In perennial agroecosystems, pest management outcomes are influenced by herbivore ecology and farming practices that shape arthropod activity. Yet, across many systems, information on taxonomic composition, spatiotemporal dynamics, and sensitivity of herbivore groups to crop management is sparse. In perennial tree crops, Auchenorrhyncha (Hemiptera) are abundant herbivores, notable for causing feeding damage and transmitting plant pathogens. Here, to strengthen the ecological understanding of Auchenorrhyncha activity in managed tree systems, we tracked the seasonal abundance and within-canopy distribution of Auchenorrhyncha in a mature pecan (Carya illinoinensis) orchard over two seasons and evaluated how these patterns interact with common canopy management interventions: hedge pruning and calendar-based pesticide applications of insecticide and fungicide. We collected 5882 Auchenorrhyncha, representing seven families. The assemblage was dominated by Cicadellidae, with over 95

The genetic basis of adaptation is a fundamental question in evolutionary biology, and understanding how species will be able to adapt to changing conditions across their range has important implications for conservation and agriculture. To accurately interrogate the genetics of adaptation and assess the adaptive capacity of a species requires also characterizing the ways other mechanisms, including geographic distance and population dynamics, shape genetic variation. Pecan is an ecologically, culturally, and economically important North American tree, and a broader understanding of the genetics of environment adaptation will aid pecan conservation, breeding, and commercial management. Here, we use an expansive set of more than 700 pecan genotypes in combination with the first haplotype-resolved genome assembly for pecan to assess species-wide genetic variation and evaluate environmental adaptation across the native distribution. We identify five gene pools in pecan, with the lowest diversity in southern gene pools, and present evidence that gene pools began differentiating during multiple glacial cycles. Using complementary genotype-environment association approaches, we infer species-wide patterns of environmental adaptation. With these results, we predict mismatches in adaptation for pecan genotypes to different environments, including future environment scenarios. We see that in all locations, present-day genotypes incur some level of predicted maladaptation to simulated future environments, but current genetic diversity may provide a valuable source of resilience to future conditions through assisted migration. These results expand the understanding of environmental adaptation in pecan and provide insight into how long-lived species will be able to adapt to future conditions. ### Competing Interest Statement The authors have declared no competing interest. United States Department of Agriculture, https://ror.org/01na82s61, SCRI-2016-51181-25408, SCRI-2022-51181-38332, 3091-21000-046-000-D

Genetic maps are essential tools for gene positional cloning and marker-assisted breeding. A pecan (Carya illinoinensis) mapping population of 119 F1 trees was developed from a cross of the widely planted cultivars ‘Pawnee’ and ‘Elliott’. Whereas ‘Pawnee’ is susceptible, ‘Elliott’ has long-standing resistance to pecan scab caused by the fungal pathogen Venturia effusa. Molecular markers were developed using genotyping by sequencing, and linkage maps were constructed for each parent following the two-way pseudo-test-cross strategy used for cross-pollinated species. The ‘Pawnee’ and ‘Elliott’ maps contain 1347 and 1050 single-nucleotide polymorphism markers spanning a genetic distance of 4493 and 3758 centimorgans, respectively. While these map lengths are likely inflated due to genotyping errors, a high level of synteny between genetic and physical distances of the markers in both parental maps was achieved. Scab resistance was evaluated through controlled inoculations in the greenhouse using two scab isolates, and a significant quantitative trait locus (QTL) for scab resistance was identified on chromosome 5 in ‘Elliott’. Candidate gene searches within the 2-logarithm of the odds interval of the scab-resistant QTL identified a number of disease resistance–related genes, including genes encoding wall-associated receptor kinases, cytochrome P450s, leucine-rich repeats receptor–like serine/threonine-protein kinases, a pectinesterase inhibitor, a cellulose synthase, a flavonol synthase, a 4-coumarate–coenzyme A ligase, caffeic acid 3-O-methyltransferase, and a myeloblastosis (MYB) domain transcription factor.

Pecan is a valuable nut crop cultivated in the southeastern United States. Among the major yield-limiting factors in the region is scab, caused by the plant pathogenic fungus Venturia effusa. Managing scab in tall trees (15 to 25+ m) in pecan orchards is challenging because of the limitations of getting sufficient spray coverage throughout the canopy. We explored the effects of hedge pruning on scab in three orchards: 14-m-tall cv. Desirable trees winter hedge pruned on alternate sides to 11 m (site 1), 18-m-tall cv. Stuart trees hedge pruned on both sides simultaneously to 11 m (site 2), and 15-m-tall cv. Caddo trees winter hedge pruned in winter versus summer to 11 m (site 3). At site 1 and 2, hedge-pruned trees were compared with nonpruned control trees. All trees received recommended fungicide applications to control scab via an air-blast sprayer. Disease incidence and/or severity was assessed at different sample heights on shoots, foliage, and fruit during three seasons (2020, 2021, and 2022). At site 1 the hedge-pruned trees often had significantly or numerically more severe scab on foliage and fruit compared with the control trees, although the differences were mostly small. The frequency of mature fruit with scab severity <10% was greatest on control trees in 2021 and 2022. At site 2, there were few differences between hedge-pruned and control trees (on fruit, scab severity was either significantly less on hedge-pruned trees or not different from the control), but the frequency of mature fruit with scab severity <10% was consistently greatest on hedge-pruned trees. At site 3, scab intensity was low, and there were no significant differences in scab severity between winter- and summer-pruning treatments. At sites 1 and 2, there was generally more severe scab at greater sample heights compared with low in the canopy. At site 3 there was little effect of height on disease. The benefit of hedge pruning likely increases with tree height in scab-susceptible cultivars. If a tree is taller than ∼15 m, a greater proportion of the fruit will be within reach of efficacious spray coverage from air-blast sprayers.

