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Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) causes an early season cotton disease including seedling deaths. This study compared two Pima cottons (Gossypium barbadense) in the infection process of FOV4 using a confocal and a scanning electron microscope. Seedlings were grown in a hydroponic system and inoculated with a virulent local FOV4 isolate. As compared with the susceptible Pima S-7, the resistant Pima PHY 841 RF had significantly fewer conidia attached and germinated on the root surface. FOV4 penetration into the root epidermis of PHY 841 RF was delayed until 24 h postinoculation (hpi) as compared with 8 hpi in Pima S-7. In Pima S-7, hyphae progressed to the xylem through the cortex between 5 and 7 days postinoculation. However, hyphae grew much slower in the cortex with no apparent hyphae observed in the xylem of PHY 841 RF. At plant maturity, no FOV4 was detected through fungal isolation and PCR in the stem of PHY 841 RF and its resistance donor parents PHY 800 and Pima S-6, as compared with Pima S-7 and DP 744 with positive results. The results demonstrate that PHY 841 RF is resistant to FOV4, due to delayed infection, reduced fungal growth and reproduction, and prevention of the fungus from invading the xylem.

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.

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.

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.

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Bacterial blight of cotton, caused by Xanthomonas citri subsp. malvacearum, and Fusarium wilt of cotton, caused by Fusarium oxysporum f. sp. vasinfectum, contribute cotton losses worldwide. Resurgences of these diseases in the United States were reported in recent years. There is a pressing need to understand pathogenicity and host responses to the pathogens and develop effective strategies for disease prevention and management. Here, we discuss the current status of bacterial blight and Fusarium wilt of cotton in the field as well as the knowledge of cotton resistance and susceptibility to these pathogens. In addition, we aim to provide insights into how these diseases are recurring and possible methods to use current technologies for biological control of these pathogens.

Flies (Diptera) are the dominant animal in the North yet are underrepresented in ecological studies. Our study aimed to examine the diversity patterns of the poorly documented acalyptrate flies across the Canadian North. Our main objective was to determine large- and small-scale drivers of species richness, abundance and community composition of acalyptrate fly assemblages. We collected flies at 12 Canadian sites in three ecoclimatic zones (Northern Boreal, Sub-Arctic and High Arctic), from two habitats (wet and mesic). We tested the effect of climatic variables and habitat on species richness and abundance using a generalized linear mixed-effects model, and on community composition using permutational multivariate analysis of variance. Species turnover between sites and ecoclimatic zones was examined by testing for multivariate homogeneity of group dispersions and visualised using non-metric multidimensional scaling. We identified 3631 acalyptrate flies, belonging to 333 species. Diversity measures and community composition were associated with seasonal and limiting temperature variables, consistent with the latitudinal diversity gradient seen in other animal groups. However, habitat only explained a small portion of the variation in our data, and only for observed species richness and species composition. Turnover patterns showed slight, statistically non-significant variation across zones. The High Arctic ecoclimatic zone was as spatially heterogenous in composition as the Northern Boreal and Sub-Arctic ecoclimatic zones but hinted at complex interplays between geographical and glacial legacies. Our results contradict the historical view of Arctic arthropod diversity as simple and uniform, and may serve as a baseline for future biodiversity monitoring.

