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The use of on-farm commercial fields and research stations provides the opportunity to evaluate cultivar performance across a wide range of environmental conditions and management situations. The Arkansas Rice Performance Trials (ARPT) utilize experiment stations and commercial fields throughout the rice-producing regions of Arkansas to evaluate the performance of commercial rice cultivars. These trials provide information on agronomic factors of cultivars such as disease resistance, lodging, plant stand, plant height, grain yield, and milling yield across a range of environmental conditions, growing practices, and soil types. Choosing a cultivar is a critical decision annually for producers. Studies in 2021 were in grower fields in Clay, Desha, Greene, Jackson, Lawrence, and Phillips counties and on research stations in Arkansas, Mississippi, Poinsett, and St. Francis counties. The average grain yield across all 11 trials was 206 bu./ac, with the highest average yielding location being Mississippi County at 227 bu./ac (Table 2). Cultivars that had the highest average grain yield across all locations include RT XP753, RT 7321 FP, RT 7401, RT 7301, RT 7521 FP, DG263L, Taurus, and Ozark. The average milling yield across all cultivars was 58/70 (%HR/%TR), with Jupiter, CLM04, Lynx, PVL02, and Taurus displaying the highest average milling yields. [ABSTRACT FROM AUTHOR]

In order to dissect the genetic complexity of grain yield (GY) in response to high nighttime temperature (HNT) stress at the reproductive stage, a panel of 81 Japonica rice accessions of the USDA Rice Mini-core Collection (URMC) was treated with HNT stress at the R2 and R5 stages. The quantifiable GY components and grain quality traits were analyzed in a correlation analysis to understand the relationship between the multiple grain yield components tested in the panel. Using the phenotyping data for GY components [total number of spikelets per panicle (TSP) and number of un-filled grains per panicle (NUFGP)], a genome-wide association study (GWAS) was conducted using a FarmCPU model with a set of 204K single nucleotide polymorphisms (SNPs), to identify novel genomic loci/SNPs associated with TSP and NUFGP. The association mapping analysis identified 42 novel, highly significant SNPs associated with TSP and 95 novel significant SNPs associated with NUFGP under HNT stress. Out of these SNPs, 9 significant SNPs associated with TSP and 12 significant SNPs associated with NUFGP were co-incident with genomic regions of previously reported quantitative trait loci (QTLs) related to GY under heat stress. These novel potential candidate genomic loci/SNPs have a potential use in SNP-based marker-assisted selection, QTL mapping, pyramiding of genomic regions related to grain yield, and HNT stress tolerance into elite Arkansas rice cultivars. [ABSTRACT FROM AUTHOR]

The Arkansas Rice Variety Advancement Trials (ARVAT) are conducted each year to evaluate promising experimental lines from the Arkansas rice breeding program compared to commercially available cultivars from public and private breeding programs. The ARVATs are planted on experiment stations and cooperating producer's fields in a diverse range of environments, soil types, and agronomic and pest conditions. The ARVATs were conducted at 6 locations during 2021. Averaged across locations, grain yields were highest for the conventional long-grain hybrid RT XP753, the FullPage long-grain hybrid RT 7521 FP, the conventional medium-grain RU1901033, the MaxAce long-grain RTv7231 MA, the Clearfield medium-grain RU2101234, the Clearfield long-grain RU2001093, the conventional long-grain RU2001185, and the conventional long-grain RU2001125. [ABSTRACT FROM AUTHOR]

The long-grain rice breeding program in the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) has a long history of successfully developing long- and medium-grain as well as specialty rice cultivars for the Arkansas rice producers and the mid-South. Selections and evaluations are strictly conducted based on the desirable characteristics that need to be improved. These important characteristics include high rough rice yield potential, high milling yields, disease resistance, abiotic tolerance, good plant stature, and superior grain quality (i.e., low chalk, processing, cooking, and eating qualities). In 2021, a total of 1,204 entries entered the yield trials of both initial and advance tests for a total of more than 4,000 yield plots, including plots for seed increases. This report presents the overall results of the 2021 breeding program that includes lines from both initial and advance tests as well as potential lines in the pipeline. [ABSTRACT FROM AUTHOR]

Overall rice acreage in the United States is declining while imports have been rising since the 1980s. Rice imports are mainly driven by the consumption of Jasmine type "aromatic" rice. The aromatic rice breeding program at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) is actively developing aromatic varieties that not only have good cooking quality and aroma but also have improved agronomic performance and adaptation to the climatic conditions in the mid-South. In 2021, 20 out of 68 entries had a significantly higher yield than the check varieties in the Stuttgart Initial Test. In the Advanced Yield Trial conducted at the RREC, 23 out of 40 entries had a significantly higher yield over the check varieties. The top 3 entries in both trials had a yield advantage of 50 bu./ac or more over Jazzman 2 or ARoma 17. Furthermore, the Uniform Regional Rice Nursery (URRN) conducted in Arkansas showed the three new aromatic lines also out-yielded the check ARoma 17. Our results showed our current selections of the top elite lines have improved the agronomic performance and can be further tested in multi-environment trials. [ABSTRACT FROM AUTHOR]

