Abstract The southern United States is responsible for 80% of the country's production of rice, approximately half of which is exported. Understanding genotypic and environmental factors impacting the historical performance of rice (Oryza sativa L.) is important for directing research efforts to optimize production of this globally important crop. A set of 429 rice genotypes including globally diverse historical parents and advanced japonica breeding lines from southern US breeding programs was phenotyped in 2008 for eight agronomic traits in Arkansas, Louisiana, and Mississippi. They were also genotyped using a single‐nucleotide polymorphism set optimized for genomic prediction/selection. Genotypic and phenotypic data were analyzed via clustering techniques and principal component analysis. Single‐trait and multi‐trait genomic prediction were used to predict genetic values on a per‐plant basis. We found that contemporary germplasm from the southern state breeding programs was highly interrelated and distinct from progenitor indica and temperate japonica genotypes. Genomic predictive abilities were high and largely consistent across environments for seed number per panicle, tiller number, and plant height. Although predictive abilities were lower for seed weight per panicle, that trait was correlated with seed number per panicle (r = 0.919), and predictive ability was higher for both traits in a multi‐trait prediction framework. Furthermore, including data from the two major genotypic clusters identified herein had no penalty on genomic predictive ability. The data and analyses presented herein could inform future genomic and phenotypic investigations and applied breeding in the southern US rice germplasm pool.

Leaf sheath blight disease (SB) of rice caused by the soil-borne fungus Rhizoctonia solani results in 10-30% global yield loss annually and can reach 50% under severe outbreaks. Many disease resistance genes and receptor-like kinases (RLKs) are recruited early on by the host plant to respond to pathogens. Wall-associated receptor kinases (WAKs), a subfamily of receptor-like kinases, have been shown to play a role in fungal defense. The rice gene WAK91 (OsWAK91), co-located in the major SB resistance QTL region on chromosome 9, was identified by us as a candidate in defense against rice sheath blight. An SNP mutation T/C in the WAK91 gene was identified in the susceptible rice variety Cocodrie (CCDR) and the resistant line MCR010277 (MCR). The consequence of the resistant allele C is a stop codon loss, resulting in an open reading frame with extra 62 amino acid carrying a longer protein kinase domain and additional phosphorylation sites. Our genotype and phenotype analysis of the parents CCDR and MCR and the top 20 individuals of the double haploid SB population strongly correlate with the SNP. The susceptible allele T is present in the japonica subspecies and most tropical and temperate japonica lines. Multiple US commercial rice varieties with a japonica background carry the susceptible allele and are known for SB susceptibility. This discovery opens the possibility of introducing resistance alleles into high-yielding commercial varieties to reduce yield losses incurred by the sheath blight disease.

Abstract Awns are needle or bristle-like structures that grow at the tip of the lemma in rice grains. In cultivated rice, awnless material is preferred for agricultural and processing practices. Most cultivated rice produces no awns or very short awns, however, the causal genetic factors responsible for the loss of awns in cultivated rice remain largely unknown. Most studies conducted to investigate the genetic factors responsible for awn formation focused on plant material derived from crosses between awnless and wild awned parents. In this study, genetic analysis of awns was carried out using a breeding population developed from U.S. elite conventional and Provisia™ awnless parents. Before the use of indica germplasm and the Provisia™ technology, awns were not typically observed in the elite U.S. breeding material, where tropical japonica is predominant. We hypothesized that the presence of awns in populations derived from crosses with Provisia™ material was due to its indica background. We mapped a 1557 Kb awn-related region on chromosome 3 that appears to be a major source of awn formation when Provisia™ material (indica-type) is used for crossing with U.S. elite varieties. Two single nucleotide polymorphism (SNP) markers, SNP261 and SNP1251 explained 26% and 28% of the phenotypic variation in awn formation and elongation. Contingency analysis of F2, F2:3, and F3:4 generations showed that the awnless, short-awned, and low percentage of awns per panicle phenotype is explained by the presence of japonica alleles. When used together, these markers help differentiate awnless material.