The objective of this research was to determine the effectiveness of using grain crops in rotation with cotton in managing Verticillium wilt of cotton over a 10-year period. The circular shaped field (52 ha) was divided into six equal sized wedges and cotton or grain crops (sorghum, corn, wheat) were rotated from 2001 to 2018, with some wedges having cotton more frequently and others rotated with grain crops more frequently. Verticillium wilt, which is caused by Verticillium dahliae, was first seen in the field in 2007. Verticillium wilt incidence increased as long-term cotton (host) frequency (HF) increased during 2008–2010 and 2012–2014, but wilt incidence was unaffected by HF in 2016–2018. Grain crops planted in rotation with cotton in one of the two previous years reduced wilt incidence in rotated cotton relative to continuous cotton in 2008–2010, but either had no affect or increased wilt incidence in rotated cotton in 2012–2014 and 2016–2018, relative to continuous cotton. Verticillium dahliae microsclerotia density (MS/cm3 soil)1/2 increased with increasing HF for all three time periods. Three consecutive years of cotton increased MS1/2 relative to rotated cotton in 2008–2010 and 2012–2014, but either did not affect MS1/2 or negatively affected MS1/2 density by 2016–2018 (relative to rotated cotton). Yield, adjusted each year to a 0 to 1 scale, decreased with increasing HF in all three time periods. Yield decreased with three consecutive years of cotton relative to rotated cotton in 2008–2010 and was unaffected by rotated cotton in 2012–2014 and 2016–2018. Crop rotation with nonhosts for management of Verticillium wilt, initially (first four years) was very effective at reducing MS, wilt incidence, and increasing yield. However, 9–11 years after the initial Verticillium wilt symptoms occurred, short-term crop rotation no longer reduced Verticillium wilt incidence, reduced microsclerotia density, or increased cotton yield.

Fusarium wilt (FW, Fusarium oxysporum f.sp. vasinfectum Atk. Sny & Hans) race 4 (FOV4) in cotton was originally identified in India and has become a serious problem in the US production. The cultivated diploid or Asiatic cotton species (Gossypium arboreum L. and G. herbaceum L.) may contain resistance to FOV4, because both the host and the pathogen originated from the same region. In addition to Pima S-6 which is currently the sole source of FOV4 resistance in Pima cotton (G. barbadense L.), other sources of resistance are urgently needed. In this study, 372 Asiatic and 152 G. barbadense accessions were evaluated for FOV4 resistance at 7, 14, 21, and 28 days after inoculation (DAI) under temperature-controlled conditions (20–23 °C). Foliar disease severity ratings (DSR) at 28 DAI were determined using a rating scale from 0 (for no symptoms) to 5 (for plant death). Significant genotypic differences were detected for FOV4 resistance within the Asiatic and the G. barbadense L. accessions. Most accessions were highly susceptible to FOV4 in that the diploid and Pima accessions had an overall DSR of 4.05 and 4.32, respectively, and 50 and 60% of the accessions exhibited 100% mortality, respectively. Ten diploid accessions were most resistant with a DSR ranging from 0.63 to 2.61. The most resistant G. barbadense accessions were Giza 67, Tanguis 84–65, XH30, PHY 800 Pima, AZK 144, Sind S.I. (AZK 271), Pima 84524, Pima 93252, PHY 805 RF and 8945-1, with a DSR ranging from 2.5 to 3.17. These accessions will provide important sources of resistance to FOV4. Heterogeneity in FOV4 resistance was detected, even in the most resistant accessions. Further pedigree selection should increase the frequencies of resistant plants in the heterogeneous accessions.

Fusarium wilt (FW) caused by race 4 (FOV4) of the soil-borne fungus Fusarium oxysporum f. sp. vasinfectum causes high cotton seedling mortality under field conditions in the west and southwest US Cotton Belt. The objectives of this study were to evaluate the dynamic responses to FOV4 infections in two introgressed Upland cotton (Gossypium hirsutum) populations using an artificial inoculation and screening method. The two populations (IL-122 with 120 introgressed lines and BIL-193 with 180 backcross inbred lines) were derived from backcrossing the same recurrent Upland parent (FOV4 resistant) to two different interspecific hybrids each with a different G. barbadense parent (FOV4 susceptible). The two populations, together with their parents and other Upland lines were evaluated in three independent replicated tests for FOV4 responses at 7, 14, 21, and 28 days after inoculation (DAI) under temperature-controlled conditions at 20–21 °C, based on three evaluating parameters- disease incidence (DI), disease severity rating (DSR) and mortality rate (MR). Wilted seedlings were observed as the initial FW symptoms in 21% of the lines within 7 DAI, and no line had 0% DI across the three tests at 28 DAI. DI, DSR and MR were highly and significantly correlated among one another at 14, 21, and 28 DAI, and 21 DAI had the strongest correlations with 14 and 28 DAI. The results suggest that responses to FOV4 infections were overall congruent among DAI in the two cotton populations, and DSR at as early as 21 DAI can be used to assess germplasm lines for FOV4 resistance. Based on responses to FOV4 at 7, 14, 21 and 28 DAI, 17 of the 88 susceptible lines in the IL-122 population at 28 DAI showed resistant responses at 7–14 and/or 7–21 DAI, and they may provide resistant responses in early stages of FOV4 infections. Among 34 resistant (R) lines at 28 DAI, 22 lines showing susceptible (S) responses at 14 and/or 21 DAI. Similar results were observed in the BIL-193 population. The result showed that there were lines with unique responses (R or S) during different DAI and represented one of the first such studies in cotton. It provides a set of unique lines for further studies at the structural, biochemical and molecular levels and an incentive to investigate the genetic and genomic basis of the dynamic responses to FOV4 through detecting DAI-specific resistance genes or quantitative trait loci (QTL).

