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a USDA-ARS, U.S. Arid Land Agricultural Research Center, 21881 N. Cardon Lane, Maricopa, AZ 85239
b Dep. of Crop & Soil Sci., Univ. Georgia, Coastal Plain Station, P.O. Box 748, Tifton, GA 31793
c USDA-ARS, 17053 N. Shafter Ave., Shafter, CA 93263
d Cotton Incorporated, 6399 Weston Pkwy., Cary, NC 27513
* Corresponding author (rpercy{at}ag.arizona.edu)
The cotton (Gossypium hirsutum L.) germplasm lines AGC85, AGC208, and AGC375 (Reg. no. GP-860, PI 641928; Reg. no. GP-861, PI 641929; Reg. no. GP-862 , PI 641930) were developed by the USDA-ARS and Cotton Incorporated and released in 2005. The lines possess superior fiber length and strength characteristics and improved yield performance under heat stress environments. The lines have been made available to public and private breeders as resources for concurrent improvement of fiber quality and heat tolerance in upland cottons of the mid-south and southeastern United States and as resources for the improvement of heat tolerance in Acala cottons of the southwestern and western USA.
All three germplasm lines originate from the cross of the commercial cultivars ‘FiberMax958’ and ‘SG248’. The pedigree of FiberMax958 is CS6S/Siokra S-324//Sicala V-1, and the pedigree of SG248 is Mo 89–117/‘DP 5415’ (Bowman el al., 2005). SG248 had been identified from prior test data as possessing good yield performance in heat stress environments. The cultivar FiberMax958 has good fiber attributes, but its performance is poor under the high temperature environments of the southwestern USA. Individual plants were selected within early generation progeny (F2 and F3) at the low desert location of Maricopa, AZ, in 2001 and 2002. Selection was conducted in two stages within each generation. The selection criterion in the first stage of selection was primarily for fruit retention under a heat stress environment. Fiber samples of selected plants were then analyzed by high volume instrumentation (HVI) in the Fiber Quality Laboratory of Cotton Incorporated, Cary, NC, and the second stage of selection for fiber quality (primarily fiber length and fiber bundle strength) was made among field selected individual plants. In 2003, a total of 70 F3:4 progeny lines were selected for evaluation in non-replicated tests at Maricopa, AZ, and Tifton, GA, and a subset of 35 lines were evaluated at Shafter, CA. Lines were evaluated for yield performance and fiber quality as determined by HVI and Advanced Fiber Information System (AFIS) instrumentation. Fourteen of the 70 lines tested in 2003 were selected for further evaluation (along with seven parent and check cultivars) in replicated tests at Tifton, GA, Maricopa, AZ, and Shafter, CA, in 2004. FiberMax 958 and Phytogen 72 were included in the trials as high fiber quality checks, and SG747 was included as a high yield performance check. Lines AGC85, AGC208, and AGC375 (tested under the designations FMax958/SG248–08–5, FMax958/SG248–20–8, and FMax958/SG248–37–5, respectively) were selected for release on the basis of overall agronomic and fiber performance across locations.
Averaged over locations, the lint yields of AGC85 (2021 kg ha–1) and AGC375 (1874 kg ha–1) were comparable to that of SG747 (1938 kg ha–1) and superior to the high fiber quality cultivars FiberMax 958 (1651 kg ha–1) and Phytogen 72 (1467 kg ha–1). AGC208 produced a lint yield (1751 kg ha–1) comparable to the FiberMax 958 parent and superior to Phytogen 72. Lint percentage of line AGC375 (43.4%) and AGC85 (42.2%) were comparable to those of the cultivars SG747 (44.0%) and Fibermax 958 (42.7%), respectively. Line AGC208 had a lower lint percentage of 39.9%. The plant height at maturity of line AGC85 (1.24 m) exceeded that of FiberMax 958 (1.00 m) and SG747 (1.06 m), but was comparable to that of Phytogen 72 (1.18 m). The plant height of AGC375 (1.16 m) exceeded that of FiberMax 958, but was similar to the heights of SG747 and Phytogen 72. The plant height of AGC208 (0.99 m) was comparable to those of FiberMax 958 and SG747, and shorter than that of Phytogen 72. The plant heights at maturity of lines AGC85, AGC208, and AGC375 generally reflected their relative maturity times, with AGC85 being the latest and AGC375 being the earliest of the three lines.