‘PVL01’ (Reg. no. CV‐153, PI 682661), a Provisia (BASF) long‐grain rice (Oryza sativa L.) cultivar, was developed by the Louisiana State University Agricultural Center at the H. Rouse Caffey Rice Research Station (HRCRRS) near Crowley, LA, and approved for release by the director of the Louisiana Agricultural Experiment Station in 2017. PVL01 is the first rice cultivar to be released as part of the Provisia Rice System (BASF) with resistance to Provisia herbicide, containing the active ingredient quizalofop, an AACase (group 1) herbicide. PVL01 was derived from the cross ‘Cheniere’/BASF1‐5 that was made in 2012 at the HRCRRS and advanced in 2014 as an F2:F3 row based on agronomic characteristics. Testing in the Provisia Preliminary Yield (PVPY) trial in 2014 and the Provisia Multilocation Test in 2015 indicated good yield potential and favorable agronomic characteristics. In 2016 and 2017, PVL01 was evaluated in 14 replicated trials across seven locations in Louisiana. Four high‐yielding commercial cultivars were included as checks, ‘CL111’, ‘Cheniere’, ‘Cocodrie’, and ‘Mermentau’. Grain yield of PVL01 was 7.5 t ha−1 compared with 7.6 t ha−1 for CL111, 8.3 t ha−1 for Cheniere, 6.8 t ha−1 for Cocodrie, and 7.5 t ha−1 for Mermentau. PVL01 is very susceptible to blast, susceptible to sheath blight and bacterial panicle blight, and moderately resistant to Cercospora spp.

Provisia (TM) rice was developed recently by the BASF Corporation for control of grass weeds and is complementary to existing Clearfield (R) technology. Our previous research showed that resistance of Provisia (TM) rice to the acetyl coenzyme-A carboxylase herbicide quizalofop-p-ethyl (QPE) in laboratory and greenhouse environments is governed by a single dominant Mendelian gene. However, these results may not be consistent in different populations or field environments. Therefore, the first objective of the current research is to determine the inheritance of resistance to QPE in rice using different segregating populations evaluated under U.S. field environments. The second objective is to evaluate the response of QPE-resistant breeding lines to various herbicide concentrations at two U.S. locations. Chi-square tests of 12 F-2 populations evaluated in Louisiana during 2014 and 2015 indicated that QPE seedling resistance at 240 g ai ha(-1) was governed by a single dominant Mendelian gene with no observable maternal effects. Similar results were obtained in five F-3 populations derived from the aforementioned F-2 populations. Allele-specific SNP markers for QPE resistance also followed Mendelian segregation in the five F-2 populations. For the second objective, six QPE-resistant inbred lines showed transient leaf injury at 1x (120 g ai ha(-1)) or 2x (240 g ai ha(-1)) field rates 7 and 21 d after treatment (DAT). However, a trend of reduced injury (recovery) from 7 through 33 DAT was observed for all breeding material. No differences in grain yield were found between untreated QPE-resistant lines and those treated with 1x or 2x QPE field rate. Single gene inheritance and good levels of QPE herbicide field resistance in different genetic populations suggest feasibility for rapid and effective development of new QPE-resistant varieties and effective stewardship of the Provisia (TM) technology.