ARoma 22 is a new high-yielding, mid-season, jasmine-type aromatic long-grain rice cultivar derived from the cross Jazzman//Drew/PI 637517/3/Taggart. The aromatic line was developed by the University of Arkansas System Division of Agriculture's Arkansas Agricultural Experiment Station and has been approved for release for the 2022 growing season. ARoma 22 offers a jasmine-type rice adapted to Arkansas growing conditions for rice producers who wish to serve the aromatic rice consumer market. [ABSTRACT FROM AUTHOR]

The cultivar CLL18 is a new and very high-yielding, short-season, long-grain Clearfield® rice cultivar derived from the cross Roy J/CL142-AR. The CLL18 Breeder Head Row seed was released to BASF and Horizon Ag by the University of Arkansas System Division of Agriculture's Arkansas Agricultural Experiment Station to produce breeder and foundation seed in 2022 and 2023, respectively. The major advantages of CLL18 are its very high yield potential, high whole kernel rice milling yield, long kernel length, and low chalk. CLL18 is a non-semidwarf standard height long-grain rice cultivar with lodging resistance similar to Roy J. CLL18 is rated moderately susceptible to rice blast, sheath blight, and bacterial panicle blight, moderately resistant to narrow brown leaf spot, and susceptible to false smut. [ABSTRACT FROM AUTHOR]

The Arkansas Rice Performance Trials (ARPTs) are conducted each year to evaluate promising experimental lines from the Arkansas rice breeding program and commercially available cultivars from public and private breeding programs. The ARPTs are planted on experiment stations and cooperating producer's fields in a diverse range of environments, soil types, and agronomic and pest conditions. The ARPTs were conducted at 4 locations during 2019. Averaged across locations, grain yields were highest for the commercial cultivars RT 7301, RT XP753, RT 7501, RT 7521 FP, DGL263, RT Gemini 214 CL, RT 7321 FP, Jupiter, Titan, and RT CLXL745. Cultivars with the highest overall milling yields during 2019 included: PVL02, CLJ01, Jazzman-2, ARoma 17, Jupiter, CL151, CL153, and CLM04. [ABSTRACT FROM AUTHOR]

The Degree-Day 50 (DD50) computer program is one of the most successful management aids developed by the University of Arkansas System Division of Agriculture. This program predicts critical growth stages that assist in increasing the effectiveness of crop management operations. In order to maintain its relevance, the computer program must be updated continually as new rice cultivars become available to growers. To accomplish this goal, studies are conducted in a controlled research environment where developmental data and DD50 thermal unit thresholds for current and new cultivars are determined. Throughout the 2019 season, DD50 thermal unit accumulation, developmental data, and the effect of seeding date (SD) on grain and milling yield potential for 20 cultivars were evaluated over six SDs under a dry-seeded, delayed-flood management system commonly used in southern U.S. rice production. Significant differences in grain and milling yield were observed for all 20 cultivars at each location. [ABSTRACT FROM AUTHOR]

The objective of the cultivar × nitrogen (N) studies is to determine the optimal N fertilizer rates for new rice (Oryza sativa L.) cultivars across the array of soils and environments encountered in the Arkansas rice-growing region. The eleven cultivars studied in 2019 were: ARoma 17, CLJ01, CLL15, CLL16, CLM04, Jewel, Lynx, PVL01, PVL02, the experimental line ARX7-1084, and Diamond. Seed treatment and seeding rates were determined following current recommendations and production practices. The grain yields were good to excellent for all the cultivars studied at the three locations in 2019: University of Arkansas System Division of Agriculture's Northeast Research and Extension Center (NEREC), Keiser, Arkansas, on a Sharkey Clay (Vertic Haplaquepts) soil; the Pine Tree Research Station (PTRS) near Colt, Arkansas, on a Calloway silt loam (Glossaquic Fragiudalfs) soil series; and the Rice Research and Extension Center (RREC), near Stuttgart, Arkansas, on a Dewitt silt loam (Typic Albaqualfs) soil. This is the first year the cultivars ARoma 17, CLJ01, CLL15, CLL16, CLM04, Jewel, Lynx, and PVL02 are included in the cultivar × N rate study; therefore there is insufficient data to make a recommendation at this time. Multiple years of results for PVL01 indicate this cultivar should have good yields with minimal to no lodging if 150 pounds (lb) of N/ac is applied in a two-way split of 105 lb N/ac at the preflood timing followed by 45 lb N/ac at midseason when grown on silt loam soils and 180 lb N/ac in a two way split of 135 lb N/ac at the preflood timing followed by 45 lb N/ac applied at midseason when grown on clay soils. [ABSTRACT FROM AUTHOR]

