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Chapter 1 Sugarcane: The Crop, the Plant, and Domestication

Paul H. Moore, Andrew H. Paterson, and Thomas Tew

SUMMARY INTRODUCTION

Sugarcane, a significant component of the econ- Sugarcane is an important food and bioenergy omy of many countries in the tropics and sub- source and a significant component of the econ- tropics, is a large, tropical grass that stores sucrose omy of many countries in the tropics and sub- in its stem and serves as an important food and tropics. The economic value of sugarcane is bioenergy crop. It has long been recognized as one based primarily on three attributes: it is highly of the world’s most efficient crops in converting productive; it efficiently uses agricultural inputs solar energy into chemical energy harvestable as (water, fertilizers, pesticides, labor); and it can sucrose and biomass. Current taxonomy divides be locally processed into added-value products– sugarcane into six species, two of which are wild sugar, molasses, ethanol, and energy–all amenable and always recognized (Saccharum spontaneum L. to storage and transport. Collectively, these crop and Saccharum robustum Brandes and Jewiet ex attributes contribute to making sugarcane a pri- Grassl). The other species are cultivated and clas- mary trade commodity of those countries where it sified variously. Of the four domesticated species is grown. of sugarcane, S. officinarum L. was the first named Sugarcanes are generally large, perennial, trop- and is the primary species for production of ical or subtropical grasses that evolved under sugar. Recent genomic data for evaluating genetic conditions of high sunlight, high temperatures, diversity within Saccharum suggest relationships and large quantities of water. Sugarcane is thus among accessions that may ultimately produce adapted to a climatic zone around the world a definitive classification for the group. Culti- between 35o north and south of the equator (Blume vated sugarcanes of today are complex interspe- 1985). Because sugarcane can be used as a trade cific hybrids primarily between Saccharum offici- commodity, it is produced by nearly 100 coun- narum, known as the noble cane, and Saccharum tries over an area of 23.8 million hectares (FAO- spontaneum, with contributionsCOPYRIGHTED from S. robustum, STAT MATERIAL 2009), which is approximately 1.5% of the S. sinense, S. barberi, and related grass genera such total world cropland area (Table 1.1). The land as Miscanthus, Narenga,andErianthus. Under- area devoted to sugarcane is small compared to standing the source and range of diversity of sug- that for the three major cereal crops, which col- arcane species and cultivars can enable breeders lectively occupy 34.6% of the world’s cropland. in the development of new varieties improved for On the basis of the relatively small area under high productivity with low inputs and wide adap- cultivation, sugarcane can be considered a special- tation to varied environments. ity crop, but of all food crops, sugarcane has the

Sugarcane: Physiology, Biochemistry, and Functional Biology, First Edition. Edited by Paul H. Moore and Frederik C. Botha. C 2014 John Wiley & Sons, Inc. Published 2014 by John Wiley & Sons, Inc.

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2 Sugarcane: Physiology, Biochemistry, and Functional Biology

Table 1.1 Crop production and daily caloric consumption of the world’s most cultivated food crops.

Productiona Rank by tonnage Consumptiona Rank by calories Areaa Fraction of Crop (Mt) produced (kcal/capita/day) consumed (Mha) cropland (%)

Sugarcane 1661 1 152 3 23.8 1.5 Maize 819 2 139 4 158.6 10.2 Wheat 685 3 530 2 225.6 14.4 Rice 685 4 533 1 158.3 10.0 Potatoes 330 5 59 7 18.7 1.2 Cassava 234 6 43 9 18.9 1.2 Sugar beet 227 7 76 6 4.3 0.3 Soybeans 223 8 105 5 99.5 6.4 Oil palm kernel 210 9 50 8 14.9 1.0 Tomatoes 153 10 9.2 12 4.4 0.3 Barley 152 11 6.5 13 54.0 3.5 Sweet potatoes 102 12 22 10 8.2 0.5 Watermelons 98 13 — — 3.4 0.2 Bananas 97 14 19 11 4.9 0.3

Total 2798 b1562 51.1

aFAO 2009. bWorld’s total cropland. Data uploaded by Viridiplantae from FAOstat (24 January 2009). Mt, megatonnes (metric tons × 106); Mha, megahectare (ha × 106).

highest level of production (1661 megatonnes) fol- the criteria employed and the taxonomic conven- lowed by the cereals (maize, wheat, and rice), the tion of the time. The original classification of cul- root or tuber crops (potatoes and cassava), and the tivated sugarcane as Saccharum officinarum L. by oil crops (soybeans and palm kernel) (Table 1.1). Linnaeus in 1753 established the genus Saccha- The high level of production recorded for sug- rum L. for sugarcane. However, the genus Saccha- arcane could be misleading because the reported rum was subsequently expanded to include many productivity is the total harvested biomass and accessions that, with the exception of inflorescence only a fraction of this (approximately 25+percent) and floral morphologies, have little in common is dry matter, whereas the dry matter percent with sugarcane. For example, a search of the Inte- of grain and tuber crops is much higher. Nev- grated Taxonomic Information System (ITIS) ertheless, the sugarcane crop provides the third database (http://www.itis.gov) lists 23 species of highest quantity of human consumed plant calo- Saccharum, seven of which are no longer accepted ries (152 kcal/capita/day) following rice (533 kcal) and five of which are currently listed as a species and wheat (530 kcal). These production statistics of wild or domesticated sugarcane. The more emphasize the very much higher productivity of extensive Kew GrassBase database (http://www. sugarcane compared to other food crops and raise kew.org/data/grasses-db.html) lists 37 species questions about the physiological bases for how of Saccharum, only four of which are currently this productivity is achieved and how it might be accepted as species of sugarcane. Current sugar- sustained or improved. cane literature recognizes six species of Saccha- rum, two of which are wild and always recognized (Saccharum spontaneum L. and Saccharum robus- SINGULAR PROPERTIES OF THE GENUS tum Brandes and Jewiet ex Grassl). The other SACCHARUM AND ITS MEMBERS species are cultivated. This review is restricted to only those Saccharum species generally recognized Taxonomy as sugarcane. Sugarcane is the common name given to a group of Sugarcane species are members of the sub- cultivated, sucrose-storing, large tropical grasses tribe Saccharinae, tribe Andropogoneae, of the that have been classified variously depending on grass family, Poaceae or Gramineae. The grass BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

