Rotation of Cotton (Gossypium hirsutum) Cultivars and Fallow on Yield and Rotylenchulus reniformis.

A three-year rotation of cotton (Gossypium hirsutum) cultivars either resistant (R) or susceptible (S) to Rotylenchulus reniformis and fallow (F) was examined for effect on cotton yield and nematode density. In year 1, 2, and 3, the resistant cultivar (DP 2143NR B3XF) yielded 78, 77, and 113% higher than the susceptible cultivar (DP 2044 B3XF). Fallow in year 1 followed by S in year 2 (F1S2) improved yield in year 2 by 24% compared with S1S2, but not as much as R1S2 (41% yield increase over S1S2). One year of fallow followed by R (F1R2) had lower yield in year 2 (11% reduction) than R1R2. The highest yield after three years of these rotations occurred with R1R2R3, followed by R1S2R3 (17% less yield) and F1F2S3 (35% less yield). Rotylenchulus reniformis density in soil averaged 57, 65, and 70% lower (year 1, 2, 3, respectively) in R1R2R3 compared with S1S2S3. In years 1 and 2, LOG10 transformed nematode density (LREN) was lower in F1, and F1F2, than for all other combinations. In year 3, the lowest LREN were associated with R1R2R3, F1S2F3, and F1F2S3. The highest LREN were associated with F1R2S3, F1S2S3, S1S2S3, R1R2S3, and R1S2S3. The combination of higher yield and lower nematode density will be a strong incentive for producers to use the R. reniformis resistant cultivars continuously.

Mapping of dynamic QTLs for resistance to Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 in a backcross inbred line population of Upland cotton.

KEY MESSAGE: A backcross inbred line population of cotton was evaluated for Fusarium wilt race 4 resistance at different days after inoculation (DAI). Both constitutively expressed and developmentally regulated QTLs were detected. The soil-borne fungus Fusarium oxysporum f. sp. vasinfectum (FOV) race 4 (FOV4) causes Fusarium wilt including seedling mortality in cotton. A backcross inbred line (BIL) population of 181 lines, derived from a bi-parental cross of moderately resistant non-recurrent Hai 7124 (Gossypium barbadense) and recurrent parent CCRI 36 (G. hirsutum), was evaluated under temperature-controlled conditions for FOV4 resistance with artificial inoculations. Based on three replicated tests evaluated at 7, 14, 21, and 28 days after inoculation (DAI), only 2-5 BILs showed lower disease severity ratings (DSR) than the parents while 22-50 BILs were more susceptible, indicating transgressive segregation toward susceptibility. Although DSR were overall congruent between DAI, there were many BILs displaying different responses to FOV4 across DAI. Genetic mapping using 7709 SNP markers identified 42 unique QTLs for four evaluation parameters- disease incidence (DI), DSR, mortality rate (MR), and area under disease progress curve (AUDPC), including 26 for two or more parameters. All five QTLs for AUDPC were co-localized with QTLs for DI, DSR, and/or MR at one or two DAI, indicating the unnecessary use of AUDPC in QTL mapping for FOV4 resistance. Those common QTLs explained the significant positive associations between parameters observed. Ten common QTLs with negative or positive additive effects were detected between DAI. DAI-specific and consistent QTLs were detected between DAI in cotton for the first time, suggesting the existence of both constitutively expressed and developmentally regulated QTLs for FOV4 resistance and the importance of evaluating genetic populations for FOV4 resistance at different growth stages.

Effects of Fusarium Wilt on Cotton Cultivars with and without Meloidogyne Incognita Resistance in Fields.

Cotton (Gossypium hirsutum) cultivar trials were conducted in four fields (6 trials total) with Meloidogyne incognita (Mi)/Fusarium oxysporum f. sp. vasinfectum (Fov) from 2019 to 2021. Cotton cultivars were divided into groups based on company/Mi resistance: S = susceptible to Mi; R-FM, R-DP, and R-PHY = resistance to Mi in FiberMax®, Deltapine®, and Phytogen® cultivars, respectively; ST 4946GLB2 (moderate resistance to Mi and observed field tolerance to Fov); and ST 5600B2XF (resistance to Mi). The S and R-FM groups had the highest transformed Mi densities LOG10(Mi + 1) (LMi = 3.22 and 3.01, respectively), while R-DP and R-PHY had the lowest LMi (2.21 and 1.85, respectively). Plant mortality (%) was higher for R-DP (28.1%) than for all other groups except ST 5600B2XF (24.8%). Mi-susceptible cultivars averaged 23.3% mortality. Relative yield (0-1 scale) was higher for ST 4946GLB2 (0.706) and R-PHY (0.635) than for R-DP (0.530), ST 5600B2XF (0.578), and S (0.491). All groups except R-DP averaged higher relative yield than the susceptible cultivars. ST 4946GLB2 had the lowest mortality (16.5%) and highest relative yield, while R-DP cultivars had the highest mortality and no difference in relative yield from the Mi-susceptible cultivars. The group of R-DP cultivars had excellent Mi resistance but were susceptible to Fov. No cultivars were identified with high resistance to Fov.