The BASF Corporation recently developed Provisia™ rice that is resistant to the ACCase inhibitor quizalofop-p-ethyl (QPE) for control of grassy weeds and that is complementary to the existing Clearfield® technology. The objective of this research was to determine the inheritance of resistance to QPE in different populations of rice evaluated under laboratory and greenhouse conditions. Five QPE-resistant lines and 13 susceptible U.S. varieties and breeding lines were used to develop 16 F1 populations that showed dominant gene control for QPE resistance in the greenhouse. Germinating seeds and young seedlings from 16 F2 and 12 BC1F1 populations, along with corresponding susceptible and resistant parents, were exposed to minimum lethal concentrations of QPE. The results indicated that resistance to QPE under the two environments was governed by a single dominant Mendelian gene with no observable maternal effects. Allele-specific SNP markers for QPE resistance were developed that also followed Mendelian segregation in four F2 and six BC1F1 populations. Results from this study have direct implications for breeding strategies of inbred and hybrids varieties resistant to QPE in the laboratory and greenhouse and for effective stewardship of the Provisia™ technology.

Two line hybrid rice (Oryza sativa L.) breeding uses environment-sensitive genic male sterile (EGMS) lines to produce sterile or fertile pollen depending on daylength and/or temperature. There is limited information on the performance and genetic control of EGMS lines under U.S. environments. Therefore, genetic characterization of two F2 and four BC1F2 populations derived from EGMS line 2009S was conducted under Louisiana field conditions. Chi squared analyses in the F2 and BC1F2 populations indicated that pollen sterility under high temperature and long daylength field conditions was controlled by a single recessive gene. Sequence comparisons at locus LOC_Os02g12290 between 2009S, CL161 (USDA-AMS 2002) and published sequences of G63S and Nipponbare revealed a single nucleotide polymorphism (SNP) that has been detected previously in several EGMS lines. Due to high GC content, a CEL1 nuclease assay was used to detect SNPs associated with pollen sterility in 177 F2 and 59 BC1F2 sampled individuals. A high percentage of lines (90–100%) across all segregating populations were identified correctly as pollen sterile using the CEL 1 assay. Results from this study suggest that single-gene control of pollen sterility in EGMS line 2009S will be compatible with a two-line system for U.S. hybrid rice development.

The initial discovery of cytoplasmic male sterile (CMS) three-line system made it possible to produce hybrids that significantly increase rice yields compared to its inbred counterparts. Further genetic and molecular studies help elucidate the mechanisms involved in CMS male sterility. Additional CMS types were also discovered with similar genetic control from wild sources by interspecific hybridization. While the three-line system was a success, the two line system using photoperiod genetic male sterile (PGMS), thermosensitive genetic male sterile (TGMS) and photoperiod and thermosensitive genetic male sterile (PTGMS) were becoming more popular due to the ease in breeding and with more hybrid combinations generated compared to the CMS types. Inheritance and molecular studies showed that the trait is controlled by one or more recessive genes depending on the genetic background and environmental conditions. Due to the sensitivity of the lines to temperature and/or photoperiod, unique breeding procedures were followed. Methods involved the use of growth chamber, timing of planting, and selection of suitable locations. These practices successfully maintained sterility for hybrid seed production or reversion to fertility for seed multiplication of parental male sterile lines.

Core Ideas Genomic data from diverse germplasm used for application in targeted breeding germplasm. Six SNPs identified that can characterize all haplotypes present at SD1 locus in diverse rice. Three alleles of the SD1 gene identified in US rice germplasm including two semidwarf alleles. Two SNPs identified and validated that differentiate the SD1 allele present in US germplasm. KASP assays designed for both SNPs for use in high‐throughput breeding applications. Plant height is an important target in US rice (Oryza sativa L.) breeding programs and the large effect of the sd1 semidwarf gene makes it a suitable target for marker‐assisted selection. Although the deletion underlying the semidwarf allele is known and a gel‐based DNA marker is available, this marker is not ideal for applied breeding because of throughput and cost constraints. The objectives of this study were to characterize the haplotype diversity at the SD1 locus within US rice germplasm and develop a single nucleotide polymorphism (SNP) assay for breeding applications. The International Rice Research Institute (IRRI) SNP‐Seek database was used to characterize the haplotype diversity present at the SD1 locus across a set of rice accessions and seven haplotypes were identified. The US rice germplasm was not well represented in the IRRI database, so a set of six SNPs was identified that could differentiate all detected haplotypes. These SNPs were designed into Kompetitive allele specific polymerase chain reaction (KASP) assays and screened across 359 elite US genotypes. Of the seven haplotypes, two were present within the US germplasm, one of which was the semidwarf deletion allele. A third haplotype was observed within the US medium‐grain germplasm and demonstrated to be a semidwarf allele derived from the induced mutation in the ‘Calrose76’. Two SNPs were identified that distinguish the three SD1 haplotypes present in the US germplasm. These SNPs were validated across the US germplasm and two biparental populations.

