Saccharum spontaneum L. has contributed important traits to modern sugarcane (S. spp. L.) cultivars such as adaptation to environmental stress and ratooning ability. There is interest in further use of S. spontaneum in sugarcane improvement for sugar or energy‐from‐biomass production systems. In this study, parents and progeny from 43 biparental crosses between sugarcane and S. spontaneum clones were evaluated in field trials in China and Australia, along with several commercial cultivars. The S. spontaneum clones were from diverse geographic origins in China. Measurements were made on biomass composition (% dry matter, brix and pol in juice and cane, purity, fiber content) and yield components. Moderate to high (>0.7) broad‐sense heritabilities and high genetic variances were observed for most traits. About half the total genetic variance was retained as among‐family variance for the biomass composition traits, but this proportion was generally <25% for biomass yields. Midparent values in an independent trial predicted biomass composition traits reasonably well (generally, r > 0.6), but less so for cane and biomass yield (0 < r < 0.4). Genetic correlations between performance of families evaluated in different countries were strong, providing preliminary evidence that results in one country could be used for identifying elite families in the other. Strategies for efficient development and selection of elite clones from S. spontaneum are suggested.

Erianthus arundinaceus has a number of important agronomic traits including good ratooning ability, tolerance to both drought and water logging, disease resistance and vigour and is of interest as a potential source of parental germplasm to sugarcane breeders. However, to date, attempts to produce fertile hybrids between sugarcane (Saccharum spp.) and E. arundinaceus have been unsuccessful. Microsatellite markers that generated genus-specific markers and were highly polymorphic within sugarcane were identified. The microsatellite markers and 5S rDNA PCR were used to screen intergeneric (F 1 ) clones from Saccharum officinarum · E. arundinaceus crosses, and two Saccharum backcross progeny (BC 1 ) populations derived from crosses between selected F 1 clones and sugarcane (Saccharum spp.), to identify genuine Saccharum spp. BC 1 progeny. The 5S rDNA PCR marker and highly polymorphic microsatellites with Erianthus-specific bands confirmed the F 1 parent of the two putative BC 1 populations was a S. officinarum · E. arundinaceus hybrid and allowed the identification of the genuine BC 1 progeny from selfs of the F 1 parent. This is the first verification of BC 1 progeny from an F 1 intergeneric hybrid · sugarcane (Saccharum spp.) clone with molecular markers and confirms the introgression of E. arundinaceus germplasm into sugarcane. It should now be possible to exploit genes of value from E. arundinaceus in sugarcane breeding programmes.

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Sugarcane smut disease caused by the fungus Sporisorium scitamineum is one of the important fungal diseases affecting sugarcane yield and sucrose content around the world. Cultivar resistance is the most appropriate control method for this disease. In this study, 37 BC 1 lines chosen from the crossing YC96-40 (F 1 of Erianthus arundinaceus) × CP84-1198 (commercial sugarcane cultivar) and 42 BC 2 lines chosen from the crossing YCE01-116 (BC 1 of E. arundinaceus) × Neijiang57-416 (commercial sugarcane cultivar) were evaluated for smut resistance using artificial inoculation. The results showed that of 79 tested BC 1 and BC 2 lines of E. arundinaceus, 10 (12.7%) were highly to moderately resistant to smut. BC 1 of E. arundinaceus had more resistant lines than BC 2 of E. arundinaceus. Of the 37 tested BC 1 lines of E. arundinaceus, seven (18.9%) were highly to moderately resistant, while three (7.1%) of the 42 tested BC 2 lines of E. arundinaceus were highly to moderately resistant to smut. The resistant lines identified in this study could be used as sources of smut resistance in sugarcane breeding programs.

ABSTRACT. Saccharum spontaneum is the most variable wild relative of sugarcane with potential for use in sugarcane improvement programs. In order to help preserve and exploit this species, 152 accessions from eight major geographical regions in China, including Hainan, Guangdong, Guangxi, Yunnan, Sichuan, Guizhou, Fujian, and Jiangxi provinces, were investigated by analyzing 20 simple sequence repeats (SSRs), including 11 genomic SSRs (gSSRs) and nine SSRs developed from expressed sequence tags (EST-SSRs). A total of 454 alleles were generated by the 20 SSRs, with 295 and 159 alleles detected by gSSRs and EST-SSRs respectively. The Mantel test showed significant correlation between genetic matrixes among the studied accessions revealed by gSSRs versus EST-SSRs, although the average polymorphism of EST-SSRs (17.7) was much lower than that of gSSRs (26.8). Among the eight provinces, collections from Guizhou were the most diverse and those from Guangdong were the most distinct. Clustering analysis and principal component analysis accordantly classified the accessions into four groups, which were "Southwest Genetic diversity of S. spontaneum L. in China group", "Hainan group", "Guangdong group", and "Guangxi group", based on the geographical origin of the major accessions in each group, demonstrating that geographical factors play an important role in the pattern of genetic structure of Chinese S. spontaneum. As two (Guizhou and Yunnan) of the three provinces with highest genetic diversity are located in southwest China, we concluded that southwest China is the region with the highest genetic diversity of S. spontaneum.

Sugarcane improvement has traditionally been conducted by nationally focussed breeding programs, with some exchange of elite cultivars among some programs. It has been generally assumed by breeders that genotype × country interactions are large, and therefore selection trial data in one country may be of limited relevance to another. However, no studies quantifying clone × country interactions have been reported to our knowledge. In research reported here, a common set of mostly unselected sugarcane genotypes was evaluated in commercial production environments in Australia and China. Consistent with past studies, genotype × site interaction was an important source of variation within each country. Overall a moderate to high genetic correlation existed between production environments in China and Australia for cane yield and sugar content (0.77 for both traits). This suggests that despite difference in environmental conditions and crop management in production environments between countries, that selection trials in China have some relevance for selecting clones for Australian environments and vice versa. It also supports the hypothesis that regular exchange of selected germplasm from effective breeding programs between countries will have mutual benefits.

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