Evaluation and genome-wide association study of resistance to bacterial blight race 18 in U.S. Upland cotton germplasm.

Bacterial blight (BB), caused by Xanthomonas citri pv. malvacearum (Xcm), is a destructive disease to cotton production in many countries. In the U.S., Xcm race 18 is the most virulent and widespread race and can cause serious yield losses. Planting BB-resistant cotton cultivars is the most effective method of controlling this disease. In this study, 335 U.S. Upland cotton accessions were evaluated for resistance to race 18 using artificial inoculations by scratching cotyledons on an individual plant basis in a greenhouse. The analysis of variance detected significant genotypic variation in disease incidence, and 50 accessions were resistant including 38 lines with no symptoms on either cotyledons or true leaves. Many of the resistant lines were developed in the MAR (multi-adversity resistance) breeding program at Texas A&M University, whereas others were developed before race 18 was first reported in the U.S. in 1973, suggesting a broad base of resistance to race 18. A genome-wide association study (GWAS) based on 26,301 single nucleotide polymorphic (SNP) markers detected 11 quantitative trait loci (QTL) anchored by 79 SNPs, including three QTL on each of the three chromosomes A01, A05 and D02, and one QTL on each of D08 and D10. This study has identified a set of obsolete Upland germplasm with resistance to race 18 and specific chromosomal regions delineated by SNPs for resistance. The results will assist in breeding cotton for BB resistance and facilitate further genomic studies in fine mapping resistance genes to enhance the understanding of the genetic basis of BB resistance in cotton.

A nonproteinaceous Fusarium cell wall extract triggers receptor-like protein-dependent immune responses in Arabidopsis and cotton.

Fusarium wilt caused by the ascomycete fungus Fusarium oxysporum is a devastating disease of many economically important crops. The mechanisms underlying plant responses to F. oxysporum infections remain largely unknown. We demonstrate here that a water-soluble, heat-resistant and nonproteinaceous F. oxysporum cell wall extract (FoCWE) component from multiple F. oxysporum isolates functions as a race-nonspecific elicitor, also termed pathogen-associated molecular pattern (PAMP). FoCWE triggers several demonstrated immune responses, including mitogen-activated protein (MAP) kinase phosphorylation, reactive oxygen species (ROS) burst, ethylene production, and stomatal closure, in cotton and Arabidopsis. Pretreated FoCWE protects cotton seeds against infections by virulent F. oxysporum f. sp. vasinfectum (Fov), and Arabidopsis plants against the virulent bacterium, Pseudomonas syringae, suggesting the potential application of FoCWEs in crop protection. Host-mediated responses to FoCWE do not appear to require LYKs/CERK1, BAK1 or SOBIR1, which are commonly involved in PAMP perception and/or signalling. However, FoCWE responses and Fusarium resistance in cotton partially require two receptor-like proteins, GhRLP20 and GhRLP31. Transcriptome analysis suggests that FoCWE preferentially activates cell wall-mediated defence, and Fov has evolved virulence mechanisms to suppress FoCWE-induced defence. These findings suggest that FoCWE is a classical PAMP that is potentially recognised by a novel pattern-recognition receptor to regulate cotton resistance to Fusarium infections.

Correction to: Phylogeography of higher Diptera in glacial and postglacial grasslands in western North America.

An amendment to this paper has been published and can be accessed via the original article.

The relationship between commercial cotton cultivars with varying Meloidogyne incognita resistance genes and yield.