The genetic arms race between pathogen and host plant is a tug of war that has been ongoing for millennia. The “battles” are those of disruption, restoration of signaling and information transmission on a subcellular level. One such battle occurs between rice an important crop that feeds 50% of the world population and the sheath blight disease (SB) caused by the fungus Rhizoctonia solani . It results in 10□30% global yield loss annually and can reach 50% under severe outbreak. Many Receptor□like kinases (RLKs) are recruited as soldiers in these battles. Wall Associated Receptor Kinases (WAKs) a subfamily of receptor-like kinases have been shown to play a role in fungal defense. Here we show that rice gene OsWAK91 , present in the major SB resistance QTL region on Chromosome□9 is a key component in defense against rice sheath blight. An SNP mutation C/T separates susceptible variety, Cocodrie (CCDR) from the resistant line MCR010277 (MCR). The resistant allele C results in the stop codon loss that results in 68 amino acids longer C□terminus carrying longer protein kinase domain and phosphorylation sites. Our genotype and phenotype analysis of the top 20 individuals of the double haploid SB population shows a strong correlation with the SNP. The susceptible allele appears as a recent introduction found in the japonica subspecies reference genome and a majority of the tropical and temperate japonica lines sequenced by the 3000 rice genome project. Multiple US commercial varieties with japonica background carry the susceptible allele and are known for SB susceptibility. This discovery opens the possibility of introducing resistance alleles into high yielding commercial varieties to reduce yield losses incurred by the disease.

‘CL153’ (Reg. No. CV‐148, PI 677005), a Clearfield (BASF, Ludwigshafen, Germany) long‐grain rice (Oryza sativa L.) cultivar, was developed by the Louisiana State University Agricultural Center at the H. Rouse Caffey Rice Research Station (RRS) near Crowley, LA, and approved for release by the Director of the Louisiana Agricultural Experiment Station in 2015. CL153 was derived from the cross 9502008‐A//AR‐1188/‘Cocodrie’/3/CFX26/9702128/4/‘Cheniere’ that was made in 2011 at the RRS and advanced in 2013 as an F3 row selection based on agronomic characteristics. Testing in the Clearfield preliminary yield trials in 2013 indicated high yield potential and favorable agronomic characteristics. In 2013, 2014, and 2015, CL153 was evaluated in 23 replicated trials across six locations in Louisiana. Three high‐yielding, long‐grain, commercial cultivars, ‘CL111’, ‘CL151’, and ‘CL152’, were included as checks. Grain yield of CL153 was 9.1 t ha−1 compared with 8.5 t ha−1 for CL111, 9.4 t ha−1 for CL151, and 8.4 t ha−1 for CL152. Plant height for CL153 was 97 cm, which is equal to CL111 and CL151 and 2 cm shorter than CL152. CL153 reached 50% heading in 86 d, which was 4 d later than CL111, 1 d later that CL151, and 1 d earlier than CL152. The leaves, lemma, and palea of CL153 are glabrous, and the spikelet and apiculus are straw‐colored. CL153 is susceptible to sheath blight, moderately susceptible to bacterial panicle blight, Cercospora, and straighthead, and moderately resistant to blast.