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.

Cotton (Gossypium spp.) is an economically important crop which provides a significant source of fiber, animal feed, and food oil worldwide. Bacterial blight (BB), caused by Xanthomonas citri pv. malvacearum (Xcm), infects the aerial part of the cotton plant at all stages and can cause a significant loss in yield and fiber quality. In this study, 288 Upland (G. hirsutum) and 8 Pima (G. barbadense) commercial transgenic cultivars and elite breeding lines were divided into 10 replicated tests and evaluated for BB resistance using the toothpick scratching method in the greenhouse in 2016–2017. Five Upland and four Pima genotypes were used as resistant and susceptible controls, respectively. The percentage of susceptible plants with water-soaking symptoms was calculated on a replication basis for each genotype. While all the commercial Pima cultivars tested were susceptible, 21 commercial Upland cultivars were resistant to Xcm race 18. A total of 22 elite public breeding lines were resistant, including 11 lines from the University of Arkansas with an active breeding program for BB resistance and 1–4 resistant lines from five other public breeding programs without an active screening component for BB resistance. Of more than 150 breeding lines developed at New Mexico State University, 11 were found to be resistant to BB. Many commercial cultivars and public breeding lines were found to contain various levels of susceptible plants and are therefore heterogeneous in BB resistance. The results suggest that the resistance to Xcm race 18 can be easily bred in breeding without a selection pressure. A pedigree analysis showed that there are likely different sources of BB resistance. The resistant cultivars and lines identified should be a valuable resource to improve BB resistance in cotton breeding.

The soil- and seed-borne fungus, Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4), causes Fusarium wilt in cotton (Gossypium spp.) and represents a significant threat to cotton production in the US. The objectives of this study were to enhance FOV4 resistance in heterogeneous Acala 1517-08 and its derivatives through three cycles of pedigree selection in 2018, 2019 and 2020 under FOV4-infested field conditions. In 2017, in a field not infested with FOV4, 46, 12, and 23 single plants were selected for productivity from a base population of 1100–1400 plants of Acala 1517-08 and its derived glandless lines, Acala 1517-18 GLS and NM 13P1125, respectively. In 2018, the single plant selections, controls and other lines were tested in progeny-rows in an FOV4 infested field for disease responses including mortality rate (MR), root vascular staining (RVS), and disease incidence (DI), resulting in 41, 15, and 26 single plants selected from progenies of the three lines, respectively, based on RVS. These single plant selections were tested in 82 progeny-rows in the same field in 2019, and the second selection cycle based on RVS advanced 40, 16, and 37 plants selected from the progenies of the three lines, respectively, for further evaluation and the third selection cycle in a progeny test in 2020. In 2020, an average of 81–84% plants died in highly susceptible controls, Pima S-7 and Pima DP 744, due to FOV4 infections, while the resistant controls, Pima S-6, Pima PHY 841 RF and NuMex COT 17 GLS, incurred up to 19–24% mortality. As a result of the three cycles of single plant selection, a total of 12 progenies were identified to be as resistant as the resistant controls. On the progeny basis, MR between years was significantly correlated, and MR at different evaluation dates was also significantly correlated with one another and with mean RVS and DI within year. However, due to possible escapes of plants from FOV4 infections, the original RVS scores of individual plant selections were not correlated with their respective progenies; and no significant differences were detected among progeny means grouped based on RVS ratings for single plant selections. The results demonstrate that early plant mortality is a superior means of selecting against FOV4 susceptibility, while using RVS rating late in the season if excluding seedling MR may inflate and distort the resistance level of genotypes, rendering it less reliable in assessing FOV4 resistance in cotton. In addition, many single plants selected for FOV4 resistance with no RVS may be escapes, necessitating repeated progeny tests and selection. The importance of pedigree selection within germplasm, choice of resistant and susceptible checks, FOV4 inoculum density, and the use of RVS, and resistance versus tolerance in response to FOV4 infections under field conditions are discussed in detail.