To reflect the recent changes of the Arkansas rice industry and streamline the delivery of new and improved rice varieties to Arkansas rice growers, the medium-grain rice breeding project has expanded its research areas and breeding populations to include both conventional and Clearfield medium- and long-grain rice as well as hybrid rice. The newest elite breeding lines/varieties from collaborating programs, as well as lines with diverse genetic origins will be actively collected, evaluated, and incorporated into current crossing blocks for programmed hybridization. To improve the efficiency and effectiveness of the program, maximum mechanized-operation, multiple generations grown in the winter nursery, and new technologies such as molecular marker-assisted selection (MAS) are rigorously pursued. [ABSTRACT FROM AUTHOR]

The growing demand for staple food crops like rice will need to be achieved predominantly through agricultural intensification, more efficient use of inputs, and advanced molecular genetics approaches. To meet this demand, it is essential that the genetic diversity within rice subspecies be fully utilized. The japonica subpopulation is considered an underappreciated genetic resource within that diversity. It has been shown that japonica rice has been well adapted to the Arkansas region and can be a potential gene pool for improving Arkansas traditional rice cultivars. For improvement of the Arkansas rice cultivars, natural genetic variation for grain yield and quality traits need to be quantified at the molecular level. A subpopulation of 81 japonica rice genotypes of the USDA Rice Mini Core-Collection (URMC) was phenotyped for grain yield and quality traits under high nighttime temperature conditions in greenhouses, and genotyped by whole genome sequencing, thereby obtaining good quality Single Nucleotide Polymorphism (SNP) molecular markers for genome wide association studies (GWAS). The GWAS was performed using the Circulating Probability Unification (FarmCPU) method with the multiple loci mixed linear model (MLMM), and identified 28 significantly associated SNPs with 100-grain weight (grain yield component), and 42 significantly associated SNPs with percent chalkiness (quality trait) in the subpopulation of 81 japonica rice genotypes of the URMC. These novel genomic loci/or SNPs have a potential use in SNP based QTL mapping, identification of candidate genes for grain yield components and quality traits, and the selection of favorable alleles for breeding Arkansas rice cultivars. [ABSTRACT FROM AUTHOR]

The deleterious effects of high nighttime temperature (HNT) negatively impact the rice industry in Arkansas, the U.S. and the world resulting in lost income for rice producers and processors. Both grain yield and grain quality are affected by HNT, but the specific responses of many cultivars important to Arkansas producers have yet to be documented. Seventy-two rice varieties and advanced lines were planted in a field study on four different dates during two years (2018 and 2019) at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center near Stuttgart, Arkansas. Grain yield, head rice yield, chalk, temperature and sunlight were measured and analyzed. The top ranked lines for grain yield, head rice yield, and chalk were determined in each of the 8 planting date by year combinations. The top ranked long-grain lines for yield included several cultivars adapted to Arkansas including Diamond, Jewel, Templeton and Francis. Varieties in the top ranked for head rice yield included Cybonnet, Chenierie, ARoma 17 and several Arkansas selections. Varieties with the lowest ranked chalk values were Cybonnet, ARoma 17, Templeton, CL172 and two Arkansas advanced lines. The high ranking long-grain lines are suggested as candidates for crosses and future development of new rice cultivars with stable grain yield and quality in both normal and HNT conditions. [ABSTRACT FROM AUTHOR]

The cultivar × nitrogen (N) fertilizer rate studies determine the proper N fertilizer rates for the new rice cultivars across the array of soil and climatic conditions which exist in the Arkansas rice-growing region. The seven rice cultivars studied in 2018 were: CL153, CL272, PVL01, Thad, and the experimental lines CLX6-1111, CLX6-1133, and CLX5-4083. In general, grain yields were good to excellent for all the cultivars studied at the three locations in 2018. This was the first year the experimental lines CLX6-1111, CLX6-1133, and CLX5-4083 were in the cultivar × N rate studies and, thus, there is not enough data to make a recommendation at this time. The multiple years of results for CL153, CL272, PVL01, and Thad indicate these cultivars should yield well with minimal to no lodging if 150 lb N/ac is applied in a two-way split of 105 lb N/ac at preflood and 45 lb N/ac at midseason when grown on silt loam soils and 180 lb N/ac in a two-way split of 135 lb N/ac at preflood and 45 lb N/ac at midseason when grown on clay soils. [ABSTRACT FROM AUTHOR]

