultivar and Saccharum spontaneum L. Journal of the NARO Research and Development, 2:21-44. https://doi.org/10.24514/00003206
12. JIRCAS research highlight. (2019). Harunoogi, a high ratoon yield sugarcane cultivar developed by interspecific hybridization between sugarcane and Saccharum spontanium. https://www.jircas.go.jp/en/publication/research_results/2019_b06