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a USDA-ARS, Crop Protection and Management Research Unit, Tifton, GA 31793
b Univ. of Georgia, Dep. of Crop and Soil Sciences, Tifton, GA 31793
* Corresponding author (Baozhu.Guo{at}ars.usda.gov).
GT601 (AM-1) (Reg. No. GP-551, PI 644026) and GT602 (AM-2) (Reg. no. GP-552, PI 644027) are yellow dent maize (Zea mays L.) lines developed and released jointly by the USDA-ARS Crop Protection and Management Research Unit and the University of Georgia Coastal Plain Experiment Station in 2006. GT601 (AM-1) and GT602 (AM-2) were developed by seven generations of self-pollination from a maize population GT-MAS:gk (PI 561859) (McMillian et al., 1993). This population was derived from a commercial hybrid ear (a Pioneer hybrid) visibly segregating for fungal infection by Aspergillus flavus and selected for resistance to the fungal infection and reduction of aflatoxin contamination (Widstrom et al., 1987). McMillian et al. (1993) released the maize population GT-MAS:gk as a source of resistance to aflatoxin accumulation.
To use the resistance traits from GT-MAS:gk, such as physical pericarp wax (Guo et al., 1995, 1996; Russin et al., 1997) and antifungal proteins (Guo et al., 1997, 1998; Chen et al., 1998), efforts of self-pollination and selection have been made since 1996 for reduced aflatoxin contamination. By evaluating S1 families, Guo et al. (2001) demonstrated that considerable variation among the individual plants within the population GT-MAS:gk was detectable using random amplified polymorphic DNA (RAPD) markers and a laboratory aflatoxin bioassay. Guo et al. (2002) also evaluated the S5 generation using 113 restriction fragment length polymorphism (RFLP) probes for genetic variation and conducted 2-yr field tests for aflatoxin contamination. The aflatoxin concentrations and maturity data among the S5 selfted lines were significantly different (Guo et al., 2002).
Field evaluation for aflatoxin contamination in 2004 and 2005, GT601 (AM-1) had 33 and 62 ng g–1, and GT602 (AM-2) had 32 and 51 ng g–1, respectively, while the resistant control Tex6 (Hamblin and White, 2000) had 69 and 120 ng g–1. The aflatoxin levels in GT601 (AM-1) and GT602 (AM-2) were significantly different from the susceptible control (276 and 219 ng g–1) but similar to the resistant control in both years. In the 2005 hybrid test, aflatoxin levels ranged from 75 to 266 ng g–1. GT601 (AM-1) x Cy1 and GT602 (AM-2) x Cy1 had 113 and 105 ng g–1 aflatoxin (Cy1 had moderate susceptibility to aflatoxin contamination), which were significantly different from the commercial hybrids P32R25 (266 ng g–1) and P31G98 (256 ng g–1).
GT601 (AM-1) and GT602 (AM-2) are adapted to the southern USA. GT601 (AM-1) flowers about 1 wk earlier than GT602 (AM-2), with about 60 to 70 d from planting to flowering depending on the planting date. GT601 (AM-1) has colorless pericarp, white cob, and browning silk, P-wwb, and GT602 (AM-2) has colorless pericarp, red cob, and browning silk, P-wrb. GT601 (AM-1) had been used in genetic quantitative trait locus (QTL) mapping studies for silk maysin production (Butrón et al., 2001) and A. flavus infection (Widstrom et al., 2003).
Seeds of GT601 (AM-1) and GT602 (AM-2) will be maintained and distributed by the USDA-ARS, Crop Protection and Management Research Unit, Tifton, GA, on written request to the corresponding author.
Acknowledgments
In memory of a good friend who was a supporter of aflatoxin research, a collaborator and CEO of Tun-Yu Seed in China, Mr. Ai-Min Hou, who passed away untimely in 2006, these two inbreds were named to GT601 (AM-1) and GT602 (AM-2), respectively. This research was supported in part by funds provided by USDA-ARS and Georgia Commodity Commission for Corn. We acknowledge the technical support of M. Cook, C. Mullis, E. Harris, and K. Lewis in the field and breeding nursery. We also acknowledge Drs. M. Krakowsky and X. Ni involved in later testing these lines.
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 December 6, 2006.
References
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