HomePlant DiseaseVol. 103, No. 7First Report of Cotton Leafroll Dwarf Virus Infecting Cotton in Georgia, U.S.A. Previous DISEASE NOTESFirst Report of Cotton Leafroll Dwarf Virus Infecting Cotton in Georgia, U.S.A.A. Tabassum, S. Bag, P. Roberts, N. Suassuna, P. Chee, J. R. Whitaker, K. N. Conner, J. Brown, R. L. Nichols, and R. C. KemeraitA. TabassumDepartment of Plant Pathology, The University of Georgia, Tifton, GA 31793, U.S.A.Search for more papers by this author, S. Bag†Corresponding author: S. Bag; E-mail Address: [email protected]http://orcid.org/0000-0003-3724-7341Department of Plant Pathology, The University of Georgia, Tifton, GA 31793, U.S.A.Search for more papers by this author, P. RobertsDepartment of Entomology, The University of Georgia, Tifton, GA 31793, U.S.A.Search for more papers by this author, N. SuassunaEmbrapa Algodão, 75375-000 Santo Antônio de Goiás, GO, BrazilSearch for more papers by this author, P. CheeDepartment of Crops and Soil Science, The University of Georgia, Tifton, GA 31793, U.S.A.Search for more papers by this author, J. R. WhitakerDepartment of Crops and Soil Science, The University of Georgia, Tifton, GA 31793, U.S.A.Search for more papers by this author, K. N. ConnerAlabama Cooperative Extension System, Auburn University, Auburn, AL 36849, U.S.A.Search for more papers by this author, J. BrownSchool of Plant Science, University of Arizona Tucson, AZ 85721, U.S.A.Search for more papers by this author, R. L. NicholsCotton Inc., Cary, NC 27513, U.S.A.Search for more papers by this author, and R. C. KemeraitDepartment of Plant Pathology, The University of Georgia, Tifton, GA 31793, U.S.A.Search for more papers by this authorAffiliationsAuthors and Affiliations A. Tabassum1 S. Bag1 † P. Roberts2 N. Suassuna3 P. Chee4 J. R. Whitaker4 K. N. Conner5 J. Brown6 R. L. Nichols7 R. C. Kemerait1 1Department of Plant Pathology, The University of Georgia, Tifton, GA 31793, U.S.A. 2Department of Entomology, The University of Georgia, Tifton, GA 31793, U.S.A. 3Embrapa Algodão, 75375-000 Santo Antônio de Goiás, GO, Brazil 4Department of Crops and Soil Science, The University of Georgia, Tifton, GA 31793, U.S.A. 5Alabama Cooperative Extension System, Auburn University, Auburn, AL 36849, U.S.A. 6School of Plant Science, University of Arizona Tucson, AZ 85721, U.S.A. 7Cotton Inc., Cary, NC 27513, U.S.A. Published Online:2 May 2019https://doi.org/10.1094/PDIS-12-18-2197-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat During the 2018 growing season, cotton plants in several fields in Georgia were observed with symptoms that included leaf curling, reddening and drooping of leaves, subsequent distortion of leaf growth above the nodes where reddened leaves were first observed, and shortening of upper internodes and their discoloration to deep green. These symptoms were visible in the upper portion of the plants, resembling “cotton blue” disease caused by cotton leafroll dwarf virus (CLRDV) (family Luteoviridae, genus Polerovirus). The symptoms were observed sporadically with less than 10% disease incidence within affected fields. CLRDV is a phloem-limited virus with single-stranded, positive-sense RNA genome, transmitted by aphids (Aphis gossypii) in a persistent, circulative, nonpropagative manner (Distéfano et al. 2010; Sharman et al. 2015). A total of 93 symptomatic and asymptomatic leaves and petioles were collected from several different commercial cotton fields in the southern part of the state. Total RNA was extracted using the modified cetyltrimethylammonium bromide method (Sharman et al. 2015). Complementary DNA (cDNA) was synthesized from 2.5 µg of total RNA using Superscript III reverse