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a Dep. of Agronomy & Plant Genetics, Univ. of Minnesota, St. Paul, MN 55108
b USDA–ARS, St. Paul, MN 55108
c Univ. of Minnesota, Crookston, MN 56716
d Dep. of Plant Pathology, Univ. of Minnesota, St. Paul, MN 55108
e USDA–ARS, Fargo, ND 58105. RB07 was developed with financial support from the Minnesota Agricultural Experiment Station, the Minnesota Wheat Research and Promotion Council, and the U.S. Department of Agriculture, under Agreement No. 59-0790-9-025. This is a cooperative project with the U.S. Wheat & Barley Scab Initiative. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture
* Corresponding author (ander319{at}umn.edu).
ABSTRACT
‘RB07’ (Reg. No. CV-1028, PI 652930) hard red spring wheat (Triticum aestivum L.) was developed by the University of Minnesota Agricultural Experiment Station and released in 2007. RB07 was tested as MN99436-6 in statewide yield trials from 2003 to 2006 and in the Uniform Hard Red Spring Wheat Regional Nursery in 2003 and 2004. RB07 was released based on its high and consistent grain yield, earliness, disease resistance and good grain end-use quality. It is well adapted to hard red spring wheat–growing regions in Minnesota, North Dakota, and South Dakota.
Abbreviations: AY, advanced yield trial • FHB, Fusarium head blight • MR, moderately resistant • PYT, preliminary yield trial • S, susceptible • URHRSWN, Uniform Regional Hard Red Spring Wheat Nursery • VSK, visually scabby kernel
‘RB07’ (Reg. No. CV-1028, PI 652930) hard red spring wheat (Triticum aestivum L.) was developed by the University of Minnesota Agricultural Experiment Station and released in 2007 on the basis of its high and consistent grain yield, earliness, resistance to leaf rust (caused by Puccinia triticina Eriks.), moderate resistance to Fusarium head blight (FHB; caused primarily by Fusarium graminearum Schwabe), and good grain end-use quality. RB07 is well adapted to hard red spring wheat–growing regions in Minnesota, North Dakota, and South Dakota. It is an F8–derived Selection from the cross of ‘Norlander’(PI 591623)/‘HJ98’ (Busch et al., 2000) made in 1995. Norlander is a hard red spring wheat cultivar developed and released by AgriPro in 1995. The cultivar HJ98 was released by the Minnesota Agricultural Experiment Station in cooperation with the USDA–ARS in 1998. The variety commemorates Dr. Robert H. Busch, former USDA–ARS wheat breeder and geneticist at the University of Minnesota who retired in 2000.
Methods
Early Generation Development
The cross (designated M1.158) resulting in RB07 was made in 1995, and the F1 generation was grown in University of Minnesota greenhouses in St. Paul, MN, in 1996. Approximately 700 F2 seed were space-planted in a St. Paul field in 1997. The field included inoculated spreader rows of wheat lines highly susceptible to leaf rust and stem rust (caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.). The F2 generation segregated for maturity, plant height, and leaf and stem rust resistance. One spike from each of 40 shorter, rust-resistant plants was selected. The F3 generation was advanced by single-seed descent in a Minnesota greenhouse during spring 1998.
Line Selection and Evaluation
In 1998, 35 F3:4 headrows were grown in St. Paul, and 7 were selected on the basis of appropriate plant height, maturity, and leaf and stem rust resistance. From each selected row, a single spike was harvested, threshed, and visually inspected for seed plumpness. Five of the seven selections were selected for increase in a winter nursery in Brawley, CA. Three of the five selections, one of which was designated MN99436, were harvested and grown in a preliminary yield trial (PYT) at Crookston, MN, in 1999. Our PYT are typically grown at three locations, but seed quantities were sufficient for only one replication of a two-row plot (approximately 0.5 m2) of this line. A sample of the harvested grain was analyzed for mixing and bread-making properties at the USDA Spring Wheat Quality Laboratory in Fargo, ND. MN99436 was also grown in a FHB nursery in Crookston in 1999. This nursery was inoculated with Fusarium-colonized sterile wheat grain inoculum and mist irrigated following the methods of Fuentes et al. (2005).
