International Scholarly Research Notices

International Scholarly Research Notices / 2015 / Article

Research Article | Open Access

Volume 2015 |Article ID 257417 | 9 pages | https://doi.org/10.1155/2015/257417

Historical Use of Cultivars as Parents in Florida and Louisiana Sugarcane Breeding Programs

Academic Editor: Harsh Raman
Received30 Aug 2014
Revised15 Dec 2014
Accepted21 Dec 2014
Published20 Jan 2015

Abstract

Sugarcane (Saccharum L. spp. hybrids) growers depend on breeding programs for new, high-yielding cultivars that have resistance to abiotic and biotic stresses, so breeders continually seek out widely adapted, high yielding germplasm to be used as parents for their programs. Cultivars are sometimes used for this purpose, but their use may be minimized to prevent genetic diversity erosion. The purpose of this study was to determine the importance of cultivars as parents in three USA (one in Florida and two in Louisiana) sugarcane breeding programs by quantifying the percentage of cultivars that had these parental groupings based on published registrations and crossing records. The percentage of cultivars with at least one commercial parent for each program was 81.8%, 77.5%, and 64.3% for the Houma (Ho), Louisiana, Canal Point (CP), Florida and Louisiana State University (LSU) programs, respectively, but cultivars were recently used as parents in only 11.8% (Ho), 16.39% (CP), and 34.3% (LSU) of crosses. The results indicate that the CP and Ho programs should consider increasing the use of cultivars as parents in their breeding programs to increase the probability of selecting potential commercial genotypes, but this should be balanced with high diversity crosses to avoid the loss of diversity.

1. Introduction

Mainland US sugarcane breeding programs employ recurrent selection principles that continually identify the highest yielding germplasm with acceptable stress resistance and make the majority of crosses in their breeding programs using these genotypes as parents. Throughout this paper, sugarcane genotype is used to denote a genetically unique individual derived from sexual recombination. Genotypes are most often tested in different stages of selection programs and are generally named in an early stage of selection. Later, once more of the data are available for a given genotype, some are used as parents in crosses. Cultivar denotes a genotype that has been publicly released for commercial use. We use the term commercial parent to describe a cultivar that is used as a parent in a cross.

Three breeding programs were researched in this study. The two USDA-ARS breeding programs are based in Houma, LA, Canal Point, FL, and the third Louisiana State University program in St. Gabriel, LA. Each breeding program has different breeding strategies that address the different regions they serve. Florida has a subtropical climate where cold tolerance is a concern, although damaging freezes do not occur every year. However, Louisiana has a colder climate with regular damaging freezes, and cold tolerance is more important in Louisiana than in Florida. The Louisiana sugarcane industry is comprised of a relatively large number of growers with smaller farms while the Florida industry has large corporations and generally much greater land areas per farm owner than in Louisiana. For example, a representative farm size for the Louisiana industry would be 404.7 ha [1] while a representative farm size in Florida would be 2000 ha [2]. Such industry characteristics result in programmatic differences in the number and type of crosses made, type of plants selected, and numbers of cultivars released.

Houma and LSU programs, whose origin can be traced to 1885 [3], are highly collaborative and mutually strive to improve productivity of the Louisiana sugarcane industry [4]. Both Louisiana programs conduct sugarcane breeding and selection activities [5]. Crossing through early stage clonal testing and selection are conducted independently by each of the two institutions, and midway through clonal selection stages promising genotypes from the two are jointly evaluated by the three Louisiana organizations. The American Sugar Cane League (ASCL) assists with the final multilocation testing stage and has primary responsibility for seed increase and distribution to growers upon varietal release. In accordance with the three-way agreement, all three Louisiana organizations jointly decide on a cultivar release [5].

