BREEDING, GENETICS, AND PHYSIOLOGY. Development of Hybrid Rice Cultivars

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1 BREEDING, GENETICS, AND PHYSIOLOGY Development of Hybrid Rice Cultivars G.L. Berger, G. Lee, Z.B. Yan, X. Sha, K.A.K Moldenhauer, J.T. Hardke, C.E. Wilson Jr., and C.W. Deren ABSTRACT In 2013, hybrid rice was produced on more than 40% of the rice production acreage in Arkansas. Development of high-yielding hybrid rice cultivars has been ongoing at the University of Arkansas System Division of Agriculture Rice Research and Extension Center (RREC) near Stuttgart, Ark., since During 2013, 26 experimental hybrids were tested in an advanced yield trial (AYT) at the RREC along with the commercial hybrid checks XL723 and XL753 and the inbred line checks Roy J and Wells. Additionally, 87 experimental hybrids were tested in a preliminary yield trial (PYT) at the RREC. Yield values ranged from 123 bu/acre to 232 bu/acre for experimental hybrids in the AYT. In the PYT, yield values ranged from 160 bu/acre to 272 bu/acre. Variability was observed for both agronomic and quality related traits in both yield trials. A large scale effort was also placed on the evaluation of existing germplasm and development of new breeding populations to address quality issues associated with hybrids in Existing germplasm was assessed on the basis of agronomic performance, apparent disease resistance, and grain quality. In total, 464 unique crosses were made using adapted germplasm as at least one parent to address agronomic and quality issues often associated with hybrids. These breeding populations will be evaluated in the field in Several steps were taken to improve the overall efficiency of the hybrid rice breeding program. These included mechanization of the program, application of improved breeding methods, and use of molecular markers. Further improvements will be made during

2 B.R. Wells Arkansas Rice Research Studies 2013 INTRODUCTION The hybrid rice program began in 2010, utilizing accessions of diverse germplasm found in the United States Department of Agriculture (USDA) rice core collection (Yan et al., 2011). While this germplasm served as an initial base for the hybrid program, much work is needed to identify genotypes adapted to the mid-south (Berger et al., 2013). A major goal of the hybrid program in 2013 was to evaluate existing male sterile, restorer, and maintainer lines for agronomic and grain quality desirability. Evaluations were made both in the field and through the use of molecular markers. Improvement of this germplasm began in 2013 and will continue as the program grows. Both preliminary and advanced yield tests were conducted at the RREC during Evaluations were made and compared with commercially available check cultivars. Additionally, development of new breeding populations utilizing adapted southern long-grain germplasm began during A major focus of the upcoming year will be continued integration of new breeding material and technologies to improve the overall efficiency of the hybrid rice breeding program. PROCEDURES During the 2013 growing season, the hybrid rice breeding program tested 26 new hybrid combinations in an advanced yield test (AYT) at the Rice Research and Extension Center (RREC) near Stuttgart, Ark. Additionally, 87 experimental hybrids were tested in a preliminary yield test (PYT). Standard agronomic practices were followed based on recommendations for Arkansas. Agronomic measurements taken included early season plant stands, 50% heading date, purity notes, plant height, lodging, and grain yield. Plots were harvested with Wintersteiger plot combines at harvest maturity. Plot weight and moisture were taken at harvest. Quality characteristics including increased amylose content, decreased chalkiness, and improved gelatinization temperature were also evaluated. A large scale effort was made to develop new breeding populations for identification of male-sterile, maintainer, and restorer lines using known sources and adapted germplasm. In total, 464 unique crosses were made in The goal is to incorporate typical U.S. long-grain quality into the hybrid breeding pipeline. Of the 464 crosses, 34 crosses were made for improvement of 2-line male steriles, 62 crosses were made for improvement of B-lines, 4 backrosses were made for development of new A/B pairs and 362 crosses were made for development of male (restorer) lines. Breeding objectives focused on improved agronomic traits, quality characteristics, disease resistance, and traits important to hybrid seed production. Agronomic traits included decreased plant height, earlier maturation, and improved lodging resistance. Quality characteristics including increased amylose content, decreased chalkiness, and improved gelatinization temperature. Traits important to the production of hybrid seed including large, exerted stigmas for effective cross pollination, restorer genes from unadapted sources, and improved combining ability. Segregating populations were also grown and selections were made. 59

