Can Cytogenetic and PCR Markers Assist Selection of High Value Erianthus-Derived Sugarcane Clones?

Intergeneric hybrids between Saccharum and Erianthus are the newest exotic addition to the Australian sugarcane breeding program. The wild species Erianthus arundinaceus, a close relative of sugarcane could be an important candidate to enlarge the gene pool of the Australian parent populations. E. arundinaceus is reported to contain numerous traits of agronomic importance including pest and disease resistance and tolerance to drought and water-logging conditions. Based on genomic in situ hybridisation (GISH) results on the Erianthus introgression clones, we have developed a molecular method to allow selection of hybrids at an early stage that have incorporated sought-after traits.  So far, five generations of fertile hybrids from intergeneric crosses between S. officinarum, E. arundinaceus and modern sugarcane cultivars have been produced. The chromosome composition of F1, BC1, BC2, BC3 and BC4 hybrids was studied by GISH and revealed a reduction of Erianthus chromosomes as well as a loss of chromosomes from the BC1 generation. We also revealed the formation of recombinant chromosomes between both genera. Individuals with low number of Erianthus chromosomes or recombined chromosomes could be an important addition to the breeding program if these chromosomes are inherited stably during crossing. The stability of recombined chromosomes is currently under investigation by studying the transmission of these recombined chromosomes in further crosses. Nevertheless, as the number of Erianthus chromosomes in the BC3 (and BC4) are lower or equivalent to the basic number of E. arundinaceus (x=10), we are aiming to develop a simple method based on PCR molecular markers which will allow the identification of individual Erianthus chromosomes in the backcross hybrids.  If important traits, such as nematode and/or pachymetra resistance can be linked to Erianthus specific chromosomes, then this method could become a valuable tool for sugarcane breeders as an effective selection screening method.