Sugarcane crosses have been made in Louisiana since 1948 [6] by Louisiana State University. The current Louisiana breeding program is conducted by Louisiana State University Agricultural Center (LSU) at St. Gabriel, LA, along with the USDA-ARS Sugarcane Research Unit at Houma, LA, in cooperation with the ASCL located at Thibodaux, LA, under a three-way cooperative agreement [7]. The ASCL is Louisiana’s sugarcane grower and processor organization and contributes professional expertise and financial support [7]. The Houma program emphasizes germplasm enhancement through basic breeding [8]. Basic breeding is a scheme to intercross the desirable alleles from diverse wild germplasm into a composite breeding material that will be used to backcross into elite cultivars [9]. The Florida and Louisiana programs have long been closely affiliated. Prior to 1972, basic- and commercial-type sugarcane crosses for the Houma program were made only at the USDA-ARS Research Station at Canal Point (CP), Florida. Since then crossing efforts specifically targeting germplasm enhancement were initiated at Houma [8]. Crossing facilities at Houma are primarily for basic-type crosses, while CP serves as the main source of Houma’s commercial-type crosses using Louisiana germplasm.

Houma cultivars from CP 65-357 to CP 79-318 received the CP name designation even though germplasm had been selected at Houma. This included the BC 1 cultivar TucCP 77-42 which was selected in Argentina from a cross made at Houma [10]. Cultivars released from the LSU program have an “L” name designation while those from the Houma program have an Ho name designation. A compound naming designation was developed to assure that a cultivar name appropriately reflected the breeding groups involved in its development [9]. For example, HoCP 85-845 indicates that the cross was made at CP and the clone was selected at Houma [11].

Sugarcane breeding in the United States for the Louisiana breeding program began in Canal Point Florida in 1919 [12] but from 1960 breeding efforts were also directed for Florida region [13]. The current Canal Point program consists of a three-way cooperative agreement between the USDA-ARS Research Field Station at Canal Point (CP), the University of Florida Everglades Research and Education Center located at Belle Glade, and the Florida Sugarcane League located at Clewiston, Florida. Cultivars are recommended for release by the vote of a committee with representatives from each of these three organizations and carry a CP name designation.

Florida and Louisiana programs also share germplasm between themselves resulting in combined LCP, HoCP, and LHo name designations.

Deren [14] traced the genealogy of US sugarcane germplasm and found that 10 clones were the source of 90% of Florida germplasm and that two ancestors were the source of 90% of Louisiana germplasm. He noted that the diversity of sugarcane was buffered due to multiple interspecific crosses in the respective breeding programs. These include wild species and early generation intergeneric and interspecific crosses used to broaden genetic diversity and increase disease resistance. This is exemplified by the Houma, LA, breeding program which maintains two general types of germplasm: basic germplasm, typically F1 to BC2 generations, and elite or nearly elite commercial germplasm (typically BC3 and higher generations) [5]. There are also basic crosses made in Canal Point which are also evaluated for cold tolerance and in the energycane program, but the main focus of the Canal Point program is sugarcane cultivar development. In most crops, including sugarcane, new cultivars are selected from the progeny of crosses of commonly grown cultivars and other elite materials [5]. There is some evidence of past successful use of cultivars as parents in other programs including POJ2878 which was the parent of 181 sugarcane varieties worldwide and Co419 that was the parent of 81 sugarcane cultivars including two of China’s most widely grown cultivars [15, 16]. Other popular cultivars in China include ROC22 which has been used as a parent in crosses since 2002 and at least five of its progeny have been released as cultivars including Guitang 04-1001, Guitang 29, [17], Dezhe 03-83 [18], and Liucheng 03-182 [16]. Cultivars are sometimes used in crosses, but their importance as breeding parents in sugarcane breeding programs has not been documented. The purpose of this study was to determine the importance of cultivars as parents in Florida and Louisiana public sugarcane breeding programs by quantifying the percentage of cultivars derived from crosses with commercial parents.

