S. officinarum is the original sugarcane species. It is supposed to have originated in the Indonesian Archipelago. The species does not occur wild in nature but was grown and maintained for a long time by the natives of these islands. Later on it came to be cultivated in south India. There are two other cultivated species: S. barberi and S. sinense. These species are believed to be hybrid derivatives involving S. officinarum and wild species. S.barberi was grown in northern parts of India, while S. sinensewas cultivated in China. These two species are no more under cultivation with the advent of improved varieties that have been developed through complex hybridization. There are several other species and genera related to sugarcane.Commercial cultivars, the products of S. officinarum, S. spontaneum, S. barberi and S. sinense, constitute the primary gene pool since potential cultivars can be fixed in the first sexual generation itself. The cultivated species S. officinarum, S. barberi and S. sinense can be considered as secondary gene pool since involvement of these species in varietal improvement would involve a few generations of breeding. S. spontaneum and S. robustum constitute the tertiary genepool since it takes a number of generations to eliminate the undesirable effects of these wild species during varietal development. The allied genera can be termed as distant gene pool and these have not been successfully utilised so far. Of these, the only cane forming species Erianthus arundinaceus is drawing a lot of attention of the breeders world wide especially because of its high biomass producing ability and resistance to biotic and abiotic stesses

From breeding point of view it is sufficient to consider only S. officinarum, S.spontaneum, S. robustum and Erianthus arundinaceus since S. barberi and S. sinense are widely believed to be materials of introgression between S. officinarum and S.spontaneum (Brandes, 1958). Among the three wild species, utilisation of S. robustum has not been very successful so far, perhaps because it is genetically very much close to S.officinarum as revealed by investigations employing molecular techniques. Hence,the cultivated S. officinarum and the wild S. spontaneum and Erianthus arundinaceus, in addition to the vast array of commercial varieties, constitute the most important materials available to the breeder for sugarcane improvement

The present day commercial varieties are the products of crossing, inter-crossing and back-crossing involving these two species in addition to the cultivated S. barberi and S.sinense. These cultivated varieties combine all the desirable attributes of S. officinarum and the resistance factors of S. spontaneum in addition to its ability to produce high biomass.

A number of hypotheses have been put forward to explain the mechanism of 2n + n transmission in sugarcane (Price, 1961). Among these are:

♦ Formation of unreduced egg cells

♦ Chromosome doubling through endo-duplication either at the dyad or tetrad stage

♦ Postmeiotic fusion of the two innermost megaspores

♦ Postmeiotic endomitosis in the egg cell

♦ Incompatability of n + n gametes due to either selective fertilization or a combination of selective fertilization and parthenogenesis, i.e. differential survival of 2n+n and n+n zygotes

♦ Failure of certain zygotic combinations due to faulty endosperm development (selective survival)

It is essential to introduce greater diversity especially of S. spontaneum genome in imparting sustained resistance against abiotic stresses. Since the time Barber successfully made crosses between S. officinarum (Vellai) and S. spontaneum (Coimbatore form), the attempt was repeated several times upto the 60’s, using different clones in the process of evolving superior varieties. However, only 11 clones of S. officinarum and two clones of S.spontaneumas given below, have been utilised so far in the development of present day varieties
S. officinarum: Ashy Mauritius, Badila, Banjermasin Hitam, Black Cheribon, Fidji,Green Sport, Kaluthai Boothan, Lahaina, Loethers, Striped Mauritius, Vellai.

S. spontaneum: Coimbatore form, Java form Realising the need to introduce diverse genetic materials in the base population, intensive work in the last 15 years has resulted in the development of potential varieties that have in their ancestry, the following genetic base.
S. officinarum: 28 NG 51, 28 NG 93, 28 NG 210, 28 NG 221, 28 NG 224, 57 NG 78,57 NG 110, NG 77-63, NG 77-92, NG 77-99, NG 77-137, Uahi-e-pele.
S. spontaneum: SES 44A, SES 69, SES 87A, SES 90, SES 91, SES 93, SES 131, SES 198, SES 275, SES 515-7, SES 517 A, SES 538 A number of promising materials developed from the above are under varietal evaluation in different areas and a few of them have been elevated to Co status.

Apart from S.spontaneum, another important cane forming wild species, related to the genus Saccharum is Erianthus arundinaceus that can be nobilized. Its potentiality in contributing useful gene complexes for high fibre, high biomass, tolerance to drought and water logging, pest and disease resistance and multi-ratooning ability appears to be very attractive. However, there are two major obstacles that are to be overcome. The first is that S. officinarum, unlike in S.spontaneum nobilization, appears to transmit only n gametes instead of 2n when it is crossed to Erianthus arundinaceus. The second is that there is manifestation of sterility in the intergeneric hybrids, precluding further improvement through breeding.A novel method of overcoming these twin difficulties has been thought of and is being implemented at this Institute. The idea is to use S.spontaneum as bridge species between S.officinarum and Erianthus arundinaceus. Towards this objective crosses have been made between Erianthus arundinaceus as female and S. spontaneum as male and vice versa. The presence of S. spontaneum genome in these intergeneric progenies, when used as males are expected to trigger 2n gametes formation in S.officinarum during the nobilization process and thus enable retention of the entire genome of S.officinarum.

