Miscanthus - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 59

Swaminathan et al. [ 115 ] used deep transcriptome sequencing (RNAseq) from two
M. sinensis accessions to define 1,536 single nucleotide variants (SNVs) for a
GoldenGate genotyping array and found that simple sequence repeat (SSR)

markers defined in sugarcane are often informative in M. sinensis . A total of
658 SNP and 210 SSR markers were validated via segregation in a full sibling F 1
mapping population. Using 221 progeny from this mapping population, we
constructed a genetic map for M. sinensis that has 19 linkage groups, the haploid
chromosome number expected based on cytological evidence. Comparative geno-
mic analysis documents a genome wide duplication in Miscanthus relative to
Sorghum bicolor , with subsequent insertional fusion of a pair of chromosomes.
The genus Miscanthus experienced an ancestral tetraploidy and chromosome fusion
prior to its diversification, but after its divergence from the closely related sugar-
cane clade. A high-resolution linkage map of Miscanthus sinensis was also created
using genotyping by sequencing (GBS), identifying all 19 linkage groups
[ 116 ]. Comparative genomics analyses of the M. sinensis composite linkage map
to the genomes of sorghum, maize, rice, and Brachypodium distachyon indicate that
sorghum has the closest syntenic relationship to Miscanthus compared to other
species. The comparative results revealed that each pair of the 19 M. sinensis
linkages aligned to one sorghum chromosome, except for LG8, which mapped to
two sorghum chromosomes (4 and 7), presumably due to a chromosome fusion
event after genome duplication. The data also revealed several other chromosome
rearrangements relative to sorghum, including two telomere-centromere inversions
of the sorghum syntenic chromosome 7 in LG8 of M. sinensis and two paracentric
inversions of sorghum syntenic chromosome 4 in LG7 and LG8 of M. sinensis .

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Seed Production

To date, plant establishment is based on vegetative propagation of M.

giganteus
owing to its sterility. Propagation by rhizomes poses problems of scaling up
industrial planting because large numbers of plants are needed to produce the
number of rhizomes required. Excavating and splitting the rhizomes to generate
separate plants and replanting are complex and costly operations and present a
bottleneck for Miscanthus commercialization.
Propagation of Miscanthus by seeds as in their wild environments is done at
some research centers for research purposes. In general, direct seed method for field
establishment is unreliable because seeds are too small to support sufficient seed
carbohydrate reserve and ensure good germination and healthy seedlings [ 42 ]. As a
result, seedling mortality is high. Consequently, Miscanthus establishment in the
field using direct seeding is not practiced. The propagation via rhizomes, on the
other hand, provides healthy seedlings and establishes plants easily. In Europe,
many plant propagation centers exist. Comparisons of propagation methods, how-
ever, revealed that vegetative propagation provides propagules at a higher cost
compared to seeds. In theory, seed-based cultivars could considerably reduce