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a Louisiana State Univ. Agricultural Center, Sugar Research Station, 5755 LSU Ag Rd., St. Gabriel, LA 70776
b Dep. of Entomology, Louisiana State Univ. Agricultural Center, Baton Rouge, LA 70803
c Dep. of Plant Pathology and Crop Physiology, Louisiana State Univ. Agricultural Center, Baton Rouge, LA 70803
d Florida Crystals Corp., 21250 U.S. Hwy. 27, South Bay, FL 33493
e School of Plant, Environmental and Soil Sciences, Louisiana State Univ. Agricultural Center, Baton Rouge, LA 70803
* Corresponding author (kgravois{at}agcenter.lsu.edu).
ABSTRACT
‘L 99-226’ (Reg. No. CV-138, PI 655533) sugarcane (a complex hybrid of Saccharum officinarum L., S. barberi Jeswiet, S. spontaneum L., and S. sinense Roxb. amend. Jeswiet) was released on 25 Apr. 2006 by the Louisiana State University Agricultural Center (LSU AgCenter) in cooperation with the USDA–ARS and the American Sugar Cane League, Inc. L 99-226 was released because of its high sugar and cane yields along with excellent sucrose content. Data from 93 outfield trials indicate that L 99-226 produced approximately 33% greater sugar yield and 9% greater sucrose content than ‘LCP 85-384’ when averaged across all crops. The new cultivar is moderately resistant to brown rust disease (Puccinia melanocephala H. and P. Sydow), mosaic diseases, and the sugarcane borer (Diatraea saccharalis F.) and moderately susceptible to smut (Ustilago scitaminea Sydow & P. Sydow) and leaf scald [Xanthomonas albilineans (Ashby) Dowson]. The cross for L 99-226 (XL94-128) was made in fall 1994. Early stage clonal selection was done as single stools in 1996 followed by first clonal line trial selection in 1997 and second clonal line trial stage selection in 1998. Testing in replicated yield trials was conducted throughout the sugarcane growing area in south Louisiana from 2000 through 2005. Plant patent no. 18,807 was issued for L 99-226 on 13 May 2008.
Abbreviations: LSU AgCenter, Louisiana State University Agricultural Center
The first clones of cultivated sugarcane grown in Louisiana originated from Saccharum officinarum. Accessions within this species are generally high in sucrose content and lower in fiber content compared with other species within the Saccharum genus. Unfortunately, clones derived from S. officinarum typically had poor ratooning ability and were particularly susceptible to diseases. Planting of these disease susceptible cultivars nearly led to the decimation of the Louisiana sugar industry from 1919 to the mid-1920s. The primary diseases were Sugarcane mosaic virus, ratoon stunting disease [Leifsonia xyli subsp. xyli (Davis et al. 1984) Evtushenko et al. 2000], and various stalk and root rotting diseases.
The solution to the disease problem in Louisiana lay in the importation of the POJ cultivars developed in Indonesia. ‘POJ 213’ and ‘POJ 234’ had the largest impact in Louisiana. These POJ cultivars were derived from crosses and backcrosses between recurrent clones of S. officinarum and nonrecurrent clones of S. spontaneum. In Indonesia, the goal of these initial crosses was to develop resistance to Sereh disease. Modern cultivated sugarcane (Saccharum spp.) is believed to have originated from complex hybridization events (termed nobilization) between S. officinarum, S. barberi, S. sinense, and the wild related species S. spontaneum and can best be described as complex interspecific aneuploids with chromosome numbers ranging from 2n = 100 to 130 (Sreenivasan et al., 1987). Modern cultivars are predominantly outcrossing and highly heterozygous and maintained by vegetative propagation.
The complex and high ploidy levels of sugarcane make breeding a challenge. Few if any meaningful traits in sugarcane are simply inherited; therefore, breeders have to deal with the issues of quantitative inheritance and genotype x environment interactions (Hogarth, 1987). Most sugarcane breeding programs rely on recurrent selection schemes. In Louisiana the commercial sugarcane breeding programs are in about their seventh cycle of recurrent selection for sucrose content and other related traits. Breeding efforts in Louisiana have been successful because sugarcane grown in Louisiana's temperate climate now approaches sucrose recoveries similar to cultivars grown in more subtropical and tropical environments (Breaux, 1984; Legendre, 1995). The release of L 99-226 (Reg. No. CV-138, PI 655533) (a complex hybrid of Saccharum officinarum L., S. barberi Jeswiet, S. spontaneum L., and S. sinense Roxb. amend. Jeswiet) marks another breeding success for developing high sucrose sugarcane cultivars adapted to Louisiana's temperate climate.
