2002 Iowa Experimental Corn Trials

Transcription

1 2002 Iowa Experimental Corn Trials Estherville Canon Falls, MN Calumet Kanawha Nashua Pocahontas Clarion Stanhope Conrad Carroll Ames Tekamah, NE Rippey Harlan Atlantic Lewis Ankeny Pella Williamsburg Crawfordsville Fairfield Tingley An electronic version (PDF format) of this document is available at Arnel R. Hallauer Kendall R. Lamkey Paul R. White Iowa Agriculture Experiment Station Agronomy Department Ames, Iowa in cooperation with Agricultural Research Service U. S. Department of Agriculture AG152

2 Page 2 The results of the Iowa Agriculture Experiment Station Corn Yields are presented annually as a service to Iowa agriculture. The single-cross data presented herein are intended to provide preliminary information on the performance of inbred lines in hybrids in comparison with lines included in previously tested hybrids. We also include lines released from other public breeding programs when they become available. The information could be of value to the breeders and seed producers who consider use of experiment-station-developed lines as additional sources of germplasm in breeding programs. Further information on the performance of specific hybrids remains the responsibility of the producers of these hybrids. Trials were planted at 23 locations and data were obtained at 21 locations in Planting dates ranged from late April to mid May with seedbed conditions variable among locations because of moist conditions in late April and early May. Harvesting was completed later than in recent years because weather conditions delayed harvest in some areas. The dates of planting and harvesting for each trial are shown in the title of each table. Conditions for planting, emergence, growth, and development in 2002 were generally favorable after planting at most locations. Dry, warm conditions occurred in the southern and western edges of the state during July and August and affected yields at the southern and western locations. Yield data were not obtained at Lewis because extreme dry conditions limited plant and ear development; grasshopper feeding also was extensive at Lewis. Data were not obtained from Fairfield, due to poor emergence resulting from ponding after planting. In contrast, growing conditions were favorable for excellent yields in central and north-central areas. Conditions during September and October were not as conducive as 1998, 1999, and 2000 for grain dry down after physiological maturity in northern Iowa. Compared with 1994 (154 bushels per acre), 1995 (121 bushels per acre), 1996 (140 bushels per acre), 1997 (142 bushels per acre), 1998 (145 bushels

3 Page 3 per acre), 1999 (152 bushels per acre), 2000 (145 bushels per acre), and 2001 (141 bushels per acre), the estimated average yield for 2002 for Iowa is 160 bushels per acre, which surpasses the record yields of 1992 and Except for 1993, we have experienced good to excellent corn yields during the past 10 years within the state. Although warm, dry conditions during July and August affected yields in some areas, other areas had excellent yields because of timely rains during and after pollination in latter part of July and early part of August to compensate for the lower yields in the droughty areas. Disease pressures were not as evident in 2002 as in previous years, but 2nd-generation European corn borer infestations tended to be higher. Plots generally were 18 feet long and included two rows spaced 30 inches (90 sq. ft. per plot) at most locations. There were minor variations in plot length among locations, and the differences in plot size were considered in yield conversions. Actual plant stands for each hybrid are shown in the 1000 s (M/ha) of plants/hectare. The plant stands can be converted to plants/acre by multiplying with a factor of 0.4 (e.g, 67,000 plants/ha x 0.4 = 27,080 plants/acre). Seedbed preparation, fertilizer application, and cultivation practices were those normally recommended for optimum corn production at the locations where the trials were grown. All trials were planted and harvested with equipment adapted for planting and harvesting small experimental corn plots. There was no gleaning of either dropped ears or ears on broken stalks at harvest, but data for stand and root and stalk lodging were recorded before harvest. Harvest losses because of root and stalk lodging and dropped ears are reflected for hybrids at the sites where lodging and dropped ears occurred. Root lodging occurred at most sites in 2002, and was severe at some locations and for some specific hybrids. Rainstorms accompanied by strong winds occurred at some locations during July and August and local hailstorms affected some