2. Materials and Methods

Three public sugarcane breeding and selection programs were included in the study: CP, Houma, and LSU. Records of cultivar pedigrees were collected using existing pedigree dendrograms and published cultivar registrations. Information for some cultivars was obtained from [19, 20]. The search was limited to cultivars grown for sugar and biofuel. Genealogies for the Florida program began with cultivar CP 63-306 which was released in 1971. Earlier cultivars in the CP program are not evaluated, but they are noted as parents thereby covering 52 years of breeding. Some CP cultivars developed by the Houma breeding program, before the compound naming system, were often planted in Florida. Early CP cultivars selected for release to the Louisiana industry were counted as Houma cultivars and those selected for release in Florida were counted as CP cultivars.

Cultivars developed by LSU in this study began with L 62-96 which was released in 1969.

Crossing records from CP for 2000–2006 and 2010–2012 and LSU for 2003–2012 and Houma from 1992 to 2012 were obtained from crossing records of each program to compare the number of cultivars that was used as parents of other cultivars and the use of cultivars as parents in the total number of crosses generated. Within the CP records all crosses are recorded including those made for CP and Houma and the crosses made for both. The years 2007–2009 were not included in CP counts because the difference between crosses used in Florida and crosses used for Houma, Louisiana was not recorded and the crosses for Florida and Louisiana could not be distinguished. Ten years were assumed to be sufficient for CP program based on the large number of crosses (6945 total crosses) included in the study. Additional years were included for the Houma program (6630 total crosses) to approximate the number crosses of the CP program. The number of crosses for LSU was restricted to 4423 total crosses as additional crossing records for this program were not available.

To calculate the percentage of cultivars with at least one commercial parent, the presence of one or two commercial parents was counted as one per cultivar progeny then divided by the total number of cultivar progeny (at least one parent cross/total number of crosses 100). The percentage of all commercial parents was calculated by adding all the commercial parents and dividing them by the total number of parents, including those with unknown parents. The percentage of cultivars calculated from crossing records was calculated by dividing the total number of times cultivar parents were used in the cross by the total number of times all parents were used and the selfs were treated as one parent use (cultivar parents/all parents 100). Two types of Chi-square tests were conducted using SAS PROC Freq: a test between the breeding locations and a proportion test of cultivar versus noncultivar within breeding locations ().

3. Results and Discussion

There were 71 cultivars from the CP program reviewed (Table 1). Of these 71 cultivars 77.5% of them had at least one cultivar parent, and 54.6% of the total parents were cultivars (Table 2). There were 42 cultivars used as parents in the crosses that developed these 71 cultivars, and each of these cultivars was a parent of another cultivar at an average of 1.83 times (sum of the times a particular cultivar was used as parent divided by the total number of cultivar parents). Cultivars were used as female parents of cultivars 47 times and as male parents 30 times including two selfs; CP 89-2143 [21] was the parent of CP 00-1101 and HoCP 91-552 [22] which was the parent of CP 00-2180 [23]. The most successful commercial parent was CP 68-1067 [24], which was used as a parent six times from which new cultivars were selected. The female and male parents of CP 68-1067 are CP 52-68 [20] and CP 57-603 [25], respectively, and they were also cultivars. Cultivar progeny of CP 68-1067 are CP 75-1082 [26], CP 75-1632 [27], CP 77-1776 [28], CP 78-1628 [29], CP 80-1743 [30], and CP 81-1384 [31]. Out of six cultivars five were produced when CP 68-1067 was used as a female parent and one (CP 80-1743) when used as male parent. CP 80-1743 was the most widely grown sugarcane cultivar in Florida for several years and CP 78-1628 was the most widely grown sugarcane cultivar on sand soils in Florida for several years [32]. Most of the cultivar progeny of CP 68-1067 had high or moderate commercial recoverable sucrose, except CP 75-1082 which had high cane tonnage and low commercial recoverable sucrose. Some of the cultivar progeny of CP 68-1067 also had cultivar grand-progeny. CP 75-1082 was the female parent of CP 86-1633 [33] and CP 80-1743 was the female parent of CP 88-1762 [34], CP 97-1944 [35], and CPCL 02-0926 [36]. CP 88-1762 became the most widely grown cultivar in Florida in 2010 [37].


