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a 115 Plant Science, Dep. of Crop, Soil, and Environmental Sciences, Univ. of Arkansas, Fayetteville, AR 72701
b Dep. of Horticulture and Crop Science, Ohio State Univ., Wooster, OH
c Dep. of Agronomy, Univ. of Florida, Gainesville, FL
d 1366 W. Altheimer Dr., Dep. of Crop, Soil, and Environmental Sciences, Univ. of Arkansas, Fayetteville, AR 72704
* Corresponding author (pchen{at}uark.edu).
Soybean [Glycine max (L.) Merr.] germplasm lines R01-416F (Reg. No. GP-356, PI 647960) and R01-581F (Reg. No. GP-357, PI 647961) were developed by the Arkansas Agricultural Experiment Station and released as maturity group V lines with high yield potential and sustained nitrogen fixation under moderate water-deficit conditions.
R01-416F and R01-581F originated as F9 plant selections from a cross between ‘Jackson’ and ‘KS4895’. Jackson (PI 548657) was released in 1953 and classified as maturity group VII (Johnson, 1958). Jackson has been reported to possess drought-tolerant nitrogen fixation, in which decline of nitrogen fixation rate occurs at lower soil water contents than other cultivars (Sall and Sinclair, 1991). KS4895 (PI 595081) is a widely adapted and high-yielding maturity group IV cultivar derived from the cross of ‘Sherman’ x ‘Bay’ (Schapaugh and Dille, 1998). However, KS4895 does not possess nitrogen fixation drought tolerance (Purcell et al., 2000). The cross of Jackson x KS4895 was made in 1993, and the plant population derived from Jackson x KS4895 was advanced to the F3 generation by single-seed descent (Fehr, 1991). The F3 plants were grown in the field, and 100 F3:4 maturity group V lines were selected for preliminary evaluation of potential nitrogen fixation under drought. These 100 selected F3:4 lines were screened for the amount of nitrogen accumulated in the shoots under drought stress in a greenhouse experiment (Sinclair et al., 2007). Subsequently, the F3:5 and F3:6 lines were evaluated in the field for agronomic performance in 1998 and 1999, respectively. Sixty F3:7 lines were then increased in a winter nursery in Costa Rica for two generations during fall 1999 to spring 2000. Ten single plants were individually harvested from each F3:8 line. In 2001 R01-416F and R01-581F were selected from 600 F8:9 lines at Fayetteville, AR.
R01-416F and R01-581F were tested in 20 and 28 environments, respectively, at five Arkansas sites from 2002 to 2006. Average yield of R01-416F over 16 irrigated environments was 3286 kg ha–1, and was greater than that of check cultivars Ozark (3232 kg ha–1) (Chen et al., 2004) and UA 4805 (3284 kg ha–1) (Chen et al., 2006). R01-416F yielded 1883 kg ha–1 on average in four nonirrigated environments. Yield of R01-416F was 16 and 27% greater than that of UA 4805 and Ozark, respectively, under nonirrigated conditions at Marianna, AR, in 2005. R01-581F yielded 3351 kg ha–1 on average over 24 irrigated environments and 2100 kg ha–1 on average in four nonirrigated environments. R01-581F exceeded the yield of UA 4805 and Ozark by 1 and 14% on average under irrigated and nonirrigated environments, respectively. When grown under nonirrigated conditions, R01-581F and R01-416F showed yield reduction of 37 and 42%, respectively, whereas average yield reduction of check cultivars was 44% compared with yield under irrigated conditions. R01-581F and R01-416F are capable of maintaining high yield potential under nonirrigated conditions due to sustained nitrogen fixation under drought stress.
The amount of shoot nitrogen accumulated under water-deficit stress in a greenhouse experiment was 115 mg plant–1 for both R01-416F and R01-581F, exceeding Jackson (75 mg plant–1) and KS4895 (91 mg plant–1) (Sinclair et al., 2007). In a flow-through acetylene reduction assay, the soil-moisture content at which nitrogen fixation activity began to decline was 6 and 22% less for R01-581F and R01-416F, respectively, compared with KS4895 (Sinclair et al., 2007).
Relative maturities of R01-416F and R01-581F are 5.2 (similar to Ozark) and 5.6 (3 to 5 d later than Ozark), respectively. The lines have purple flower, gray pubescence, and determinate growth habit. Their mature heights are 3 to 5 cm taller than Ozark (61 cm on average) under irrigated environments and 7 to 10 cm shorter than Ozark under nonirrigated environments. Both lines have yellow cotyledons with dull yellow seed coats and mixed hila (buff and imperfect black). Individual seed mass of these two germplasm lines is approximately 1.5 mg less than that of Ozark. When grown under irrigated conditions, protein and oil concentrations on dry-weight basis were 39.6 and 22.9%, respectively, for R01-416F and 39.9% and 22.2%, respectively, for R01-581F.
U.S. Plant Variety Protection will not be pursued for R01-416F and R01-581F soybean germplasm lines. Seeds of R01-416F and R01-581F are available from the Soybean Breeding and Genetics Program at the University of Arkansas, 115 Plant Science Building, Fayetteville, AR 72701. Small quantities of seeds will be available for research purposes and cultivar development from the corresponding author. It is requested that appropriate recognition be made if these germplasm lines contribute to the development of a new germplasm line or cultivar. Seeds of R01-416F and R01-581F will also be deposited in the USDA Soybean Germplasm Collection.
Acknowledgments
We greatly appreciate the continued support from the United Soybean Board for the drought tolerance research and the development of these germplasm 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 January 24, 2007.
References
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