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a Dep. of Plant Sciences, North Dakota State Univ., Fargo, ND 58105-5051
b Dep. of Plant Pathology, North Dakota State Univ., Fargo, ND 58105
c Dep. of Soil Science, North Dakota State Univ., Fargo, ND 58105. Research supported by grants from the North Dakota Soybean Council
* Corresponding author (Ted.Helms{at}ndsu.edu).
ABSTRACT
‘Cavalier’ soybean [Glycine max (L.) Merr.] (Reg. No. CV-499, PI 654358) was first tested as ND02-2019, and was developed by the North Dakota Agricultural Experiment Station, North Dakota State University. Cavalier was released in January 2008 and is a Maturity Group 00 conventional cultivar (00.7), generally adapted as a full-season cultivar from 48 to 49° N latitude. Cavalier was released because it has (i) resistance to race 4 of Phytophthora sojae (M.J. Kaufmann and J.W. Gerdemann), (ii) high yield in North Dakota environments, (iii) lodging resistance, and (iv) tolerance to iron-deficiency chlorosis.
Abbreviations: NDSU, North Dakota State University
‘Cavalier’ soybean [Glycine max (L.) Merr.] (Reg. No. CV-499, PI 654358) was developed by the North Dakota Agricultural Experiment Station, North Dakota State University (NDSU), and was first tested as ND02-2019. Cavalier was released in January 2008 and is a Maturity Group 00 conventional cultivar (00.7), generally adapted as a full-season cultivar from 48 to 49° N latitude. Cavalier was released because it has resistance to race 4 of Phytophthora sojae (M.J. Kaufmann and J.W. Gerdemann), high yield in North Dakota environments, lodging resistance, and tolerance to iron-deficiency chlorosis. Cavalier is intended to replace the conventional cultivar Jim (PI 602897; Helms and Nelson, 1998a). Jim is highly susceptible to Phytophthora sojae, whereas Cavalier is resistant to race 4, the most common race in this region (B.D. Nelson, personal communication, 2006).
Methods
Parent Choice and F1 Development
Cavalier is an F4–derived line, originally designated ND02–2019, with the pedigree ‘Sargent’ (PI 615585) x ND96-1006 (Helms et al., 2002a). The line ND96-1006, developed by NDSU, has the pedigree ‘Glacier’ (PI 592523) x ‘Council’ (PI 587091) (Orf and Denny, 1997; Helms and Halvorson, 1996). ND96-1006 was never released as a named cultivar. The objective of the cross was to develop early-maturity, high-yielding, phytophthora-resistant experimental lines. The cross leading to Cavalier was made in summer 1999 at Casselton, ND. The F1 plants were grown in the 1999–2000 Chile winter nursery.
Early-Generation Population Development
The F2 population was grown in summer 2000 and advanced to the F3 generation by the single-pod bulk method (Fehr, 1991). Approximately 250 seeds were harvested each generation of the single-pod bulk method, and 100 seeds were selected at random for generation advance. The F3 population was grown in the 2000–2001 Chile winter nursery and advanced to the F4 generation by the single-pod bulk descent method. Individual F4 plants were harvested from the Casselton, ND, nursery and threshed in autumn 2001. One hundred and ten F4:5 plant-rows of the Sargent x ND96-1006 population were evaluated in 2002 at Prosper, ND, using nonreplicated, single rows that were 3.3 m long.
Line Selection and Evaluation
Twenty-eight of the 110 plant-rows (25%) were selected on the basis of visual appearance for lodging resistance. Seed from each selected F4:5 row was bulked. The 28 plant-rows were not tested for race 4 resistance at this stage since both parents were known to have a major gene for resistance to Phytophthora sojae. Cavalier was first tested for yield as ND02-2019, using three replicates of an 8 by 8 incomplete lattice design at Casselton, ND, in 2003. Fifteen out of 61 experimental lines from that particular experiment were selected for advanced, multiple-location yield tests for the 2004 cropping year. In all yield tests, the plots were planted as two rows 6.3 m long with 0.76 m between-row spacing and later end-trimmed to 4.2 m for harvest.
Cavalier was evaluated by the NDSU soybean breeding program in advanced yield trials, for a total of 33 location-years that included 2004 to 2007. Advanced yield testing of Cavalier in North Dakota included 3 locations in 2004, 8 locations in 2005, 8 locations in 2006, and 14 locations in 2007. Lodging was rated on a 1 to 5 visual scale, with 1 being the best and 5 the worst.
