Improvement of Yield per se in Sugarcane - Translational Genomics for Crop Breeding: Abiotic Stress, Yield and Quality - page 217

sugarcane germplasm ( Saccharum spp.). The
number of ancestral accessions that gave rise to
the interspecific founders used as progenitors in
breeding programs worldwide does not exceed
20 accessions originating from S. officinarum
species and even fewer from S. spontaneum
species (Arceneaux 1967; Roach 1989).

Modern Sugarcanes and Yield Progress

Modern cultivars have a large, complex aneu-
ploid and polyploid genome consisting of 100-
130 chromosomes of about 10 Gbp (D'Hont
2005). Seventy to eighty percent of the chro-
mosomes are inherited from S. officinarum ,10
to 20% are inherited from S. spontaneum, and
10 to 20% are derived from recombination of the
two species (Figure 13.5) (Cuadrado et al. 2004;
D'Hont et al. 1996; Piperidis and D'Hont 2001;
Piperidis et al. 2010). Modern sugarcane culti-
vars are highly heterozygous genotypes result-
ing from the well-known relative intolerance of
the plant to inbreeding. As shown in Figure
13.5b, the genome of modern interspecific and
aneuploid sugarcanes comprises 10 homeology
groups (HG), each containing between 11 and 14
chromosomes. Chromosomes mainly form biva-
lents at meiosis, but, depending on the genotype
and the HG, pairing may vary from preferential
(0 to 40%) to complete (100%) affinities, lead-
ing to complex chromosome segregation patterns
associating disomic with more or less polysomic
behavior (Jannoo et al. 2004). This complex
chromosome segregation pattern may invali-
date several assumptions underlying the theory
of quantitative genetics developed for conven-
tional diploid (Hogarth 1977) or autopolyploid
species. Using these models, estimates of genetic
variance components derived from experimen-
tal mating designs are believed to be frequently
biased. The development of specific population
genetics or quantitative genetic models adapted
to sugarcane is highly unlikely. This makes
classical sugarcane breeding somewhat more

Fig. 13.5. Double structure of the genome of modern sug-
arcane cultivars. About 80% of the chromosome is inherited
from S. officinarum, 10% from S. spontaneum and 10% are
recombinant.
(a) Genomic in situ hybridization (GISH) using labeled total
DNA of S. officinarum (yellow fluorescence) and of S. spon-
taneum (red fluorescence) on chromosome preparations of
the cultivar R570 (from D'Hont et al. 1996, with kind per-
mission from Springer Science and Business Media).
(b) Schematic representation of the genome of modern inter-
specific cultivars deduced from molecular cytogenetic data
and mapping works. Modern cultivars are highly polyploid
and aneuploid with about 120 chromosomes. Colored bars
correspond to chromosomes. Chromosome colors are func-
tions of their origins: yellow for S. officinarum and red for S.
spontaneum . Chromosomes from the same row are homolo-
gous (or homeologous). Chromosomes of the S. officinarum
and S. spontaneum part of the genome of the modern cultivars
are distributed in 10 (X = 10) and 8 (X = 8) homology groups
respectively. (Modified from Grivet and Arruda 2002). For a
color version of this figure, please refer to the color plate.