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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).
ABSTRACT
Arkot JJ46 (Reg. No. GP-890, PI 651855), Arkot 9610 (Reg. No. GP-891, PI 651856), and Arkot 9620 JJ46 (Reg. No. GP-892, PI 651857) are noncommercial breeding lines of cotton (Gossypium hirsutum L.) released by the Arkansas Agricultural Experiment Station in September 2007. Arkot JJ46 was derived from a cross between ‘SG 125’ and ‘HyPerformer HS46’. Arkot 9610 was derived from a cross between ‘SG 404’ and Arkot 8606. Arkot 9620 was derived from crossing Arkot 8712 with an advanced breeding line. The lines were evaluated in replicated tests in Arkansas from 2003 through 2006. With some specific adaptation, lint yields of the lines were generally comparable to two check cultivars. Fiber quality, particularly fiber length, and line-specific host plant resistance traits—resistance to Fusarium wilt [caused by Fusarium oxysporum Schlect. f. sp. vasinfectum (Atk.) Snyd. & Hans.], Verticillium wilt (caused by Verticillium dahliae Kleb.), bacterial blight [caused by Xanthomonas campestris pv. malvacearum (Smith) Dye], and tarnished plant bugs [Lygus lineolaris (Palisot de Beauvois)]—make these lines valuable to cotton breeding programs.
Arkot JJ46 (Reg. No. GP-890, PI 651855), Arkot 9610 (Reg. No. GP-891, PI 651856), and Arkot 9620 (Reg. No. GP-892, PI 651857) are noncommercial breeding lines of cotton (Gossypium hirsutum L.) that were released by the Arkansas Agricultural Experiment Station in September 2007. Arkot JJ46 was derived from a 1994 cross between ‘SG 125’ (PVP 940063) and ‘HyPerformer HS46’ (PVP 8900104). Arkot 9610 was derived from a 1996 cross of ‘SG 404’ (PVP 940049) and Arkot 8606 (PI 628634, Bourland and Benson, 2002). Arkot 9620 was derived from a 1996 cross of Arkot 8712 (PI 636101, Bourland et al., 2005) and 8715-01, an advanced line developed by crossing F1 (Miscot T8-27 [PI 518655, Bourland and Bridge, 1988]/Miscot 7913-51 [PI 511348, Bourland, 1988])//F1 (‘H1330’ [PI 583875, Bourland, 1996]/Miscot 7803-52 [PI 520753, Bourland and White, 1989]).
In replicated tests in Arkansas from 2003 through 2006, the three lines displayed good yielding ability, improved fiber quality, and enhanced resistance to Fusarium wilt [caused by Fusarium oxysporum Schlect. f. sp. vasinfectum (Atk.) Snyd. & Hans.], bacterial blight [caused by Xanthomonas campestris pv. malvacearum (Smith) Dye], and tarnished plant bugs [Lygus lineolaris (Palisot de Beauvois)] compared with check cultivars.
Methods
Early Generation Population and Line Development
All three lines were developed using the generalized procedures outlined by Bourland (2004). The F1 and F2 populations of the cross leading to the development of Arkot JJ46 were grown at the Southeast Branch Station at Rohwer, AR, in 1995 and 1996, respectively. No selection was done in the F1 population, but bolls from visually superior individual F2 plants were harvested and bulked. Individual plants were selected from the subsequent F3 populations grown at Rohwer in 1997. Seed from the individual plants were evaluated in progeny rows at Clarkedale (Delta Branch Station) and Rohwer, AR, in 1998. One progeny designated as JJ46-28 was among the ones advanced and tested in replicated strain tests in 1999 and 2000. Individual plant selections from the F6 generation were evaluated as progenies in 2001. One of these selections produced Arkot JJ46 (tested as JJ46-28-06).
The F1 populations that gave rise to Arkot 9610 and Arkot 9620 were grown at Rohwer in 1997. The subsequent F2 bulk populations were grown at the Northeast Research and Extension Center (Keiser, AR) in 1998, and superior individual plants were selected and harvested separately. Two of the individual plants were designated as 9610-18 and 9620-25 and were evaluated with other progenies at Keiser and Rohwer in 1999, 2000, and 2001. In 1999 and 2000, superior progenies were selected and advanced to the next year. Individual plant selections from the F5 generation in 2001 were evaluated as progenies in 2002. Two of these selections produced Arkot 9610 (tested as 9610-18-09) and Arkot 9620 (tested as 9620-25-07).
Field Test Evaluations
From 2003 through 2006, Arkot JJ46 (12 tests), Arkot 9610 (16 tests), and Arkot 8620 (16 tests) were compared with the check cultivars PSC 355 (PVP 200000167) and SG 105 (PVP 9900190) in replicated field tests at five Arkansas Agricultural Research Station sites. Test sites included the Northeast Research and Extension Center at Keiser in 2003 through 2006, the Delta Branch Experiment Station at Clarkedale in 2004, the Judd Hill Cooperative Research Site at Judd Hill in 2005 and 2006, the Lon Mann Cotton Research Station at Marianna in 2004 through 2006, and the Southeast Branch Experiment Station at Rohwer in 2003 through 2006.