3 AAES Research Series 617 Isolated hybrid seed production tests were located in several bays at the RREC in New small-plot hybrid production methods were tested. Development of more efficient hybrid test cross methods will aid in production of new hybrid combinations. Further improvements will be made upon the methods in RESULTS AND DISCUSSION During 2013, 26 experimental hybrids were tested in the AYT at the RREC. Heading dates (days from emergence to heading) for experimental hybrids ranged from 80 days to 96 days (Table 1). For several hybrid combinations, heading dates were similar to those of the check hybrids XL723 (81 days) and XL753 (85 days). Plant heights ranged from 37 inches to 46 inches which were similar to the check cultivars Wells and Roy J, and check hybrids XL723 and XL753. Grain yield of experimental hybrids ranged from 123 bu/acre to 232 bu/acre. Experimental hybrids 13UAXH-61, 13UAXH-64, 13UAXH-67, and 13UAXH-74 produced yields similar to that of XL723 and XL753. In total, 18 experimental hybrid yields exceeded that of the check cultivar Roy J. Variability was noted for milling yields, amylose content, gel type, and cook type. A larger set of experimental hybrids were planted in the 2013 PYT. This set of experimental hybrids was more variable in terms of heading date, plant heights, and grain yield and quality. Heading dates of the 87 experimental hybrids ranged from 65 days to 96 days. Plant heights ranged from 37 inches to 51 inches. Grain yields ranged from 144 bu/acre to 272 bu/acre. A subset of these lines with amylose contents greater than 20 g/kg and the commercial checks Roy J and Francis are displayed in Table 2. These experimental hybrids are the most promising in terms of grain quality. Crosses focusing on the development of sterile, maintainer, and restorer lines resulted in 464 new combinations. During the fall and winter of 2013, 34 F 1 populations for s-line development, 36 F 1 populations for maintainer (B-line) development, and 60 F 1 populations for male (restorer) line development were grown in the greenhouse to rapidly advance generations. The remaining F 1 populations will be planted in the field during A total of 140 hybrid combinations were produced for testing during The winter nursery in Lajas, Puerto Rico, is being evaluated as a location to develop new hybrid combinations. Test crosses between male (restorer) and sterile lines will be made during the spring of The long term goal is to develop 1000 new hybrid combinations to test per year. SIGNIFICANCE OF FINDINGS The research presented shows the significant advances made by the hybrid rice breeding program during Further growth of the program will continue in Development of improved sterile lines (both 2- and 3-line) and male (restorer) lines which began in 2013 will be further expanded on in Additionally, new projects will be developed to answer questions pertaining to hybrid rice breeding and production. Continued research promises to identify high yielding hybrids adapted to Arkansas. 60

4 B.R. Wells Arkansas Rice Research Studies 2013 ACKNOWLEDGMENTS Funding for this project was supported by the Arkansas Rice Research and Promotion Board. Special thanks to Dr. Xueyan Sha, Dr. Jarrod Hardke, Tony Beaty, and Donna Frizzell for aid in planting and harvest during Additional thanks goes to the cooperators of the Uniform Regional Rice Nursery. LITERATURE CITED Berger, G.B., Z.B. Yan, and C.W. Deren Development of hybrid rice cultivars. In: R.J. Norman and K.A.K. Moldenhauer (eds.). B.R. Wells Arkansas Rice Research Studies University of Arkansas Agricultural Experiment Station Research Series 609: Fayetteville. Yan, Z.B., W.G. Yan, C.W. Deren, and A. McClung Hybrid rice breeding. In: R.J. Norman and K.A.K. Moldenhauer (eds.). B.R. Wells Arkansas Rice Research Studies University of Arkansas Agricultural Experiment Station Research Series 561: Fayetteville. 61

5 AAES Research Series 617 Table 1. Agronomic data for 26 experimental hybrids and check cultivars grown in the Advanced Yield Trial (AYT) at the RREC in Maturity Plant Line Yield date height Lodging Head rice Total rice Amylose Gel type Cook type (bu/acre) (50% heading) (inches) (0-9) (%) (g/kg) XL Int High Mix Long 13UAXH Int Low Mix Atypical 13UAXH Int Atypical XL Int Long 13UAXH Int High Mix Atypical 13UAXH Int Low Mix Atypical 13UAXH Int High Low Mix Atypical 13UAXH Int Low Mix Long 13UAXH Int Low Mix Long 13UAXH Int Long 13UAXH Int High Mix Atypical 13UAXH Int Atypical 13UAXH Int Low Mix Atypical 13UAXH Int Long 13UAXH Int Low Mix Atypical 13UAXH Int Low Mix Atypical 13UAXH Int Low Mix Long 13UAXH Int Low Mix Long 13UAXH Int Low Mix Long 13UAXH Int Atypical Roy J Int Long 13UAXH Int Low Mix Atypical Wells Int Long 13UAXH Int Long 13UAXH Int Atypical 13UAXH Int High Low Mix Atypical 13UAXH Int Atypical 13UAXH Int Low Mix Long 13UAXH Int Low Mix Long 13UAXH Int Long LSD (P = 0.05)

6 B.R. Wells Arkansas Rice Research Studies 2013 Table 2. Agronomic data for 23 experimental hybrids and check cultivars grown in the Preliminary Yield Trial (PYT) at the Rice Research and Extension Center in Maturity Plant Line a Yield date height Lodging Head rice Total rice Amylose Gel type Cook type (bu/acre) (50% heading) (inches) (0-9) (%) (g/kg) 13UAXH High Int Mix Atypical 13UAXH High Int Mix Atypical 13UAXH Low Int Mix Atypical 13UAXH Int Low Mix Long 13UAXH Int Low Mix Long 13UAXH Int High Mix Long 13UAXH Int High Mix Long 13UAXH Int Long 13UAXH Int Low Mix Long 13UAXH Int High Mix Long 13UAXH Int Low Mix Long 13UAXH Int Low High Mix Long 13UAXH Int High Mix Long 13UAXH High Int Mix Atypical 13UAXH Int High Mix Long 13UAXH Int Ex Hi Amy 13UAXH Int Long 13UAXH Int High Mix Long 13UAXH Int Long 13UAXH Int Ex Hi Amy 13UAXH Int Long Francis Int Long Roy J Int Long 13UAXH Int Low High Mix Long 13UAXH Int Low Mix Ex Hi Amy RU Int Long a Subset of lines tested in 2013 at the RREC. 63