Sugarcane: The Crop, the Plant, and Domestication 3

family is large, including approximately 10,000 species classified into 600 to 700 genera. The 2n= Mbp/1C= tribe Andropogoneae contains 85 genera and Sorghum bicolor 20 736 Pansorghum 960 species (Clayton & Renvoize 1986 as cited Sorghum halepense 40 ? Eusorghum by Spangler et al. 1999), many of which have Sorghum propinquum 20 690 high economic value, including the C4 crops Sorghum nitidum 20 4307 Saccharum officinarum L. (sugarcane), Sorghum Vacoparis macrospermum 40 1014 bicolor (L.) Moench (sorghum), and Zea mays Vacoparis laxiflorum 40 1220 L. (maize). Miscanthus Anderss. is an additional Sarga angustum 10 1813 Sarga intrans C4 grass that shows considerable potential as a 10 1117 Sarga leiocladum 10 2254 germplasm source for cold tolerance (Clifton- Heterosorghum Brown & Lewandowski 2000), as a biomass crop Saccharinae Sarga plumosum 30 3748 for renewable energy production, and as raw mate- Sarga purpureo-sericeum 10 2048 rial for the cellulose and paper industries (Bullard Sarga timorense 10 622 et al. 1995; Dohleman et al. 2009). Sarga trichocladum ? ? Classical taxonomy based on cytological Parasorghum Sarga versicolor 10, 20 1592, 3268 Cleistachne and morphological characters has been used Miscanthus sinensis 38 2824-3786 to describe probable evolutionary relationships Miscanthus x. giganteus 57 3916-4576 within Saccharinae, and recently molecular data Miscanthus sacchariflorus 76 2234-2867 have allowed for more definitive relationships. M. sacchariflorus ‘Robustus’ 38 Spangler et al. (1999) used chloroplast DNA Microstegium nudum markers to show broad relationships among the Saccharum spontaneum 36-128 Andropogoneae and probable polyphyletic origins Saccharum cultivars 100-130 4183 of Sorghum, Miscanthus,andSaccharum (Fig. 1.1). Saccharum officinarum 70-140 Hodkinson et al. (2002) used DNA sequences of a Saccharum robustum 60-170 nuclear ribosomal gene and two plastid sequences Zea mays 20 2300 to confirm the polyphyletic origin of Miscanthus and Saccharum and to distinguish between them. Fig. 1.1. Phylogenetic relationship of selected members of The other members of the subtribe Saccharinae the Saccharinae clade. Phylogenetic interpretation from Span- could not be completely resolved with such lim- gler et al. (1999). Genome size estimates from Arumuganathan ited data. & Earle (1991), Bennett & Leitch (2003), and Price et al. (2005). The present compilation of Saccharum species does not have a stable history. The first edition of Species Plantarum (Linnaeus 1753) listed two sugarcane to six. Two of them (S. spontaneum and species of Saccharum: S. officinarum and S. spi- S. robustum) are wild and always recognized; the catum. Subsequent taxonomic treatments up to remaining four (S. barberi, S. edule, S. officinarum, the time of revision by Jeswiet in 1927 listed up and S. sinense) are cultivated forms and have been to 22 species of Saccharum (discussed in Irvine accorded the status of species, but because they 1999 and presented as Table 8 in Daniels & Roach do not survive in the wild, there is an increasing 1987). Jeswiet (1927) reassigned many of those trend to consider these as cultigens (Irvine 1999; added species to different genera and went on Grivet et al. 2004, 2006). to describe four natural groups consisting of S. The identification and delineation of those spontaneum L., S. sinense (Roxb) Jesw., S. barberi species grouped as sugarcane have been compli- Jesw., and S. officinarum L. to be included in Sac- cated by hybridizations, both natural and man- charum L. Subsequently, two forms of Saccharum made, among themselves and with related species. discovered in New Guinea (S. robustum Brandes Many members of the interbreeding group have & Jeswiet ex Grassl. [Grassl 1946] and S. edule different genome structures that produce inter- Hassk. [Whalen 1991]) were added to the genus to mediate forms, and some of those intermediate bring the number of widely recognized species of forms have totally new genome structure due to BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

4 Sugarcane: Physiology, Biochemistry, and Functional Biology

different types of chromosome transmission. Wide The morphological differences among the hybridization has resulted in a mixture of sug- members of the Saccharum complex are mostly arcane euploids and aneuploids. Layered on top related to floral characters but also include some of this genetic complexity are the selection pres- vegetative structure characters such as the num- sures applied by nature and man to drive dif- ber of rows of nodal root primordia, axillary bud ferent population structures. Cultivars of sugar- development, and presence or absence of a leaf cane are hybrids of different species of the genus dewlap (Table 1.2). A significant difference among Saccharum and may include germplasm from the members of the Saccharum complex is the level nine related genera, Imperata, Eriochrysis, Eccol- of sucrose accumulation in the stems of Saccha- ipus, Spodiopogon, Miscanthidium, Erianthus sect. rum spp., ranging from very low levels in the wild Ripidium, Miscanthus, Sclerostachya, and Narenga, Saccharum species S. spontaneum and S. robus- which are included in the subtribe Saccharinae tum to high levels in the domesticated species S. (Clayton 1972, 1973). officinarum, S. sinense,andS. barberi (Table 1.3). Mukherjee (1954) revised the genus Saccha- Sugarcane species designation has been based on rum based on phytogeographical data, morphol- chromosome numbers, floral characters, sugar and ogy, cytology, and breeding evidence to combine fiber content, and stalk diameter. However, the the genus with three other Saccharinae gen- free intercrossing among the species, the strong era (Erianthus sect. Ripidium, Sclerostachya, and influence of environment on the quantitative phe- Narenga) into an informal taxonomic group he notypic characters, and the wide overlap of mea- called the “Saccharum complex.” Later, Daniels sured values do not always allow for clear species et al. (1975) added the genus Miscanthus to the differentiation. More recently, molecular cytoge- Saccharum complex because it was considered netics and genomics have revealed evolutionary that Miscanthus also contributed to the origin relationships among the Saccharum species that of Saccharum. Although the Saccharum complex aremoredefinitive. concept has proven useful in guiding sugarcane Of the four cultivated groups of Saccharum, S. breeders toward utilizing the species within it officinarum L. (2n = 80) was the first named and as part of the gene pool available for sugarcane is the primary group for production of sugar. S. improvement, recent molecular data raise serious officinarum accessions have thick stalks with low doubts about some of the earlier proposed origins fiber and high sucrose contents (Table 1.2). Sac- and genetic relationships of the Saccharum species charum barberi Jeswiet (2n = 82–124) in India and (Irvine 1999; Grivet et al. 2004, 2006). Saccharum sinense Roxb. (2n = 88) in China have

Table 1.2 Morphological differences at the generic level between members of the Saccharum complex as described by Mukherjee (1954) and revised by Daniels et al. (1975).