MN99436 and all other experimental lines at the PYT stage or later were grown as single 1-m-long rows, 0.3 m apart, in an inoculated rust nursery in St. Paul in 1999. The nursery contained a mixture of leaf and stem rust–susceptible spreader rows sown perpendicular to the experimental lines in every other alley. The alternate alleys were sown with winter wheat. Spreader rows were inoculated with common leaf rust and stem rust races following the methods of Roelfs et al. (1992).
MN99436 was entered in the Advanced Yield (AY) Trials grown in Crookston, Morris, and St. Paul in 2000 and 2001. These and all subsequent yield trials were sown in three-replicate randomized complete blocks with a plot size of 4.5 to 5.5 m2 and row spacing of 0.15 to 0.20 m. A sample of the harvested grain from two to three locations each year (except 2005) was analyzed for mixing and bread-making properties at the USDA–ARS Spring Wheat Quality Laboratory in Fargo. MN99436 was grown in inoculated, mist-irrigated FHB nurseries at two to three Minnesota locations (Crookston, Morris, and St. Paul) each year starting in 2000. The Crookston and Morris FHB nurseries used colonized grain inoculum, and the St. Paul nursery used a spray applied macroconidial suspension following the methods of Fuentes et al. (2005). The FHB data collected included disease incidence, severity (recorded on a 0–5 scale 18–21 d after anthesis), 30-spike seed weight, visually scabby kernels (VSKs), and the deoxynivalenol content of mature seed (Fuentes et al., 2005). Beginning in 2005, we also measured grain volume weight of the VSK sample in a 15.7-mL cylinder measuring 20 mm in diameter and 50 mm in height.
In 2002, MN99436 was entered into Minnesota statewide testing (Advanced Yield 1 [AY1]) at seven locations—Crookston, Lamberton, Morris, Stephen, St. Paul, Roseau, and Waseca—following procedures described earlier. A reselection, MN99436-6 (see "Seed Purification and Increase" below) from MN99436 replaced it in all yield trials beginning in 2003. From 2003 through 2006, MN99436-6 was grown in the statewide AY1 trial. In 2003 and 2004, MN99436-6 was tested in the Uniform Regional Hard Red Spring Wheat Nursery (URHRSWN). From 2004 to 2006, MN99436-6 was grown in three to five on-farm performance trials near Fergus Falls, Hallock, Oklee, Perley, and Strathcona, MN. Preharvest sprouting was evaluated by harvesting 10 intact spikes at physiological maturity from each of two replications grown at Crookston, Morris, and St. Paul. Spikes were air dried for 5 d and stored at –20°C. Spikes were placed in a dew chamber at 22°C for 7 d and rated for degree of sprouting on a scale of 1 (no visible sprouting) to 10 (extensive sprouting over entire spike).
Seed Purification and Increase
In 2000, 10 random heads were harvested from an F8 AY trial plot of MN99436, threshed, and planted in a winter nursery near Lincoln, New Zealand. Seven of the 10 lines were selected on the basis of uniformity and plant height and grown in separate 4.5-m2 plots in St. Paul in 2001. One selection, designated MN99436-6, was selected on the basis of its greater uniformity in plant height. MN99436-6 was grown in 16 4.5-m2 plots in St. Paul in 2002, and approximately 50 plants were removed due to excessive height. Two hundred random heads were harvested, and the remaining seed was harvested in bulk. One hundred grams of the bulk harvested seed of MN99436-6 were planted in a New Zealand winter nursery. Two hundred random heads were selected from the New Zealand winter nursery plot, and the remaining seed was harvested and used to seed the 2003 AY1 trial. To continue purification of MN99436-6, 160 headrows derived from the sample of 200 hand-harvested heads from each of two locations (2002 in St. Paul and 2003 in New Zealand) were grown in St. Paul in 2003. A total of 25 of the 320 headrows were removed because of susceptibility to leaf rust, lateness, or height differences. The remaining 295 headrows were combine harvested. An increase of MN99436-6 was planted on 0.13 ha in St. Paul in 2004, and 390 kg of Breeder seed was produced. A 0.6-ha winter increase in California produced 2500 kg of seed that was planted on 31 ha at the Riopelle Farm near Argyle, MN, in 2005. Fifty-four metric tons of Foundation seed was produced. Further seed increase was arranged by the Minnesota Crop Improvement Association in 2006.