4 Page 4 locations. Root lodging was more severe at Pocahontas, Waverly, Kanawha, Carroll, Crawfordsville, and Ankeny. Planting of ISU trials started April 23, 2002 at Ames, and all locations were planted by May 6, Planting dates for the cooperators were similar to those for the ISU trials. Harvest of the ISU trials started later in 2002 than in previous four years. Because of cooler, wetter conditions in September and October, corn matured slower and grain moistures at harvest were generally higher than for recent years, particularly in northern Iowa. Harvest of ISU trials started October 7 at Ames, and harvest was completed October 23 at Calumet. The cooperators had similar dates of harvest. Conditions were generally good during harvest throughout the state, but harvest interruptions did occur because of either local rains or snow showers. The quality of data varied among locations because of the incidence of extensive root lodging at some locations. Weather and pests usually have important effects on corn evaluation trials. These effects are not predictable and the ranges of conditions experienced were evident in The major weather factor at some locations was limited rainfall and warm conditions during July and August after a wet May and June. Some locations were affected by more windstorms (e.g., Ankeny and Kanawha) than others but root lodging was greater than normal at most locations. Weather conditions during anthesis were generally warm and dry, but timely rains during pollination occurred at most locations. At Ames, for example, excellent rains occurred July 10 (3 inches), July 12 (2 inches), July 27 (0.6 inch), and August 3 (1.5 inches). Although it was warm during pollination, the timely rains minimized stress conditions for pollen shed and silk emergence. Single crosses tested were produced between lines released by ISU and other states. Because fewer lines are being released by other public breeding programs, fewer single crosses

5 Page 5 that included lines released from other states were available for testing. Data are presented for the lines that have experiment station designations and for a few experimental lines from the ISU breeding program that have survived testcross and initial single-cross evaluations. We have included data for each of the 2002 locations, data averaged over locations for the three sets (5 locations for earlier maturity, 5 locations for mid-maturity, and 13 trials for later maturity) of trials, and 3-year averages for each location. Three-year averages are more reliable for comparing hybrid performance. Yields are given in quintals/hectare (q/ha). Yields in bushels/acre are obtained by multiplying the values in the tables by a factor of 1.6 (e.g., 90 q/ha x 1.6 = 144 bu/acre). We have included a column in the tables designated as adjusted value. Adjusted value is the value in dollars per acre assuming $2.00 per bushel for corn, 1.35% shrinkage, and $0.035 per bushel per point drying cost. Single-cross trials conducted at 23 locations included 10 locations handled by ISU and 13 handled by commercial plant breeders. Data were obtained for all locations except for the ISU trial at Lewis. Data from additional locations provide a better basis for discriminating among hybrids for consistency of performance. Least Significant Differences (LSD values) are shown at the bottom of each table. LSD values for means across locations were calculated using the location by hybrid interaction mean square. Differences among hybrids are due to genetic differences, variations in soil type, soil fertility, moisture availability, temperature stress, insect and disease pressures, and planting and harvesting techniques. Differences among hybrids greater than the LSD value can be attributed to genetic differences; differences less than the LSD value are not statistically different and could be due to other factors.

6 Page 6 ACKNOWLEDGMENTS We wish to acknowledge the following individuals and their respective organizations for assisting us in conducting the 2002 single-cross trials. Individual Organization Location of test Kermit Bohning Mycogen Conrad Dwight Bostwick Novartis Seeds Harlan Philippe Chartier Pau Seeds, Inc. Waverly Dan Currier IFS Clarion Arlen Eggerling Hawkeye Hybrids, Inc. Pella Bill Forgey Pau Seeds, Inc. Tingley Jon Geadelmann Holdens Foundation Seeds Cannon Falls, MN Bob Getschman Monsanto Global Seeds Pocahontas Duane Grensteiner Golden Harvest Estherville Kory Maughan Golden Harvest Stanhope Robert Miller Novartis Seeds Washington David Peters Monsanto Global Seeds Atlantic Lance Veldboom Holdens Foundation Seeds Williamsburg