Character Saccharum Erianthus Sclerostachya Narenga Miscanthus

Root eyes 2 or more rows Only 1 row if Absent Absent 1 or 2 rows if present present Bud Well developed, Scaly, except in 2 Absent Scaly, not Well developed, reproductive species reproductive reproductive Dewlap Present Absent Present Present Present Spikelet pair Sessile and Sessile and Both pedicellate Sessile and Sessile and pedicellate pedicellate pedicellate pedicellate Callus hairs ≥ 2–3 times length ∼ same as spikelet ∼ 0.5 length of ≤ length of spikelet 0.5–2 times length of spikelet spikelet of spikelet

Source: Modified from Amalraj & Balasundaram [2006]. Note: Mukherjee revised the genus Saccharum and noted three species (Erianthus, Sclerostachya, and Narenga) that are closely related and interbreeding with sugarcane. He grouped these three species with Saccharum, referring to the group as the Saccharum complex (1954), to indicate a large breeding pool involved in the origin of sugarcane (1957). Daniels et al. (1975) added Miscanthus to the Saccharum complex postulating it also contributed to the origin of sugarcane. BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

Sugarcane: The Crop, the Plant, and Domestication 5

Table 1.3 Principal characteristics of six species of Saccharum and Erianthus with the number of accessions in two of the world collections.

Germplasm No. Sucrose Fiber Stem accessions Species (chromosome Common content content diameter number) name (% f.wt) (% f. wt) (cm.) Adaptability USa Indiab

S. officinarum Noble High Low Thick Tropical 748 764 (2n = 80) (1825) (5–15) 2.8 ± 0.30 S. sinense Chinese Medium High Medium Tropical 61 29 (2n = 110–120) (12–15) (10–15) (1.4–2.2) and subtropical S. barberi Indian Medium High Medium Tropical 57 43 (2n = 81–124) (13–17) (10–15) (1.7–2.1) and subtropical S. spontaneum Wild Very low Very high Slender Tropical/through 635 598 (2n = 40–128) (1–4) (25–40) (05–0.9) temperate S. robustum Wild Low Very high Medium Tropical 128 145 (2n = 60–194, usually 80) (3–7) (20–35) (1.1–1.7) wetlands S. edule Edible Low Low Medium Tropical 22 16 (2n = 60, 80, up to 122) (3–8) ? (1.1–1.8) Erianthusc Related Very low Very high Slender Subtropical and 282 (2n = 20, 30, 40, 60) temperate

Note: Sucrose, fiber, and stem diameter values are either the range or the mean ± SD measured by the Sugarcane Breeding Institute, Coimbatore, India, reported in the germplasm catalogs: Sugarcane Genetic Resources I. Saccharum spontaneum L. (1983); II. Saccharum barberi, Jeswiet; Saccharum sinense, Roxb. amend Jeswiet; Saccharum robustum, Brandes et Jeswiet ex Grassl; Saccharum edule, Hassk (1985); III. Saccharum officinarum L. (1991). aSaccharum germplasm inventory maintained by the USDA, ARS, Miami, Florida; data from http://www.ars-grin.gov National Plant Germplasm System (GRIN) of the USDA/ARS web site 3-30-2010. bGermplasm inventory maintained by the Sugarcane Breeding Institute, Coimbatore, India; data from http://sugarcane- breeding.tn.nic.in/genresources.htm 3-30-2010 and the germplasm catalogs “Sugarcane Genetic Resources Vols. I, II, III.” cErianthus germplasm, classified in GRIN as Saccharum spp. (arundinaceum, bengalense, gigantium, brevibarbe, etc.) is main- tained at several germplasm repositories.

been cultivated since prehistoric times, but are tum populations and preserved by humans (Grivet seldom, if ever, cultivated today; they exist pri- et al. 2006). marily in germplasm or garden collections. These Among the wild species, S. spontaneum (2n = two species are sometimes grouped together as a 40–128, with chromosome numbers frequently as single species, or as historical cultigens, having multiples of eight) is highly variable in morphol- thin to medium stalks, low to moderate sucrose ogy, cytology, and geographic distribution broadly content, and higher fiber and greater tolerance to throughout tropical and subtropical regions from stress than does S. officinarum. The fourth domes- Africa to the Middle East, China, and Malaysia, ticated species, Saccharum edule Hassk. (2n = through the Pacific to New Guinea. S. sponta- 60 or 80 sometimes up to 122), has an aborted neum accessions exhibit phenotypic, cytological, and edible inflorescence and is cultivated from and cytoplasmic and nuclear DNA sequences that New Guinea to Fiji as a vegetable. Based on are quite different from those of the other Sac- its geographical distribution and vegetative mor- charum species. It is a perennial grass, from short phology, S. edule was proposed to be an inter- bushy types with no stalk, to large-stemmed clones generic hybrid between either S. officinarum or S. over 5 m in height, but typically with pencil-thin robustum and a related genus, or to be a mutant stalks and very low sucrose content (Table 1.2). It of either of these Saccharum species (Daniels & is free tillering with robust rhizomes and has con- Roach 1987; Roach & Daniels 1987). However, tributed toward the development of modern cul- molecular data now indicate that S. edule may be tivars by conferring resistance to most major dis- a series of mutant clones selected from S. robus- eases, providing vigor and hardiness for increased BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

