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a Univ. of Arkansas Division of Agriculture Northeast Research and Extension Center, P.O. Box 48, Keiser, AR 72351
b Cotton Incorporated, 6399 Weston Pkwy., Cary, NC 27513
* Corresponding author (bourland{at}uark.edu).
Two breeding lines of cotton, Gossypium hirsutum L., designated as Arkot 9506 (Reg. No. GP-874, PI 643442) and Arkot 9513 (Reg. no. GP-875, PI 643443) were released by the Arkansas Agricultural Experiment Station in 2006. The lines were developed using the generalized procedures outlined by Bourland (2004).
Arkot 9506 was derived from a 1993 cross between two advanced breeding lines, 8703-25-07 and 8726-10-01. The breeding line 8703-25-07 was derived from the double cross of F1 (‘DP90’/‘ST825’)/F1(Miscot 7918/Miscot 7803-52). The breeding line 8725-10-01 was derived from crossing La. HG-063 (Jones et al., 1988) and F1 (Miscot T8-27/Miscot 7803-52). Miscot 7918 (Bourland and White, 1989b), Miscot 7803-52 (Bourland and White, 1989a), and Miscot T8-27 (Bourland and Bridge, 1988) were developed by crossing lines from the Texas A&M Multi-Adversity Resistance Cotton Breeding program (Bird, 1982) with lines adapted to the Mississippi River Delta region. Arkot 9513 was derived from a 1993 cross of Arkot 8712 (Bourland et al., 2005) and 8923-11, an advanced breeding line derived from crossing ‘H1330’ (Bourland, 1996) and St 81-29-2,26B (a sister line of M-92, M-249, and M-272; Shepherd et al., 1996).
Within F2 populations grown at the Southeast Branch Station at Rohwer, AR, in 1997, bolls from visually superior plants were harvested and bulked. The F3 bulk populations were grown at Rohwer in 1998, and superior individual plants were selected and harvested separately. The resulting F4 progeny rows were evaluated at Clarkedale (Delta Branch Station), and Rohwer, AR, in 1999. Progenies designated as 9506-40 and 9513-28 were among the ones promoted and tested in different replicated strain tests in 2000. Individual plant selections from the F5 generation of these two strains were made from seed increase blocks planted at Keiser, AR, in 2000. Seed from these selected plants were evaluated as progenies in 2001. Two of these selections produced Arkot 9506 (tested as 9506-40-05) and Arkot 9513 (tested as 9513-28-01).
From 2002 through 2005, the two lines were compared to ‘PSC 355’ and ‘SG 105’ in 13 replicated field tests at five Arkansas Agricultural Research Station sites, two on-farm sites in northeast Arkansas, four Stoneville, MS, sites and one Tifton, GA, site. Arkot 9513 was also evaluated in the 2004 Regional High Quality Strain Test. Both lines were evaluated in the 2005 Regional Breeders' Testing Network (RBTN), which included 10 locations from South Carolina to west Texas (www.cottonrbtn.com).
Over all Arkansas tests, mean lint yields of Arkot 9506 exceeded the check cultivars by more than 6%, while yields of Arkot 9513 were similar to the check cultivars. When compared over years, Arkot 9506 yielded more than the mean of the check cultivars at all five Arkansas sites but yielded relatively more at sites with sandy or silt loam soil located in central and northern Arkansas. Mean yields of Arkot 9513 were greater than the mean of the check cultivars at only three of the five locations.
In 2004, both Arkot 9506 and Arkot 9513 yielded about 14% less than either check cultivar at Tifton, GA. Over four Stoneville, MS, tests, yields of Arkot 9506 were equal to the check cultivars, but yields of Arkot 9513 were 12% less than the check cultivars. Out of 20 entries in the 2005 RBNT, lint yields of Arkot 9506 and Arkot 9513 ranked 9th and 16th, respectively.
In the Arkansas tests, Arkot 9506 and Arkot 9513 expressed higher lint percentages (3 and 1% points greater, respectively), higher lint index (0.5 g more lint per 100 seed), 11% more fibers per seed, and fewer seed per acre (2.8 and 8.2%, respectively) than the check cultivars. According to Lewis et al. (2000), this combination of yield components (i.e., increased reliance on high lint index relative to seeds per acre) should contribute to more stable yield production. The high lint index of Arkot 9506 is impressive since its seed index (weight of 100 seed) was 0.45 g less than the check cultivars.
Compared with the check cultivars, Arkot 9506 averaged about 9 mm shorter fiber length and 31 kN m kg–1 weaker fiber strength. In contrast, fiber of Arkot 9513 was 6 mm longer and 19 kN m kg–1 stronger than the check cultivars. Micronaire and length uniformity of the two lines were similar to the check cultivars.
Mean plant height of Arkot 9506 was about 14 cm shorter than Arkot 9513 and the check cultivars. Open boll percentages for Arkot 9513 in 2004 and 2005 were 13 points higher than Arkot 9506 and the check cultivars. Based on a rating system developed by Bourland et al. (2003), leaf pubescence of both lines were equal to the smooth leaf cultivar, SG 105. Marginal bract trichome density for Arkot 9506 and Arkot 9513 was equal to SG 105 but 23 and 40%, respectively, less than PSC 355.
Arkot 9506 and Arkot 9513 display good host plant resistance traits. During selection, both lines were screened for resistance to multiple races of Xanthomonas campestris pv. malvacearum (Smith 1901) Dye 1978b, the causal agent of bacterial blight. Resistance to the multiple races conveys resistance to all known U.S. races of this pathogen. The lines exhibited resistance to bacterial blight in annually produced seed increase blocks that were inoculated with the pathogen. In 2004, Arkot 9513 had significantly more wilted plants associated with Verticillium wilt (caused by Verticillium dahliae Kleb.) than SG 105. Increased wilt symptoms are sometimes associated with early maturation. No differences in Verticillium wilt were detected in 2005. In the 2004 and 2005 National Cotton Fusarium Wilt Test in Tallassee, AL, both lines had significantly less Fusarium wilt [caused by Fusarium oxysporum Schlectend.:Fr. f. sp. vasinfectum (Atk.) W.C. Snyder & H.N. Hans.] than the susceptible check (Glass et al., 2004, 2005). In both years, Arkot 9513 had less Fusarium wilt than Arkot 9506. In 2004 and 2005, both lines were more resistant to tarnished plant bug [Lygus lineolaris (Palisot de Beauvois)] than the susceptible frego bract check and equal to the check cultivars. Although Arkot 9506 has a bronze wilt susceptible line in its parentage (Miscot T8-27), no bronze wilt has been observed in this line.
Specific combinations of yield adaptation, fiber properties, and host plant resistance traits make the lines valuable to cotton breeding programs. Both Arkot 9506 and Arkot 9513 displayed early maturity, high lint percentage, high lint index, and good host plant resistance traits. Compared with the commercial check cultivars, Arkot 9506 produced higher yields and Arkot 9513 produced superior fiber quality. Development of the two lines was supported in part by funding from Cotton Incorporated. Small quantities of Arkot 9506 and Arkot 9513 seed may be obtained for breeding purposes from the corresponding author. Unless specifically approved by the Arkansas Agricultural Experiment Station, the lines may not be used as recurrent parents in a breeding program.
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 September 28, 2006.
References
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