7 Page 7 Table 1. Agronomic data for single crosses grown near Calumet, Iowa in 2002 (planted April 26 harvested October 23). Grain Plants Grain Lodging Dropped Adjusted Ear Pedigree yield per ha moisture root stalk ears Value height q/ha x 1000 % % % % $ 1-5 A635/B A681/B A681/BS21(R)C5) A681/BS21(R)C6) A681/BS21(R)C6) A681/SD A681/SD B100/LH B102/A B102/H B102/LH B102/N B102/SD B103/A B103/B B103/B B103/B B103/B B103/H B103/LH B104/B B104/B B104/BS21(R)C5) B104/BS21(R)C6) B104/BS21(R)C6) B105/B B106/A B107/LH B109/B B109/BS21(R)C6) B109/BS21(R)C6) B110/B B111/B B113/LH B114/A B114/B B114/BS21(R)C5) B114/LH B114/LH B114/SD B87/B B87/LH B90/B B91/A B91/LH

8 Page 8 Table 1. Agronomic data for single crosses grown near Calumet, Iowa in 2002 (planted April 26 harvested October 23). Grain Plants Grain Lodging Dropped Adjusted Ear Pedigree yield per ha moisture root stalk ears Value height q/ha x 1000 % % % % $ 1-5 B97/A B97/B B97/BS13(S)C6) B97/LH B97/N B97/SD B99/B B99/LH B99/SD BS21(R)C5) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS22(R)C5) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B DK LH176/LH N196/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

9 Page 9 Table 2. Agronomic data for single crosses grown near Kanawha, Iowa in 2002 (planted May 6 harvested October 21). Grain Plants Grain Lodging Dropped Adjusted Ear Pedigree yield per ha moisture root stalk ears Value height q/ha x 1000 % % % % $ 1-5 A635/B A681/B A681/BS21(R)C5) A681/BS21(R)C6) A681/BS21(R)C6) A681/SD A681/SD B100/LH B102/A B102/H B102/LH B102/N B102/SD B103/A B103/B B103/B B103/B B103/B B103/H B103/LH B104/B B104/B B104/BS21(R)C5) B104/BS21(R)C6) B104/BS21(R)C6) B105/B B106/A B107/LH B109/B B109/BS21(R)C6) B109/BS21(R)C6) B110/B B111/B B113/LH B114/A B114/B B114/BS21(R)C5) B114/LH B114/LH B114/SD B87/B B87/LH B90/B B91/A B91/LH

10 Page 10 Table 2. Agronomic data for single crosses grown near Kanawha, Iowa in 2002 (planted May 6 harvested October 21). Grain Plants Grain Lodging Dropped Adjusted Ear Pedigree yield per ha moisture root stalk ears Value height q/ha x 1000 % % % % $ 1-5 B97/A B97/B B97/BS13(S)C6) B97/LH B97/N B97/SD B99/B B99/LH B99/SD BS21(R)C5) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS22(R)C5) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B DK LH176/LH N196/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

11 Page 11 Table 3. Agronomic data for single crosses grown near Nashua, Iowa in 2002 (planted May 4 harvested October 16). Grain Plants Grain Lodging Dropped Adjusted Ear Pedigree yield per ha moisture root stalk ears Value height q/ha x 1000 % % % % $ 1-5 A635/B A681/B A681/BS21(R)C5) A681/BS21(R)C6) A681/BS21(R)C6) A681/SD A681/SD B100/LH B102/A B102/H B102/LH B102/N B102/SD B103/A B103/B B103/B B103/B B103/B B103/H B103/LH B104/B B104/B B104/BS21(R)C5) B104/BS21(R)C6) B104/BS21(R)C6) B105/B B106/A B107/LH B109/B B109/BS21(R)C6) B109/BS21(R)C6) B110/B B111/B B113/LH B114/A B114/B B114/BS21(R)C5) B114/LH B114/LH B114/SD B87/B B87/LH B90/B B91/A B91/LH

12 Page 12 Table 3. Agronomic data for single crosses grown near Nashua, Iowa in 2002 (planted May 4 harvested October 16). Grain Plants Grain Lodging Dropped Adjusted Ear Pedigree yield per ha moisture root stalk ears Value height q/ha x 1000 % % % % $ 1-5 B97/A B97/B B97/BS13(S)C6) B97/LH B97/N B97/SD B99/B B99/LH B99/SD BS21(R)C5) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS22(R)C5) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B DK LH176/LH N196/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