6 Sugarcane: Physiology, Biochemistry, and Functional Biology

abiotic stress tolerance (such as cold and drought), species S. barberi is not listed in the Kew database increasing tillering, and improving ratoonability GrassBase (http://www.kew.org/data/grasses- (Panje 1971). db.html) but is included as S. sinense. The other wild species of Saccharum, S. robus- tum, (two cytotypes predominate as 2n = 60 or 80, but with some accessions having chromosome Genome structure of modern cultivars numbers as high as 194) has its center of diversity Modern cultivars are highly polyploid and ane- in New Guinea in the same region as the domes- uploid with around 120 chromosomes. They are ticated S. officinarum (2n = 80). S. robustum has derived from interspecific hybridization between thick stalks and low sucrose content. It is dis- S. officinarum and S. spontaneum. As a conse- tinguished from S. spontaneum, but similar to S. quence of the different basic chromosome num- officinarum, by its lack of rhizomes, thickness and bers of S. officinarum (x = 10) and S. spontaneum height of stalks, and larger inflorescences. (x = 8), two distinct chromosome organizations Recent genomic data for evaluating genetic coexist in modern cultivars. (See the section titled diversity within Saccharum suggest relationships “Breeding through nobilization to produce nobi- among accessions that may ultimately produce a lized cultivars” for details on chromosome inher- definitive classification for the genus. The first itance in these wide species hybrids.) GISH of molecular evidence came from restriction frag- total genomic DNA suggests that 10 to 20% of ment patterns of nuclear ribosomal DNA that were modern cultivars chromosomes are inherited in used to separate accessions of S. spontaneum,which their entirety from S. spontaneum; 70 to 80% are showed the widest within-species variation, from inherited entirely from S. officinarum; and around accessions of S. robustum, S. officinarum, S. barberi, 10% are the result of recombination between chro- and S. sinense (Glaszmann et al. 1990). Restriction mosomes from the two ancestral species (D’Hont fragment length polymorphism (RFLP) analyses et al. 1996; Cuadrado et al. 2004; Piperidis, G. of the mitochondrial genome showed an identical et al. 2010). pattern among 18 S. officinarum clones and 15 of 17 Cultivated sugarcane is rare among major S. robustum clones (D’Hont et al. 1993). RFLP pat- crops in being an interspecific aneuploid. The terns were similar among S. officinarum, S. barberi, occurrence of chromosomal segment exchanges S. sinense, and S. edule, all of which were distinc- between S. officinarum and S. spontaneum chro- tively different from S. spontaneum. Restriction mosomes is supported by both fluorescence in patterns of the chloroplast genome suggested that, situ hybridization (FISH) (D’Hont et al. 1996) except for S. spontaneum,theSaccharum species all and by genetic mapping (Grivet et al. 1996; Hoa- have the same chloroplast restriction sites (Sobral rau et al. 2001) and disproves the prior assump- et al. 1994). RFLP analyses of nuclear genomic tion (Price 1963, 1965; Berding & Roach 1987) DNA confirmed observations about the cytoplas- that no recombination occurs between the chro- mic genomes that suggested distinctively greater mosomes of the two species. Collectively, these diversity within S. spontaneum than within the data were used to propose a schematic representa- four other species (Burnquist et al. 1992; Lu et al. tion (Fig. 1.2) of the genomic organization of mod- 1994a, b; Nair et al. 1999). More recent genomic ern sugarcane cultivars genomes (D’Hont 2005). in situ hybridization (GISH) analysis supports Sugarcane’s polyploid nature and interspecific ori- the hypothesis that S. barberi and S. sinense were gin contribute substantially to high levels of het- derived from interspecific hybridization between erozygosity detected among modern cultivars (Lu S. officinarum and S. spontaneum (D’Hont et al. et al. 1994b; Jannoo et al. 1999a; D’Hont et al. 2002). These authors concluded that genetic sim- 1996; Lima et al. 2002). On the other hand, the ilarities between S. barberi and S. sinense acces- recent origin of modern sugarcane cultivars from sions do not support the taxonomic separation a small germplasm base results in strong linkage of these two groups into separate species. The disequilibrium with some haplotypes conserved in BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

Sugarcane: The Crop, the Plant, and Domestication 7

S. spontaneum group (Mukherjee 1957; Daniels et al. 1975). Eri- anthus sect. Ripidium includes chromosome num- S. officinarum recombinants bers of 2n = 20, 30, 40, and 60 with a basic chro- mosome set of x = 10, the same basic number as favored for Saccharum (Whalen 1991). This group of related genera has a number of traits desired by sugarcane breeders for improving cul- tivar performance, including a wide environmen- tal distribution due to their tolerance of cold and drought, vigor, good ratooning, and disease resis- tance (Berding & Roach 1987). Sugarcane breeders have long tried to introgress agronomic characteristics of Miscanthus and Eri- anthus arundinaceus into sugarcane hybrids. How- ever, it has been difficult to produce fertile progeny and to identify true hybrids involving E. arundinaceus on the basis of morphological characters (Grassl 1965). Molecular diagnostic tools including species-specific DNA markers and GISH have been used in attempts to identify Sac- charum x Erianthus hybrids at the seedling stage and to follow the introgressed genes into later gen- Fig. 1.2. Schematic of the genome of a typical modern sug- erations (D’Hont et al. 1995; Alix et al. 1998, 1999; arcane cultivar. Each bar represents a chromosome; open boxes represent regions originating from S. officinarum and Piperidis et al. 2000). GISH allowed analysis of the shaded boxes regions originating from S. spontaneum. Chro- chromosome complement of intergeneric hybrids mosomes aligned in the same row are hom(oe)ologous and involving Erianthus and Miscanthus (D’Hont et al. represent a homology group (HG). Chromosomes assembled 1995) and revealed that chromosome elimination vertically correspond to monoploid genomes (MG) of S. offic- occurs in Saccharum x E. arundinaceus hybrids inarum and S. spontaneum. The key characteristics of this genome are the high level of ploidy, the aneuploidy, the bis- (D’Hont et al. 1995; Piperidis et al. 2000). pecific origin of the chromosomes, the existence of structural GISH revealed a high contrast between the differences between chromosomes of the two origins, and the chromosomes of the two genera in Saccharum x presence of interspecific chromosome recombinants. Modi- E. arundinaceus hybrids as compared to those of fied from D’Hont (2005). Reproduced with permission from S. officinarum x S. spontaneum hybrids. Because Genetics Society of America. GISH is based on the presence of species-specific repeated sequences that evolved quickly during segments extending for at least 10 cM (Jannoo et al. speciation, the greater contrast between Saccha- 1999b), far greater than in most other crops. rum and Erianthus could reflect a greater genetic distance between these two genera than might be expected based on morphological character- SECONDARY AND TERTIARY GENE istics. This difference in chromosome structure POOLS, GERMPLASM RESOURCES may explain the occurrence of chromosome elimi- nation and the difficulties encountered by breeders Related genera attempting to exploit Erianthus. Several Erianthus Saccharum, Erianthus sect. Ripidium, Sclerostachya and Miscanthus specific repeated sequences were (2n = 30), Narenga (2n = 30), and Miscanthus cloned. Their distribution on the chromosomes (2n = 38 and 40) were added into the “Saccha- was analyzed by FISH and revealed two subtelom- rum complex” as a closely related interbreeding eric families (Alix et al. 1998), one centromeric BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