Small plot cotton cultivar trials (12 trials) were conducted from 2016 to 2019 in fields infested with Meloidogyne incognita. Entries in these trials included commercial cultivars with partial and high resistance to M. incognita, as well as cultivars with no known resistance. Different resistant groups were created based on different cotton seed companies and their descriptions of the M. incognita resistant cultivars. Groups were none (susceptible); partial resistance found in Stoneville or Fibermax cultivars (PR-FM/ST); partial resistance found in PhytoGen cultivars (PR-PHY); resistance (unknown gene(s)) in Deltapine cultivars (NR-DP); and highly resistant cultivars homozygous for RK1 and RK2 resistant genes in PhytoGen cultivars (HR-PHY). The highest lint yields using a mixed model analysis were found in the PR-FM/ST (1,396 kg lint/ha), HR-PHY (1,327 kg lint/ha), and PR-PHY (1,314 kg lint/ha) groups. Yield for NR-DP (1,234 kg lint/ha) was not different (p > 0.05) than yield for susceptible cultivars (1,243 kg lint/ha). If the older resistant cultivars from Deltapine and PhytoGen (those with only Roundup Ready® herbicide technology) were removed from the analysis, then HR-PHY yields increased by 133 kg of lint/ha to 1,460 kg lint/ha and NR-DP yields remained approximately unchanged (1,227 kg lint/ha). Newer HR-PHY had much improved yield over the first HR-PHY cultivars. Newer HR-PHY averaged 17% higher yield than the susceptible group. LOG10 (M. incognita eggs/500 cm3 soil + 1) were highest for the susceptible cultivars (3.2), followed by PR-FM/ST (2.6), NR-DP (2.4), PR-PHY (2.1), and lowest with HR-PHY (1.4). The newer HR-PHY cultivars (those with ENLIST® herbicide technology) combine excellent yields (17% higher than susceptible cultivars) with high (96%) suppression of M. incognita.Small plot cotton cultivar trials (12 trials) were conducted from 2016 to 2019 in fields infested with Meloidogyne incognita. Entries in these trials included commercial cultivars with partial and high resistance to M. incognita, as well as cultivars with no known resistance. Different resistant groups were created based on different cotton seed companies and their descriptions of the M. incognita resistant cultivars. Groups were none (susceptible); partial resistance found in Stoneville or Fibermax cultivars (PR-FM/ST); partial resistance found in PhytoGen cultivars (PR-PHY); resistance (unknown gene(s)) in Deltapine cultivars (NR-DP); and highly resistant cultivars homozygous for RK1 and RK2 resistant genes in PhytoGen cultivars (HR-PHY). The highest lint yields using a mixed model analysis were found in the PR-FM/ST (1,396 kg lint/ha), HR-PHY (1,327 kg lint/ha), and PR-PHY (1,314 kg lint/ha) groups. Yield for NR-DP (1,234 kg lint/ha) was not different (p > 0.05) than yield for susceptible cultivars (1,243 kg lint/ha). If the older resistant cultivars from Deltapine and PhytoGen (those with only Roundup Ready® herbicide technology) were removed from the analysis, then HR-PHY yields increased by 133 kg of lint/ha to 1,460 kg lint/ha and NR-DP yields remained approximately unchanged (1,227 kg lint/ha). Newer HR-PHY had much improved yield over the first HR-PHY cultivars. Newer HR-PHY averaged 17% higher yield than the susceptible group. LOG10 (M. incognita eggs/500 cm3 soil + 1) were highest for the susceptible cultivars (3.2), followed by PR-FM/ST (2.6), NR-DP (2.4), PR-PHY (2.1), and lowest with HR-PHY (1.4). The newer HR-PHY cultivars (those with ENLIST® herbicide technology) combine excellent yields (17% higher than susceptible cultivars) with high (96%) suppression of M. incognita.

Phylogeography of higher Diptera in glacial and postglacial grasslands in western North America.

