About Sugarcane – ICAR-SUGARCANE BREEDING INSTITUTE

Botanical Name

The present day commercial sugarcane varieties are man-made hybrid clones involving Saccharum officinarum L., and S.spontaneum with a few genes incorporated from, S. barberi Jesw., S. sinense Roxb. and to a limited extent S. robustum Brandes.

Prior to the development of the man made varieties the S. officinarum clones were being cultivated in the tropical areas

Clones belonging to S. barberi and S. sinense were cultivated in northern India and parts of China in the sub-tropics.

North Indian canes differ from S. officinarum by

♠ Floral characteristics

♠ Thin to medium stalks

♠ Low to moderate sucrose content

♠ Higher fibre

♠ Greater tolerance to adverse conditions

S. sinense identical with Barbers’ Indian sugarcane group Pansahi.

S.sinense was used for chewing as well as for sugar manufacture, while the thinner, harder stalks of S. barberi were used for sugar production.

Evolution- The Sacchrum complex

Click this link here for a Pictorial view of Saccharum Complex

Saccharum, Erianthus, Sclerostachya and Narenga are closely related interbreeding group involved in the origin of sugarcane (Mukherjee, 1957). Daniels et al. (1975) suggested to include Miscanthus also to it.

Saccharum consists of six species:

Wild: S. spontaneum L. and S.robustum Brandes & Jesw ex Grassl

Cultivated: S. officinarum L; S. barberi Jesw.; S. sinense Roxb. and S. edule Hassk.

On current geographical distributions, Miscanthus and Erianthus sect. Ripidium are seen as primary in the Saccharum complex are closely related to Saccharum.

Miscanthus is the most primitive in the Saccharinae sub-tribe of Andropogoneae.

Sclerostachya and Narenga evolved much later.

Saccharum -centre of origin and low chromosome numbers in India – probably also later in evolution.The geographical origin of the noble canes (S. officinarum) is thought of at Melanesian region and the subject of their botanical origin has been of much speculation. The taxonomic researches of Grassl are of greatest importance in elucidating the likely origin of the noble canes. In addition to the part played by S. robustum in the ancestry of the group, it was proposed to have the involvement of Erianthus maximus Brogn. (Stevenson, 1965). Erianthus maximus, which was thought to be involved in the origin of S. officinarum, was later found to be a hybrid between S. officinarum and Miscanthus (Daniels and Roach, 1987).

The studies on flavonoid chemotaxonomic markers were undertaken by Daniels et al. (1989) to give evidence to the proposition of Daniels and Roach (1987) that S. officinarum evolved from complex introgression between S. spontanem, E. arundinaceus and Miscanthus sinensis. The intermediate products of this introgression were the groups of S. robustum, the generally recognized progenitor of S. officinarum. In the S. robustum groups there are only three- Red fleshed, Port Moresby and Teboe Salah – from which S. officinarum could have been selected. The most likely S. officinarum clones taken to Pacific and ultimately to Hawaii had the red fleshed characteristic. And the most likely population from which S. officinarum arose is the red fleshed populations on the Sepik. It was evident that Miscanthus was involved in the phylogeny of S. officinarum.

S. officinarum most probably developed in the East Indonesian/New Guinea area, east of Wallace Line from S. spontaneum, Miscanthus and Erianthus arundinaceus, and S. robustum is the intermediate form (Daniels and Roach, 1987). Evidences from the chemotaxonomic studies indicated that New Guinea S. spontaneum is atypical of the species found elsewhere and S. officinarum is closely related to it. Hypothesis for the evolution of S. officinarum via S. robustum include:

Geographical Distributuin

S. spontaneum is a highly polymorphic, wild grass, widely distributed in the tropics and sub tropics.

S. robustum is with tall and thick canes, seen on the river banks of New Guinea and Indonesia.

S. officinarum, the noble sugarcane, is present only under domesticated conditions and large variability is maintained as chewing canes in the native gardens in New Guinea and Indonesia.

S. barberi and S. sinense are the north Indian and Chinese canes that were under cultivation for sugar production.

S. edule is a polymorphic species with chromosome numbers 2n = 60, 70 and 80, and also forms with aneuploidy. It is cultivated in Pacific islands for its aborted inflorescence, which is used as a vegetable. The cane of S. edule resembles that of S. robustum and is considered to be a natural hybrid involving S. robustum, S. officinarum and Miscanthus spp

Cytogenetical Studies

Chromosomal numbers

♣ S.spontaneum L. 2n = 40-128

♣ S.robustum Brandes & Jesw ex Grassl 2n = 60-170

♣ S.officinarum L. 2n = 80

♣ S.barberi Jesw. 2n = 81-124

♣ S.sinense Roxb. 2n = 111-120

♣ S.edule Hassk. 2n = 60-80

♣ Irvine (1999) suggested only two species in Saccharum viz.,S. spontaneum and S. officinarum, which include S. robustum, S. officinarum, S. edule, S. barberi and S. sinense.

♣ Cytoplasmic DNA sequences from S. spontaneum differ from the other forms.

♣ Chloroplasts, mitochondria, and ribosomal DNA from S. spontaneum differ in base pair sequences from those of S. officinarum, S. robustum, S. sinense and S. barberi; and these four are indistinguishable from each other

Reproduction Mechanism

Sugarcane is a cross-pollinating species although selfing occurs at low levels. Although sugarcane flowers often have reduced male fertility they are rarely male sterile. Sugarcane pollen is very small and wind dispersed. It is rapidly desiccated after dehiscence, having a half-life of only 12 minutes, and is no longer viable beyond 35 minutes, under unmodified environmental conditions (26^o C and 67% relative humidity). As a result, viable pollen is not expected to disperse far in the field. Sugarcane pollen stored at 4^oC under 90 -100 % relative humidity retains some viability for up to 14 days.