Conservation of biodiversity is growing in interest, and wetlands are disappearing at an alarming rate, so understanding how communities are assembled and how interactions among species and ecosystems influence evolution is critical to the management of threatened habitats. We compared diversity and assemblages of peatland Diptera within and between ecoregions in Québec, Canada. We then determined the phylogenetic structure of peatland Diptera communities and how the structure differed with spatial scale (trap, site, ecoregion). Finally, we tested alpha and beta diversity along environmental and spatial gradients to determine which processes influence Diptera communities and diversity. Bogs across the three ecoregions support similar abundance, species richness, and functional diversity. We found that the major forces structuring Diptera assemblages in bogs across Québec are stochastic processes such as dispersal limitations. However, those random patterns change to clustering when anthropogenic disturbances modify the landscape. Assembly rules are mostly dictated by patch and landscape parameters specific to each ecoregion affecting dispersal and establishment between sites. Conservation of mobile organisms in habitats such as bogs will depend on conservation plans focusing on both patch quality and surrounding landscape, and that different conservation strategies need to be applied in different ecoregions.

Bacterial blight (BB, caused by Xanthomonas citri pv. malvacearum, Xcm) is a worldwide disease of cotton (Gossypium spp.). The disease has been effectively controlled through the use of BB resistant cultivars and planting of acid-delinted seed. However, a resurgence of BB has been noted in the US in recent years due to the spread of Xcm race 18 and growing of susceptible transgenic cultivars, which calls for a renewed effort to develop new BB resistant cultivars. However, there has been a paucity of information in genetics and breeding for BB resistance since the 1990s due to the lack of research efforts. This review was prepared to fill this void with an objective to provide detailed results from past qualitative and quantitative genetic studies on BB resistance, including genetic designs and specific germplasm used for conducting research. More than 20 major resistance B genes (B1 to B8, B9K, B9L, B10K, B10L, B11, B12, BIn, Bn, Bs, and more than 4 unnamed genes), with at least two polygene complexes (BSm and BDm), have been identified. One B gene may be resistant to a single or multiple Xcm races, and pyramiding of several B genes can enhance resistance to a single or multiple Xcm races. Allelic relationships among some of the genes are currently unknown. Quantitative genetics has been employed to estimate heritability, gene effects, additive and dominance variances, and effective number of genes for BB resistance. The studies suggest that the additive effect and additive variance play a predominant role in BB resistance, while the dominant effect and variance play a reduced role in resistance. Heritability estimates are moderate to high depending on environmental errors, and 1–2 effective numbers of genes have been estimated, consistent with Mendelian genetic studies. Studies in molecular mapping of several BB resistance genes (B2, B3, b6, and B12) have been conducted with the focus on B12 as it is resistant to races 1 through 19. Portable DNA markers have been developed and used in marker-assisted selection for BB resistance. Finally, areas where there is a lack of information and controversies are identified and assessed. This review provides an updated comprehensive account of the genetic basis for BB resistance in cotton.

