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Registration of Arkot 8918 and Arkot 9103 cotton germplasm lines. (Registrations Of Germplasm).

Two cotton (Gossypium hirsutum L.) germplasm lines, designated Arkot 8918 (Reg. no. GP-744, PI 628638) and Arkot 9103 (Reg. no. GP-745, PI 628639), were developed by the Arkansas Agricultural Experiment Station and released in 2001. The lines possess agronomic, fiber quality, and host-plant resistance traits that make them valuable as breeding lines.

Both lines were derived from crosses with one common parent, `H1330' (Bourland, 1996). The second parent of Arkot 8918 was Mo F86-28, an advanced strain derived from the cross of `Delcot 311' (Sappenfield, 1980) by Auburn 623 RNR (Shepherd, 1974), then backcrossed to Delcot 311. The second parent of Arkot 9103 was 8517-18, an advanced strain from the cross of DES 237-7 (Bridge, 1987) and Miscot 7824 (Bourland and White, 1992).

Arkot 8918 (tested as 8918-01-08) was derived from an [F.sub.3] individual plant selection (8918-01) made in 1991, with a second cycle of selection made from the [F.sub.7] generation in 1995. The second cycle selection was evaluated as a progeny row in 1996 and as a line in replicated tests from 1997 through 2000. Arkot 9103 (tested as 9103-38-01) was derived from an [F.sub.3] individual plant selection (9103-38) made in 1993, with a second cycle of selection made from the [F.sub.6] generation in 1996. The second cycle selection was evaluated as a progeny row in 1997 and as a line in replicated tests from 1998 through 2000. Procedures of Bird (1982), modified to permit selection for lateral root development, were used in the first cycle of selection for both lines. Second cycle selections were based on visual performance of individual plants and their corresponding progeny rows.

Agronomic traits of the lines were evaluated in 10 tests conducted from 1997-2000 at four Arkansas Agricultural Experiment Station sites in the Mississippi River Delta. Lint yields of Arkot 8918 and Arkot 9103 were, respectively, 9% less than and equal to `Stoneville 474'. Yields of both lines were relatively higher at north Arkansas locations (Keiser and Clarkedale) than at central (Marianna) and south (Rohwer) locations. However, maturity of the lines was similar to Stoneville 474. Fiber properties of both lines were superior (3% longer with 1.2% higher uniformity index, 10% stronger) than those of Stoneville 474. Micronaire readings of Arkot 8918 and Arkot 9103 were 8% lower than and equal to Stoneville 474, respectively. Lint fractions of the two lines averaged 36.9%, compared with 40.9% for Stoneville 474. The lines are morphologically similar, but somewhat shorter than Stoneville 474. Leaves of Arkot 9103 are less pubescent than those of Stoneville 474.

During selection, Arkot 8918 and Arkot 9103 were screened for resistance to races 1, 2, 7, and 18 of Xanthomonas campestris pv. malvacearum (Smith) Dye, the causal agent of bacterial blight. Resistance to these races conveys resistance to all known U.S. races of this pathogen. In subsequent tests, Arkot 8918 and Arkot 9103 have not exhibited symptoms of bacterial blight in testing even after field inoculations with the pathogen. In the presence of intense thrips (Frankliniella spp.) pressure in 2000, both lines yielded significantly more fiber and had less relative plant injury than Stoneville 474. With less thrips pressure, differences were not significant in 1999.

The superior fiber properties and specific adaptation of Arkot 8918 and Arkot 9103 should make them valuable as breeding lines. Small quantities of Arkot 8918 and Arkot 9103 seed may be obtained for breeding purposes from the corresponding author.

Development of these lines was supported in part by funding from Cotton Incorporated.

F.M. BOURLAND * AND N.R. BENSON

References

Bird, L.S. 1982. The MAR (Multi-Adversity Resistance) system for genetic improvement of cotton. Plant Dis. 66:172-176.

Bourland, F.M. 1996. Registration of `H1330' cotton. Crop Sci. 36:813.

Bourland, F.M., and B.W. White. 1992. Registration of Miscot 7801 and Miscot 7824 germplasm lines of cotton. Crop Sci. 32:834.

Bridge, R.R. 1987. Registration of DES 237-7 cotton germplasm. Crop Sci. 27:1316.

Sappenfield, W.P. 1980. Registration of Delcot 311 cotton. Crop Sci. 20:669.

Shepherd, R.L. 1974. Registration of Auburn 623 RNR cotton germplasm. Crop Sci. 14:911.

Northeast Research and Extension Center, P.O. Box 48, Keiser, AR 72351. Registration by CSSA. Accepted 31 Jan. 2002. * Corresponding author (bourland@uark.edu).
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Author:Bourland, F.M.; Benson, N.R.
Publication:Crop Science
Date:Jul 1, 2002
Words:715
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