The Arkansas Rice Performance Trials (ARPTs) are conducted each year to evaluate promising experimental lines from the Arkansas rice breeding program and commercially available cultivars from public and private breeding programs. The ARPTs are planted on experiment stations and cooperating producer's fields in a diverse range of environments, soil types, and agronomic and pest conditions. The ARPTs were conducted at five locations during 2018. Averaged across locations, grain yields were highest for the commercial cultivars RT 7801, RT 7501, RT Gemini 214 CL, RT XP753, RT XP760, RT 7521 FP, RT 7321 FP, RT 7311 CL, Diamond, and Jupiter. Four advanced experimental lines, CLXAR19, CLX-1030, ARX7-1121, and CLX6-1111 also outperformed many current commercial cultivars. Cultivars with the highest overall milling yields during 2018 included: CL153, CL172, ARX7-1087, ARoma 17, and CLX6-1111. [ABSTRACT FROM AUTHOR]

The Degree-Day 50 (DD50) computer program is one of the most successful management aids developed by the University of Arkansas System Division of Agriculture. This program predicts critical growth stages that assist in increasing the effectiveness of crop management operations. In order to maintain its relevance, the computer program must be updated continually as new rice cultivars become available to growers. To accomplish this goal, studies are conducted in a controlled research environment where developmental data and DD50 thermal unit thresholds for current and new cultivars are determined. Throughout the 2018 season, DD50 thermal unit accumulation, developmental data, and the effect of seeding date (SD) on grain and milling yield potential for twenty cultivars were evaluated over six SDs under a dry-seeded, delayed-flood management system commonly used in southern U.S. rice production. Significant differences in grain and milling yield were observed for all twenty cultivars at each location. [ABSTRACT FROM AUTHOR]

Disease resistance in rice is one of many goals rice breeders and pathologists work on at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) near Stuttgart, Arkansas. The breeding and pathology support group evaluates preliminary and advanced breeding lines against major diseases of economic importance in both the greenhouse and field. At RREC, preliminary and advanced breeding materials are evaluated using artificial inoculation for sheath blight in the field and blast diseases in the greenhouse. Advanced breeding materials are tested in the field for blast resistance with artificial inoculation at the University of Arkansas System Division of Agriculture's Pine Tree Research Station (PTRS) near Colt, Arkansas. Large amounts of disease inocula are prepared in the laboratory and applied to rice plants following specific protocols. The rice breeders utilize these data to make selections. The breeding program advanced yield plots are also evaluated in the field for diseases including the rice blast, sheath blight, bacterial panicle blight, kernel smut and false smut. Selected lines are used either to transfer genes for resistance into adapted and high yielding varieties or to advance entries for further agronomic testing. The evaluation of preliminary breeding materials helps breeders eliminate extremely susceptible materials, thus saving time and resources. The breeding and pathology technical support group is fully involved in extension plant pathology programs with applied research on bacterial panicle blight, including collaborative interdepartmental, industry, and multi-state research endeavors. [ABSTRACT FROM AUTHOR]

To reflect the recent changes of the Arkansas rice industry and streamline the delivery of new and improved rice varieties to Arkansas rice growers, the medium-grain rice breeding project has expanded its research areas and breeding populations to include both conventional and Clearfield medium- and long-grain rice as well as hybrid rice. The newest elite breeding lines/varieties from collaborating programs, as well as lines with diverse genetic origins will be actively collected, evaluated, and incorporated into current crossing blocks for programmed hybridization. To improve the efficiency and effectiveness of the program, maximum mechanized-operation, multiple generations grown in the winter nursery, and new technologies such as molecular marker-assisted selection (MAS) are rigorously pursued. [ABSTRACT FROM AUTHOR]

The major focus of the Hybrid Rice Program in 2018 was to produce experimental hybrid lines by crossing newly developed male-sterile lines with elite cultivars/advanced lines. Moreover, two experimental hybrid lines will be evaluated in a 2019 Arkansas hybrid yield trial (ARPT). The hybrid breeding program successfully constructed a pipeline for production of male-sterile lines for the two-line hybrid system which includes populations from early through advanced generations. Development of parental material required for developing hybrid rice through the three-line hybrid system has also been expanded. [ABSTRACT FROM AUTHOR]

Yield is a quantitative trait that is controlled by genetic and environmental factors. La- Grue, a high-yielding long-grain rice cultivar developed by the University of Arkansas System Division of Agriculture has been used as a parent in the development of other elite rice cultivars. There is limited information on the genetics that give LaGrue its high-yielding advantage. The objectives of this study are to identify agronomic traits that give LaGrue its high-yielding potential and to identify quantitative trait loci (QTL)/genes associated with the yield traits. A third objective of this study is to develop two recombinant inbred lines (RIL) for use in genetic studies. Four cultivars including LaGrue, Bengal, Lemont, and Mars were tested in a field study done at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) near Stuttgart, Arkansas. Results from the study showed that LaGrue exceeded all three cultivars at number of seeds/panicle, number of primary panicle branches/panicle, and seed weight/panicle. We also developed two bi-parental populations by crossing LaGrue with Lemont and Mars for QTL mapping and RIL line development. The results from this study can be used in the development of rice cultivars through marker-assisted selection. [ABSTRACT FROM AUTHOR]