Methods
Crossing and Early Stage Selection
A more comprehensive summary of the Louisiana State University Agricultural Center (LSU AgCenter) sugarcane breeding program is provided by Bischoff and Gravois (2003). The cross for L 99-226 (XL94-128) was made in the fall of 1994 (Table 1
). The pedigree of L 99-226 included the female parent, HoCP 89-846, and the male parent, LCP 81-30. During the outfield testing stage of the breeding program, HoCP 89-846 was found to be susceptible to leaf scald disease [Xanthomonas albilineans (Ashby) Dowson] and was dropped from active testing. This experimental clone was vigorous and had excellent ratooning ability, most likely because it was a BC4–derived progeny from the S. spontaneum clone US 56-15-8. LCP 81-30 was a near commercial clone with excellent sucrose content but was not well suited to Louisiana's whole stalk harvesting system and was subsequently dropped for commercial release.
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Replicated Yield Trials
Replicated on-station nursery trials were conducted at the Sugar Research Station in St. Gabriel, LA, the USDA–ARS Ardoyne Farm in Schriever, LA, and the Iberia Research Station in Jeanerette, LA. Single-row (1.8-m-wide) plots were planted at a rate of two running stalks placed side by side, with a total of six stalks used to plant an entire plot. The plot length was 4.9 m. The experimental design at each location was a randomized complete block (two replications). Data collected in the plant-cane, first-ratoon, second-ratoon, and third-ratoon crops included sugar yield (Mg ha–1), cane yield (Mg ha–1), sucrose content (g kg–1), stalk weight (kg), and stalk population (stalks ha–1).
Millable stalk counts of the entire plot were made in early August. Stalk population was calculated as the number of millable stalks per hectare. At harvest, a random 10-stalk hand-harvested sample from each plot was stripped of the leaves and immature tops and weighed to estimate stalk weight (kg). Afterward, a sucrose analysis was performed on each sample at the Sugar Research Station sucrose laboratory. Brix and pol readings were used to determine sucrose content (g kg–1) (Gravois and Milligan, 1992). Cane yield was estimated as the product of stalk population and stalk weight and then divided by 1000. Sugar yield was estimated as the product of cane yield and sucrose content divided by 1000.
Replicated off-station nursery trials were conducted at the D & N Farm in Cecilia, LA, Newton Cane Co. in Bunkie, LA, and Joel Landry Farms in Paincourtville, LA. Single-row (1.8-m-wide) plots were planted at a rate of two running stalks placed side by side, with a total of eight stalks used to plant an entire plot. These plots were 6.1 m long with a 1.5-m alley between plots. The experimental design for each trial was a randomized complete block design, and there were two replications. Stalk population, stalk weight, sugar yield, cane yield, and sucrose content were estimated as described for the on-station nursery trials.
Infield trials were planted in the same year as off-station nursery trials and were conducted at the USDA–ARS Ardoyne Farm in Schriever, LA, Blackberry Farms in Vacherie, LA, and Sugarland Farms in Youngsville, LA. Two-row plots were planted at a rate of two running stalks placed side by side, with a total of 20 stalks used to plant an entire plot. These plots were two rows 7.6 m long with a 1.5-m alley between plots. Cane yield data were obtained using a combine harvester and a high-dump weigh wagon equipped with electronic load cells to record cane weight. Plot weights were used to calculate cane yield. The experimental design for each trial was a randomized complete block design, and each trial had two replications.
The name of the final yield testing stage of the LSU AgCenter sugarcane breeding program is "outfield trials" Outfield trials were conducted in cooperation with the USDA–ARS and the American Sugar Cane League. Mechanically harvested outfield trials were conducted across 10 south Louisiana locations during 2003 through 2007. A 15-stalk sample was collected before harvest to determine stalk weight and to conduct sucrose analyses. Plots were harvested in a manner similar to the infield trials. No burning was done before harvest.
Sugarcane sucrose levels are an important aspect when determining sugarcane harvest schedules. Sucrose content was assessed at regular intervals throughout the harvest. Maturity tests were conducted by researchers at the USDA–ARS Sugarcane Research Unit in Houma, LA. Ten-stalk samples were taken monthly from plant-cane tests and biweekly from first-ratoon tests to monitor the accumulation of sucrose. Each test was replicated four times and planted as a randomized complete block design.
Numerous commercial sugarcane cultivars were included for comparison in the different trials, ‘CP 70-321’ (Fanguy et al., 1979), ‘LCP 85-384’ (Milligan et al., 1994), ‘CP 89-2143’ (Glaz et al., 2000), ‘HoCP 85-845’ (Legendre et al., 1994), ‘HoCP 91-555’ (Legendre et al., 2000), ‘Ho 95-988’ (Tew et al., 2005a), ‘HoCP 96-540’ (Tew et al., 2005b), and ‘L 97-128’ (Gravois et al., 2008). At the release date in 2006, LCP 85-384 was the leading sugarcane cultivar grown in Louisiana (Legendre and Gravois, 2007); therefore, comparisons focused primarily on LCP 85-384.