Ratings of pollen sterility due to heat stress were recorded at the Maricopa location in 2004. The rating scale used was as follows: 1 = 100% fertility, 2 = 25% pollen sac nondehiscence, 3 = 50% nondehiscence, 4 = 75% nondehiscence, and 5 = total sterility. Averaged across three dates, lines AGC85, AGC208, and AGC375 exhibited pollen sterility rates (1.8, 2.0, and 1.8, respectively) higher than that of SG747 (1.3) but significantly lower than those of the high fiber quality cultivars Fibermax 958 (2.8) and Phytogen 72 (2.7).
Fiber lengths (UHM) of lines AGC208 and AGC375 (30.2 and 29.5 mm) were superior to that of the FiberMax 958 parent (28.7 mm) when averaged across locations. The fiber length of AGC208 was superior to that of the Acala cultivar, Phytogen 72 (29.5 mm). Line AGC85 exhibited a fiber length comparable to the FiberMax 958 parent. Fiber length uniformity of AGC375 (82.2%) was comparable to that of FiberMax 958 (82.5%), whereas AGC85 and AGC208 had a higher length uniformities (83.2%) comparable to that of SG747 (83.4%) and Phytogen 72 (83.5%). Short fiber contents (HVI) of AGC85 (9.1%) and AGC375 (9.6%) were similar to that of the commercial cultivar SG747 (9.6%). Line AGC208 produced a short fiber content (8.8%) comparable to the Acala cultivar Phytogen 72 (8.1%). Fiber bundle strengths of AGC85 (33.3 cN), AGC208 (32.9 cN) and AGC375 (33.6 cN) were stronger than the FiberMax 958 parent (31.4 cN). Two lines, AGC85 and AGC375, exhibited fiber strength comparable to that of Phytogen 72 (34.0cN). Fiber elongations of AGC85 (4.3%), AGC208 (3.3%), and AGC375 (3.4%) were lower than those of the cultivars SG747 (6.0%) and Phytogen 72 (4.9%). However, the fiber elongation of AGC208 and AGC375 were comparable to that of the parent cultivar FiberMax 958 (3.4%), and the fiber elongation of AGC85 was superior to FiberMax 958. Fiber micronaire values were extremely high in the tests in 2004, as evidenced by the micronaire of 5.83 obtained for the cultivar SG747. Micronaire values of AGC85 (5.28), AGC208 (4.95), and AGC375 (5.33) were all lower than that of SG747. One line, ACG208, produced a micronaire value lower than that of FiberMax 958 (5.30) or Phytogen 72 (5.28). Fiber fineness (AFIS) of AGC85 (181 mtex), AGC208 (174 mtex), and AGC375 (181 mtex) were lower than that of SG747 (196 mtex). The fiber fineness of AGC208 was lower than that of either of the high fiber quality cultivars FiberMax 958 (181mtex) or Phytogen 72 (178 mtex).
Small quantities of seed (25–50 g) are available to cotton breeders, geneticists, and other research personnel on written request to the corresponding author or R.G. Cantrell for at least 5 yr. Requests for seed from outside the USA must be accompanied by an import permit allowing entry into the requestor's country. The USDA-ARS and Cotton Incorporated may not be able to certify that seed is free of certain insects or pathogens specified on import permits, and in such cases seed cannot be supplied. Individuals requesting seed should note that PCR testing of AGC85, AGC208, and AGC375 has revealed the presence of promoter sequences sometimes associated with transgenes. The frequency of seed containing these promoter sequences was very low (<0.23%, <0.16%, and <0.70%, respectively, at the 95% confidence range), but there is a slight probability that a seed sample obtained by a requesting individual could contain an adventitious transgene. 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. Genetic material of this release will be deposited in the National Plant Germplasm System where it will be available after 5 yr for research purposes, including development and commercialization of new cultivars.
NOTES
Received for publication December 15, 2005.
REFERENCES
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  M. Ulloa, R.G. Percy, R. Hutmacher, and R.G. Cantrell Registration of SJ-U86 Cotton Germplasm Line with High Yield and Excellent Fiber Quality Crop Sci., September 8, 2006; 46(5): 2336 - 2338. [Full Text] [PDF]
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