CultivarFemale parentMale parentCultivarFemale parentMale parent

CP 63-306CP 50-28aCP 52-15CP 88-1508CP 81-1238aCP 78-1610
CP 63-588Cl 54-1910aCP 57-120CP 88-1540CP 78-1610CP 81-1238a
CP 68-1026Cl 47-83CP 57-614aCP 88-1762CP 80-1743a85 P6b
CP 68-1067CP 52-68aCP 57-603aCP 88-1834CP 72-1210aLCP 81-30
CP 69-1052CP 56-59aCP 62-374aCP 89-1509CP 80-1827aPolycrossb
CP 70-1133CP 56-63a67 P6bCP 89-2143CP 81-1254aCP 72-2086a
CP 70-1527CP 62-374aCP 57-526CP 89-2376UnknownUnknown
CP 71-1038CP 52-68aCP 56-59aCP 89-2377UnknownUnknown
CP 72-1210CP 65-357aCP 56-63aCP 92-1213CL 73-0239aCP 85-1498
CP 72-2086CP 62-374aCP 63-588aCP 92-1641CP 80-1827aCP 84-1322
CP 73-1547CP 66-1043CP 56-63aCP 92-1666CP 82-1592aCP 84-1322
CP 74-2005CP 66-1043CP 63-588aCP 94-1100CP 81-1238aCP 88-2045
CP 75-1082CP 68-1067aCP 70-1133aCP 94-1340CP 87-1733CP 86-1665
CP 75-1553CP 68-1026a73 P2bCP 96-1252CP 90-1533CP 84-1198a
CP 75-1632CP 68-1067aCP 70-1133aCP 96-1602CP 81-1425Polycrossb
CP 77-1776CP 68-1067aCP 68-1022CP 97-1944CP 80-1743aPolycrossb
CP 78-1247CP 68-1067aCP 57-614aCP 97-1989CP 75-1091CL 61-620a
CP 78-1628CP 65-357aCP 68-1026aCP 98-1029CP 91-1980CP 94-1952
CP 78-2114UnknownUnknownCP 00-1101CP 89-2143aCP 89-2143a
CP 80-1557CP 71-1194PolycrossbCP 00-1446CP 93-1607CP 91-1150
CP 80-1743CP 72-2083aCP 68-1067aCP 00-2180HoCP 91-552aHoCP 91-552a
CP 80-1827CP 70-1133aCP 73-1311CP 01-1372CP 94-1200CP 89-2143a
CP 81-1238CP 71-1027PolycrossbCP 04-1566CP 89-2377aCP 96-1252a
CP 81-1254CP 72-1210aPolycrossbCP 04-1844CP 97-1989aCP 84-1198a
CP 81-1302CP 72-2079CP 71-1086CP 04-1935CP 94-2059CP 84-1322
CP 81-1384CP 68-1067aCP 74-2013CP 05-1526CP 98-1029aCP 88-1162
CP 82-1172CP 75-1091CP 75-1283CPCL 97-2730CL 75-0853aCL 88-4730a
CP 82-1592CP 72-1210aCP 70-1133aCPCL 99-4455CL 90–4643CP 84-1198a
CP 84-1198CP 70-1133aCP 72-2086aCPCL 00-4111CL 83-3431aCL 89-5189a
CP 84-1591CP 72-1370CP 68-1022CPCL 02-0926CP 80-1743aCL 92-0046
CP 85-1308R 567CP 74-2013CPCL 02-1295CP 88-1762aCL 91-1637
CP 85-1382CP 74-2005a82 P 14bCPCL 02-6848CL 92-2533Poly 01-9b
CP 85-1432CP 70-1527aPolycrossbCPCL 05-1102CL 89-5189aCL-88-4730a
CP 85-1491CP 75-1553aCP 72-2086aCPCL 05-1201CL 87-2882CL 93-2679
CP 86-1633CP 75-1082aCP 78-1140CPCL 05-1791CP 96-1252aCL 90-4725a
CP 88-1165CL 61-620aCP 81-1302a

Indication that clone was a cultivar used as a parent.
bMale polycross (pollen mix).