The Arkansas rice breeding program has the ongoing goal to develop new long- and medium-grain cultivars as well as specialty cultivars including aromatics and Japanese quality short-grains. Cultivars are evaluated and selected for desirable characteristics. Those with desirable qualities which require further improvement are utilized as parents in future crosses. Important components of this program include: high-yield potential, excellent milling yields, pest and disease resistance, improved plant type (i.e., short stature, semidwarf, shorter maturity, erect leaves), and superior grain quality (i.e., low chalk, cooking, processing and eating). New cultivars are continually being released to rice producers for traditional Southern U.S. markets as well as for emerging specialty markets, which are gaining in popularity with rice consumers. This report describes the progress of the long-grain and specialty rice pure-line rice breeding efforts at the University of Arkansas System Division of Agriculture. [ABSTRACT FROM AUTHOR]

We report here on the analysis of a random subset of rice genotypes of indica and japonica subspecies, treated with high nighttime temperature (HNT) stress during flowering, to compare the natural variation between the rice subspecies for HNT tolerance quantified by grain yield and quality. The genotypes were screened in temperaturecontrolled greenhouses for HNT initiated at the R2 and R5 reproductive stages and continued until physiological maturity. A set of 10 indica and 10 japonica diverse rice genotypes were randomly selected from the USDA rice mini-core (URMC) collection. Phenotypic analysis of the genotypes showed that the japonica genotypes had a higher percentage of filled grains per panicle (yield component) when treated with HNT at the R2 and R5 growth stages, and a lower percentage of chalkiness in rice brown grains at the R5 growth stage under HNT compared to indica. We conclude that in this pilot study, the japonica subspecies lines used exhibited more HNT tolerance than the indica subspecies lines in terms of grain yield and quality and represents an important genepool to dissect the genetic mechanisms/pathways involved in the HNT tolerance traits. The identification of genetic markers for grain yield and quality under HNT, would be useful for rice breeders to develop improved U.S. rice cultivars stable for HNT. [ABSTRACT FROM AUTHOR]

Seventy-two entries including advanced lines were selected for their agronomic value and/or suspected tolerance to high nighttime temperature (HNT). Entries were planted on four different dates to analyze the effects of a range of environmental conditions on desired traits such as grain yield and grain quality. Air temperature above the plant canopy in the field was recorded hourly, and the correlation values between the number of hours above two critical thresholds [77 °F (25 °C) and 82.4 °F (28 °C)], four different yield measurements (grain yield, brown rice yield, milling rice yield and head rice yield) and chalk were obtained. Entries showing high yield, low chalk and high milling yield are presented. [ABSTRACT FROM AUTHOR]

Currently 4 rice breeding programs and cooperative extension activities utilize the molecular genetics laboratory at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) near Stuttgart, Arkansas. Much of the effort over the last 18 years has been devoted to the genotypic characterization of parental lines and progeny in the areas of new long-grain and medium-grain cultivar development, hybrid rice breeding, aromatic rice breeding, backcross populations, genomic mapping of specific traits, seed purification, and genetic fingerprinting. In 2018, genetic analysis was performed on 9 major projects for the rice breeding group involving DNA marker-assisted selection (MAS) for the important traits of cooking quality, aroma, rice blast disease resistance, plant height, leaf texture, and Clearfield technology. Eight other smaller projects were conducted for the breeding programs as well. The Molecular Genetics lab screened 3697 test samples and 292 DNA reference samples with up to 29 markers. The rice molecular analysis projects included parental materials, male sterile and restorer lines, selected F1 hybrid lines, and early and advanced generations of conventional breeding materials currently in development. In total, the lab generated 28,425 data points for the year. The work was accomplished using 75 DNA template plates, 347 polymerase chain reaction (PCR) plates, 72 runs on the ABI 3500xL to analyze simple sequence repeat (SSR) markers, and 171 PACE runs to analyze single nucleotide polymorphism (SNP) markers. [ABSTRACT FROM AUTHOR]

Successful large-scale hybrid rice seed production relies on developing suitable male-sterile lines. The University of Arkansas System Division of Agriculture's Rice Research and Extension Center, Hybrid Rice Breeding program developed a new environmental genic male sterile (EGMS) line for two-line hybrid rice production. The new EGMS line contains genes/quantitative trait loci associated with desirable phenotypic and cooking quality characteristics. It produces acceptable male-sterile seeds and has been tested for hybrid rice production. [ABSTRACT FROM AUTHOR]

