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a Louisiana State Univ. Agricultural Center, Sugar Research Station, 5755 LSU Ag Rd., St. Gabriel, LA 70776
b Dep. of Plant Pathology and Crop Physiology, Louisiana State Univ. Agricultural Center, Baton Rouge, LA 70803
c Dep. of Entomology, 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 99-233’ (Reg. No. CV-139, PI 655534) 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 in cooperation with the USDA–ARS and the American Sugar Cane League Inc. L 99-233 was released because of its high sugar and cane yields along with excellent ratooning ability. Data from 93 outfield trials indicate that L 99-233 produced approximately 18% greater sugar yield than LCP 85-384 when averaged across all crops. The sucrose content of L 99-233 was similar to LCP 85-384. The new cultivar is resistant to brown rust (Puccinia melanocephala H. and P. Sydow) and leaf scald [Xanthomonas albilineans (Ashby) Dowson], moderately susceptible to smut disease (Ustilago scitaminea Sydow & P. Sydow), moderately resistant to mosaic diseases, and susceptible to the sugarcane borer (Diatraea saccharalis F.). The cross for L 99-233 (XL94-8) was made in the fall of 1994. Early stage clonal selection was made from 1996 to 1998, which culminated in permanent clonal assignment in 1999. Replicated yield trials were conducted in south Louisiana from 2000 through 2005. Plant Patent no. 18,826 was issued for L 99-233 on 20 May 2008.
Abbreviations: LSU AgCenter, Louisiana State University Agricultural Center
Recurrent selection is commonly used in cross-pollinated crops as a means of improving traits that are under quantitative genetic control. Few if any meaningful traits in sugarcane (Saccharum spp.) are simply inherited; therefore, breeders have to deal with the issues of quantitative inheritance and genotype x environment interactions (Hogarth, 1987). These facts as well as the complex and high ploidy levels of sugarcane make breeding a challenge.
The recurrent selection scheme of sugarcane breeding has been ongoing in Louisiana since the mid-1920s. The release of L 99-233 (Reg. No. CV-139, PI 655534) (a complex hybrid of Saccharum officinarum L., S. barberi Jeswiet, S. spontaneum L., and S. sinense Roxb. amend. Jeswiet) is another mark of breeding success for developing high sucrose sugarcane cultivars adapted to Louisiana's temperate climate.
Methods
Crossing and Early-Stage Selection
L 99-233 was in the same assignment series as ‘L 99-226’ (Bischoff et al., 2009), so the selection and cultivar testing were similar. A more detailed summary of the LSU AgCenter sugarcane breeding program is provided by Bischoff and Gravois (2003).
The cross for L 99-233 (XL94-8) was made early in fall 1994. The female parent, CP 79-348, progressed to the outfield testing stage in the breeding program but was not released due to low sucrose content. HoCP 91-552, the male parent, was dropped from active clonal testing in 1997 after obtaining first-ratoon data in outfield trials in 1996. The main reason for dropping HoCP 91-552 was its high fiber content. However, in 2007 due to its high fiber content and cane yield, HoCP 92-552 was released as a commercial sugarcane cultivar with potential for biofuel applications.
Characteristics
Field Performance
L 99-233 was given its permanent cultivar assignment in 1999 during evaluation in the first-ratoon crop of the second line trials. Subsequently, L 99-233 was evaluated in on-station nursery trials during 2000 to 2003 in the plant-cane through third-ratoon crops (Table 1
). The new cultivar was compared with the commercial standard cultivar at the time, ‘LCP 85-384’ (Milligan et al., 1994). For all crops, L 99-233 was not significantly different from LCP 85-384 for sugar yield (Mg ha–1), cane yield (Mg ha–1), and sucrose content (g kg–1). The new cultivar was similar to LCP 85-384 because of its low stalk weight (kg) and high stalk number (no. ha–1). Ratoon crop data indicated L 99-233 to be an excellent ratooning cultivar. L 99-233 was replanted in off-station nursery and infield trials in 2000 and evaluated in plant-cane through third-ratoon crops during 2001 to 2004 with similar results (data not shown).
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After planting in the fall, L 99-233 emerges quickly. During Louisiana's cool wet winters, sugarcane becomes dormant and then regrows each spring from underground buds. Compared with most other cultivars, L 99-233 emerges quickly in the spring and grows vigorously throughout the summer. The new cultivar lodges easily and is best suited for mechanical harvesting by combines rather than whole-stalk harvesting systems.
Maturity Trials
L 99-233 demonstrated average sucrose content values across all sample dates, with values slightly less than that of LCP 85-384 in the first-ratoon crop (Table 3
) and values slightly higher than LCP 85-384 in the plant-cane crop (Table 4
). Late-September sugarcane harvest start dates are becoming more common in Louisiana. Because of its excellent ratooning ability and vigorous growth habit, many sugarcane growers have planted L 99-233 in their heavy clay soils. Crops on heavy clay soils tend to be harvested early in Louisiana. The use of a ripener is recommended to augment sucrose content in the new cultivar during September through mid-November harvest dates.