8 Sugarcane: Physiology, Biochemistry, and Functional Biology

family, and one family apparently dispersed along environmental influences and most have a signifi- the genome (Alix et al. 1999). cant genotype × environment interaction. More recently, AFLP markers clearly identi- fied hybrids between S. officinarum or sugarcane cultivars and Erianthus rockii (Aitken et al. 2006). Phenotypic evaluation Both crosses produced progeny all showing n + n Phenotypic evaluation of germplasm in the collec- inheritance. All of the progeny from the S. offic- tions is a lengthy and costly process of examining inarum cross were hybrids but only 10% of the accessions for traits of significance; however, it progeny from the sugarcane cultivars were hybrids adds tremendous value to the collections. of E. rockii. The remaining 90% were identified Clones of S. sinense, S. barberi,andS. robus- as selfs. tum were evaluated for agronomic and quality characters and to estimate the genetic diversity within and between the populations. Thirty clones Germplasm resources of each species were evaluated in two environ- Sugarcane breeders have long realized that a large, ments for eight phenotypic characteristics. Sig- diverse germplasm collection is essential for sus- nificant differences were found among the three tained crop improvement. At least 31 separate species as well as for clones within species. The collecting expeditions across the complete natural genetic repeatability for every character, except distribution of Saccharum species were made from stalk number, was high, indicating that this infor- 1892 through 1985 to collect genotypes focusing mation would be useful for breeders interested in on those that were resistant to pests and diseases, using the material in commercial crosses (Brown were highly productive, or had high sugar con- et al. 2002). Additional phenotypic evaluation tent (Berding & Roach 1987). Clones from these is in progress to characterize this germplasm collections have been deposited in the two world for quality-related characteristics (sucrose, starch, collections, one maintained in India and one in the etc.) and to estimate its tolerance to environmental United States. These collections serve as genetic stresses (freezing temperatures, diseases, etc.). reservoirs to be used in breeding new cultivars for specific agronomic needs and to broaden the genetic base of commercially grown cultivars. The Core collections reported number of accessions for each species in The potential usefulness of establishing core col- the World Collection of Sugarcane and Related lections of Saccharum species has been analyzed in Grasses located at the India and U.S. sites is listed both the India and United States world collections. in Table 1.3. With the exceptions of S. spontaneum and S. offic- inarum, the numbers of accessions of species that have been characterized are so few that Tai and Passport and descriptor information Miller (2001) considered the entire United States Passport data, including taxonomic designation collection of those limited species to function as and information about where an accession was col- cores. Workers in India analyzed their collections lected, and phenotypic descriptor data are avail- of both S. spontaneum and S. officinarum, while able from the Germplasm Resources Informa- workers in the United States limited their analysis tion Network (GRIN) database maintained by to their collection of S. spontaneum. In the United the National Plant Germplasm System (NPGS) States, Tai and Miller (2001) evaluated 11 meth- of the USDA at http://www.ars-grin.gov/cgi- ods using 11 quantitative traits to estimate the bin/npgs/html/crop.pl?101. The 102 descriptors number of randomly selected accessions needed are classified into eight categories, with the largest for a representative core to be approximately 75. categories being morphology (69 descriptors) and Although the authors did not suggest any one core disease reactions (19). These data are useful for as the best, they did list members of the core based classification of accessions, but they are subject to on cluster analysis within each geographic region BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

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based on retained principal components for mor- Cultivated sugarcanes of today are complex phological traits and random selection of entries interspecific hybrids primarily between Saccha- within each cluster. Workers in India analyzed a rum officinarum, known as the noble cane, and set of 21 qualitative and 10 quantitative descrip- Saccharum spontaneum with contributions from S. tors on 617 accessions of S. spontaneum and found robustum, S. sinense,andS. barberi. Early author- most characters would be represented in a core size ities hypothesized additional contributions from of about 60 randomly sampled accessions (Amal- related grasses of the Saccharum complex (Bran- raj et al. 2006). In a separate study, workers in des 1956; Daniels & Roach 1987; Roach & Daniels India analyzed a set of 27 qualitative morpho- 1987; Sreenivasan et al. 1987), but such proposals logical descriptors for computing the Shannon- are not supported by the limited molecular evi- Weaver diversity index and a list of 10 quantita- dence available (Irvine 1999; Grivet et al. 2004; tive descriptors for principal component analysis Grivet et al. 2006). Based on vegetative characters of 690 accessions of S. officinarum to find a core and native distribution, the species S. officinarum, optimum of about 164 accessions (Balakrishnan with high sucrose content, is believed to have been et al. 2000). Reports from both world collections derived from S. robustum in New Guinea (Bran- emphasized the smaller diversity in S. officinarum des 1956, 1958). It has been postulated (Brandes than in S. spontaneum. Although the potential for 1956) and widely accepted from various evidence establishing core collections of Saccharum has been (Daniels & Roach 1987; Roach & Daniels 1987) shown in both world collections, both collections that S. officinarum spread during prehistoric times continue to be preserved in their entirety. from New Guinea to Indonesia, the Malay Penin- sula, China, India, Micronesia, and Polynesia, and by 500 AD, from Indonesia to southern Arabia and east Africa. As detailed below, S. barberi and EVOLUTION AND IMPROVEMENT OF S. sinense were likely derived from interspecific SUGARCANES hybridization between S. officinarum and S. spon- taneum (Grivet et al. 2004, 2006) and possible The origin of sugarcane introgression from other species (Brown et al. Sugarcane prehistory apparently occurred across a 2007). The distribution of S. officinarum from vast area of Southeast Asia, including the Malayan Polynesia to Hawaii probably took place with Archipelago, New Guinea, India, and some of the native migrations around 500–1000 AD. island groups of Melanesia. The preponderance of evidence indicates that domestication of sugar- cane probably occurred in New Guinea with the Origins of S. barberi and S. sinense selection of S. officinarum from the wild species S. Sugarcanes indigenous to North India and China robustum (Brandes 1956; Daniels & Roach 1987; and cultivated from prehistoric times are referred Grivet et al. 2006). Hypotheses about possible to as S. barberi (2n = 81–124) and S. sinense contributions to sugarcane of genera other than (2n = 110–120), respectively. S. sinense cultivated Saccharum, specifically Erianthus, Sclerostachya, in China and Pansahi India was used for chewing as Narenga,andMiscanthus (Barber 1920; Jeswiet well as for sugar production, whereas the thinner, 1930; Parthasarathy 1948; Brandes 1956; Mukher- harder stalks of S. barberi cultivated in northern jee 1957), were based on cytology and breeding India may have been primarily for crushing. The evidence, morphology, and overlapping geograph- two cultivated sugarcanes were probably the result ical distribution. These hypotheses were reviewed of natural hybrids of S. officinarum and S. sponta- in Daniels & Roach (1987), who produced the neum with other genera about 1000 BCE. S. bar- synopsis supporting the scenario developed by beri subsequently spread from India to the Middle Brandes (1956), which has been supplemented by East, the Mediterranean, and to the New World molecular data (Grivet et al. 2004, 2006) and is beginning with the second voyage of Columbus in presented as Figure 1.3. 1493. Today, S. sinense and S. barberi exist only in BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