Testing for iron-deficiency chlorosis was conducted in 2005 at four sites located in eastern North Dakota, based on three replicates per site. The four sites were classified as Aeric Calciaquolls, with a seasonal high water table, and free CaCO3 on the surface. The four sites were selected on the basis of a past history of iron-deficiency chlorosis symptoms. The experimental unit consisted of hills planted with eight seeds and thinned to three seeds per hill. Hills were spaced on a 0.76-m grid. Iron-deficiency chlorosis was rated at the 2 to 3 trifoliate stage and the 5 to 6 trifoliate stage, using a 1 to 5 visual scale. In this scale, a rating of 1 represents no chlorosis; 2 represents a slight yellowing of the upper leaves of a general (not interveinal) nature; 3 represents interveinal chlorosis of the upper leaves without stunting or necrosis; 4 represents an interveinal chlorosis of the upper leaves with reduced growth or the beginning of necrosis; and 5 represents severe stunting, chlorosis, and damage to the growing point. Ratings were recorded ±0.5 chlorosis unit for each rating for each hill.
Screening for resistance to Phytophthora sojae was conducted using the hypocotyl-injection method developed by Haas and Buzzell (1976). The race 4 isolate was originally baited from North Dakota soils and previously tested for virulence on soybean (Nelson et al., 2005). Plants were inoculated when 8 to 9 d old with the unifoliate leaves unfolded. Plants were maintained in a growth room at 24 ± 2°C for 10 d and then evaluated as resistant and susceptible from a sample of 12 plants. Resistant plants survived and susceptible plants died. The cultivars Walsh (PI 615586; Helms et al., 2002b) and LaMoure (PI 634813; Helms et al., 2005) were used as the resistant and susceptible checks, respectively. Twelve seedlings were evaluated for each cultivar in each test. In both tests, all inoculated Cavalier plants survived, while 90% of the susceptible plants died.
Protein and oil data are reported on a 13% moisture basis, based on data collected from USDA Uniform Regional Trials: Northern States (Abney, 2007). Seed composition was measured by the USDA-ARS National Center for Agricultural Utilization Research, Peoria, IL, using near infrared transmittance (Abney, 2007). For yield evaluation in the Uniform Regional Tests, plot length and between-row spacing varied among test participants.
Seed Purification and Increase
Purification of Cavalier was initiated in 2005 by threshing 112 individual F4:8 plants. Seed of each plant was placed in a separate envelope and evaluated for uniformity of hila color and seed coat luster between different envelopes. Seed of 80 plants that had imperfect yellow hila (Cober et al., 1998) and dull seed coat luster were selected for planting in 2006. Seed from each envelope was planted in a 3.3 m row. In 2006, these purification rows (F4:9) were grown and inspected for uniformity of flower and pubescence color as well as maturity. Of the 40 purification rows grown at Prosper, ND, seed of 32 rows was selected for uniformity and blended. This seed was then sent to the 2006–2007 Chile winter nursery for seed increase to develop Breeder seed (F4:10). Foundation seed (F4:11) was increased at Casselton and Carrington, ND, in summer 2007. Cavalier was observed to be uniform and stable for a 2-yr period.
Statistical Analyses
Data were analyzed using the SAS software (SAS Institute, Cary, NC). All data were analyzed as a randomized complete block design. Genotype was considered a fixed effect and environment was considered random. Analysis of variance was performed with 
= 0.05 level of Type I error.
Characteristics
Agronomic and Botanical Description
Cavalier is an indeterminate cultivar with a relative maturity of 00.7. In USDA Uniform tests, Cavalier matured 10 September, which is 2 d later than Jim and 4 d earlier than ‘Traill’ (PI 596541) (Helms and Nelson, 1998b) (Table 1
). Cavalier has purple flower color, tawny pubescence, brown pod color, imperfect yellow hila (Cober et al., 1998), and dull seed coat luster. In North Dakota sites, Cavalier showed good lodging resistance (Table 2
). Plant height of Cavalier was similar to Jim and MN0071 (Table 1). When Cavalier was evaluated for iron-deficiency chlorosis in North Dakota, Cavalier was classified as moderately resistant with a mean score of 2.6, compared with Jim with a score of 2.2 and Traill with a score of 1.9 (LSD 0.05 = 0.2).
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Seed Composition
Results from the USDA uniform tests show that protein content of Cavalier was slightly less than Jim, while oil content was slightly higher than Jim (Table 1). Seed weight was slightly greater than Jim. In North Dakota testing locations, protein and oil content were evaluated only at those sites where the USDA uniform trials were conducted.
Availability
Breeder seed of Cavalier will be maintained by the Seed Stock Project of North Dakota State University. A small sample of seed for research purposes can be obtained from the corresponding author for at least 5 yr. Protection for Cavalier under the U.S. Plant Variety Protection Act Title V is pending. Seed of Cavalier was deposited at the National Center for Genetic Resource Preservation, Fort. Collins, CO, 80521-4500. Seed may be used for crossing or testing purposes by signing a Material Transfer Agreement with the North Dakota State University Research Foundation located at 1735 NDSU Research Park Drive, Fargo, ND, 58105-5002.
Acknowledgments
Technical support was provided by Tracy Christianson, Dave Hanson, Larry Martin, and Brian Johnson. This research was supported by the North Dakota Soybean Council.
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 June 27, 2008.
References
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