Cotton (Gossypium spp.) is the most widely-grown natural fiber crop used by the textile industry. Fusarium wilt, caused by Fusarium oxysporum f. sp. vasinfectum (FOV) comprised of eight nominal pathogenic races, is one of the most destructive diseases in cotton. FOV race 4 (FOV4) is an emerging threat to cotton production in the US. In this study, a total of 3258 lines including 3080 Upland (G. hirsutum) and 178 Pima (G. barbadense) germplasm lines were evaluated in 21 tests under greenhouse or temperature-controlled conditions for resistance to FOV4. A total of 2224 lines from 13 tests were screened in a commercial potting soil in the greenhouse under higher temperature (HT) conditions (24–32 °C), while 1204 lines from 8 tests were screened in a naturally FOV4-infected farm soil at a lower temperature (LT) setting (20–21 °C), both with artificial inoculations. The 170 Pima lines were evaluated in both temperature regimes. The results showed that, at 30 days post inoculation, both temperature regimes produced similar disease incidence (81.2% for HT vs. 86.8% for LT), but LT caused significantly higher disease severity ratings (DSR, 3.86 vs. 1.94) and plant mortality (81.7% vs. 7.5%) than did HT. DSR and morality rate were highly significantly correlated (r = 0.849–0.941) at LT. Significant genotypic variations in DSR were detected in all studies except two, and the broad-sense heritability estimates for DSR were 0.59–0.83 with an average of 0.70 at HT and 0.61–0.72 with an average of 0.69 at LT, indicating that 70% the phenotypic variation in FOV4 resistance was determined by genetic variation. Using the naturally FOV4-infected farm soil and LT to screen 1034 Upland and 170 Pima germplasm lines (with 20–40 plants for each line) with artificial inoculations, 48% showed 100% mortality; 22% had a mortality rate between 70 and 99%; 5% had mortality below 30%; and 0.5% (6 lines) did not display any apparent FOV4 symptoms. The results indicated that many existing available germplasm lines may be heterogeneous for FOV4 resistance and pedigree selection within germplasm may increase frequencies of resistant plants. This study represents one of the first publicly reported large-scale screenings of cotton for FOV4 resistance in the US and provides useful information for breeding cotton with resistance to FOV4.

In the summer of 2004 an epidemic of Sclerotinia blight of peanut, a disease caused by Sclerotinia minor, occurred in Texas in fields where the disease was never previously detected. The disease was observed on many plants within one of the fields (>3,000 disease foci), though most foci were < 1 m. We hypothesized that these observations were inconsistent with the recent introduction of a monocyclic pathogen, even if disease developed under conducive environmental conditions. The pattern of disease is most suggestive of the presence of foliar (ascospore) infections, though air temperature was above the known limits for apothecia development if the pathogen had arrived in the field in 2004 peanut seed. To further examine this epidemic, 232 isolates were collected, across a variety of spatial scales spanning this field and other Texas peanut fields, and evaluated for aggressiveness, fungicide sensitivity, and genotypic diversity. There was wide variation among isolates for the phenotypic characteristics measured, but there was no evidence that a genotypically unique, highly aggressive, and fungicide resistant isolate had been introduced or evolved. The predominant genotype, TX1, which contained 154 isolates, was found in every county and field population. This article is protected by copyright. All rights reserved.

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.

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.

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.

Most investigations of fungi as nematode antagonists have focused on their interactions with nematodes in the soil. This study tested a foliar-isolated endophytic Phialemonium inflatum for its effects against the root-knot nematode as an endophyte in cotton using a seed treatment inoculation. Cotton seeds were inoculated with P. inflatum spore suspensions prior to planting. Nematode infection and reproduction were quantified at Day 12 and 6 weeks after nematode egg inoculation, respectively. To establish whether the observed negative effects on nematodes were due to P. inflatum in the soil or as an endophyte in the plant, we also applied a soil fungicide treatment at the seedling stage to kill the fungi outside the plant. Persistent suppression of nematode penetration and galling, as well as subsequent reproduction, were observed in endophyte-treated plants independent of fungicide treatment, consistent with an endophytic mode of nematode suppression; and these negative effects did not depend on the concentration of fungal inoculum used to treat to the seed. Our study highlights a novel role for P. inflatum as part of a plant-fungal defensive symbiosis in cotton, as well as the need for a broader understanding of endophyte-plant-nematode ecological interactions.