Development of disease resistant rice is one of many goals rice breeders work on at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) near Stuttgart, Arkansas The center's plant pathology group assists by screening preliminary to advance breeding entries for disease reaction under greenhouse and field conditions. Breeding materials are evaluated after using artificial inoculum for sheath blight at the RREC and blast disease at the RREC and the University of Arkansas System Division of Agriculture's Pine Tree Research Station (PTRS) near Colt, Arkansas. Both sheath blight and blast inocula are produced in the laboratory and applied to plants using specific protocols for each disease. Sheath blight is screened under field conditions, but blast screening utilizes both greenhouse and field environments. The major objectives of this technical support are to provide data that not only helps breeders remove the most susceptible lines early in their program, but also to support advancement of lines or transfer of genes for resistance into adapted and high yielding varieties. The breeding and pathology technical support group assists extension plant pathology programs with applied research to manage diseases that prevail in rice fields, as well as, collaborative interdepartmental, industry, and multi-state research endeavors. [ABSTRACT FROM AUTHOR]

In 2019 the major project reported here involved the analysis of rice blast disease resistance conferred by the gene Pi40. We also performed genetic analysis on 10 major projects for rice breeding involving DNA marker-assisted selection (MAS) for the important traits of cooking quality, aroma, rice blast disease resistance, plant height, leaf texture, and the herbicide resistance systems Clearfield and Provisia at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC), near Stuttgart, Arkansas. Three smaller projects were conducted for the breeding programs as well. The Molecular Genetics lab screened 4663 test samples with up to 24 markers. The rice molecular analysis projects included parental materials, male sterile and restorer lines, selected F1 hybrid lines, and early and advanced generations of conventional breeding materials currently in development. In total, the lab generated 51,701 data points for 7 clients. The work was accomplished using 53 DNA template plates, 577 PCR plates, 118 runs on the ABI 3500xL to analyze simple sequence repeat (SSR) markers, and 218 PACE runs to analyze single nucleotide polymorphism (SNP) markers. In 2018 a line from the International Rice Research Institute (IRRI) which has the rice blast resistance gene Pi40 was crossed with some elite lines in the long-grain breeding program in order to introduce this powerful resistance gene into breeding materials with agronomic traits preferred by Arkansas farmers. The crosses resulted in 4 F2 populations grown in the field in 2019. A total of 880 plants was screened with 24 markers, with 14 of them linked to 6 blast resistance genes. Through this analysis, it was determined that the IRRI line had the genes Pi-b and Pi-ta in addition to the Pi40 gene. The Arkansas parents of two of the populations also had Pi-ta and Pi-kh. Analysis of the progeny revealed that approximately 25% of the plants had inherited the Pi40 gene. Molecular analysis was essential in determining the total rice blast disease resistance potential for the progeny so that selections could be made to promote further advancement in the program. [ABSTRACT FROM AUTHOR]

Jewel is a new short season, high yielding, long-grain rice cultivar with the Pi-ta gene for blast resistance and the Cheniere cook type developed from a complex cross with many parents, some of which are: Katy, Newbonnet, Drew, Lebonnet, Starbonnett, LaGrue, Lemont, Wells, Radiated Bonnet 73, short strawed Starbonnet, Dawn, and Bluebonnet 50. Jewel has been approved for release, by the University of Arkansas System Division of Agriculture's Arkansas Agricultural Experiment Station, to qualified seed growers for the summer of 2020. The major advantages of Jewel are its blast tolerance, yield potential, high whole kernel rice milling yield, long kernel length, low chalk and L-202 cook type. Jewel is a non-semidwarf standard long-grain rice cultivar with lodging resistance approaching that of Roy J. Jewel is rated moderately susceptible to rice blast, sheath blight and false smut, and rated susceptible to bacterial panicle blight. [ABSTRACT FROM AUTHOR]

The cultivar x nitrogen (N) fertilizer rate studies determine the proper N fertilizer rates for the new rice cultivars across the array of soil and climatic conditions which exist in the Arkansas rice-growing region. The six rice cultivars studied in 2017 were: Diamond, Titan, Horizon AG's Clearfield CL153 and CL272, BASF and Horizon AG's PVL01, and Thad. Grain yields were excellent for most of the cultivars studied in 2017 at the chosen locations, except at the University of Arkansas System Division of Agriculture's Pine Tree Research Station (PTRS) location where a phosphorus deficiency played a role in reducing yields for all of the cultivars, except possibly Diamond. This was the first year PVL01 and Thad were in the cultivar x N-rate studies and thus there is not enough data to make a recommendation at this time. The multiple years of results for Diamond, Titan, CL153 and CL272 indicate these cultivars should yield well with minimal to no lodging if 150 lb N/acre is applied in a two-way split of 105 lb N/acre at preflood and 45 lb N/acre at midseason when grown on silt loam soils and 180 lb N/acre in a two-way split of 135 lb N/acre at preflood and 45 lb N/acre at midseason when grown on clay soils. [ABSTRACT FROM AUTHOR]