10 Sugarcane: Physiology, Biochemistry, and Functional Biology

Several Million Years Several Thousand Years

Ancient hybrids S. spontaneum S. sinense (x = 8, 2n = 40 - 128) = (2n = 116 to 120) S. barberi (2n = 81 to 124)

Modern hybrid cultivars S. robustum = fiber for fencing (2n = 100 to 130) (x = 10, 2n = 60 or 80 + up to ca 200)

S. officinarum = noble (x = 10, 2n = 80) S. edule = vegetable (x = 10, 2n = 60 to 122) Miscanthus M. (less sect. Diandra) = E. Asia & Pacific (x = 19, 2n = 38, 57, 76, 95, 114) M. sect. Diandra = Himalayas to S. China (x = ?, 2n = 40) Miscanthidium Stapf = Africa (x = 7, 2n = 28,30) Erianthus E.. (less sect. Ripidium) = new world (x = 2n = 30, 34 -38, 60) E.. (sect. Ripidium) = old world Cultivated (x = 10, 2n = 20, 30, 40, 60) Wild ?

Fig. 1.3. Hypothetical pathway for sugarcane evolution and domestication based on molecular data indicating only members of the Saccharum clade contributed directly to sugarcane cultivars through allopatric speciation of S. spontaneum west of Sulawesi and S. robustum east of Sulawesi (Grivet et al. 2006). Miscanthus and Erianthus, previously proposed as contributing to sugarcane, are recognized as sharing common ancestors. Following Saccharum speciation, S. robustum in New Guinea contributed to cultivars of S. officinarum for sugar, S. edule for vegetables, and S. robustum for fencing and construction. S. officinarum was moved by humans from the tropics to more temperate India and China where it hybridized to native S. spontaneum, giving rise to S. barberi and S. sinense as locally adapted sugarcane cultigens. Chromosome numbers are from a compilation by Daniels and Roach (1987). Strongest evidence for the evolution and domestication are indicated with solid lines; weaker evidence is indicated with dashed lines. Modified after Grivet et al. (2006) and D’Hont et al. (2008).

collections (Stevenson 1965; Blume 1985; Heinz and Miscanthus (Brown et al. 2007). Artschwa- et al. 1994). ger and Brandes (1958) and Whalen (1991) con- Leading hypotheses on the origins of S. bar- sidered S. barberi to be a horticultural vari- beri and S. sinense (reviewed by Daniels & Daniels ant of S. sinense, as does the Kew database 1975; Paton et al. 1978; Daniels & Roach 1987; GrassBase (http://www.kew.org/data/grasses- Roach & Daniels 1987; D’Hont et al. 2002; Grivet db.html) even though it lists 37 species in the et al. 2004, 2006) are that (1) S. barberi and genus Saccharum. S. sinense arose from hybridization of S. offici- The hypotheses about the origins of S. sinense narum with S. spontaneum in India and China, and S. barberi were tested by GISH performed (2) S. barberi was developed from S. sinense in using total genomic DNA from S. spontaneum and India, and (3) S. barberi and S. sinense arose S. officinarum as probes on chromosome prepara- through introgression between S. officinarum, S. tions of genotypes representative of S. barberi and spontaneum, or other genera such as Erianthus S. sinense. In all clones analyzed, GISH clearly BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

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identified two distinct populations of chromo- Cultivated noble canes for sugar somes or chromosome fragments, thus revealing production the interspecific origin of S. barberi and S. sinense (D’Hont et al. 2002). GISH showed no genomic As mentioned above, sugarcane culture spread regions lacking color, nor was there a third color from India to the Middle East, Mediterranean, pattern that would have been the case if a third and to the New World in 1493, well before Lin- species were involved, especially if it belonged to naeus established classification in 1753 and before another genus. For example, GISH performed on the discovery of “noble” canes in the islands of intergeneric hybrids between S. officinarum x Eri- the South Seas. The first of the noble canes anthus or S. officinarum x Miscanthus showed that left Tahiti with Bougainville in 1768, eventu- total genomic DNA of one genus gave a very weak ally arriving in the Caribbean in 1789 (Deerr hybridization signal on the other genus (D’Hont 1921, 1949; Machado et al. 1987). The sugar- et al. 1995; Piperidis et al. 2000; and unpublished cane that spread across the Mediterranean to results of these workers). These results are corrob- the New World was the Indian cultivar known orated by the absence of Erianthus or Miscanthus ‘Creole’ in French, ‘Criola’ in Spanish, or genus specific sequences in S. barberi and S. sinense ‘Crioula’ in Portuguese. on Southern hybridization patterns (Alix et al. ‘Creole’ was quickly replaced in cultivation by 1998, 1999). These results, together with cyto- the noble cultivar ‘Otaheite’ when Bligh brought plasmic (D’Hont et al. 1993) and nuclear molec- it to Jamaica from Tahiti in 1793 (Machado et al. ular marker analyses (Glaszmann et al. 1990; Lu 1987). From there it was distributed throughout et al. 1994a), are in agreement with the hypoth- the Caribbean and the Americas. Original noble esis that S. barberi and S. sinense originated from canes collected from the Pacific Islands quickly hybridizations between S. officinarum (female) and replaced the less productive Indian varieties and S. spontaneum (male). were the only source of cultivars for plantations for The proportion of chromosomes from the two the world’s sugar production for over a hundred species was variable in the clones studied with years. Before sugarcane breeding programs were 61% S. officinarum: 39% S. spontaneum for 2n = started in 1888, the most important noble culti- 82 clones, 68%: 32% for a clone with 2n = 91, vars were the ‘Otaheite’ (‘Bourbon’, ‘Lahaina’) of and 66%: 33% for a clone with 2n = 116. From Tahiti, ‘Cheribon’ (‘Louisiana Purple’) of Java, 0 to 4 chromosomes per cell appeared to result and ‘Caledonia’ of New Hebrides. ‘Bourbon’ was from interspecific intrachromosomal exchanges extremely susceptible to root rot, mosaic, and (D’Hont et al. 2002). Considering the frequency gumming disease; ‘Cheribon’ to sereh, mosaic, and of such exchanges in modern cultivars, this indi- root rot; and Caledonia to mosaic (Edgerton 1958; cates that a very small number of meiotic events Stevenson 1965). These initial cultivars were must have occurred since interspecific hybridiza- replaced by new hybrids selected from emerging tion. Further RFLP analyses indicated that the S. sugarcane breeding programs (Fig. 1.4). Today, barberi and S. sinense clones are clustered into a few clones of S. officinarum are in breeding collections groups, each derived from a single interspecific and/or cultivated as garden canes for chewing. hybrid that has subsequently undergone somatic The first sugarcane breeding programs began mutations. These groups correspond quite well in Java and Barbados in 1888, following the obser- with those already defined based on morphological vations independently in Java (1858) and Barba- characters and chromosome numbers (reviewed dos (1859) that sugarcane was capable of pro- by Daniels et al. 1991). However, the calculated ducing viable seed (Stevenson 1965; Kennedy genetic similarities do not support the existence & Rao 2000). Varieties produced by the Proef- of two distinct taxa. The “North Indian” and station Oost Java, identified as POJ varieties, “Chinese” sugarcanes thus represent a set of hor- became foundational for germplasm development ticultural groups rather than established species in other countries, which soon established their (D’Hont et al. 2002). own breeding stations to produce locally adapted BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