Two‐line hybrid rice (Oryza sativa L.) breeding in the United States and China uses photoperiod/thermosensitive genetic male sterility (PTGMS) to produce lines with fertile or sterile pollen, depending on temperature and/or daylength. Although studied in China for >30 yr, genetic analysis of PTGMS in US environments is lacking. We therefore conducted genetic studies of male sterility over 3 yr in five F2 and BC1F2 populations derived from PTGMS line 2008S in Louisiana and Arkansas. Chi‐squared analyses in all populations indicated that sterility was controlled at both locations by two or three recessive genes. Inheritance and expression of PTGMS was found to be influenced by the particular combination of population and year (environment). Sequence comparisons of two regions in PTGMS loci LOC_Os07g12130 and LOC_Os12g36030 from six fertile and sterile lines revealed a diagnostic single‐nucleotide polymorphism (SNP) at each locus. Two‐way ANOVA in two F2 populations inferred that interaction of the two SNP‐containing regions contributed up to 65% variation for sterility in one Louisiana environment. Selective genotyping of the 2008S/CL131 F2 population detected new quantitative trait loci with R2 values ranging from 5 to 27% using single‐marker and composite‐interval mapping. Results from this study indicate that 2008S can be used as parental material for development of two‐line hybrids in Louisiana and Arkansas, but extensive testing of populations across years and locations will be required.

‘CL272’ (Reg. No. CV‐149, PI 677004), a Clearfield (BASF, Ludwigshafen, Germany) medium‐grain rice (Oryza sativa L.) cultivar, was developed by the Louisiana State University Agricultural Center at the H. Rouse Caffey Rice Research Station (RRS) near Crowley, LA, and approved for release by the Director of the Louisiana Agricultural Experiment Station in 2015. CL272 was derived from the cross ‘Neptune’//‘Bengal’/‘CL161’ that was made in 2009 at the RRS and advanced in 2011 as an F3 row selection. Testing in the Clearfield preliminary yield trials in 2012 indicated high yield potential and favorable agronomic characteristics. In 2013, 2014, and 2015, CL272 was evaluated in 30 replicated trials across six locations in Louisiana. Three high‐yielding, medium‐grain, commercial cultivars—‘CL271’, ‘CL261’, and ‘Jupiter’—were included as checks. Grain yield of CL272 was 9.1 t ha−1 compared with 9.3 t ha−1 for CL271, 8.2 t ha−1 for CL261, and 9.2 t ha−1 for Jupiter. Plant height for CL272 was 97 cm, which is equal to CL261 and 2 cm taller than CL271 and Jupiter. CL272 and CL271 reached 50% heading in 87 d, while CL261 reached 50% heading in 84 d and Jupiter in 88 d. The leaves, lemma, and palea of CL272 are glabrous, and the spikelet and apiculus are straw‐colored. CL272 is moderately resistant to Cercospora and moderately susceptible to bacterial panicle blight, sheath blight, blast disease, and straighthead disorder.

Current advances in sequencing technologies and bioinformatics revealed the genomic background of rice, a staple food for the poor people, and provided the basis to develop large genomic variation databases for thousands of cultivars. Proper analysis of this massive resource is expected to give novel insights into the structure, function, and evolution of the rice genome, and to aid the development of rice varieties through marker assisted selection or genomic selection. In this work we present sequencing and bioinformatics analyses of 104 rice varieties belonging to the major subspecies of Oryza sativa. We identified repetitive elements and recurrent copy number variation covering about 200 Mbp of the rice genome. Genotyping of over 18 million polymorphic locations within O. sativa allowed us to reconstruct the individual haplotype patterns shaping the genomic background of elite varieties used by farmers throughout the Americas. Based on a reconstruction of the alleles for the gene GBSSI, we could identify novel genetic markers for selection of varieties with high amylose content. We expect that both the analysis methods and the genomic information described here would be of great use for the rice research community and for other groups carrying on similar sequencing efforts in other crops.