Nobilization is very central to sugarcane breeding activities. Use of S.spontaneum in crossing with S. officinarium as female laid the foundation on which the sugarcane breeding activities have been built up. Cytogenetically, S.spontaneum has triggered 2n gamete functioning in S. officinarium enabling the hybrids to retain the entire genome of cultivated S. officinarium which is essential for further improvement

Agronomically, S.spontaneum has contributed desirable attributes like high biomass, resistance to pests and diseases and tolerance to adverse environmental factors. Thus, S.spontaneum has played a very effective role in sugarcane improvement. Erianthus arundinaceus, that is related to the genus Saccharum appears to be a very promising candidate for nobilization. Since sterility and absence of 2n + n chromosome transmission are the problems faced in nobilization E. arundinaceus, use of S. spontaneumas bridge species is being attempted and the preliminary results obtained are quite encouraging.Out of several crosses attempted during 2001 crossing season in E. arundinaceus x S. spontaneum, 13 seedlings (confirmed hybrids) were obtained in two crosses as reported earlier. Out of these seedlings raised during 2002, four perished without forming stem. In the remaining nine seedlings, only three were healthy and came to flowering. The other six seedlings showed varying intensity of disorder in synthesising chlorophyll pigments. Because of this, they became very weak and did not come to flowering. The three progenies which were healthy, showed high pollen sterility. Thus, it is very clear that ‘ hybrid inviability ‘ and ‘hybrid sterility’ (as enunciated by Stebbins, 1951 in the context of seed propagated species) operate as reproductive barriers.

Chromosome number from root tip cells could be examined in four progenies in IK 76-92 x SES 286. Assuming n + n transmission the progenies should give a somatic number 62 (30 + 32). However, the 2n number was far less (50, 52, 54 and 58) indicating that there is en block elimination of chromosomes.

Although hybridity of these progenies was beyond doubt as ascertained by morphological features, molecular technique was employed to further confirm hybridity. Five of these nine surviving progenies were subjected to STMS (Sequence Tagged Microsatellites Sites) marker analysis and S. spontaneum specific markers were found, confirming hybridity. The three healthy progenies which showed 0 % pollen fertility as seedlings, gave certain degree of pollen fertility (5 to 15 %) after clonal propagation. These hybrid progenies were further utilised in making crosses. In the reciprocal group S. spontaneum x E. arundinaceus, several progenies were very vigorous and showed peculiar twining habit. The hybridity of these progenies is yet to be ascertained beyond doubt. Further investigation would reveal whether this new technique would bring in the much needed fertility to the intergeneric hybrids.

Preliminary indications are that although the pollen fertility of the intergeneric hybrids between E. arundinaceus and S. spontaneum is very low (20 % or less), these clones when used as females in further hybridization, have given genuine hybrid progenies as indicated above.

→ Brandes, E.W. 1958. Origin, classification and characteristics. In E. Artschwager and E.W. Brandes. Saccharum officinarum L. U.S. Dept. of Agric. Handbook. pp. 122 Bremer, G. 1923.A cytological investigation of some species and species hybrids within the genus Saccharum. Genetica, 5: 97-148.2.

→ Bremer, G.1961. Problems in breeding and cytology of sugarcane. 1. A short history of sugarcane breeding – the original form of Saccharum. Euphytica, 10: 59-68.

→  D’Hont, A, Grivet, L., Feldmann, P.,Rao, S., Berding, N., and Glaszmann, J.C. 1996. Characterisation of the double genome structure of modern sugarcane cultivars (Saccharum spp.) by molecular cytogenetics. Molecular Genetics and Genomics. 250: 405-413.

→  Piperidis, G., Christopher, M.J., Carroll, B.J., Berding, N. and D’Hont, A. 2000. Molecular contribution to selection of intergeneric hybrids between sugarcane and the wild species Erianthus arundinaceus. Genome, 43(6): 1033-1037.

→  Price, S. 1957. Cytological studies in Saccharum and allied genera. IV. Hybrids from S.officinarum (2n = 80) x S. spontaneum (2n + 96). J. Hered., 48: 141-145.

→  Price, S. 1961. Cytological studies in Saccharum and allied genera. VII. Maternal chromosome transmission by S. officinarum in intra- and interspecific crosses. Bot.Gaz.,122, No.4.

→  Stebbins,G.L. 1951. Variation and evolution in Plants.Columbia Univ. Press. New York, p.625.

→  Stevenson,G.C. 1965.Genetics and Breeding of Sugarcane.Longmans, London, pp.284.