Statistical Analyses
All statistical analyses were performed using Data Desk version 6.2 (Data Description, Inc., Ithaca, NY). Statewide data for days to heading, plant height, straw strength, and grain yield were subjected to analysis of variance across environments with each location-year combination as a separate environment. A mixed model was used with genotypes as fixed factors and environments and replications within environments as random factors. The LSD test (P = 0.05) was used to compare means for the genotype effects.
Characteristics
Agronomic and Botanical Description
RB07 has erect juvenile plant growth, a recurved flag leaf, white glumes with a square shoulder, and an acuminate beak. The spike is awned, mid-dense, and tapering. The kernel is red and ovate in shape with angular cheeks and a narrow, mid-deep crease. The brush on the kernel has a collar and is medium in length. RB07 heads relatively early, averaging 48.8 d after planting in Minnesota locations (Table 1
). This is similar to ‘Oklee’ (49.5, Anderson et al., 2005) and ‘Glenn’ (49.0, Mergoum et al., 2006a) but significantly (P < 0.05) earlier than other currently popular varieties such as ‘Freyr’ (51.5, PI 634823) and ‘Knudson’ (52.2, PI 619609). RB07 is relatively short, averaging 72.4 cm, measured from soil level to the tip of the spike, excluding awns (Table 1). This height is similar to Oklee (71.2) and Knudson (74.8) but significantly (P < 0.05) shorter than Freyr (76.5) and Glenn (79.2). The straw strength of RB07 is better than average, with a score of 0.5 on a 0 to 9 scale in the eight locations where some lodging occurred from 2004 to 2006 (Table 1). This level of straw strength is not significantly different from most other currently grown cultivars. In the 2004 URHRSWN, the lodging score of RB07 was 0.6, averaged over the six locations in which lodging occurred (Table 2
). This score was not significantly (P < 0.05) different from Glenn (0.9) but was significantly better than ‘Steele-ND’ (2.2, Mergoum et al., 2005) and ‘Howard’ (2.5, Mergoum et al., 2006b).
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Disease Resistance
On the basis of seedling resistance to races MBRJ, MCDS, SBDG, TDBJ, THBJ, and TLGF of leaf rust, the lack of susceptible infection types in field trials, and results of DNA marker testing (Talbert et al., 1994), RB07 is postulated to have leaf rust seedling resistance gene Lr21. Gene Lr21 provides low infection type to all known races of leaf rust in the United States and also is postulated to be present in recent releases from North Dakota State University. RB07 is highly resistant to leaf rust, with only trace levels of infection in field plots in all years of testing. RB07 is highly resistant to prevalent races (QFCS, QTHJ, RCRS, RKQQ, TPMK, and TTTT) of stem rust at the seedling and adult plant stages. Since the beginning of field evaluations in 1998, natural infection by stem rust on RB07 has not been observed. RB07 has been evaluated in FHB nurseries since 1999 and has moderate resistance to this disease. Its performance in six FHB nurseries from 2004 to 2006 indicates a level of resistance comparable to the resistant check, ‘BacUp’ (Busch et al., 1998), and the best currently available cultivars in the region, including ‘Alsen’ (Frohberg et al., 2006), Freyr, and Glenn (Table 3
).
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The Minnesota Agricultural Experiment Station, St. Paul, MN, 55108, will maintain Breeder seed of RB07. Foundation seed will be produced and maintained by the Minnesota Crop Improvement Association, 1900 Hendon Ave., St. Paul, MN 55108. RB07 has been approved for U.S. Plant Variety Protection (PVP no. 200800115) with seed certification option. Contact the corresponding author for all seed requests. The National Plant Germplasm System cannot distribute protected seed until PVP expires after 20 years.
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 August 12, 2008.
References
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