CultivarsAt least one cultivarCommercial parents in crossesaTotal crosses
%(no.)

CP54.6177.46*16.39*‡6945
Houma56.8281.82*11.77*‡6630
LSU42.8664.29 34.29*‡4423

For CP crosses are from 2000 to 2006 and 2010 to 2012, for LSU crosses are from 2003 to 2012, and for Houma crosses are from 1993 to 2012.
*Significantly different at 0.05 for the Chi-square test of equal proportions (cultivar versus noncultivar within each program).
Significantly different at 0.05 for the Chi-square test comparing the percentages of the different breeding programs.

If one could rate the breeding success of a cultivar by having the most progeny that become cultivars, then the second most successful cultivar parent in the CP program was CP 70-1133 [38], which had five of its progeny that became cultivars (Table 1). CP 56-63 [39], which was the female parent of a polycross that created CP 70-1133, was also a cultivar. The cultivar progeny of CP 70-1133 were CP 75-1082, CP 75-1632, CP 80-1827 [40], CP 82-1592 [41], and CP 84-1198 [42]. CP 80-1827 was the most widely grown sugarcane cultivar in Florida from 1995 to 1998 [43]. There are also cultivar grand-progeny of CP 70-1133: CP 75-1082 was the female parent of CP 86-1633; CP 80-1827 was the female parent of CP 89-1509 [44] and CP 92-1641 [45]; CP 82-1592 was the female parent of CP 92-1666 [46]; and CP 84-1198 was the male parent of CP 96-1252 [47], CP 04-1844 [48], and CPCL 99-4455 [49].

The parents of 22 Houma cultivars were reviewed (Table 3). Of these 22 cultivars 81.8% had at least one cultivar parent, and 56.82% of the total parents were cultivars (Table 3). The most successful cross in the Houma program was between CP 65-357 [50] and L 65-69 [51]. The hugely successful Louisiana cultivar, CP 65-357, was grown on more land area (71%) than the sum of all other cultivars in 1980 [52]. It took two decades before another cultivar, LCP 85-384, assumed an equally prominent lead above all other cultivars, with 91% of the acreage in 2004 [53]. The cross of cultivars CP 65-357 × L 65-69 produced four cultivars: CP 73-351 [54], CP-74-383 [55], CP 76-331 [56], and CP 79-318 [57]. None of the cultivars from the L 65-69 × CP 65-357 crosses parented other cultivars. CP 65-357 was not a parent of any LSU cultivar (Table 4). More cultivars and parents were shared between the two Louisiana programs (Tables 3 and 4) than between Louisiana and Florida programs (Table 1), probably reflecting the different cultivar specific requirements of their respective industries.


CultivarFemale parentMale parent

CP 65-357CP 52-68aCP 53-17
CP 67-412CP 44-155aCP 53-16
CP 70-321CP 61-39CP 57-614a
CP 70-330CP 61-39CP 57-614a
CP 72-370CP 61-37aCP 52-68a
CP 72-356CP 63-361CP 62-258a
CP 73-351CP 65-357aL 65-69a
CP 76-331CP 65-357aL 65-69a
CP 79-318CP 65-357aL 65-69a
CP 74-383CP 65-357aL 65-69a
Ho 00-961US 94-1HoCP 91-552a
Ho 02-113SES 234LCP 85-384a
Ho 05-961CP 83-644TucCP 77-42a
Ho 07-613 HoCP 00-905HoCP 96-540a
Ho 95-988CP 86-941US 89-12
HoCP 00-950HoCP 93-750HoCP 92-676
HoCP 04-838HoCP 85-845aLCP 85-384a
HoCP 85-845CP 72-370aCP 77-403
HoCP 91-552LCP 81-10CP 72-356a
HoCP 91-555CP 83-644LCP 82-94
HoCP 96-540LCP 86-454aLCP 85-384a
TucCP 77-42CP 71-321US 72-19