The Arkansas Rice Performance Trials (ARPTs) are conducted each year to evaluate promising experimental lines from the Arkansas rice breeding program and commercially available cultivars from public and private breeding programs. The ARPTs are planted on experiment stations and cooperating producer's fields in a diverse range of environments, soil types, and agronomic and pest conditions. The ARPTs were conducted at five locations during 2017. Averaged across locations, grain yields were highest for the commercial cultivars XP753, XP760, RT7812CL, RTGemini214CL, RT7311CL, Diamond, and Jupiter. Two advanced experimental lines, AREX7-1084 and AREX7-1124 also outperformed many current commercial cultivars. Cultivars with the highest overall milling yields during 2017 included: CL153, CL163, CL172, and Roy J. [ABSTRACT FROM AUTHOR]

The computer program termed Degree-Day 50 (DD50) has become one of the most successful management tools developed by the University of Arkansas System Division of Agriculture. The program predicts critical growth stages that assist in increasing the effectiveness of crop management operations. In order to maintain its relevance, the computer program must be updated continually as new rice cultivars become available to the grower. In pursuit of this goal, studies are conducted in a controlled research environment where developmental data and DD50 thermal unit thresholds for current and new cultivars are determined. Throughout the 2017 season, DD50 thermal unit accumulation, developmental data, and the effect of seeding date (SD) on grain and milling yield potential data for 20 cultivars were evaluated over 6 SDs under a dry-seeded, delayed-flood management system commonly used in southern U.S. rice production. [ABSTRACT FROM AUTHOR]

ARoma 17, a new high yielding Jasmine-type aromatic, mid-season, long-grain rice cultivar, originated from the cross 'Jazzman'/PI 597046. The aromatic line has been approved for release for the 2018 growing season. ARoma 17 offers a Jasmine-type rice adapted to Arkansas growing conditions for rice producers who want to serve that consumer market. [ABSTRACT FROM AUTHOR]

Development of disease resistant rice is one of many goals rice breeders work on at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) near Stuttgart, Ark. The center's plant pathology group assists by screening preliminary to advance breeding entries against rice diseases under greenhouse and field conditions. Breeding materials are evaluated using artificial inoculation for sheath blight and blast diseases at the RREC and University of Arkansas Systems Division of Agriculture's Pine Tree Research Station (PTRS) near Colt, Ark. Large amounts of disease inocula are prepared in the laboratory and applied to plants using specific protocols. Sheath blight is screened under field conditions, but blast screening utilizes both greenhouse and field environments. The breeding programs utilize these data to make selections. Selected lines are used either to transfer genes for resistance into adapted and high yielding varieties or to advance entries for further agronomic testing. The breeding and pathology technical support group also assists extension plant pathology programs with applied research to manage major prevailing and newly emerging diseases, including collaborative interdepartmental, industry, and multi-state research endeavors. [ABSTRACT FROM AUTHOR]

In 2010, the University of Arkansas System Division of Agriculture, established the rice hybrid program to develop very high yield rice hybrids with good seed quality for the mid-Southern United States. In 2017 potential environment sensitive male-sterile lines (EGMS) possessing genes associated with good cooking quality for the "Two-line hybrid rice system" were developed. We continued developing several restorer lines (R line) for the "Three-line hybrid rice system". Hybrid (F1) seeds were produced from crosses between the U of A male-sterile lines and Arkansas elite cultivars. Experimental hybrid lines developed during the summer of 2016 were evaluated for yield and quality characteristics. Combinating ability of experimental male-sterile lines was evaluated in a heterosis study. New sources of Environmental genic male-sterile lines were introduced from the International Rice Research Institute (IRRI) in the Philippines. Several advanced lines from the long and medium grain programs were selected to be used in hybrid rice development. Extensive phenotypic and molecular evaluations were completed to improve disease resistance and cooking quality, and to identify semi dwarf, non-aromatic plants. [ABSTRACT FROM AUTHOR]

To reflect the recent changes of the state rice industry and streamline the delivery of new and improved rice varieties to the Arkansas rice growers, the new medium-grain rice breeding project will expand its research areas and breeding populations to include both conventional and Clearfield medium- and semidwarf long-grain rice, as well as hybrid rice. Newest elite breeding lines/varieties from collaborating programs, as well as lines with diverse genetic origins will be actively collected, evaluated, and incorporated into the current crossing blocks for the programmed hybridization. To improve the efficiency and effectiveness, maximum mechanized-operation, multiple generations of winter nursery, and new technologies such as molecular marker-assisted selection (MAS) will also be rigorously pursued. [ABSTRACT FROM AUTHOR]