Giant Salvinia (Salvinia molesta Mitchell) is a floating aquatic fern introduced from South America whose rapid growth impairs health of plants and animals in lakes, rivers, and bayous in various southern U.S. states. To assist in development of long-term control strategies, we examined in 2009 the range of diversity at the whole-plant and molecular level within and across six populations of S. molesta in Louisiana and Texas. Significant variation was observed for all five morphological traits measured both within and across collection sites. Root length was moderately associated with colony width, rhizome length, and leaf width when averaged across sites, but not when each location was evaluated separately. Cluster analysis revealed that S. molesta could be grouped into three to five distinct groups depending on the trait under consideration. Fruiting bodies (sporocarps) were observed only at one south Louisiana location. The salvinia weevil, Cyrtobagous salviniae Calder & Sands, was not found at any location during this study. Analysis of Molecular Variance of AFLP markers and DNA sequence analysis of the gapCp gene showed that the majority of molecular variation was detected within populations (87-93%) compared to diversity among populations (7-13%). Location (environment) was considered to be the most important source of variation for all measured traits. Principal Component Analysis (PCA) of AFLP and gapCp data revealed distinct clusters comprised of members across different collection sites. Although substantial morphological and molecular variations were detected both within and among populations, all data from this study suggested that these six populations were derived originally from the same clonal or related populations. (C) 2015 Elsevier B.V. All rights reserved.

Most agronomically important traits, including resistance against pathogens, are governed by quantitative trait loci (QTL). QTL-mediated resistance shows promise of being effective and long-lasting against diverse pathogens. Identification of genes controlling QTL-based disease resistance contributes to breeding for cultivars that exhibit high and stable resistance. Several defense response genes have been successfully used as good predictors and contributors to QTL-based resistance against several devastating rice diseases. In this study, we identified and characterized a rice (Oryza sativa) mutant line containing a 750 bp deletion in the second exon of OsPAL4, a member of the phenylalanine ammonia-lyase gene family. OsPAL4 clusters with three additional OsPAL genes that co-localize with QTL for bacterial blight and sheath blight disease resistance on rice chromosome 2. Self-pollination of heterozygous ospal4 mutant lines produced no homozygous progeny, suggesting that homozygosity for the mutation is lethal. The heterozygous ospal4 mutant line exhibited increased susceptibility to three distinct rice diseases, bacterial blight, sheath blight, and rice blast. Mutation of OsPAL4 increased expression of the OsPAL2 gene and decreased the expression of the unlinked OsPAL6 gene. OsPAL2 function is not redundant because the changes in expression did not compensate for loss of disease resistance. OsPAL6 co-localizes with a QTL for rice blast resistance, and is down-regulated in the ospal4 mutant line; this may explain enhanced susceptibility to Magnoporthe oryzae. Overall, these results suggest that OsPAL4 and possibly OsPAL6 are key contributors to resistance governed by QTL and are potential breeding targets for improved broad-spectrum disease resistance in rice.

'CL271' (Reg. No. CV-147, PI 672550), a Clearfield (BASF, Ludwigshafen, Germany) medium-grain rice (Oryza sativa L.) cultivar, was developed by the Louisiana State University Agricultural Center at the Rice Research Station near Crowley, LA, and approved for release by the director of the Louisiana Agricultural Experiment Station in 2011. CL271 was derived from the cross 'Neptune'//'Bengal'//'CL161' made in 2009 and advanced in 2011 as an F-2:3 bulked selection. Testing in the Clearfield preliminary yield trial in 2011 indicated high yield potential and favorable agronomic characteristics. In 2012 and 2013, CL271 was evaluated in 11 statewide yield performance trials, along with check cultivars 'CL261', 'Caffey', and 'Jupiter'. Grain yield of CL271 was 10.2 Mg ha(-1) compared with 9.0, 8.4, and 9.2 Mg ha(-1) for CL261, Caffey, and Jupiter, respectively. Plant height for CL271 was 97 cm compared with 99 cm for CL261, Caffey, and Jupiter. CL271 reached 50% heading in 90 d, whereas CL261 reached 50% heading in 87 d, and Caffey and Jupiter in 92 d. CL271 has a semi-erect flag leaf, and the leaves are dark green and display an intermediate leaf angle. The lemma and palea are straw-colored and glabrous, and the apiculus, light purple at heading, is colorless as the grain approaches harvest maturity. CL271 is resistant to blast disease (caused by Magnaporthe grisea), moderately susceptible to sheath blight (caused by Rhizoctonia solani), and susceptible to bacterial panicle blight (caused by Burkholderia spp.).