Indication that clones was a cultivar used as a parent.
Cultivars were released through a three-way agreement between Houma, Louisiana State University, and the American Sugar Cane League.

CultivarFemale parentMale parent

L 60-25CP 52-68aCP 48-103a
L 62-96CP 52-68aCP 44-154a
L 65-69CP 52-1CP 48-103a
LCP 82-89CP 52-68aCP 72-370a
LHo 83-153CP 77-405CP 74-339
LCP 85-384CP 77-310CP 77-407
L 79-1002CP 52-68aTainan
LCP 86-454CP 77-310CP 69-380
L 99-226HoCP 89-846CP 81-30
L 99-233CP 79-348HoCP 91-552a
L 03-371CP 83-644LCP 82-089
L 97-128LCP 81-10LCP 85-384a
L 01-299L 93-365LCP 85-384a
L 01-283L 93-365LCP 85-384a

Indication that clone was a cultivar used as a parent.
Cultivars were released through a three-way agreement between USDA-ARS Houma, LSU, and the American Sugar Cane League.

The parents of 14 LSU cultivars were reviewed and of these 64.3% had at least one cultivar parent, and 42.86% of the total parents were cultivars. Of these, three cultivars were repeated as parents. CP 52-68 [20] was a parent of three commercial progenies. CP 48-103 [20] had two commercial progenies and LCP 85-384 [58] had three commercial progenies (Table 4).

It is likely that these programs actually have higher percentages of cultivars with commercial parents. For example, if we evaluate the parents in the CP program that were not identified as cultivars, we find that there were six unknown genotypes because of labeling issues and 12 unknown males because they were in polycrosses. Thus, there is a chance that some of these 18 unknown parents were cultivars. The paternity of these polycrosses could be determined with further study using molecular markers [59].

A total of 46 genotypes that were parents of commercial progeny in the CP program were noncommercial mostly elite germplasm. The most successful of these parents was CP 84-1322; it was the male parent of three cultivars. For two of three cultivars the female parent was also a cultivar (crosses that developed CP 92-1641 and CP 92-1666). Also, the parents of CP 84-1322 were both commercial cultivars (CP 52-068 [20] and CP 72-2086 [60]). CP 72-2086 was the most widely grown cultivar in Florida in 1994 [43]. Most noncommercial germplasm only parented commercial progeny one or two times. The Houma program had two noncommercial elite parents producing commercial progeny two times each CP 83-644 and CP 61-39, and the LSU program also had two noncultivar elite parents producing commercial progeny two times each CP 77-310 and L 93-365.

Four cultivars from Houma were derived from basic parental clones (Table 3) including SES 234 (S. spontaneum L.) and three US clones. Houma clones selected in basic breeding were previously assigned US [United States] breeding numbers, but basic selections are now given Ho designations. Basic clones typically were used in the breeding program as nonrecurrent parents for backcrossing with selected interspecific hybrids used as recurrent parents [10], and cultivars were often the recurrent parent. In practice, crosses usually were constructed taking into consideration the parental pedigrees to minimize potential effects of inbreeding. For example, LCP 85-384 [58] has occurred frequently as a parent in the Louisiana programs (Tables 3 and 4), so caution is needed to minimize full- and half-sib crosses with this cultivar. The high number of noncommercial crosses in the Houma program (Table 2) indicates that the basic program is strong. But since the released cultivars have ancestry which is primarily commercial, new methods should be sought to incorporate basic germplasm in such a way to develop successful cultivars that utilize better the diversity of the basic program.