BACKGROUND: Pleistocene glaciations have had an important impact on the species distribution and community composition of the North American biota. Species survived these glacial cycles south of the ice sheets and/or in other refugia, such as Beringia. In this study, we assessed, using mitochondrial DNA from three Diptera species, whether flies currently found in Beringian grasslands (1) survived glaciation as disjunct populations in Beringia and in the southern refugium; (2) dispersed northward postglacially from the southern refugium; or (3) arose by a combination of the two. Samples were collected in grasslands in western Canada: Prairies in Alberta and Manitoba; the Peace River region (Alberta); and the southern Yukon Territory. We sequenced two gene regions (658 bp of cytochrome c oxidase subunit I, 510 bp of cytochrome b) from three species of higher Diptera: one with a continuous distribution across grassland regions, and two with disjunct populations between the regions. We used a Bayesian approach to determine population groupings without a priori assumptions and performed analysis of molecular variance (AMOVA) and exact tests of population differentiation (ETPD) to examine their validity. Molecular dating was used to establish divergence times. RESULTS: Two geographically structured populations were found for all species: a southern Prairie and Peace River population, and a Yukon population. Although AMOVA did not show significant differentiation between populations, ETPD did. Divergence time between Yukon and southern populations predated the Holocene for two species; the species with an ambiguous divergence time had high haplotype diversity, which could suggest survival in a Beringian refugium. CONCLUSIONS: Populations of Diptera in Yukon grasslands could have persisted in steppe habitats in Beringia through Pleistocene glaciations. Current populations in the region appear to be a mix of Beringian relict populations and, to a lesser extent, postglacial dispersal northward from southern prairie grasslands.

Neotropical Agromyzidae (Diptera) of the Mission Géodésique de l'Équateur: Becker (1920) revisited.

The Ecuadorian Agromyzidae described by Theodor Becker from the Mission du service géographique de l'armée pour la mesure d'un arc de méridien équatorial en Amérique du Sud are revised and several taxonomic changes are proposed. The eight named species identified by Becker actually comprise 14 species of Agromyzidae (3 Melanagromyza, 4 Cerodontha, 6 Liriomyza, 1 Nemorimyza) and one species of Heleomyzidae. Three new species are described: Cerodontha (Cerodontha) angela Boucher sp. n.; Liriomyza biensis Boucher sp. n.; Melanagromyza pontis Boucher sp. n. New species records for Ecuador include Melanagromyza memoranda Spencer; M. lini Spencer; Cerodontha (C.) colombiensis Spencer; Liriomyza nigra Spencer and Nemorimyza fuscibasis (Malloch). Cerodontha (C.) nigricornis Becker is redescribed, including the first description of the male genitalia. Liriomyza biformata (Becker) is redescribed and two species are included as junior synonyms of L. biformata: Agromyza braziliensis Frost syn. n. and A. ecuadorensis Frost syn. n. Agromyza bipartita Becker is transferred to the family Heleomyzidae as Notomyza bipartita comb. n.

Cotton GhBAK1 mediates Verticillium wilt resistance and cell death.

Virus-induced gene silencing (VIGS) offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resistant to Verticillium wilt, one of the most devastating diseases worldwide. We showed here that highly efficient VIGS was obtained in a cotton breeding line (CA4002) with partial resistance to Verticillium wilt, and GhMKK2 and GhVe1 are required for its resistance to Verticillium wilt. Arabidopsis AtBAK1/SERK3, a central regulator in plant disease resistance, belongs to a subfamily of somatic embryogenesis receptor kinases (SERKs) with five members, AtSERK1 to AtSERK5. Two BAK1 orthologs and one SERK1 ortholog were identified in the cotton genome. Importantly, GhBAK1 is required for CA4002 resistance to Verticillium wilt. Surprisingly, silencing of GhBAK1 is sufficient to trigger cell death accompanied with production of reactive oxygen species in cotton. This result is distinct from Arabidopsis in which AtBAK1 and AtSERK4 play redundant functions in cell death control. Apparently, cotton has only evolved SERK1 and BAK1 whereas AtSERK4/5 are newly evolved genes in Arabidopsis. Our studies indicate the functional importance of BAK1 in Verticillium wilt resistance and suggest the dynamic evolution of SERK family members in different plant species.

New species of Calamoncosis Enderlein (Diptera: Chloropidae) from South Africa.

Three new and atypical species of Afrotropical Calamoncosis are described: Calamoncosis agricola sp. n. (type locality- South Africa: 15 km E Klaserie); Calamoncosis flavida sp. n. (type locality-South Africa: Roodewal); and Calamoncosis unicornis sp. n. (type locality-South Africa: 15 km E Klaserie). Calamoncosis unicornis exhibits extreme modification and sexual dimorphism in the antenna; in males the arista is reduced to a minute stub and the first flagellomere is greatly elongate and long setulose; in females the arista is well-developed and the first flagellomere is somewhat elongate and pubescent. Calamoncosis agricola is unusual for the genus in that crossvein dm-cu is absent, and C. flavida has an enlarged, rounded first flagellomere. The combination of characters seen in these species expands the known range of morphological variation, and thus the generic limits, of Calamoncosis. Recognition of these new species more than doubles the known Afrotropical fauna of Calamoncosis, previously represented only by C. aenescens (Becker) and C. pauliani (Séguy).