'CL152' (Reg. No. CV-141; PI 666059), a Clearfield (BASF, Ludwigshafen, Germany) long-grain rice (Oryza sativa L.) cultivar, was developed by the Louisiana State University Agricultural Center at the Rice Research Station near Crowley, LA, and approved for release by the director of the Louisiana Agricultural Experiment Station in 2011. CL152 was derived from the cross TACAURI/3/CYPRESS//L-202/TEBONNET/4/CL161 that was made in 2003 at the Rice Research Station. CL152 originated in 2005 as an F-2:3 line selected based on agronomic characteristics. Testing in the Clearfield preliminary yield trials in 2010 indicated high yield potential and favorable agronomic characteristics. In 2009 and 2010, CL152 was evaluated in 38 statewide yield performance trials, along with two, high-yielding Clearfield check cultivars, 'CL111' and 'CL151.' Grain yield of CL152 was 8.7 Mg ha(-1) compared with 8.7 and 9.2 Mg ha(-1) for CL111 and CL151, respectively. Plant height for CL152 was 101 cm compared with 101 cm and 100 cm for CL111 and CL151, respectively. CL152 reached 50% heading in 83 d while CL111 reached 50% heading in 77 d and CL151 in 81 d. CL152 has a semi-erect flag leaf, and the leaves are dark green and display an intermediate leaf angle. The lemma and palea are straw-colored and glabrous, and the apiculus, light purple at heading, is colorless as the grain approaches harvest maturity. CL152 is susceptible to sheath blight disease, moderately resistant to blast disease and moderately resistant to straighthead disorder.

'Mermentau' (Reg. No. CV-144, PI 665688), a conventional long-grain rice (Oryza sativa L.) cultivar, developed by the Louisiana State University Agricultural Center at the Rice Research Station near Crowley, LA, and approved for release by the director of the Louisiana Agricultural Experiment Station in 2012. Mermentau was derived from the cross AR 1188/Cocodrie//9502008/LaGrue, made in 2001 at the Rice Research Station. Mermentau originated in 2005 as an F-2:4 selected line based on height, maturity, grain yield, and gain quality. In 2010, 2011, and 2012, Mermentau was evaluated in 27 statewide yield performance trials, along with two, high-yielding conventional check cultivars, 'Catahoula' and 'Cheniere'. Grain yield of Mermentau was 7.4 Mg ha(-1) compared with 7.7 Mg ha(-1) for both Catahoula and Cheniere. Plant height for Mermentau, Catahoula, and Cheniere was 94.0 cm. Mermentau reached 50% heading in 82 d while Catahoula reached 50% heading in 83 d and Cheniere in 82 d. Mermentau has a semierect flag leaf, and the leaves are dark green and display an intermediate leaf angle. The lemma and palea are straw colored and glabrous, and the apiculus, light purple at heading, is colorless as the grain approaches harvest maturity. Mermentau is susceptible to rice sheath blight [caused by Rhizoctonia solani Kuhn AG1-1A; teleomorph: Thanatephorus cucumeris (A. B. Frank) Donk.] and bacterial panicle blight (caused by Burkholderia spp.) and moderately susceptible to straighthead disorder and blast [caused by Magnaporthe grisea (T.T. Hebert)].