The flowering of sugarcane is a subject of considerable significance. On one hand, it is essential for breeders to develop new varieties and on other hand, farmers do not favour it. Sugarcane flowers naturally in some regions but does not flower or rarely flowers in some other regions. It decreases as we proceed from south to northwest. Day length (photoperiod), temperature, moisture, latitudinal displacement affect flowering behaviour in various degrees.

Jeswiet (1925) gave an excellent account of description of changes taking place at the time of floral initiation, development of panicle and its ultimate emergence. It is possible to know the floral initiation in a stalk by observing the leaf size at top position. After progressive shortening of leaves at the top, the topmost leaf becomes very short, called as ‘short blade’‚ after which the inflorescence or ‘arrow’ emerges. The duration of days from floral initiation to short blade and to the time of complete emergence of arrow differs with species and clones.

Fertilization

In commercial hybrids, flowering season is spread over a period of two months (October – November). Time taken from short blade to arrow emergence ranges from 7 to 27 days. As the arrow emerges out, generally the branches (rachilla) begin to spread out. The time of opening of flowers (anthesis) is variable, but the order of opening is always from top downwards and from end (tip) of branches towards the centre (axis or rachis). In S.spontaneum, S.barberi and S.sinense, pedicellate spikelets open first and sessile spikelets open next day. While in S.officinarum, S.robustum and Erianthus, sessile spikelets open first and pedicellate later. Rarely, both open together in some S.barberi and S.officinarum clones (Dutt et al, 1938a). Generally, anthesis takes place early in the morning. In Erianthus species, it also took place in the evening (about 4 pm).

Species	Time of Anthesis
S.spontaneum	05.30 – 07.00 am
S.officinarum	05.45 – 11.00 am
S.robustum	06.00 – 10.30 am
Sugarcane	05.00 – 11.00 am

Natural Cross Pollination

At the time of anthesis, outer glumes (I & II) slightly spread out. Filaments elongate rapidly, pushing the mature anthers out of the spikelet in between the glumes, so that the anthers become pendulous and oscillate in the wind. Dehiscence is through a pore or partial slit and pollen is carried by wind (wind pollination). Later the empty anthers dry and fall off. Usually, the style also elongates exerting the feathery receptive stigma to catch the wind borne pollen.

After pollination, the spikelets close. Male sterility observed in some clones (particularly sugarcane) may be due to non-emergence of anthers, non-dehiscence, defective pollen, grain agglutination of pollens or poor pollen fertility (Dutt et al, 1954). Protogyny is observed in some clones of S.spontaneum. Weather conditions have some influence on the time of anthesis and dehiscence. Cold, cloudy or rainy day delays anthesis or dehiscence while a sunny, dry and windy day hastens anthesis or dehiscence.

Dutt et al., (1938b) reported more seed setting in sessile spikelets than in pedicellate ones and more germination in seeds developed from sessile spikelets and the seedlings were also relatively more vigorous. The above description is the general pattern in species of Saccharum and Erianthus. Variations occur in the time and duration only.

Sugarcane seed or ‘fuzz’‚ is the entire flower panicle without the main flower axis and larger lateral axes. Mature fuzz consists of the mature dry fruit (caryopsis), glumes, callus hairs, anthers and stigma. The superfluous parts of the inflorescence are generally handled, stored and sown with the seed because it is not practical to separate them. Although many commercial varieties of sugarcane can produce seed, fuzz is only used in breeding programmes, as the proportion of sugarcane seedlings with agronomic qualities near to those of the parental commercial clones is extremely low. Sugarcane

fuzz is short lived, loosing 90% of its viability in 80 days at 28^oC if not desiccated.

References

♦ Daniels, J., Smith, P., Paton, N. and Williams, C.A. 1975. The origin of the genus Saccharum. Sugarcane Breed. Newsl. 36: 24-39.

♦ Daniels, J and Roach, B.T. 1987. Taxonomy and evolution. In: D.J. Heinz (ed.) Sugarcane Improvement through Breeding. Elsevier, Amsterdam, The Netherlands. Pp. 7-84.

♦ Daniels, J., Paton, N. H., Smith, P. and Roach, B.T. (1989) Further studies on the origin of sugar canes Saccharum L., S. barberi Jesw. and S. sinense Roxb. Using flavonoid chemotaxonomic markers. Sugarcane 1989 (Autumn 1989 Supplement): 7-15.

♦ Dutt, N.L., Krishnaswami, M.K. and Rao, K.S.S. 1938a. On certain floral characters in sugarcane. Proc. ISSCT. 6 (1938): 154-170.

♦ Dutt, N.L., Krishnaswami, M.K. and Rao, K.S.S. 1938b. A note on seed setting and seed germination in certain sugarcanes. Ind J. Agri. Sci. 8: 429-433.

♦ Dutt, M.L., Ethirajan, A.S. and Hussainy, B.A. 1954. Different types of male sterility in sugarcane. Proc. II Bienn. Conf. Sugarcane Res. & Dev. Workers. 1954: 1-3.

♦ Irvine, J. E. 1999. Saccharum as horticultural classes. Theor. Appl. Genet. 98: 186-194.

♦ Jeswiet, J. 1925. Besehrijring der sorten von heit suikkerriet. II de Bidragdge Pridrage1st de Systematic van hat gestacht Saccharum. Arch V. Suikk. Ned. Indie. Meded. 33: 391-404.

♦ Mukerjee, S.K. (1957). Origin and distribution of Sachharum. Bot. Gaz. 119: 55-61.

♦ Stevenson, G.C. 1965. Genetics and Breeding of Sugar Cane. Longmans, London, 284 pp.