Fostering the rebirth of natural history.

Natural history as we have known it is in decline. A growing movement is emerging across disciplines, to understand its decline, and nurture its rebirth. A network of like-minded scientists, resource managers, educators, writers and artists-natural historians-recently convened four consecutive Natural History Initiative workshops to move past the forensic study of natural history, and instead focus on solutions, conspiring to identify opportunities that dovetail the practice of natural history with essential needs of modern science and society, and suggest ways forward. This series of workshops occurred at various locations in the western United States during the winter and spring of 2011, and recently culminated in a Synthesis Summit on 20-24 June 2011.

Studies of Evaluation Methods for Resistance to Fusarium Wilt Race 4 (Fusarium oxysporum f. sp. vasinfectum) in Cotton: Effects of Cultivar, Planting Date, and Inoculum Density on Disease Progression.

Fusarium wilt caused by Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) is an early season disease causing root rot, seedling wilt, and death. To develop an appropriate field evaluation method for resistance to FOV4 in cotton breeding, the objectives of this study were to investigate the effects of cultivar, planting date, and inoculum density on disease progression in 2020-2021. Results showed that the usual local mid-April planting had the lowest disease severity (DSR) or mortality rate (MR) in 2020 and 2021. DSR or MR increased at the late April and early May plantings in both years and reached the highest at the early May planting in 2020, while MR in 2021 was followed by a decrease in the late May planting and reached the highest in the mid-June planting. Local daily low temperatures between mid-April and mid-June were favorable for FOV4 infections, whereas daily high temperatures at 35°C or higher suppressed wilt severity. When seedlings at the 2-true leaf stage were inoculated with 104, 105, 106, and 107 conidia ml-1 per plant in 2020, DSR was low but a linear relationship between inoculum density and DSR was observed. When a FOV4-infested soil supplemented with artificial inoculation was used, disease progression in three moderately susceptible or moderately resistant cultivars followed a linear model, while it followed a quadratic model in the highly susceptible Pima S-7 cultivar only. Among the other three cultivars, FM 2334GLT had the lowest DSR or MR except for one planting date in both years, followed by PHY 725 RF and Pima PHY 881 RF in ascending order, which were consistent with the difference in regression coefficients of the linear models. This study demonstrates that disease progression curves due to FOV4 can be used to compare responses to FOV4 infections among cotton genotypes in cotton breeding and genetic studies, regardless of planting date and inoculation method.

Revision of the Nearctic genus Tritoxa Loew (Diptera: Ulidiidae).

The species of the Nearctic genus Tritoxa Loew are revised. Seven species of Tritoxa are recognized, including two new species: T. californica sp. nov. (type locality: near Spring Garden, California), T. cuneata Loew, T. decipiens sp. nov. (type locality: near Smithers, British Columbia), T. flexa (Wiedemann), T. incurva Loew, T. pollinosa Cole and T. ra Harriot. One species from California and Nevada based on female specimens remains undescribed. A key to all species is provided, species are illustrated and their distributions mapped. Wing patterns may be used to differentiate among all species, although confident identification of certain sympatric species requires confirmation by examination of male genitalia.

Evaluation and Selection of Interspecific Lines of Groundnut (Arachis hypogaea L.) for Resistance to Leaf Spot Disease and for Yield Improvement.

Early and late leaf spot are two devastating diseases of peanut (Arachis hypogaea L.) worldwide. The development of a fertile, cross-compatible synthetic amphidiploid, TxAG-6 ([A. batizocoi × (A. cardenasii × A. diogoi)]4x), opened novel opportunities for the introgression of wild alleles for disease and pest resistance into commercial cultivars. Twenty-seven interspecific lines selected from prior evaluation of an advanced backcross population were evaluated for resistance to early and late leaf spot, and for yield in two locations in Ghana in 2006 and 2007. Several interspecific lines had early leaf spot scores significantly lower than the susceptible parent, indicating that resistance to leaf spot had been successfully introgressed and retained after three cycles of backcrossing. Time to appearance of early leaf spot symptoms was less in the introgression lines than in susceptible check cultivars, but the opposite was true for late leaf spot. Selected lines from families 43-08, 43-09, 50-04, and 60-02 had significantly reduced leaf spot scores, while lines from families 43-09, 44-10, and 63-06 had high pod yields. One line combined both resistance to leaf spot and high pod yield, and several other useful lines were also identified. Results suggest that it is possible to break linkage drag for low yield that accompanies resistance. However, results also suggest that resistance was diluted in many of the breeding lines, likely a result of the multigenic nature of resistance. Future QTL analysis may be useful to identify alleles for resistance and allow recombination and pyramiding of resistance alleles while reducing linkage drag.