transcription (Invitrogen, U.S.A.) and specific reverse primers targeting different open reading frames (ORFs) of the virus genome. The cDNA was used for polymerase chain reaction (PCR) with primers CLRDV3675F and Pol3982R targeting ORF 3 of the virus (310-bp product, Sharman et al. 2015) and primers 17 and 18 targeting ORF 5 (1,065-bp product, Distéfano et al. 2010). A new set of primers, SB11F (5′-AGGTTTTCTGGTAGCAGTACCAATATCAACGTTA-3′) and SB11R (5′-TATCTTGCATTGTGGATTTCCCTCATAA-3′), was developed to amplify the 803-bp fragment spanning complete ORF 3 and ORF 4, encoding virus coat protein and movement protein genes. Using the three different sets of primers, products of predicted sizes were amplified from the symptomatic tissues, but not from asymptomatic tissues collected from fields and negative controls including asymptomatic leaves from plants grown in an insect-free controlled growth chamber and DNase/RNase free water (Invitrogen). Reverse transcription PCR products were gel purified, cloned into TOPO-TA cloning vector (Invitrogen), and sequenced using Sanger sequencing (GeneScript, NJ). The consensus sequence of three clones for ORF 3 and 4 from this study (MK290759 and MK290760) when analyzed using NCBI-BLASTn showed 97% sequence identity with the Brazilian and Argentinean isolates (KF906261.1 and KF359947.1, respectively) and many other isolates from South American and Asian countries. ORF 3 and 4 sequences from Georgia shared 98 to 99% identity among themselves. The partial sequences for ORF 5 (MK513938 and MK513939) shared 95% identity with the isolate from Argentina (KF359946.1 and KF359947.1). The presence of the virus was detected in all the symptomatic samples collected from 14 counties in Georgia, covering the entire cotton growing region of the state. To the best of our knowledge, this is the first report of CLRDV in Georgia, U.S.A. CLRDV infection of cotton has been reported in other cotton-growing regions in Africa, Asia, South America, and, more recently, in Alabama, U.S.A. (Avelar et al. 2018; Corrêa et al. 2005; Distéfano et al. 2010; Mukherjee et al. 2012). With its rapid spread, this virus could pose an imminent threat and cause severe economic losses to the cotton industry. Further research is needed to elucidate epidemiology, symptomatology, vector transmission, and crop losses owing to CLRDV in the United States.The author(s) declare no conflict of interest.References:Avelar, S., et al. 2018. Plant Dis. 103:592. Link, ISI, Google ScholarCorrêa, R., et al. 2005. Arch. Virol. 150:1357. Crossref, ISI, Google ScholarDistéfano, A. J., et al. 2010. Arch. Virol. 155:1849. Crossref, ISI, Google ScholarMukherjee, A. K., et al. 2012. New Dis. Rep. 25:22. Crossref, Google ScholarSharman, M., et al. 2015. Australas. Plant Dis. Notes 10:24. Crossref, ISI, Google ScholarA. Tabassum and S. Bag contributed equally.The author(s) declare no conflict of interest.Funding: The authors acknowledge the funding and support provided by Hatch Act and State of Georgia funding, Georgia Cotton Commission (project number 18-101GCC), and Cotton Incorporated (project number 18-780).DetailsFiguresLiterature CitedRelated Vol. 103, No. 7 July 2019SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionApple cultivar Joya Cripps Red lesions caused by Colletotrichum fructicola (Nodet et al.). Photo credit: P. Nodet. Symptoms of Lotus powdery mildew caused by Erysiphe takamatsui (Zhou et al.). Photo credit: C. Liang. Symptoms of tar spot (Phyllachora maydis) on maize leaves (Dalla Lana et al.). Photo credit: F. Dalla Lana. Metrics Article History Issue Date: 20 Jun 2019Published: 2 May 2019First Look: 4 Mar 2019Accepted: 