Black Cheribon S. off: 2n=80 POJ 213 S. hyb: 2n=124-128 Chunnee S. barb: 2n=91-92 Co 213 S. hyb: 2n=118 Kansar S. barb: 2n=92 Co 221 Kaludai Boothan S. hyb: 2n=1?? S. off: 2n=80 M2 Co 290 S. hyb: 2n=?? Unknown India S. hyb: 2n=118 S. spont: 2n=64 Rose Bamboo S. off: 2n=80 D 74 S. hyb: 2n=80 Unknown S. off: 2n=80 Banjermasin Hitam S. off: 2n=80 POJ 100 S. hyb: 2n=89 Loethers S. hyb: 2n=99 POJ 2364 S. hyb: 2n=148 POJ 2878 Unknown Java S. hyb: 2n=120 S. off: 2n=80 Kassoer S. hyb 2n=136 EK 28 Unknown Java S. off hyb: 2n=80 S. spont 2n=112

Co 312 Vellai S. Off: 2n=80 Co 244 S. hyb: 2n=118 Co 205 S. hyb: 2n=120 S. hyb: 2n=112 Unknown India S. spont 2n=64

Ashy Mauritius Co 281 S. hyb: 2n=120 S. off: 2n=80 Co 206 S. hyb: 2n=112 Unknown India S. pont: 2n=64

Striped Mauritius S. off: 2n=80 Green Sport S. off: 2n=80 Unknown India Co 285 S. off: 2n=80 S. hyb: 2n=112 Unknown India S. spont: 2n=64 Early Cultivars Species Modern HYBRIDIZATION Accessions Cultivars

Fig. 1.4. Sugarcane hybrid foundations. Accessions of Saccharum species and the early crosses among them serve as the foundation for all modern cultivars of sugarcane. The early selections from crosses by Proefstation Oost Java are named as a series of POJ cultivars and those conducted in Coimbatore, India, are named as a series of Co cultivars. The accessions of S. officinarum (2n = 80), S. spontaneum (2n = 64–112), and S. Barberi (2n = 92) were named where discovered and served as the original sugarcane cultivars. Early generation crosses among S. officinarum produced a new series of S. officinarum hybrids (S. off hyb: 2n = 80), or when a different species was crossed to S. officinarum the lines produced are Saccharum hybrids (S. hyb: 2n = 112-148). Courtesy of Genetics Society of America.

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varieties. Notable among the early sugarcane developed, found in the pedigrees of almost all breeding efforts for producing varieties with wide of the dominant cane varieties grown around the adaptation was Coimbatore, India (1912), that world. developed Co and NCo varieties (Fig. 1.3). In The first step of the nobilization process the sugarcane breeding history that follows, we involved “doubling” of the S. officinarum gametic describe these changes in four stages: (1) breed- chromosome number to the somatic chromosome ing among noble canes (S. officinarum) to produce number in the fertilized egg with the addition noble cultivars; (2) breeding through nobilization, of the gametic chromosome number of the wild i.e., interspecific hybridization with backcross- clones of S. spontaneum used as males. The mech- ing to noble cultivars to produce nobilized cul- anism to explain maternal transmission of diploid tivars; (3) breeding of nobilized canes to produce chromosome numbers seems to involve the fusion hybrid cultivars; and (4) breeding to broaden the of daughter nuclei after the second meiotic divi- genetic base. sion in the innermost megaspore dyad cell of S. officinarum (Narayanaswami 1940). However, doubling also occurs in crosses involving the Interbreeding of S. officinarum to species S. sinense as shown by Price (1957) and produce noble cultivars even modern cultivars (Piperidis, N. et al. 2010). Progenies of open-pollinated noble canes were Subsequent steps in nobilization involved back- selected for sugar production. Each selected crossing the F1 to another noble cane, where there seedling was assigned a call sign followed with could be a second doubling of maternal chromo- a seedling number. ‘Otaheite’ (‘Lahaina’, ‘Bour- somes, and then crossing the F2 once again to a bon’) produced the EK seedlings in Java, ‘H109’ in noble cane, at which time normal n + n transmis- Hawaii, and ‘B716’ in Barbados. In Queensland, sion seems to be the norm. Australia, ‘Q813’ came from Badila, the famous More than 90% of the accessions classified as chewing cane that originated in New Guinea. S. officinarum have 2n = 80, x = 10 chromosomes These selected noble cultivars were important for whereas the most frequent chromosome number sugar production in the early 1900s. The origi- in S. spontaneum is 2n = 64, x = 8(Panje& nal noble canes and selected noble progenies were Babu 1960; Irvine 1999). Using these two chromo- found susceptible to disease and insects and lim- some complements as an example, one can envi- ited to particular tropical environments. Breeders sion nobilization in the simplified crossing scheme soon realized that the genetic base of the noble where NN = noble, 2n = 80; SS = spontaneum, canes needed to be broadened to improve their 2n = 64 (Table 1.4). adaptabilities and disease and insect resistance Progeny of F1 and BC1 have the nonreduced (Stevenson 1965). somatic complement (2n) of the female parents plus the gametic number (n)ofthemale.Most cultivated nobilized canes (BC s, BC s, etc.) have Breeding through nobilization to produce 2 3 100–130 chromosomes with about 5–10% from S. hybrid cultivars spontaneum (Fig. 1.1). Clones with chromosome Nobilization is the pollination of noble cane S. numbers outside of this range are rarely suited for officinarum with its wild relative S. spontaneum commercial production. followed by repeated backcrosses to noble canes. Following efforts to achieve interspecific The wild relatives were considered “nobilized” crosses between S. officinarum and S. spontaneum, through the breeding process and the selected early sugarcane breeders realized that resultant hybrid progenies are referred to as “nobilized F1 progeny were distinctively more robust than canes” (Bremer 1961). A key event of early nobi- either parent. When S. officinarum clones were lization breeding was the production of the nobi- used as the female parent, progeny tended to be lized cultivar ‘POJ2878’ in 1921 (Fig. 1.3), which larger stalked, higher in sucrose levels, and gen- became the most universal breeding cane ever erally more vigorous than when S. spontaneum BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