Verticillium wilt is responsible for substantial yield losses in cotton. The use of cultivars with partial resistance to Verticillium wilt is a preferred management strategy. Cotton breeders utilize rating scales based on severity of foliar symptom expression and/or defoliation when making cultivar selections. The objective of this research was to determine the yield relationship with cultivars grouped by both incidence of Verticillium wilt during the boll filling stage, and late season defoliation in fields with a history of Verticillium wilt. Small plot, replicated cultivar trials were conducted over an 11 year period in west Texas. Cultivars were divided into four classes (A–D) based on normalized wilt incidence (NW) and four classes based on normalized defoliation ratings (ND). Classes were determined through a mixed model analysis of cultivars, with T-test comparisons between a partially resistant check (Fibermax 2484B2F) and a susceptible check (Deltapine 0912B2RF). The A and C classes did not differ (P = 0.05) from the partially resistant and susceptible checks, respectively. Classes were used in a mixed model analysis with lint yield. In a model with only NW classes, lint yield decreased significantly as NW increased with least square mean values of 1421, 1385, 1284 and 1204 kg/ha, for classes A, B, C and D, respectively. In a model with both NW and ND classes, the A/A class combination of NW and ND had a significantly (P ≤ 0.05) higher lint yield (1776 kg/ha) than any other combination. NW/ND class combinations of A/B, B/A, B/B, and C/A had intermediate yields, and ND classes of C or D had the lowest yields. Cultivars with both low wilt and defoliation incidences should result in higher yields in fields infested with Verticillium dahliae. Furthermore, these two rating criteria could be used to standardize the process for developing resistant cultivars.

Peanut pod rot, which can be caused by Pythium spp. and Rhizoctonia solani , is difficult to manage with fungicides. The objective of this study was to compare the effects of a calendar-based (CB) versus threshold-based (INC) fungicide application timings on pod rot incidence, yield, value of the crop, and returns minus fungicide cost. Large plot replicated trials were conducted in five fields with a history of pod rot. Pod rot was assessed weekly throughout the season following development of pods. Disease incidence was reduced by the preventative CB compared with INC or the non-fungicide treated control (NONE) in three of five sites. Disease was very low in the remaining two sites. Yield was not affected by treatment at individual sites, but in a combined analysis, INC at 1–2% incidence had higher yields than CB treated with mefenoxam or NONE. Occurrence of segregation 2 kernels, which results in a substantial reduction in price, was more frequent with INC and NONE than with CB at two sites. CB and INC had a higher value/ha than NONE, but there were no differences in return minus fungicide costs. CB had less pod rot during the season and a lower risk of segregation 2 kernels at harvest than INC. These results suggest that preventative CB applications made at early pegging should be used to manage pod rot. This recommendation is based on the reduction of risk to segregation 2 kernels, not because of a higher value/ha of the crop.

Arthropod species inhabiting disjunct xeric grasslands in the Yukon Territory, Canada may be relicts of Pleistocene steppe assemblages widespread in Beringia during glaciation, or they may be recent remnants of northward expansion of southern grassland communities during the early-Holocene Hypsithermal. To assess the likely origin of the Yukon grassland arthropod community, grassland-associated Chloropidae (Diptera) were compared from three regions: the Canadian Prairies, the Peace River region of Alberta and the southern Yukon. If Yukon grassland insect communities, like those in the Peace region, result primarily from northward dispersal during the Hypsithermal, chloropid assemblages in all regions would be similar, except that species richness would decline with increasing latitude. If, however, they are primarily relicts of Pleistocene steppe communities, Yukon chloropid assemblages would be distinct from southern assemblages. There was a latitudinal gradient of decreasing species richness and Yukon assemblages were distinct from Prairie and Peace region assemblages, based on cluster analysis, non-metric multidimensional scaling and pairwise comparisons of Morisita similarity indices. Community-level analyses suggest that Yukon assemblages have been separated from those in the Prairies and Peace regions since before the Hypsithermal and likely contain a mix of relict populations inhabiting Pleistocene steppe remnants in East Beringia with recent northward post-glacial dispersal from the southern Prairies. Dispersal from eastern Russia via Beringia appears to have been negligible.