The crossing records at CP were gathered from recent records to see how the programs have acted recently and see how they might change. Programs differed significantly in the percentage of cultivars used in crosses in the order LSU > CP > Houma, 34.3, 16.4, and 11.8%, respectively (Table 2). LSU had nearly a 2- to 3-fold greater use of cultivars as parents than the other programs. Overuse of cultivars in crosses could cause a reduction in genetic diversity.

Of the 71 CP program cultivars surveyed, 55 (77.8%) had at least one commercial parent. Over half of the parents () of cultivars in the CP program were cultivars. According to the crossing records examined, cultivars were used in only 16.4% of the crosses in this program (Table 2). Houma used cultivars as parents in significantly (Chi-square ) fewer crosses (11.8%) but had a larger percentage of parent cultivars (56.8%) and cultivars with at least one parent (81.8%) but these differences were not significant. But the proportions of cultivars with at least one cultivar parent to those with no cultivar parentage in the CP (77.46) and Houma (81.82) programs were significantly unequal. The proportion of at least one cultivar parent in the LSU (64.29) program was not significantly unequal indicating that the CP and Houma programs have released proportionally more cultivars with commercial parents. The LSU breeding program used cultivars in a greater percentage of their crosses (34.3%) than CP and Houma. However, there were fewer cultivars with parent cultivars (42.9%) and few cultivars with at least one cultivar parent (64.3) compared to the CP or Houma programs. The crossing percentages from the different programs do not directly relate to the percentages of cultivars with cultivar parents because the crossing period examined does not correspond with the time periods when most of the older cultivars were developed. The current crossing records do indicate that commercial cultivar crossing is not a priority and could be increased. The difference between programs for total commercial parents and cultivars, at least one cultivar parent, was not significantly different between the breeding programs, but the percentage of cultivars used in crossing was significantly different between programs. Our results indicate that cultivars are an excellent source of successful parents in all three programs and even though the programs have different breeding strategies, the cultivars they release are not significantly different in their proportions of total cultivar parents. LSU uses significantly more cultivars in crosses, but the proportion of at least one cultivar parent is proportional to noncultivars unlike the other programs (Table 2). The Houma program had percentages similar to CP even though it differs somewhat from the other two programs due to its emphasis on germplasm enhancement through basic breeding [5], with lesser importance placed on commercial crosses. Basic and commercial germplasm gradually merge through recurrent selection to the point at which cultivars are released for sugar or bioenergy. Cultivars also were used in 16.4% (CP), 11.8% (Houma), and 34.3% (LSU) of total crosses demonstrating their importance for contributing superior genes in the breeding pool at each location. The lower frequency of cultivars in total crosses at Houma probably reflects the greater use of basic germplasm in this program compared to that at LSU. But the genotype crosses at CP include mostly elite germplasm crosses and a few basic and energycane crosses. Energycane breeding which represented 13% of the CP crosses (159 crosses) in 2012 overlaps somewhat with basic breeding at CP and the industry for energycane is relatively new so not many cultivars have been released. There is also proportion of basic crosses shared between Houma and CP programs.

The choice of germplasm for breeding is biased in subtropical climates by the problem of unreliable flowering [61]. Often promising germplasm or cultivars are not selected for crossing because they will not flower under the conditions at the breeding station. Some promising foreign germplasm at Canal Point is not selected for crossing because they will not flower (personal communication). This could explain why there is less exotic material in the pedigrees of cultivars. Also lack of flowering synchrony will limit the types of crosses that can be made [61]. This could have skewed the use of cultivars in crossing at each breeding program.