14 Sugarcane: Physiology, Biochemistry, and Functional Biology

Table 1.4 Nobilization crossing scheme showing the numbers and origin of chromosomes in each progeny generation (F1, BC1,andBC2) and the percentage of progeny chromosomes that are of S. spontaneum origin.

Progeny Female X Male → chromosomes (2n)(%Spontaneum)

NN(80) X SS(64) → F1 (80+32=112) S = 29% (100 × 32/112) NN(80) X F1(112) → BC1 (80 + 56 = 136) S = 12% (100 × 16/136) NN(80) X B1(136) → BC2 (40 + 68 = 108) S = 7% (100 × 8/108)

NN = noble, S. officinarum 2n = 80; SS = wild, S. spontaneum,2n = 64. clones were used as the female parent. Reciprocal Natal, South Africa, in the same year. One of the differences in vigor were eventually explained by progeny selected in 1939, ‘NCo310’, became the the cytological phenomenon of a high frequency most important cultivar of the world in the 1950s of “2n + n” progeny in S. officinarum (female) × and 1960s (Anonymous 1945; Nuss & Brett 1995). S. spontaneum (male) crosses (Bremer 1923). Even as late as the 1980s, ‘NCo310’ still ranked In Coimbatore, India, nobilization of S. barberi first in growing area in Japan, Texas (US), and and S. spontaneum with S. officinarum produced Uruguay; second in Malawi and Gabon; third in the famous early nobilized trispecies hybrids of Mexico; and fourth in Ecuador (Tew 1987). “Co” seedlings (Fig. 1.4) that gained wide accep- Commercial cultivars and hybrids from tance in subtropical regions in India, South Africa, advanced stages of selection have been the main Australia, Louisiana, Argentina, and Brazil. The breeding materials for the development of cur- “Co” cultivars also were used on the poorer soils rent cultivars since the 1950s. The names of the and under marginal growth conditions in the current cultivars, rank in percent of area occu- tropics. pied, immediate parents, and breeding stations of The brief period (1920–1930) of nobilization the world are listed in the Sugar Cane Variety breeding was followed by a longer period (from Notes (Machado 2001), the Sugarcane Varieties then up to today) of crossing among nobilized lines (Machado 2002), and the World Sugarcane Vari- to produce hybrid cultivars and introgression of ety Census–Year 2000 (Tew 2003). specific traits into the hybrid cultivars (Stevenson 1965; Simmonds 1976; Ethirajan 1987). Breeding to broaden the genetic base Modern cultivars are essentially derivatives of no Breeding of nobilized canes to produce more than 15–20 nobilized cultivars that in turn hybrid cultivars trace back to the initial nobilized genetic base Crosses among nobilized canes in the 1930s developed in Java and India (Roach 1989). Genetic produced many important hybrid cultivars for diversity in today’s advanced breeding popula- sugar production in the next three decades (Fig. tions is expected to be somewhat narrower than 1.4). Breeding of ‘POJ2878’ with other nobi- that in the initial germplasm following more than lized POJ canes produced cultivars ‘POJ3016’ and 100 years of directional selection (Walker 1987). ‘POJ3067’. Together they occupied more than Attempts to increase this narrow base, called the 85% of the cane area of Java in 1960. Cross- base broadening program (BB-program), were ing of ‘Co312’ and ‘POJ2878’ produced Hawaii’s started in Barbados in 1965 using clones different most important cultivar, ‘H32–8560’, which was from those initially used in Java and India. The responsible for 65% of the cane area of Hawaii in BB-program started with nobilization crosses fol- 1945. ‘POJ2878’ x ‘Co290’ produced ‘Co419’ for lowed by hybridization of nobilized canes. The the tropical area of India. The cross of ‘Co421’ BB-program has produced many semicommercial x ‘Co312’ was made in Coimbatore in 1938 to type clones that have been incorporated into the produce progeny of the cross that was grown in gene pool of advanced breeding populations since BLBS138-c01 BLBS138-Moore Printer: Yet to Come September 19, 2013 8:2 246mm×189mm

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the late 1980s (Kennedy & Rao 2000). Other coun- inarum L. germplasm based on quantitative-morphological tries have tried BB-programs over the past 50 years data. Genetic Resources and Crop Evololution, 47,1–9. Barber, C.A. (1920) The origin of sugarcane. International by crossing wild canes with their commercial cul- Sugar Journal, 22, 249–251. tivars. However, none of these efforts was as long Bennett, M.D. & Leitch, I.J. (2003) Angiosperm DNA term or as broad based as the BB-program of Bar- C-values Database (release 8.0, Dec. 2012). Available at: bados and Louisiana. http://data.kew.org/cvalues/ (accessed 4 July 2013). Berding, N. & Roach, B.T. (1987) Germplasm collection, Our inability to trace or follow the incorporated maintenance, and use. In: Sugarcane Improvement through germplasm into the germplasm of the advanced Breeding (ed. D.J Heinz), pp. 143–210. 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