Theor Appl Genet (1995) 91:320-326 9 Springer-Verlag 1995 A. D'Hont 9 P. S. Rao 9 P. Feldmann 9 L. Grivet N. Islam-Faridi 9 P. Taylor- J. C. Glaszmann Identification and characterisation of sugarcane intergeneric hybrids, Saccharum officinarum • Erianthus arundinaceus, with molecular markers and DNA in situ hybridisation Received: 13 March 1995 / Accepted: 17 March 1995 Abstract Molecular markers were used to characterise sugarcane intergeneric hybrids between S. officinarum and E. arundinaceus. Very simple diagnostic tools for hybrid identification among the progeny were derived from iso- zyme electrophoresis and a sequence-tagged PCR. Two en- zyme systems (GOT and MDH B) and PCR amplification revealing spacer-size variation in the 5s-rDNA cluster were found most convenient. Specific characterisation of the two genomic components was possible using RFLP and in situ hybridisation. The strong molecular differentiation between S. officinarum and E. arundinaceus allows the identification of numerous Erianthus-specific RFLP bands in the hybrids. Genomic DNA in situ hybridisation allows for the differentiation of the chromosomes contributed by S. officinarum and E. arundinaceus in chromosome prep- arations of the hybrids. In situ hybridisation with the 18s- 5.8s-25s rDNA probe highlights the basic chromosome numbers in the two parental species. The potential of these techniques to monitor the Erianthus genome during the in- trogression process is discussed. Key words Saccharum. Intergeneric hybrids. Isozymes 9 RFLP - STS-PCR 9 In situ hybridization - rDNA Communicated by H. F. Linskens A. D'Hont ([]). R Feldmann 9 L. Grivet. J. C. Glaszmann CIRAD, BP 5035, 34032 Montpellier, France R S. Rao WICSCBS, Groves, st. George, Barbados, West Indies N. Islam-Faridi CIMMYT, Lisboa 27, Apdo. Postal 6-641, Mexico D.F. 06600, Mexico R Taylor BSES, PO Box 86, Indooroopilly, Qld 4068, Australia Introduction The genera Saccharum, Erianthus (=section Ripidium), Miscanthus (section Diantra), Sclerostachya and Narenga constitute a closely related interbreeding group, assumed to be involved in the origin of sugarcane and, thus, referred to as the "Saccharum complex". Sugarcane belongs to the genus Saccharum, a complex genus which comprises six species, all characterised by a high ploidy level. Modern sugarcane varieties (Saccharum ssp., 2n=100-130) are derived from interspecific crosses, performed early this century, between the sugar-producing species Saccharum officinarum (2n=80) and wild relatives, mainly S. spontaneum (2n=40-128). Only a few parental clones were involved in these crosses (Arceneaux 1965; Price 1965). Thus the genetic base of modern varieties ap- pears to be very narrow and could be the reason for the present slow progress in sugarcane breeding. To broaden this genetic base, interest has turned to the use of other gen- era from the Saccharum complex, mainly Erianthus arun- dinaceus section Ripidium (Berding and Roach 1987; Roach and Daniels 1987; Walker 1987). E. arundinaceus (2n=60) is a large grass with tall and thick stalks which has useful agronomic traits such as vigour, drought and water- logging resistance, good ratooning ability, and disease re- sistance. Despite several attempts, over many years, to introgress E. arundinaceus characters in sugarcane varieties, no con- clusive success has been achieved. The first difficulty ap- pears to be the identification of true hybrids using morpho- logical traits. Two other factors suggested to be respon- sible for this lack of success are chromosome erosion dur- ing the successive back crossing and the lack of recombi- nation between the chromosomes of the two genera. In order to attempt to resolve these problems, isozyme analysis, sequence-tagged PCR, RFLP analysis and ge- nomic in situ hybridization were applied to specifically de- tect the E. arundinaceus genome in intergeneric hybrids between S. officinarum and E. arundinaceus. Isozyme and sequence-tagged-site PCR markers are shown to be sire-