New sources of resistance to major diseases from wild relatives of sugarcane.

THE HYBRIDISATION OF noble sugarcane, Saccharum officinarum, with its wild relative S. spontaneum in the early 1900s was responsible for greatly improved resistance to a number of diseases, increased vigour and improved ratooning. New crosses made in Australia with S. spontaneum clone Mandalay during the 1960s resulted in the important parent clone, QN66-2008, which is the parent of 25 and grandparent of 18 'Q' varieties. Introgression breeding requires many years of crossing, screening of progeny and backcrossing to retain the beneficial characteristics while reducing the negative characters associated with the wild relatives, such as low sugar and high fibre. A collaborative introgression breeding program between CSIRO, BSES/SRA and Chinese research organisations commenced in 2000. Chinese breeders made crosses with Erianthus spp. and S. spontaneum from Asia. Seed and clones from this program were imported into Australia through quarantine and have been tested for yield and disease resistance. A selection of over 600 introgression clones has been screened for resistance to pachymetra root rot, root knot nematode, root lesion nematode and smut. Some clones from the advanced backcrosses that are resistant to these diseases have been identified and are currently being further tested for potential as commercial varieties or as parents to provide new sources of resistance to the diseases and to broaden the genetic base of commercial varieties. This paper reports on the variation in resistance to diseases of the introgression crosses from sugarcane wild relatives including the disease resistance of true crosses with the genus Erianthus.