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Agronomic and Botanical Description
Plants of L 99-233 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 sugarcane's genotype.
A moderate white wax bloom covers the stalks of L 99-233. Under the wax layer (unexposed to sunlight), L 99-233 had a light green stalk. The stalk color of L 99-233 was more yellow when exposed to sunlight.
L 99-233 emerged quickly after planting and attained an average mature stalk height (ground level to the top visible dewlap) of 288 cm at the time of characterization (Table 5 ). The average stalk diameter of L 99-233 was 21.2 mm. L 99-233 exhibited a cylindrical and conoidal-shaped internode. L 99-233 had glabrous (lacking hair) growth rings with a width of 2.66 mm and a root band width of 6.17 mm. The root band was glabrous with straight sides and exhibited unequally distributed rows of irregularly shaped root primordia with approximate diameters ranging between about 0.25 and 0.50 mm. The root bands of L 99-233 exhibited no wax layer. The internodes of L 99-233 were smooth and glabrous with few, if any, corky patches; however, one main characteristic of the new cultivar was growth cracks. The average internode length of L 99-233 at midculm was 16.8 cm. The internodes of L 99-233 exhibited no bud furrow. The buds were located just above the leaf scar and were raised above the surface of the root band. L 99-233 exhibited ovate shaped buds (at the fourth node) with a central germ pore. Bud diameters were just over 5 mm, which is slightly smaller than bud diameters of cultivars with a larger stalk diameter. Bud color of L 99-233 was yellow without any wax on the bud surfaces. The new cultivar exhibited no setaceous or pilose hairs on the buds.
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The average leaf blade length and width of L 99-233, at the third leaf below the topmost visible dewlap, were 149 and 3.97 cm, respectively. The leaf color of L 99-233 was green but had more yellowish hues than HoCP 96-540 (Tew et al., 2005) and L 99-226. Leaf blades were acuminate. L 99-233 exhibited 4- to 8-mm-wide midribs distinctly raised on their abaxial sides. The abaxial midrib color was a slightly lighter green than the color of leaf blades. Adaxial side midribs of L 99-233 had smooth to concave surfaces, which were whitish in color and lighter than their leaf blades. Both leaf blades and midribs of L 99-233 were linear, glabrous with a smooth surface, and relatively thin. Dewlaps of L 99-233 were double crescent deltoid. L 99-233 exhibited a slight necrotic leaf sheath margin; auricles were necrotic; the average auricle shape was falcate. Auricles were measured on the fourth leaf from the topmost visible dewlap. L 99-233 exhibited a broad crescent-shaped ligule that was tan with a length and width of about 5.16 and 17.9 mm, respectively. The ligule region of L 99-233 exhibited pubescence.
Disease and Insect Reactions
Sugarcane disease and sugarcane borer (Diatraea saccharalis F.) ratings important to Louisiana sugarcane production were obtained from Bischoff et al. (2009). Diseases and insect ratings were obtained either in controlled innoculated tests and observations in yield trials or seed increases. L 99-233 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). Mosaic viruses in sugarcane have been controlled by the use of disease-free tissue culture seed-cane sources.
L 99-233 exhibited moderate susceptibility to smut (Ustilago scitaminea Sydow & P. Sydow). Smut is a systemic disease in sugarcane and has been managed by the use of disease-free tissue culture seed-cane sources.
The new cultivar is resistance to brown rust (Puccinia melanocephala H. and P. Sydow), unlike LCP 85-384, which is susceptible to this disease. Brown rust is a damaging disease of sugarcane in Louisiana.
L 99-233 is rated as resistant to leaf scald [Xanthomonas albilineans (Ashby) Dowson].
The effect of Sugarcane yellow leaf virus on the yield of L 99-233 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 99-233, which is unknown at this time. At this time, orange rust had not been reported in Louisiana.
Similar to most commercial cultivars grown in Louisiana, L 99-233 exhibited significant yield loss in ratoon crops from ratoon stunting disease (caused by Clavibacter xyli subsp. xyli Davis). In addition, the disease appears to spread rapidly once established in the cultivar.
Ratoon stunting disease is spread by the planting of infected seed material and through mechanical means, such as harvesters. The primary successful means of control of ratoon stunting disease has been through the propagation of disease-free seed-cane via tissue culture.
L 99-233 is moderately susceptible to the sugarcane borer insect pest of sugarcane. Fields of this new cultivar should be scouted for infestations of the sugarcane borer and should be treated when the threshold level of 5% live larvae are found. L 99-233 should not be grown where insecticides cannot be applied. The Mexican rice borer (Eoreuma loftini Dyar) was discovered in Louisiana in December 2008. Preliminary data indicate that L 99-233 is moderately susceptible to infestations of the Mexican rice borer (Reagan et al., 2007).
Field observations indicated that L 99-233 and LCP 85-384 have similar tolerances to herbicides commonly used for weed control in Louisiana.
Availability
L 99-233 received Plant Patent no. 18,826. The LSU AgCenter will make available small quantities of seed-cane for research purposes that 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 99-233 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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