Impacts of Verticillium Wilt on Photosynthesis Rate, Lint Production, and Fiber Quality of Greenhouse-Grown Cotton (Gossypium hirsutum).

Verticillium wilt, caused by Verticillium dahliae Kleb., leads to significant losses in cotton yield and fiber quality worldwide. To investigate Verticillium wilt impact on photosynthesis rate, yield, and fiber quality, six upland cotton genotypes, namely Verticillium susceptible (DP 1612 B2XF) and partially resistant (FM 2484B2F) commercial cultivars and four breeding lines, were grown to maturity under greenhouse conditions in soil either infested or not infested with V. dahliae microsclerotia. Photosynthetic rate, lint, and seed yield were all higher (p < 0.05) for FM 2484B2F than DP 1612 B2XF when infected with V. dahliae. When comparing healthy (H) to Verticillium wilt (VW) affected plants, fiber properties were greatly impacted. Micronaire decreased from 5.0 (H) to 3.6 (VW) with DP 1612 B2XF and 4.4 (H) to 4.1 (VW) with FM 2484B2F. The maturity ratio decreased from 0.90 (H) to 0.83 (VW) for DP 1612 B2XF and was unchanged for FM 2484B2F (0.90). Fiber properties such as short fiber content, nep count, fineness, and immature fiber content were also significantly affected under Verticillium wilt pressure. With Verticillium wilt affected plants, lines 16-13-601V and 17-17-206V performed similarly to FM 2484B2F for photosynthetic rate, yield, and all fiber properties measured. When selecting for improved cultivars in the presence of Verticillium wilt, it is important to select for relatively unchanged fiber properties under disease pressure in addition to reduced disease severity and increased yield.

Systematics of Paraleucopis Malloch with proposal of Paraleucopidae, a new family of acalyptrate Diptera.

Paraleucopidae Wheeler fam. nov. is proposed for the previously unplaced New World genera Paraleucopis Malloch, Mallochianamyia Santos-Neto and Schizostomyia Malloch and undescribed Australian species. A key to genera of Paraleucopidae is provided. Paraleucopis is revised and includes nine species: P. auripes Wheeler Sinclair sp. nov. (type locality: Andalgala, Argentina); P. bispinosa Wheeler Sinclair sp. nov. (type locality: Socos, Coquimbo, Chile); P. boharti Wheeler Sinclair sp. nov. (type locality: Andalgala, Argentina); P. boydensis Steyskal (type locality: nr. Palm Desert, California, USA); P. corvina Malloch (type species of genus; type locality: New Mexico, USA); P. mexicana Steyskal (type locality: Kino Bay, Mexico); P. nigra Wheeler Sinclair sp. nov. (type locality: Portal, Arizona, USA); P. paraboydensis Wheeler Sinclair sp. nov. (type locality: Willis Palms Oasis, California, USA); P. saguaro Wheeler Sinclair sp. nov. (type locality: Usery Mtn Park, Arizona, USA). A key to the species of Paraleucopis is provided. The distribution of Paraleucopis is disjunct, with six species in the western United States and northwestern Mexico and three species in northern Chile and northern Argentina.                The sister group and superfamilial assignment of the Paraleucopidae cannot be established based on current knowledge although the family has affinities to some families of the Asteioinea sensu J.F. McAlpine. A well-supported hypothesis on the relationships of the families of the Acalyptratae will be required before the sister group relationships of Paraleucopidae can be determined.

Rhamphomyia Meigen of the Canadian Arctic Archipelago, Greenland and Iceland (Diptera: Empididae).

