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a Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS
b USDA-ARS, Crop Science Research Lab., Box 5367, Mississippi State, MS 39762
c Mississippi Agricultural and Forestry Experiment Station, Delta Research and Extension Center, Stoneville, MS
d Plant and Soil Sciences Dep., Mississippi State Univ., Mississippi State, MS
e Cotton Incorporated, Cary, NC
* Corresponding author (jnjenkins{at}ars.usda.gov).
The cotton (Gossypium hirsutum L.) germplasm lines MS-01RKN (Reg. No. GP-882, PI 644074), MS-24RKN (Reg. No. GP-883, PI 644075), MS-30RKN (Reg. No. GP-884, PI 644076), MS-33RKN (Reg. No. GP-885, PI 644077), MS-35RKN (Reg. No. GP-886, PI 644078), and MS-37RKN (Reg. No. GP-887, PI 644079) were developed by the Mississippi Agricultural and Forestry Experiment Station, the USDA-ARS, and Cotton Incorporated and were released in 2006. The lines combine resistance to the southern root-knot nematode (RKN), [Meloidogyne incognita (Kofoid & White) Chitwood] with good yield and fiber quality. These germplasm lines provide both public and private breeders with germplasm resources with resistance to root-knot nematode and acceptable yield and fiber quality for the Mid-South and southeastern USA.
The nematode resistance in these lines is from the Auburn 634 RNR source (GP166), Shepherd, (1982). The nematode-resistant parent in all the crosses was M-240 RNR (PI592511) (Shepherd et al., 1996). M-240 RNR was developed with the cultivar Deltapine 61 as the recurrent parent. The nematode-resistant line M-240 RNR was crossed with ‘Suregrow 501’ (SG501), ‘Suregrow 125’ (SG125), and ‘DES119’. These F1s were then crossed with commercial cultivars or released elite breeding lines. R.G. Creech evaluated progeny of the three-way crosses in the greenhouse for resistance to root-knot nematode, using methods similar to those described by Shepherd (1979), and individual plants were selected and their progeny were grown in field plots, without nematodes, for agronomic evaluations. Selections that yielded similar to commercial cultivars grown in the test were again evaluated in the greenhouse for root-knot nematode resistance and individual plant selections were made and planted in field plots without nematodes. Details of the number of cycles of progeny evaluation and selection are not available; however, we believe two or more cycles were involved.
Pedigrees of the released lines are as follows: MS-01RKN is SG404/(M240/SG501); MS-24RKN is (M240/SG125)/SG125: MS-30RKN is DES211-39/(M240/SG125); MS-33RKN is SG501/(M240/SG125); MS-35RKN is (DES119/M240)/DES119; and MS-37RKN is (DES119/M240)/DES119.
Following the retirement of R.G. Creech, seed of several of his selections were increased and evaluated for agronomic performance in two field trials on a Leeper silty clay loam in 2004 and one field trial on a Leeper silty clay loam and one on a Marietta sandy clay loam in 2005 at Mississippi State, MS. They were also evaluated in two greenhouse evaluations for root knot nematode resistance using gall score and eggs produced as the criteria for resistance. Three replications of five plants each were grown in each evaluation. Galls were scored on a 1 to 5 scale (1, very light galling: 2, light: 3, moderate: 4, heavy: 5, very heavy galling). Roots of the five plants in each replication were bulked by entry, and eggs were extracted and counted (Haire, 2006). Selected lines were also planted in the National Cotton Fusarium Wilt Nursery, Tallassee, AL, in 2005. In this nursery, plants from many cotton breeding programs are grown on an Independence loamy fine sand highly infested with the Fusarium wilt fungus [Fusarium oxysporum Schlect. f. sp. vasinfectum (Atk.) Snyd. & Hans.] and southern root-knot nematode. The major damage to cotton in this nursery appears to be caused by root-knot nematode (Glass et al., 2005). Wilted plants were counted and removed four times during the season and data were expressed as percentage of plants wilted.
On the basis of evaluations, six lines were chosen for germplasm release and registration. Data from the two greenhouse RKN evaluations in 2005 showed that the RKN gall index for the six lines ranged from 2.0 to 2.7; whereas the gall index on the RKN resistant check M-315 RNR was 1.8, the susceptible RKN check M8 was 4.0, and the resistant cultivar check Acala Nemx was 2.5. Eggs per plant on the six lines ranged from 5387 to 18,305; whereas, eggs per plant on M-315 RNR, M8, and Acala Nemx were 5612; 90,625, and 17,424, respectively. Each of the six lines had significantly less wilted plants (2–12% wilted) than ‘Rowden’ (48–63% wilted), the susceptible check cultivar, in the National Fusarium Wilt Nursery in 2005, indicating resistance to both root-knot nematode and Fusarium wilt. In two years of field trials at Mississippi State, yield and yield components of the six lines were equal to or better than ‘Stoneville 474’ (ST474), the agronomic cultivar check. Boll weights ranged from 4.96 to 5.27 g, with ST474 being 4.82 g. Three lines had significantly heavier bolls than ST474. Lint percentage ranged from 40.3 to 42.1%, with ST474 being 43.6%. All lines had significantly lower lint percentages than the high lint percentage of ST474. Lint yield ranged from 827 to 1016 kg ha–1 with ST474 being 858 kg ha–1. No line was significantly different in yield from ST474. Fiber properties (HVI) were equal to or superior to ST474. Micronaire ranged from 4.9 to 5.1, with ST474 at 5.3. Three lines had significantly lower micronaire than ST474. Fiber length ranged from 28.3 to 29 mm, with ST474 at 28.6 mm. No lines had fiber length significantly different from ST474. Fiber strength ranged from 279 to303 kNm kg–1, with ST 474 at 286 kNm kg–1. One line (MS-35RKN) had fiber strength of 303 kNm kg–1, significantly greater than ST474.
Small quantities of seed are available to cotton breeders, geneticists, and other research personnel on written request to the corresponding author. Request for seed from outside the USA must be accompanied by an import permit allowing entry into the requestor's country. The USDA-ARS may not be able to certify that seeds are free of certain insects or pathogens specified on import permits, and in such cases seed cannot be supplied. It is requested that appropriate recognition of the source be given when these germplasm lines contribute to the development of a new breeding line, hybrid, or cultivar. Seed of this release will be deposited in the National Plant Germplasm System.
Acknowledgments
Names are necessary to report factually the available data; however, the USDA neither guarantees nor warrants the standard of products or services, and the use of the name by the USDA implies no approval of product or service to the exclusion of others that may also be suitable.
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 November 30, 2006.
References
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