Hybrid rice production using the two-line system requires developing environment genetic male-sterile (EGMS) lines which become male-sterile in certain environmental conditions. An EGMS line contains genes that can be induced to express by temperature (TGMS), daylight (PGMS), or both (PTGMS). This study will determine (1) the genetic sources (TGMS, PGMS, PTGMS) of several Arkansas EGMS lines, (2) the environmental thresholds of each line, and (3) the optimum/absolute planting dates to induce full sterility of these lines in Arkansas. A total of eight EGMS lines are being tested including 4 lines designated as 236s, 801s, 805s, and 811s developed by the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) near Stuttgart, Ark.; and 4 mutant male-sterile lines designated as GSOR 1, GSOR 2, GSOR 3, and GSOR 4 developed by the Dale Bumpers National Rice Research Center (DBNRRC-USDA-ARS) near Stuttgart, Ark. First, the lines were screened in growth chambers using different temperatures to identify the genetic source and environmental threshold for each line. Plants were tested at the heading stage for pollen sterility via the pollen stain method. Next, each line was planted in a randomized block design with 3 replications and 3 planting dates to determine the optimum planting dates at field conditions at RREC in summer 2017. The percentage of sterility from selected single plants of each line as well as the overall percentage of sterility from each plot were recorded. The results from the growth chamber study revealed that 801s and 811s expressed sterility at a daytime temperature >29.4 °C and nighttime temperature >26.7 °C, while 236s expressed sterility when daytime temperature >32.2 °C and nighttime temperature >29.4 °C. The results also suggested that the different day lengths did not affect sterility in these lines. The field study showed that 811s expressed sterility in all three planting dates indicating that the optimum planting was May 10th. The 236s plants tested from the 1st planting date expressed sterility indicating that the absolute planting date was April 25. All GSOR lines in the growth chamber conditions remained fertile, however, in the field test a few plants of GSOR 2, GSOR 3, and GSOR 4 showed sterility. All GSOR 1 plants were fertile in the field condition. [ABSTRACT FROM AUTHOR]

The Arkansas rice breeding program has the ongoing goal to develop new long- and medium-grain cultivars as well as specialty cultivars including aromatics and Japanese quality short-grains. Cultivars are evaluated and selected for desirable characteristics. Those with desirable qualities which require further improvement are utilized as parents in future crosses. Important components of this program include: high-yield potential, excellent milling yields, pest and disease resistance, improved plant type (i.e. short stature, semidwarf, shorter maturity, erect leaves), and superior grain quality (i.e. low chalk, cooking, processing and eating). New cultivars are continually being released to rice producers for the traditional Southern U.S. markets as well as for the emerging specialty markets, which are gaining in popularity with rice consumers. This report describes the progress of the long-grain and specialty rice pure line rice breeding effort at the University of Arkansas System Division of Agriculture. [ABSTRACT FROM AUTHOR]

In 2021 molecular genetics staff at the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) performed genetic analysis for rice breeding projects involving DNA marker-assisted selection (MAS) for the traits of cooking quality, rice blast disease resistance, and the herbicide resistance technologies Clearfield and Provisia. The lab screened a total of 890 test samples with up to 8 markers. The rice molecular analysis projects included parental materials, backcross populations, and early and advanced generations of conventional breeding materials currently in development. In total, the lab generated 6,189 data points for 3 clients. The work was accomplished using 10 DNA template plates, 68 PCR plates, 10 runs on the ABI 3500xL to analyze simple sequence repeat (SSR) markers, and 29 PCR Allele Competitive Extension (PACE™) runs to analyze single nucleotide polymorphism (SNP) markers. Fifty-six percent of the data points were generated using the ABI 3500xL, while 44% were generated using an endpoint fluorescence platform (FLUOstar Omega SNP Reader) with PACE™ universal master mix. While developing new allele-specific SNP markers linked to the cooking quality gene Waxy and the rice blast disease resistance gene Pi-ta the molecular genetics lab also modified existing SNP markers linked to the traits of gelatinization temperature, aroma, and glabrous leaf and sheath. [ABSTRACT FROM AUTHOR]

Consumers in the United States are exploring new food products and enjoying the farm-to-table experience. Interest in aromatic rice has increased with the advent of nouveau cuisine and the 'identity preservation' ideals of the farm-to-table movement. Sales of aromatic rice have led rice imports to increase over 30% in the last ten years. The University of Arkansas System Division of Agriculture's Aromatic Rice Breeding Program at the Rice Research and Extension Center (RREC), Stuttgart, Arkansas, was implemented to develop aromatic rice varieties for the southern rice-producing regions. Evaluating cultural practices is essential for selecting advanced lines in the breeding program as well as for growers. Information regarding successful cultural practices of aromatic rice varieties is limited for the southern United States growing regions, and especially for Arkansas. [ABSTRACT FROM AUTHOR]