Rhamphomyia of the Canadian Arctic Archipelago, Greenland and Iceland, comprising 23 species, including five new species, are revised: R. (Ctenempis) albopilosa Coquillett, R. (Dasyrhamphomyia) erinacioides Malloch, R. (Dasyrhamphomyia) hovgaardii Holmgren, R. (Dasyrhamphomyia) leptidiformis Frey, R. (Dasyrhamphomyia) nigrita Zetterstedt, R. (Eorhamphomyia) shewelli Sinclair, Vajda, Saigusa Shamshev sp. nov., R. (Pararhamphomyia) diversipennis Becker, R. (Pararhamphomyia) filicauda Henriksen Lundbeck, R. (Pararhamphomyia) frigida Sinclair, Vajda, Saigusa Shamshev sp. nov., R. (Pararhamphomyia) helleni Frey, R. (Pararhamphomyia) hilariformis Frey, R. (Pararhamphomyia) hoeli Frey, R. (Pararhamphomyia) kjellmanii Holmgren, R. (Pararhamphomyia) lymaniana Sinclair, Vajda, Saigusa Shamshev sp. nov., R. (Pararhamphomyia) omissinervis Becker, R. (Pararhamphomyia) petervajdai Sinclair, Vajda, Saigusa Shamshev sp. nov., R. (Pararhamphomyia) septentrionalis Sinclair, Vajda, Saigusa Shamshev sp. nov., R. (Pararhamphomyia) simplex Zetterstedt, R. (Pararhamphomyia) ursinella Melander, R. herschelli Malloch, R. hirtula Zetterstedt, R. laevigata Loew, R. setosa Coquillett. The following six new synonyms are proposed: R. calvimontis Cockerell, 1916 and R. wuorentausi Frey, 1922 = R. albopilosa Coquillett, 1900; R. fridolini Frey, 1950 = R. laevigata Loew, 1861; R. hirticula Collin, 1937 = R. setosa Coquillett, 1895; R. uralensis Becker, 1915 = R. kjellmanii Holmgren, 1880; R. zaitzevi Becker, 1915 = R. hovgaardii Holmgren, 1880. Lectotypes are designated for the following species: R. diversipennis Becker, R. filicauda Henriksen Lundbeck, R. helleni Frey, R. herschelli Malloch, R. hirticula Collin, R. hoeli Frey, R. leptidiformis Frey, R. omissinervis Becker, R. setosa Coquillett, R. uralensis Becker, R. wuorentausi Frey, R. zaitzevi Becker. A neotype is designated for R. laevigata Loew. Keys to male and female species of Rhamphomyia and distribution maps of this region are provided. DNA barcode data are presented for 16 species of arctic Rhamphomyia.

Detection of Suppressiveness against Rotylenchulus reniformis in Soil from Cotton (Gossypium hirsutum) Fields in Texas and Louisiana.

Rotylenchulus reniformis is a major problem confronting cotton production in the central part of the cotton belt of the United States of America. In this study, the hypothesis that natural antagonists in some cases are responsible for unusually low densities of the nematode in certain fields was tested by assaying soils from 22 selected fields for the presence of transferable agents in pots containing cotton plants. In one field, soil from four different depth ranges was tested. In the first of two types of assays, 1 part nematode infested soil was added to 9 parts test soil that was left untreated or autoclaved before mixing; this mixture was used to fill pots. In the second type of assay, 1 part test soil was added to 9 or 19 parts pasteurized fine sand, and nematodes were introduced in aqueous suspension. In three experiments representing both types of assay, transferable or autoclavable agent(s) from four fields in South Texas suppressed nematode populations by 48, 78, 90 and 95%. In one experiment, transferable agents in five fields in Louisiana suppressed populations from 37 to 66%. Identification and evaluation of these agents for biological control of R. reniformis merits further study.

Chloropid flies (Diptera, Chloropidae) associated with pitcher plants in North America.

We review the taxonomy and ecology of Chloropidae (Diptera) associated with pitcher plants (Sarraceniaceae) in North America. Tricimba wheeleri Mlynarek sp.n. is described from the pitchers of Sarracenia alata Alph.Wood and S. leucophylla Raf. in the southeastern United States (Alabama, Mississippi). Aphanotrigonum darlingtoniae (Jones) associated with Darlingtonia californica Torr. in northern California is redescribed, including the first description of male genitalic characters. A lectotype is designated for A. darlingtoniae. Published records of other species of Tricimba Lioy in pitcher plants in North America are considered accidental or facultative occurrences; published records of Aphanotrigonum Duda as pitcher plant associates in eastern North America are probably errors in identification.