13 Page 13 Table 4. Agronomic data for single crosses grown near Cannon Falls, Minnesota in 2002 (planted May 4 harvested November 3). Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value Weight q/ha x 1000 % % % % $ lbs A635/B A681/B A681/BS21(R)C5) A681/BS21(R)C6) A681/BS21(R)C6) A681/SD A681/SD B100/LH B102/A B102/H B102/LH B102/N B102/SD B103/A B103/B B103/B B103/B B103/B B103/H B103/LH B104/B B104/B B104/BS21(R)C5) B104/BS21(R)C6) B104/BS21(R)C6) B105/B B106/A B107/LH B109/B B109/BS21(R)C6) B109/BS21(R)C6) B110/B B111/B B113/LH B114/A B114/B B114/BS21(R)C5) B114/LH B114/LH B114/SD B87/B B87/LH B90/B B91/A B91/LH

14 Page 14 Table 4. Agronomic data for single crosses grown near Cannon Falls, Minnesota in 2002 (planted May 4 harvested November 3). Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value Weight q/ha x 1000 % % % % $ lbs B97/A B97/B B97/BS13(S)C6) B97/LH B97/N B97/SD B99/B B99/LH B99/SD BS21(R)C5) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS22(R)C5) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B DK LH176/LH N196/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

15 Page 15 Table 5. Agronomic data for single crosses grown near Estherville, Iowa in 2002 (planted May 1 harvested September 29) Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value Weight q/ha x 1000 % % % % $ lbs A635/B A681/B A681/BS21(R)C5) A681/BS21(R)C6) A681/BS21(R)C6) A681/SD A681/SD B100/LH B102/A B102/H B102/LH B102/N B102/SD B103/A B103/B B103/B B103/B B103/B B103/H B103/LH B104/B B104/B B104/BS21(R)C5) B104/BS21(R)C6) B104/BS21(R)C6) B105/B B106/A B107/LH B109/B B109/BS21(R)C6) B109/BS21(R)C6) B110/B B111/B B113/LH B114/A B114/B B114/BS21(R)C5) B114/LH B114/LH B114/SD B87/B B87/LH B90/B B91/A B91/LH

16 Page 16 Table 5. Agronomic data for single crosses grown near Estherville, Iowa in 2002 (planted May 1 harvested September 29) Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value Weight q/ha x 1000 % % % % $ lbs B97/A B97/B B97/BS13(S)C6) B97/LH B97/N B97/SD B99/B B99/LH B99/SD BS21(R)C5) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS21(R)C6) /LH BS22(R)C5) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B BS22(R)C6) /B DK LH176/LH N196/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

17 Page 17 Table 6. Agronomic data for single crosses grown near Pocahontas, Iowa in 2002 (planted May 3 harvested October 17). Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value weight q/ha x 1000 % % % % $ lbs A681/B A681/B B100/LH B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C7) B102/LH B102/W B103/B B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C7) B103/N B104/B B104/B B104/W B105/B B107/A B107/B B107/W B108/SD B109/(B97/B99) B109/B B109/W B110/B B110/B B113/A B113/LH B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C7) B114/LH B87/LH B90/B B90/B B90/B B90/LH B90/N B91/B B91/B B91/B B91/B

18 Page 18 Table 6. Agronomic data for single crosses grown near Pocahontas, Iowa in 2002 (planted May 3 harvested October 17). Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value weight q/ha x 1000 % % % % $ lbs B91/B B91/BS13(S)C6) B91/BS13(S)C7) B91/LH B91/N B97/A B97/B B97/B95) /LH B97/B99) /LH B97/B99) /LH B97/B99) /LH B97/BS13(S)C6) B97/LH B97/LH B97/N B99/A B99/B BS13(S)C6) /B BS13(S)C6) /B HC33/LH LH185/LH LH198/B N196/B W570/B W572/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

19 Page 19 Table 7. Agronomic data for single crosses grown near Conrad, Iowa in 2002 (planted May 14 harvested October 17). Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value weight q/ha x 1000 % % % % $ lbs A681/B A681/B B100/LH B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C7) B102/LH B102/W B103/B B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C7) B103/N B104/B B104/B B104/W B105/B B107/A B107/B B107/W B108/SD B109/(B97/B99) B109/B B109/W B110/B B110/B B113/A B113/LH B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C7) B114/LH B87/LH B90/B B90/B B90/B B90/LH B90/N B91/B