Statistical Analyses
Data were analyzed by year (crop) across locations for multilocation yield trials. The Proc Mixed procedure was used to analyze the linear model (SAS v. 9.0 [SAS Institute, Cary, NC]). Cultivar–clone was considered a fixed effect, and location and replication were considered random effects. Least square means were generated for each cultivar–clone and were separated using the PDIFF option (P = 0.05).
Characteristics
Field Performance
On-station nursery trials were conducted during 2000 to 2003 for the 1999 assignment series of which L 99-226 was a part (Table 2
). All cultivars–clones were compared with L 99-226. For the plant-cane crop and the first-ratoon crops, L 99-226 was not significantly different from LCP 85-384 for sugar yield, cane yield, and sucrose content. In the second- and third-ratoon crops, the sugar and cane yields of L 99-226 were higher than those of LCP 85-384. In the third-ratoon crop, the sucrose content of L 99-226 was higher than the sucrose content of LCP 85-384. The new cultivar is also characterized as having larger stalk weight with a lower stalk number than LCP 85-384. The 1999 assignment series (of which L 99-226 was a part) was replanted in off-station nursery and infield trials during 2001 to 2004 with similar results (data not shown).
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After planting in the fall, L 99-226 emerges quickly, but not nearly as quickly and completely as HoCP 00-950 (Tew et al., 2009). During Louisiana's cool wet winters, sugarcane becomes dormant and then regrows each spring from underground buds. Compared with most other cultivars, L 99-226 has average spring emergence. Cool weather in early spring can produce an obvious anthocyan pigment in the leaves. As temperatures warm, the cultivar tillers well and grows vigorously through the summer months. The new cultivar is not as erect as HoCP 96-540 and L 97-128 and is therefore more suitable for mechanical combine harvesting systems rather than whole-stalk harvesting systems.
In first-ratoon maturity trials (Table 4 ), L 99-226 had significantly higher sucrose content than HoCP 91-555, Ho 95-988, and CP 89-2143, the most widely grown cultivar in Florida (Glaz 2008). By the 6 October harvest date, L 99-226 had sucrose content either similar to or significantly higher than all cultivars included in the trial. In the first sampling date of the plant cane trial, L 99-226 had sucrose content values that were superior to CP 89-2143 and HoCP 96-540 but significantly lower than L 97-128 (Table 5 ). By the 20 November harvest date, L 99-226 was superior to all cultivars with the exception of HoCP 91-555. Although the sucrose content of L 99-226 is considered high by Louisiana standards, Tew et al. (2009) reported that cultivar HoCP 00-950 was superior to L 99-226 in sucrose content in a first-ratoon maturity trial. Earlier sugarcane harvest start dates are the trend in Louisiana. Sugarcane cultivars with high sucrose content early in the harvest season are important for the Louisiana sugarcane industry.
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Agronomic and Botanical Description
The plants of L 99-226 described here were characterized on 11 September through 19 September 2006 at approximately 160 to 175 d in age from spring emergence. The stalks characterized were from inner rows unexposed to direct sunlight. Both color and other phenotypic expressions may vary with differences in growth and environment and cultural conditions, without any change in the genotype of the L 99-226.
An extensive white wax bloom covers the stalk of L 99-226, which was more abundant than the wax bloom of either parent, HoCP 89-846 and LCP 81-30. L 99-226 had a dark green stalk with purple hues. The stalk color can become more of a purple-red hue when exposed to direct sunlight.
L 99-226 exhibited an average mature stalk height (ground level to the top visible dewlap) of 289 cm with an average stalk diameter of 25.3 mm (Table 6 ). The new cultivar had conoidal-shaped internodes (fourth internode from ground level) and glabrous growth rings. Growth-ring width for L 99-226 was 3.85 mm. Root bands (4.69 mm) were glabrous with straight sides and exhibited unequally distributed rows of irregularly shaped root primordia. Root bands of L 99-226 exhibited a wax layer. Internodes of L 99-226 were smooth and glabrous, with few, if any, corky patches or cracks, and exhibited an average length at the midculm of 14.8 cm. Internodes of L 99-226 did not exhibit a bud furrow. The bud was located just above the leaf scar and was raised above the surface of the root band. L 99-226 exhibited a narrow ovate bud shape (at the fourth node) with a central germ pore. Bud diameter of L 99-226 was just over 6 mm. Buds of L 99-226 were yellow, without any wax on the surface, and had no setaceous or pilose hairs.