Each field test was arranged in a randomized complete block design with four replications of two-row plots (12–14 m by 1 m). Standard production practices, including furrow irrigation, were followed in each test. Leaf pubescence was rated each year using the rating system established by Bourland et al. (2003). Bracts were sampled, and marginal trichome density was determined using methods of Bourland and Hornbeck (2007). Percentage of open bolls was visually rated just before defoliation of the plots. Seedcotton yields were determined by machine picking of all replications. Hand-harvested boll samples, collected from two of the four replications, were ginned on a laboratory gin. Variables determined using the gin data and subsequent samples included lint fraction, seed index, lint index, fibers per seed, seed per area, and HVI (high volume instrument) fiber parameters. All data were analyzed by SAS v. 9.1 PROC GLM (SAS Institute, Cary, NC).
Pest Resistance Evaluations
During selection, nurseries and seed increases of Arkot 9610 and Arkot 9620 were inoculated with multiple races of X. campestris pv. malvacearum (Smith) Dye, the causal agent of bacterial blight. Susceptible plants were rogued from the early-generation populations and subsequent seed increases.
Percentages of wilted plants associated with Verticillium wilt were visually estimated in field tests at Clarkedale in 2004 and at Judd Hill in 2005 and 2006. Both of these test sites have a history of naturally occurring infestations of this pathogen. Response of the lines to Fusarium wilt was determined in the 2005 and 2006 National Cotton Fusarium Wilt Test at Tallassee, AL.
Response to tarnished plant bug was determined in small plot tests conducted at Keiser, AR, from 2004 through 2006. Single-row plots, 6 m by 1 m, were replicated 12 times and were managed to encourage tarnished plant bug populations. White flowers having any damaged flowers, as indicated by discolored anthers, were sequentially examined five to eight times over a 2-wk period in August of each year. A collective measure of percentage of damaged flowers over the sequential samples was determined for each plot. All pest resistance data, except bacterial blight data, were analyzed within years using SAS v. 9.1 PROC GLM (SAS Institute, Cary, NC).
Characteristics
Field Performance
Lint yields of Arkot JJ46 and Arkot 9620 were equal to the check cultivars on the clay soil at Keiser, while lint yields of Arkot 9610 were equal to the check cultivars on the silt loam soils of the other locations (Table 1
). Arkot JJ46 and Arkot 9620 produced their lowest relative yields at Clarkedale and Judd Hill, where the highest incidence of Verticillium wilt was observed. Both Arkot 9610 and Arkot 9620 produced significantly higher and lower yields than the check cultivars in a similar number of tests (Table 2
). Lint yields of Arkot JJ46 were equal to the check cultivars in the majority of tests but were not significantly higher than either check in any test. Plant height, open bolls, and seed per area of the three lines were similar to check cultivars. Exceptions were that Arkot 9610 tended to be taller than SG 105 and Arkot 9620 tended to be earlier maturing as indicated by higher percentage open bolls than either check cultivar. Lint fraction, seed index, lint index, and fibers per seed of the lines tended to be similar to the check cultivars (Table 3
).
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Leaf pubescence and marginal bract trichome density of the three lines were similar to the smooth-leaf check cultivar, SG 105, and less pubescent than PSC 355 (Table 4 ). All other morphological traits of the lines are not distinctive from SG 105 and PSC 355.
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During selection, Arkot 9610 and Arkot 9620 were screened for resistance to multiple races of X. campestris pv. malvacearum (Smith) Dye, the causal agent of bacterial blight. Resistance to the multiple races conveys resistance to all known U.S. races of this pathogen. Both lines exhibited resistance to bacterial blight in annually produced seed increase blocks that were inoculated with the pathogen (data not shown). Arkot JJ46 is susceptible to bacterial blight.
Both Arkot 9610 and Arkot 9620 had significantly more wilted plants associated with Verticillium wilt than the check cultivars in 2004 (Table 4). However, no differences in Verticillium wilt were detected among the three lines and check cultivars in 2005 or 2006. Expression of the disease is dependent on environmental conditions. All three lines had significantly less Fusarium wilt than the susceptible check in the 2005 and 2006 National Cotton Fusarium Wilt Tests at Tallassee, AL (Glass et al., 2005, 2007).
Availability
Small quantities of Arkot JJ46, Arkot 9610, and Arkot 9620 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.
Acknowledgments
Arkot JJ46, Arkot 9610, and Arkot 9620 were developed with financial support from Arkansas Agricultural Experiment Station and Cotton Incorporated.
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 February 5, 2008.
References
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