20 Page 20 Table 7. Agronomic data for single crosses grown near Conrad, Iowa in 2002 (planted May 14 harvested October 17). Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value weight q/ha x 1000 % % % % $ lbs B91/B B91/B B91/B B91/B B91/BS13(S)C6) B91/BS13(S)C7) B91/LH B91/N B97/A B97/B B97/B95) /LH B97/B99) /LH B97/B99) /LH B97/B99) /LH B97/BS13(S)C6) B97/LH B97/LH B97/N B99/A B99/B BS13(S)C6) /B BS13(S)C6) /B HC33/LH LH185/LH LH198/B N196/B W570/B W572/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

21 Page 21 Table 8. Agronomic data for single crosses grown near Stanhope, Iowa in 2002 (planted April 28 harvested October 6) Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value weight q/ha x 1000 % % % % $ lbs A681/B A681/B B100/LH B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C7) B102/LH B102/W B103/B B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C7) B103/N B104/B B104/B B104/W B105/B B107/A B107/B B107/W B108/SD B109/(B97/B99) B109/B B109/W B110/B B110/B B113/A B113/LH B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C7) B114/LH B87/LH B90/B B90/B B90/B B90/LH B90/N B91/B B91/B B91/B B91/B

22 Page 22 Table 8. Agronomic data for single crosses grown near Stanhope, Iowa in 2002 (planted April 28 harvested October 6) Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value weight q/ha x 1000 % % % % $ lbs B91/B B91/BS13(S)C6) B91/BS13(S)C7) B91/LH B91/N B97/A B97/B B97/B95) /LH B97/B99) /LH B97/B99) /LH B97/B99) /LH B97/BS13(S)C6) B97/LH B97/LH B97/N B99/A B99/B BS13(S)C6) /B BS13(S)C6) /B HC33/LH LH185/LH LH198/B N196/B W570/B W572/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

23 Page 23 Table 9. Agronomic data for single crosses grown near Hampton, Iowa in 2002 (planted May 9 harvested October 17). Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value weight q/ha x 1000 % % % % $ lbs A681/B A681/B B100/LH B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C7) B102/LH B102/W B103/B B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C7) B103/N B104/B B104/B B104/W B105/B B107/A B107/B B107/W B108/SD B109/(B97/B99) B109/B B109/W B110/B B110/B B113/A B113/LH B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C7) B114/LH B87/LH B90/B B90/B B90/B B90/LH B90/N B91/B B91/B B91/B B91/B

24 Page 24 Table 9. Agronomic data for single crosses grown near Hampton, Iowa in 2002 (planted May 9 harvested October 17). Grain Plants Grain Lodging Dropped Adjusted Test Pedigree yield per ha moisture root stalk ears Value weight q/ha x 1000 % % % % $ lbs B91/B B91/BS13(S)C6) B91/BS13(S)C7) B91/LH B91/N B97/A B97/B B97/B95) /LH B97/B99) /LH B97/B99) /LH B97/B99) /LH B97/BS13(S)C6) B97/LH B97/LH B97/N B99/A B99/B BS13(S)C6) /B BS13(S)C6) /B HC33/LH LH185/LH LH198/B N196/B W570/B W572/B Experiment Minimum Experiment Maximum Experiment Mean LSD(0.05)

25 Page 25 Table 10. Agronomic data for single crosses grown near Clarion, Iowa in 2002 (planted April 17 harvested September 30). Grain Plants Grain Lodging DroppedAdjusted Pedigree yield per ha moisture root stalk ears Value PLTHT EARHT q/ha x 1000 % % % % $ cm cm A681/B A681/B B100/LH B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C6) B102/BS13(S)C7) B102/LH B102/W B103/B B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C6) B103/BS13(S)C7) B103/N B104/B B104/B B104/W B105/B B107/A B107/B B107/W B108/SD B109/(B97/B99) B109/B B109/W B110/B B110/B B113/A B113/LH B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C6) B114/BS13(S)C7) B114/LH B87/LH B90/B B90/B B90/B B90/LH B90/N B91/B B91/B B91/B B91/B