Breeding Sugar Cane (Saccharum sp.)

The document describes in detail the systematics, origin and distribution of sugarcane, the history of sugarcane in Zimbabwe and different hybridization methods of sugarcane.

1. SUGAR CANE Saccharum sp Providence T Moyo L0160550A

2. INTRODUCTION Sugar cane in Zimbabwe is grown under canal irrigation in the lowveld area of Triangle and Hippo Valley, in the Chiredzi District, Masvingo Province About 80 percent of Zimbabwe`s sugar cane crop is produced by two large estates, namely, the Triangle Sugar Estate and Hippo Valley Estate. Private farmers, including large scale farmers and newly resettled farmers, produce about 20 percent of the country's sugar cane crop. There are two sugar mills in Zimbabwe, the Hippo Valley Estates Ltd and Triangle Sugar Estates Ltd, with a combined sugar production capacity of about 640,000 MT and installed milling capacity of 4.8 Million MT of sugar cane per annum.

3. The main diseases of concern in the Zimbabwe sugar industry include Smut, Ratoon Stunt Disease (RSD), Leaf Scald, Brown Rust, Orange Rust (no official reported case), and Sugar Cane Yellow Leaf Virus. The main pests of concern in include Eldana , Sugar Cane Yellow Aphid; and Black Maize Beettle . Viral diseases in crops are not closely monitored and controlled. The Zimbabwe Sugar Association Experiment Station (ZSAES) routinely scouts for pests and diseases in all sugar cane farms, including those subsistence farms that produce chewing sugar cane as part of the industry biosecurity and risk mitigating measures.

4. Zimbabwe has fourteen major varieties of sugar cane approved for growing by farmers. While the industry seeks to limit each variety to a maximum of 40 percent in order to minimize and diversify risks, the N14 variety currently accounts for about 60 percent of the sugarcane production. One of the new varieties ZN10 has been gaining popularity with farmers because of its high sucrose content.

5. SYSTEMATICS, ORIGIN AND DISTRIBUTION

6. They have six species of perennial grasses all of which originated in old world and only two are occurring in a wild state i.e S.spontaneum and S.robustum The other four species are cultigens: S.officinarum - Noble cane of New guinea. S.barberi - North Indian canes S.sinensis - Chinese cane. S.edule - Melenesian cane.

7. Saccharum spontaneum (2n = 40 - 128) A perennial grass, free tillering , often with Rhizomes. S.spontancum represents a polyploid series. Natural hybridization with S.officinarum would have produced S.barberi and S.sinense Used in breeding programmes through nobilisation with S.officinarum . Spontaneum provides vigour , hardiness and resistance against diseases.

8. Saccharum robustum : (2n = 60 - 194) Origin is New guinea Vigorous perennial. Robustum would have given rise to S.officinarum with which it is interfertile. S.robustum is highly susceptible to mosaic virus and leaf scale and because of this its use in breeding programmes is very much limited.

9. Saccharum officinarum (2n = 80) Origin : South pacific. Chewing cane. Noble cane This cane is suited to tropical conditions and requires favourable soil and climate. The stems are stout thick high in sucrose, low in fibre and with soft rind. The noble canes are susceptible to most of the diseases. Some of the earlier cultivars are Bourbon, Cheribon noble canes.

10. S. barberi (2n = 82 – 124) S.barberi is short medium to slender in thickness, with high fibre content, medium sucrose content and poor yielder. S.sinense : (2n = 18) Chinese cane. Tall vigorous, slender, high fibre content. Poor juice quality. S.edule : Polynesian cane (2n = 118) Slender, weed like form. Seeds are edible. Not much used.

11. NOBILISATION IN SUGAR CANE Nobilisation is crossing the noble cane S. officinatum with S.barberi , S.spontaneum and infusing disease and pest resistance in the noble cane. The first successful use of nobilisation was made and variety cheribon was crossed with S.barberi variety and progenies having resistance to sereh disease were evolved. Susceptible to mosaic and inferior in sucrose content. By subsequent crossing with S.officinatrum i.e. second and third nobilisation good varieties like POJ 2878 were evolved.

12. BREEDING OBJECTIVES FOR SUGARCANE Breeding varieties suitable for Jaggery making. Breeding varieties for factory purposes - high Brix value. Breeding varieties resistant to shoot borer. Breeding varieties resistance to disease shoot disease, Rust, Brown spot. Breeding varieties with high ratooning ability. Breeding varieties with drought resistance. Breeding varieties with more number of productive tillers. Varieties with shorter duration without yield.

13. BREEDING THE SUGARCANE Cross pollination is the rule in sugarcane. Self male and female sterility, protogyny and hanging down of anthers away from the stigma at the time of anthesis promote self pollination. Stigma protrudes out first and anthers dehisce afterwards. Flower opening will be from top to downwards. It will take about 10 days for complete opening of spikelets . Flowering in sugarcane is location specific and influenced by environment. Natural pollination is by wind.

14. SELFING Selfing is done by covering the arrow with a bamboo frame work or cage which is covered with muslin cloth or polythene paper (the lantern). It prevents accidental cross pollination. The lantern has to be supported by bamboo poles. The lantern has to be opened once in a day to reduce the temperature that might build up inside during the day time. Usually the cover has to be retained in position till the seeds are set. Within one week or 10 days we can get selfed seeds.

15. CROSSING Hybridization is very difficult because: It is mostly vegetatively propagated. Some varieties seldom flowers outside tropics. Some varieties flowers once in 6 to 8 months. It is highly controlled by photoperiods. Spikelets are minute. So, hand emasculation is not possible. Self sterility of both pollen and ovule predominates in almost in all the varieties. Hot water treatment can not possible.

16. HYBRIDISATION METHODS

17. COIMBATORE METHOD During flowering period, the sugarcane stem will be cut leaving one or two buds. The cut stem can be transferred to a mud pot having moist mud. Within 10 days the buds will develop into roots and there will be good root system. This can be transferred to the breeding block. In the crossing block, the male and female plants are covered with common lantern. Free shedding pollen over female plant will occur. We can harvest both selfed and crossed seeds from the female parent. The selfed seeds can be identified by chromosome number by raising it in the nursery. Selfed seeds thus removed retaining crossed seeds.

18. MARCOTTING METHOD During flowering, cut around the stem and tie a polythene bag with nutrients (growth medium). The bud near cut end give rise to roots. This can be cut and used for hybridization purposes. This method is called marcotting.

19. LANTERN METHOD Providing Lantern for a female plant before anthesis starts. From the desired male parent cut the arrow. That arrow can be introduced into the Lantern and shaken up and thereby crossing can be effected. This will be repeated for 2-3 days in order to have more seed set.

20. HAWAII METHOD (SULFUROUS ACID TECHNIQUE) Both male and female flowering arrows are cut along with small portion of stem. These cut end will be immersed in a vessel containing 0.01% sulphuric acid and 0.01% phosphoric acid. The cut end at the lab is brought nearer and effect cross pollination. They absorb the weak acids. A weak solution is added daily to replace the acid taken by stem. Once in a week, the solution is completely changed. This is done for 20-30 days. During this time, the seed will mature.

21. Cont … In a modified method of the Hawaii method, the female plant alone is cut and kept in weak acid at the time of flowering the male parent can be brought nearer and the pollen can be shed by shaking as done in Lantern method.

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