24 Feb 2019 Page: 1803 Information© 2019 The American Phytopathological SocietyFundingHatch Act and State of Georgia fundingGeorgia Cotton CommissionGrant/Award Number: project number 18-101GCCCotton IncorporatedGrant/Award Number: project number 18-780Keywordscotton blue diseasecotton leafroll dwarf virusatypicalGeorgiacottonThe author(s) declare no conflict of interest.Cited byDifferential sensitivities of photosynthetic component processes govern oxidative stress levels and net assimilation rates in virus-infected cotton20 July 2023 | Photosynthesis Research, Vol. 158, No. 1Analysis of Cotton Leafroll Dwarf Virus P0 Gene Sequences from South Carolina Reveals Low Variability Among IsolatesWilliam W. 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Historically, the primary objective of cotton (Gossypium hirsutum L.) breeding programs was to improve the quantity and quality of cotton fiber. Because of the added value of cottonseed and its many uses, including a feed and human food source, there is interest in developing cotton breeding programs that focus improvement efforts simultaneously on cotton fiber and seed. Genetic analysis of cottonseed traits, such as protein and oil, is a prerequisite to building new joint fiber and seed cotton breeding programs. In this study, we conducted a genetic analysis of a diverse set of elite upland cotton germplasm for cottonseed protein and oil. Environment was responsible for a sizeable portion of the total variation for protein and oil, and genetics accounted for a larger portion of variation for oil than protein. Genotype × environment (G × E) interactions significantly impacted oil but not protein. Genotypic correlation analysis found a strong, negative relationship between protein and oil. Positive genotypic correlations were found for protein and several agronomic traits including lint yield; whereas, negative correlations were found between oil and lint yield along with other agronomic traits. Overall, results showed very little association between protein, oil, and fiber quality traits. These findings indicate that altering protein and oil seed composition will impact yield and yield component traits. However, alterations in seed composition should not impact fiber quality.

ABSTRACTGenotype × environment (G × E) interactions and trait correlations significantly impact efforts to develop high‐yield, high‐quality, and environmentally stable Upland cotton (Gossypium hirsutum L.) cultivars. Knowledge of both can and should be used to design optimal breeding programs and effective selection criteria. In this study, we examined the G × E interactions and trait correlations present in the 70‐yr Pee Dee cotton germplasm enhancement program. Since beginning in 1935, the Pee Dee program has employed a variety of unique germplasm and breeding methods to release >80 improved germplasm lines and cultivars. Results suggest that significant G × E interactions exist for several agronomic and fiber quality performance traits that are mostly due to changes in magnitude. Negative genotypic correlations still persist between lint percent/lint yield and fiber length/fiber strength. However, apparently the breeding methods and selection criteria used over 70 yr have lessened the negative relationship between agronomic performance and fiber quality over time to some degree. The results provide cotton breeders a resource to select specific Pee Dee germplasm lines for increased environmental stability. Cotton breeders can also use the information herein to select specific Pee Dee germplasm lines that represent rare recombination events that combine high yield and fiber quality potential.