Fungus-growing ants (Attini) are abundant and diverse, yet only one taxon of flies (Phoridae) and one of wasps (Diapriinae) are known parasitoids, and the biology of most species is not well known. Here we describe the first evidence for an ant parasitoid in the family Chloropidae (Diptera), in which larvae of Pseudogaurax paratolmos Wheeler, new species, parasitize larvae of the ant, Apterostigma dentigerum Wheeler, 1925. Larval flies are solitary ectoparasitoids, each of which attaches to a single ant larva and develops from larva to pupa in ∼2 wk, consuming nearly the entire host, and then ecloses as an adult ∼1 wk later. Overall parasitism prevalence was 6.8% of 203 nests, and flies were active during both the dry and rainy seasons. Intensity of parasitism ranged from 18.2 to 100% of larvae attacked per parasitized nest. No other species of Apterostigma that nested in the same localities were parasitized by the flies, including A . pilosum (Mayr, 1865) ( n = 93 nests) and A . auriculatum (Wheeler, 1925) ( n = 10 nests). All immature ants, parasitized or not, as well as immature stages of Pseudogaurax paratolmos , were attended by adult ants that exhibited normal brood care behavior, including covering immatures with mycelia, grooming, and maintaining brood in the fungus garden.

During August 2004, Cylindrocladium parasiticum Crous, M.J. Wingf., & Alfenas (teleomorph Calonectria ilicicola Boedijin & Reitsma) was isolated from peanut (Arachis hypogaea L.) cv. NC 7 taken from an irrigated field in Terry County, TX. On 24 September, the mean length of patches with symptoms of dead plants and confirmed for the presence of C. parasiticum was 40 cm (averaged over 52 patches). Pods, pegs, roots, and lower stems of affected plants had decayed black lesions. No perithecia were observed. Roots were plated on water agar, and mycelia growth was transferred to potato dextrose agar (PDA). Conidia and microsclerotia typical of C. parasiticum had formed at 14 days. After 21 days on PDA, the following mean measurements were recorded: macroconidia 57 × 7 μm (usually two septations); stipe 115 × 4 μm; and sphaeropedunculate vesicle 15 × 10 μm. These are within reported ranges for C. parasiticum (1). Four-week-old cultures were comminuted in tap water and added (mycelium and microsclerotia) to potting medium (noninfested nonsterile peanut field soil/peat moss potting mix, 1:1). Peanut-specific Bradyrhizobium sp. was applied before planting. Three 3-day-old peanut cv. Tamrun 88 seedlings were transplanted in infested soil (four replicate pots, five isolates). Root, hypocotyl, pod, peg, and lower stem lesions were evident after 8 (Trial 1, one isolate) and 16 weeks (Trial 2, four isolates). Virulence varied among isolates (3). C. parasiticum was reisolated on acidified PDA after both trials. In Trial 3, six plant species (three replicate pots, five plants per pot) were challenged with one isolate by drenching a tap water suspension of comminuted microsclerotia and mycelium from 4-week-old PDA cultures into potting medium and transplanting peanut seedlings or planting seeds for other hosts. Root rot severity (0 to 5 index) (3) and reisolation percentages were cv. Tamrun 88 peanut 2.0, 100%; cv. Tamrun 96 peanut 2.0, 92%; cv. Hutcheson soybean (Glycine max (L.) Merr.) 3.3, 64%; cv. Blue Lake 274 green bean (Phaseolus vulgaris L.) 2.7, 40%; cv. California Blackeye 8046 southern pea (Vigna unguiculata (L.) Walp. 2.0, 70%; and cv. Jubilee Hybrid sweet corn (Zea mays L.) 0.0, 100%. Noninoculated peanut controls in all trials had no black decayed root lesions and attempts to isolate the fungus were unsuccessful. Peanut seeds planted in the production field were obtained from the southeastern United States. This field had been scheduled for seed production until C. parasiticum was identified. Temperatures and rainfall amounts during the 2004 growing season were less and greater than long-term averages, respectively. No other infested peanut fields have been confirmed or suspected in the region or state. There is continued risk of contamination from shipments of infected seeds from infested areas (2). This pathogen may pose a serious threat to >100,000 ha of peanut production in western Texas and eastern New Mexico. References: (1) P. W. Crous. Taxonomy and Pathology of Cylindrocladium (Calonectria) and Allied Genera. The American Phytopathological Society, St. Paul, MN, 2002. (2) B. L. Randall-Schadel et al. Plant Dis. 85:362, 2001. (3) R. C. Rowe and M. K. Beute. Phytopathology 65:422, 1975.