If breeding programs increase the percentage of cultivars in their crossing programs, it should be done strategically to ensure that robust sources of diversity are maintained. Loss of diversity could hamper long-term breeding progress. Broadness of germplasm among the parental pool is an important measure of genetic diversity [62], and restricting parents to cultivars would narrow the parental gene pool. Maintaining a diverse germplasm and having the flexibility to import new germplasm are also important because of the constant need to incorporate new disease resistance genes into the parental pool, but the selection of these for crossing could be affected by the ability of these parents to flower. A possible reason why cultivars with cultivar parents are chosen is adaptability. The short cold Louisiana season and the muck organic soils in Florida are unique environments that probably favor particular gene combinations within existing cultivars. A future challenge will be to find efficient ways to quickly incorporate diversity and disease resistance into high performing germplasm like commercial cultivars.

There is a group of cultivars (Table 5) that did not produce commercial progeny. This could be due to not being crossed or deficiencies in their progeny. This should be investigated in the future to clarify better what useful germplasm is. It could be that the yield of some commercial and elite germplasm is due to heterosis and nonadditive genes. As molecular breeding technology becomes more practical and economically feasible it would be interesting to locate quantitative trait loci (QTL) of good parents then trace them within a lineage and compare them to cultivars that did not have successful progeny. This would allow us to understand better how QTLs from diverse backgrounds interact [63].


Co 281CP 55-30CP 88-1165 Ho 05-961
Co 290CP 59-73 CP 88-1508 Ho 07-613
CP 00-1101 CP 63-306 CP 88-1540 Ho 95-988
CP 00-1446 CP 67-412CP 88-1834 HoCP 00-950
CP 00-2180 CP 70-321CP 89-1509 HoCP 04-838
CP 01-1372 CP 70-330CP 89-2376 HoCP 85-845
CP 04-1566 CP 71-1038 CP 92-1213 HoCP 91-555
CP 04-1844 CP 73-1547 CP 92-1641 L 01-283
CP 04-1935 CP 73-351CP 92-1666 L 01-299
CP 05-1526 CP 74-383CP 94-1100 L 03-371
CP 28-11 CP 75-1632 CP 94-1340 L 60-25
CP 28-19 CP 76-331CP 96-1602 L 62-96
CP 29-103 CP 77-1776 CP 97-1944 L 79-1002
CP 29-116 CP 78-1247 CPCL 00-4111 L 97-128
CP 29-120 CP 78-1628 CPCL 02-0926 L 99-226
CP 29-320 CP 78-2114 CPCL 02-1295 L 99-233
CP 33-243 CP 79-318CPCL 02-6848 LCP 82-89
CP 33-310 CP 80-1557 CPCL 05-1102 LHo 83-153
CP 33-425 CP 807CPCL 05-1201 Louisiana purple
CP 34-120 CP 81-1384 CPCL 05-1791 Louisiana striped
CP 34-92 CP 82-1172 CPCL 97-2730 NCo 310
CP 36-13 CP 84-1591 CPCL 99-4455 Otaheite
CP 36-183 CP 85-1308 Black Cheribon (Creole) POJ 213
CP 36-19 CP 85-1382D-74POJ 234
CP 43-47 CP 85-1432 D-95POJ 36
CP 44-101 CP 85-1491 Ho 00-961POJ 36M
CP 47-193 CP 86-1633Ho 02-113

4. Conclusions

Sugarcane cultivars have been found to be acting as successful parents in all three breeding programs. A large percentage of the total number of cultivars in all programs has at least one commercial parent. In the LSU sugarcane breeding program the proportion of commercial parents to noncommercial parents was not significantly different but in the more recent crossing time period analyzed cultivars were crossed significantly more frequently than in the other programs.

The Canal Point and Houma programs did have significantly higher proportion of their cultivars with at least one commercial parent. Programmatic differences reflect, to some extent, philosophical approaches and responses to their respective industries. For example, the Florida program is larger than the two Louisiana programs combined, serves a subtropical climate with a longer growing season, and releases more cultivars to larger growers. Conversely, the Louisiana industry serves many growers with smaller farming operations with a shorter growing season who prefer that cultivars demonstrate early maturity prior to release.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

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