To explore types, levels and patterns of genetic divergence among diploid Gossypium (cotton) genomes, 780 cDNA, genomic DNA and simple sequence repeat (SSR) loci were re-sequenced in G o ssypium herbaceum (A1 genome), G. arboreum (A2), G. raimondii (D5), G. trilobum (D8), G. sturtianum (C1) and an outgroup, Gossypioides kirkii . Divergence among these genomes ranged from 7.32 polymorphic base pairs per 100 between G. kirkii and G. herbaceum (A1) to only 1.44 between G . herbaceum (A1) and G. arboreum (A2). SSR loci are least conserved with 12.71 polymorphic base pairs and 3.77 polymorphic sites per 100 base pairs, whereas expressed sequence tags are most conserved with 3.96 polymorphic base pairs and 2.06 sites. SSR loci also exhibit the highest percentage of ‘extended polymorphisms’ (spanning multiple consecutive nucleotides). The A genome lineage was particularly rapidly evolving, with the D genome also showing accelerated evolution relative to the C genome. Unexpected asymmetry in mutation rates was found, with much more transition than transversion mutation in the D genome after its divergence from a common ancestor shared with the A genome. This large quantity of orthologous DNA sequence strongly supports a phylogeny in which A–C divergence is more recent than A–D divergence, a subject that is of much importance in view of A–D polyploid formation being key to the evolution of the most productive and finest-quality cottons. Loci that are monomorphic within A or D genome types, but polymorphic between genome types, may be of practical importance for identifying locus-specific DNA markers in tetraploid cottons including leading cultivars.

One of the most significant, long‐term public U.S. Upland cotton ( Gossypium hirsutum L.) germplasm enhancement programs is known as the Pee Dee germplasm program. The unique, genetic foundation of the Pee Dee germplasm was created using germplasm from Upland, Sea Island ( Gossypium barbadense L.), and primitive diploid cottons. Since the program's inception in 1935, the Pee Dee germplasm program has released >80 improved germplasm lines and cultivars. In this study, the agronomic and fiber quality performance of Pee Dee germplasm was evaluated across southeastern U.S. environments to estimate genetic improvement within the Pee Dee germplasm program. Results suggest that the Pee Dee germplasm enhancement program has (i) maintained usable genetic variation and (ii) maintained high fiber quality potential while concomitantly improving agronomic performance. Although the results highlight the need to continue improving lint percent, lint yield, and bolls m −2 , there is also evidence to suggest that Pee Dee germplasm can continue being utilized to develop the next generation of high‐fiber‐quality and high‐yielding cotton cultivars.

Few sources of resistance to root-knot nematodes (Meloidogyne incognita) in upland cotton (Gossypium hirsutum) have been utilized to develop resistant cultivars, making this resistance vulnerable to virulence in the pathogen population. The objectives of this study were to determine the inheritance of resistance in five primitive accessions of G. hirsutum (TX1174, TX1440, TX2076, TX2079, and TX2107) and to determine allelic relations with the genes for resistance in the genotypes Clevewilt-6 (CW) and Wild Mexico Jack Jones (WMJJ). A half-diallel experimental design was used to create 28 populations from crosses among these seven sources of resistance and the susceptible cultivar DeltaPine 90 (DP90). Resistance to M. incognita was measured as eggs per g roots in the parents, F(1) and F(2) generations of each cross. The resistance in CW and WMJJ was inherited as recessive traits, as reported previously for CW, whereas the resistance in the TX accessions was inherited as a dominant trait. Chi square analysis of segregation of resistance in the F(2) was used to estimate the numbers of genes that conditioned resistance. Resistance in CW and WMJJ appeared to be a multigenic trait whereas the resistance in the TX accessions best fit either a one or two gene model. The TX accessions were screened with nine SSR markers linked to resistance loci in other cotton genotypes. The TX accessions lacked the allele amplified by SSR marker CR316 and linked to resistance in CW and other resistant genotypes derived from this source. Four of five TX genotypes lacked the amplification products from the marker BNL1231 that is also associated with the resistant allele on Chromosome 11 in WMJJ, CW, NemX, M120 RNR and Auburn 634 RNR. However, all five TX genotypes produced the same amplification products from three SSR markers linked to the resistant allele on Chromosome 14 in M120 RNR and M240 RNR. The TX accessions have unique resistance genes that are likely to be useful in efforts to develop resistant cotton cultivars with increased durability.