A large diversity of saproxylic Empidoidea from a temperate deciduous forest in southern Quebec is documented. Adults of 43 empidoid species representing 19 genera in 12 subfamilies and three families were collected from in situ sealed emergence traps placed over decayed logs of American beech (Fagus grandifolia Ehrhart) and sugar maple (Acer saccharum Marshall). The results of this technique give a clear indication of the saproxylic larval and pupal habitat of these species. The importance of Empidoidea as larval predators in decayed wood niches is noted.

The phylogenetic relationships of the chloropid tribe Elachipterini were analysed. Sixty-eight exemplar species and seven outgroup species were included in a cladistic analysis based on 76 morphological characters of adult specimens in order to test existing, non-phylogenetic, classifications of the tribe. Nine genera are recognized in the Elachipterini: Allomedeia Mlynarek & Wheeler, Alombus Becker, Anatrichus Loew, Ceratobarys Coquillett, Disciphus Becker, Elachiptera Macquart, Goniaspis Duda, Melanochaeta Bezzi and Sepsidoscinis Hendel. Myrmecosepsis Kertesz is synonymised with Anatrichus , and Togeciphus Nishijima and Cyrtomomyia Becker are synonymised with Elachiptera . Ceratobarys is removed from synonymy with Elachiptera and all Neotropical species and two Nearctic species previously assigned to Elachiptera are transferred to Ceratobarys . Melanochaeta is a valid genus; the type species Melanochaeta capreolus clusters with other species of Melanochaeta and not Oscinella . New combinations include Anatrichus hystrix (Kertesz, 1914) ( Myrmecosepsis ); Anatrichus taprobane (Andersson, 1977) ( Myrmecosepsis ), Ceratobarys attenuata (Adams, 1908) ( Elachiptera ); Ceratobarys cultrata (Wheeler & Forrest, 2002) ( Elachiptera ); Ceratobarys flavida (Williston, 1896) ( Elachiptera ); Ceratobarys melinifrons (Mlynarek & Wheeler, 2008) ( Elachiptera ); Ceratobarys fucosa (Mlynarek & Wheeler, 2008) ( Elachiptera ); Ceratobarys queposana (Mlynarek & Wheeler, 2008) ( Elachiptera ); Ceratobarys rubida (Becker, 1912) ( Elachiptera ); Ceratobarys sacculicornis (Enderlein, 1911) ( Elachiptera ); Ceratobarys willistoni (Sabrosky, 1948) ( Elachiptera ), Elachiptera ensifer (Sabrosky, 1951) ( Cyrtomomyia ); Elachiptera ericius (Kanmiya, 1983) ( Togeciphus ); Elachiptera katoi (Nishijima, 1955) ( Togeciphus ); Elachiptera maculinervis (Becker, 1910) ( Cyrtomomyia ); Elachiptera punctulata (Becker, 1912) ( Cyrtomomyia ); Elachiptera subelongata (Kanmiya, 1983) ( Disciphus ); Elachiptera truncatus (Liu & Yang, 2012) ( Togeciphus ); Elachiptera tuberculata (Adams, 1905) ( Cyrtomomyia ) and all the species that were placed in Lasiochaeta are returned to Melanochaeta. A key to genera of the tribe Elachipterini is provided and diagnoses are provided for all genera. The tribe is divided into two geographically distinct clades: the Anatrichus clade includes the Old World tropical genera Allomedeia , Alombus , Anatrichus , Disciphus and Sepsidoscinis ; the Elachiptera clade includes the primarily Neotropical genera Goniaspis and Ceratobarys and the widespread, but primarily Holarctic, genera Elachiptera and Melanochaeta .