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The average leaf blade length and width of L 99-226, at the third leaf below the top most visible dewlap, was 178 and 4.26 cm, respectively. L 99-226 exhibited green leaf blades at the second visible dewlap. The leaf blade was acuminate. L 99-226 had 4- to 8-mm-wide midribs that were distinctly raised on their abaxial side. The midrib color on the abaxial side of the leaf was similar to the color of the leaf blade. On the adaxial side, the midrib of L 99-226 had a smooth to concave surface and a whitish color, which was much lighter than its leaf blade. Both the leaf blade and midrib of L 99-226 were linear, glabrous with a smooth surface, and relatively thin. The dewlap of L 99-226 was ascending approximately square. Dewlap colors for L 99-226 were brownish but not as dark as dewlaps of HoCP 85-845. L 99-226 exhibited a slight, necrotic leaf sheath margin. The auricle of L 99-226 was necrotic. The average auricle shape for L 99-226 was long lanceolate. Auricles were measured on the fourth leaf from the top most visible dewlap. The ligule shape was broad crescent. L 99-226 exhibited a tan ligule with a length of 3.97 mm and a width of 19.28 mm. The ligule region of L 99-226 exhibited slight pubescence. The leaf sheaths adhered tightly to the stalks and were a particular problem for this cultivar during planting and harvesting. Stalks of L 99-226 tend to lodge as growth approaches late summer and early fall.
Under normal growing conditions in Louisiana's temperate climate, L 99-226 does not flower, but it flowers easily under controlled photoperiod regimes. The new cultivar has been used extensively for crossing in Louisiana where it produces abundant pollen and is typically used as a male parent.
Disease and Insect Reactions
Diseases and sugarcane borer (Diatraea saccharalis F.) ratings were observed in controlled tests, yield trials, or seed increases (Table 7
). L 99-226 is resistant to Sugarcane mosaic virus and moderately resistant to Sorghum mosaic virus. Strain I has been identified at extremely low levels in the new cultivar (Mike Grisham, personal communication, 2009). The mosaic viruses have been controlled by the use of disease-free tissue culture seed sources.
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L 99-226 exhibited moderate resistance to brown rust (Puccinia melanocephala H. and P. Sydow), unlike LCP 85-384 and Ho 95-988, which exhibited susceptibility to this disease. Brown rust resistance is extremely important to the Louisiana sugar industry. LCP 85-384 was resistant to sugarcane brown rust on its release in 1993 but is now extremely susceptible to the new races that have formed (Hoy et al., 2000). Moderate levels of rust have been observed in L 99-226 when the cultivar is planted next to susceptible cultivars.
L 99-226 was rated as moderate susceptible to leaf scald under both innoculated and natural field infection conditions. Leaf scald was more commonly seen after periods of extended dry weather in the late summer and fall.
Similar to most commercial cultivars grown in Louisiana, L 99-226 exhibited significant yield loss in ratoon crops from ratoon stunting disease. This disease is controlled either by tissue culture propagation of disease-free seed stock or the heat treatment of whole stalks.
The effect of yellow leaf on the yield of L 99-226 is unknown. Orange rust [Puccinea kuehnii (Krüger) E. Butler] was recently discovered in sugarcane grown in Florida. Trials have been initiated in Florida to determine the orange rust reaction of L 99-226, which is unknown at this time. To date, orange rust has not been detected in Louisiana.
L 99-226 was moderately resistant to the sugarcane borer, the most important insect pest of sugarcane. Fields of the new cultivar should be scouted for the sugarcane borer and treated only when the threshold level of 5% live larvae is found. The Mexican rice borer (Eoreuma loftini Dyar) was discovered in Louisiana in December 2008. Preliminary data indicated that L 99-226 was moderately resistant to the Mexican rice borer (Reagan et al., 2007).
Field observations indicated that L 99-226 is no more susceptible to herbicides commonly used for weed control in Louisiana than LCP 85-384. Bittencourt (2009) determined that L 99-226 had the best shading capability of Louisiana sugarcane cultivars and would be the most competitive against troublesome weeds.
Availability
L 99-226 has received Plant Patent no. 18,807. The LSU AgCenter will make available small quantities of seed-cane for research purposes, which may be obtained from the corresponding author for at least 5 years from the date of this publication via a Material Transfer Agreement with the LSU AgCenter. Seed-cane of L 99-226 has been deposited in the USDA–ARS National Center for Genetic Resources Preservation, where it will become freely available for distribution after the expiration of the plant patent.
Footnotes
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication April 20, 2009.
References
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