Unexpected inheritance pattern of Erianthus arundinaceus chromosomes in the intergeneric progeny between Saccharum spp. and Erianthus arundinaceus.

Erianthus arundinaceus is a valuable source of agronomic traits for sugarcane improvement such as ratoonability, biomass, vigor, tolerance to drought and water logging, as well as resistance to pests and disease. To investigate the introgression of the E. arundinaceus genome into sugarcane, five intergeneric F1 hybrids between S. officinarum and E. arundinaceus and 13 of their BC1 progeny were studied using the genomic in situ hybridization (GISH) technique. In doing so, we assessed the chromosome composition and chromosome transmission in these plants. All F1 hybrids were aneuploidy, containing either 28 or 29 E. arundinaceus chromosomes. The number of E. arundinaceus chromosomes in nine of the BC1 progeny was less than or equal to 29. Unexpectedly, the number of E. arundinaceus chromosomes in the other four BC1 progeny was above 29, which was more than in their F1 female parents. This is the first cytogenetic evidence for an unexpected inheritance pattern of E. arundinaceus chromosomes in sugarcane. We pointed to several mechanisms that may be involved in generating more than 2n gametes in the BC1 progeny. Furthermore, the implication of these results for sugarcane breeding programs was discussed

GISH analysis of the F₁ hybrids and BC₁ progeny.

<p><i>Saccharum</i> spp. chromosomes were visualized in red and <i>E</i>. <i>arundinaceus</i> chromosomes in green. (A) YCE 96-66 (F₁): 29 chromosomes from <i>E</i>. <i>arundinaceus</i> and 40 chromosomes from <i>Saccharum</i> spp.; (B) YCE 01–102 (BC₁): 22 chromosomes from <i>E</i>. <i>arundinaceus</i> and 96 chromosomes from <i>Saccharum</i> spp.; (C) YCE 01–36 (BC₁): 36 chromosomes from <i>E</i>. <i>arundinaceus</i>, 96 chromosomes from <i>Saccharum</i> spp. and one terminally translocated chromosome; (D) YCE 01–61 (BC₁): 31 chromosomes from <i>E</i>. <i>arundinaceus</i> and 85 chromosomes from <i>Saccharum</i> spp.; (E) YCE 01–69 (BC₁): 31 chromosomes from <i>E</i>. <i>arundinaceus</i> and 88 chromosomes from <i>Saccharum</i> spp.; (F) YCE 01–92 (BC₁): 35 chromosomes from <i>E</i>. <i>arundinaceus</i>, 95 chromosomes from <i>Saccharum</i> spp. and one terminally translocated chromosome. The arrowhead in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110390#pone-0110390-g001" target="_blank">Figure 1C</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110390#pone-0110390-g001" target="_blank">Figure 1F</a> shows the translocated chromosome. Scale bars: 5 µm.</p

Chromosome composition of F₁ hybrids and BC₁ progeny.

<p><b>Note:</b> The modal number of chromosomes is presented for the sugarcane clones analysed, since small variation of chromosome counts can occur due to the loss or the overlapping of a few chromosomes from the preparation.</p><p>Chromosome composition of F₁ hybrids and BC₁ progeny.</p

The intergeneric F₁ hybrids and their BC₁ progeny between <i>Saccharum</i> spp. and <i>E</i>. <i>arundinaceus.</i>

<p>The intergeneric F₁ hybrids and their BC₁ progeny between <i>Saccharum</i> spp. and <i>E</i>. <i>arundinaceus.</i></p

Schematic of seven meiosis scenarios with two pairs of homologous chromosomes.

<p>(A) NM: normal meiosis; (B) FDR: first meiotic division restitution; (C) SDR: second meiotic division restitution; (D) NHC: nondisjunction of homologous chromosomes in first meiotic division; (E) NSC: nondisjunction of sister chromatids in second meiotic division; (F) NHC+SDR: nondisjunction of homologous chromosomes in first meiotic division and second division restitution; (G) FDR+NSC: first division restitution and nondisjunction of a chromosome with sister chromatids in the second meiotic division. For simplicity, recombination events are not illustrated in these meiosis schematics.</p

The relationship between NSC and the total number of <i>E</i>. <i>arundinaceus</i> chromosomes in each gamete (blue curve), and the interrelationship of two gametes (red curve).

<p>Note: g and g’ are the total number of <i>E</i>. <i>arundinaceus</i> chromosomes in each gamete after meiosis, j is the number of NSC.</p

The relationship between NHC and the total <i>E</i>. <i>arundinaceus</i> chromosome number of gametes (blue curve), and the interrelationship of two gametes (red curve).

<p>Note: g and g’ are the total number of <i>E</i>. <i>arundinaceus</i> chromosomes in each gamete after meiosis, i is the number of NHC.</p