The upland cotton (Gossypium hirsutum L.) germplasm line CRB 252 (Reg. No GP‐925, PI 658596) was developed, evaluated, and jointly released in 2009 by the USDA‐ARS, the Louisiana Agricultural Experiment Station, the Georgia Agricultural Experiment Station, and Cotton Incorporated. The purpose of the release was to provide a broadly adapted, high fiber‐quality resource for facilitating fiber improvement efforts across the U.S. Cotton Belt. CRB 252 originated from the cross ‘Suregrow 248’/‘Phytogen 72’//‘Stoneville 474’/‘Acala Maxxa’, followed by individual plant selection in the F2 and F3 generations at the low‐desert location of Maricopa, AZ and F3.5 progeny selection at five locations distributed across the Cotton Belt. Evaluation of CRB 252 occurred in 13 location‐year environments at Florence, SC; Blackville, SC; Tifton, GA; Plains, GA; Alexandria, LA; Maricopa, AZ; and Shafter, CA in 2007 and 2008. CRB 252 displayed fiber length and micronaire values superior to those of the high fiber‐quality check cultivars Phytogen 72 and FM 958. The fiber strength and short‐fiber content of CRB 252 was superior to those of FM 958. Lint yield of CRB 252 was superior to that of Phytogen 72 and did not differ from FM 958. CRB 252 is an excellent source of quality fiber, with acceptable yield potential that appears to be stable across production environments.

The National Plant Germplasm System (NPGS) is a cooperative effort among State, Federal and Private organizations aimed at preserving one of agriculture’s greatest assets: plant genetic diversity. The NPGS serves the scientific community by collecting, storing, and distributing germplasm as well as maintaining a searchable database of trait descriptors. Serving the NPGS, a Crop Germplasm Committee (CGC) is elected for each crop and is comprised of a group of scientists concerned with development, maintenance, characterization, and utilization of germplasm collections. Each CGC serves in an advisory role and provides a status report every seven years to determine scientific efforts, adequacy of germplasm base representation, and progress in breeding through utilization of germplasm. In addition, each committee can call attention to areas of concerns regarding facilities and staffing associated with the maintenance, collection, and taxonomic activities for a specific crop within the system. The following report was developed by the CGC for cotton and provides a record of collections, activities, concerns, crop vulnerabilities, and recommendations associated with the cotton collection for the period 1997–2005. Information provided within this document is a much expanded and detailed description of a report provided to the NPGS and includes the most exhaustive citation of germplasm depositions and research activity descriptions available anywhere in the USA for this time period. This documentation will be a valuable resource to breeders, geneticists, and taxonomists with an interest in this important food and fiber crop.

Knowledge of genetic diversity and relationships among breeding materials is essential to the improvement of crop species. Genetic similarity estimates among cultivars are helpful to select parental combinations for segregating populations so as to maintain genetic diversity in a breeding program. The objective of this study was to determine the correspondence between pedigree‐ and restriction fragment length polymorphism–based genetic similarity (RFLP‐GS) estimates for a set of 36 Upland cotton (Gossypium hirsutum L.) cultivars. Coefficients of parentage (COPs) and genetic similarity estimates based on 261 codominant RFLP markers for all possible pairs of cultivars were compared. A significant though moderate association (r = 0.41, P < 0.001) was detected between the COP and RFLP‐GS matrices. Spearman's rank correlation for the 142 pairs of related cultivars (COP ≥ 0.1) was somewhat higher (rS = 0.53, P < 0.001). There was a significant linear relationship between COP and RFLP‐GS for the pairs of related cultivars; however, the coefficient of determination was low (R2 = 0.25), indicating that the COP only explained a small portion of the variation observed for RFLP‐GS. COP and RFLP‐GS estimate different types of genetic resemblance; however, the moderate association may have also resulted from violations to the assumptions made when computing COP. RFLP‐GS is a more accurate estimate of true genetic resemblance among cotton cultivars. Nevertheless, the pedigree‐ and RFLP‐based dendrograms were somewhat similar, suggesting that pedigree information will continue to be useful to inexpensively identify diverse parents in a breeding program.