Pecan scab, caused by the fungal pathogen Venturia effusa, is the most devastating disease of pecan (Carya illinoinensis) in the southeastern United States. Resistance to this pathogen is determined by a complex interaction between host genetics and disease pathotype with even field-susceptible cultivars being resistant to most scab isolates. To understand the underlying molecular mechanisms of scab resistance in pecan, we performed a transcriptome analysis of the pecan cultivar, ‘Desirable’, in response to inoculation with a pathogenic and a non-pathogenic scab isolate at three different time points (24, 48, and 96 hrs. post-inoculation). Differential gene expression and gene ontology enrichment analyses showed contrasting gene expression patterns and pathway enrichment in response to the contrasting isolates with varying pathogenicity. The weighted gene co-expression network analysis of differentially expressed genes detected 11 gene modules. Among them, two modules had significant enrichment of genes involved with defense responses. These genes were particularly upregulated in the resistant reaction at the early stage of fungal infection (24 h) compared to the susceptible reaction. Hub genes in these modules were predominantly related to receptor-like protein kinase activity, signal reception, signal transduction, biosynthesis and transport of plant secondary metabolites, and oxidoreductase activity. Results of this study suggest that the early response of pathogen-related signal transduction and development of cellular barriers against the invading fungus are likely defense mechanisms employed by pecan cultivars against non-virulent scab isolates. The transcriptomic data generated here provide the foundation for identifying candidate resistance genes in pecan against V. effusa and for exploring the molecular mechanisms of disease resistance.

The pecan leafroll mite, Aceria caryae (Keifer) (Acari: Eriophyidae), is a small cigar-shaped mite, normally measuring 0.1–0.2 mm long. The mite uses a ventral sucker located on its caudal end for attachment to the host plant while it feeds using piercing mouthparts that are short and thus limiting feeding to the epidermal cells (Grasswitz 2012, USDA Forest Service Proceedings, New Mexico). There are nearly 2,000 species of eriophyid mites (Davis and Beddes 2011, Utah Pests Fact Sheet, ENT-149-11) and most are host specific, which makes some species ideal for biological control of weed species (Skoracka et al. 2010, In E.D. Uekermann [ed.], Eriphyoid Mites: Progress and Prognoses, Springer, NY). Feeding symptoms vary, but can include galls, stunting, blisters, leaf curl, rust, silvering, fruit russeting, witches' broom, stunting and deformities of seedlings.On pecan, Carya illinoinensis (Wangenheim) Koch, the adult pecan leafroll mite feeds on the lateral edge of the adaxial surface of young, expanding leaflets during the early spring (Davis and Beddes 2011). Feeding along the leaf edge causes cells on the adaxial surface to grow slower than those cells on the abaxial side, hence forming a gall-like deformation along the lateral leaf margin and causing the leaf edge to curl up in a tight roll. Although this distortion to the leaf occasionally turns brown, defoliation does not occur. For many host plant species, damage is generally cosmetic and not a significant problem, allowing control by pruning infested branches or removing damaged leaves (Grasswitz 2012). However, the large size of many infested pecan trees precludes this as an option.During migration between plant tissues, the eriophyid mites are more exposed and vulnerable to natural enemies such as predaceous mite species (Stigmaeidae and Phytoseiidae), spider mite destroyer lady beetle, Stethorus punctum (LeConte) (Coleoptera: Coccinellidae), and predaceous midge larvae (Diptera: Cecidomyiidae) (Skoracka et al. 2010). In addition, plant defense mechanisms such as dense setae on leaves or buds, thicker plant cell walls, or secondary plant compounds may protect against mites feeding on the host plant (Skoracka et al. 2010). The objective of the study was to assess whether foliar feeding by the pecan leafroll mite negatively affects leaf area and leaf chlorophyll content and gas exchange parameters.The experiment was conducted from July to September 2022 in an approximately 25-yr-old pecan orchard of cv. Desirable near Fort Valley, GA (32.55559 N, −83.82753 W). Three trees were randomly selected for data collection. Compound leaves, with or without pecan leafroll mite injury, were selected for examination of gas exchange parameters and leaf area. Leaf readings were taken from attached leaves with and without leafroll injury by using a LI-6800 portable meter (LI-COR, Lincoln, NE) and included net carbon assimilation rate (A), transpiration rate (E), and stomatal conductance to water vapor (gsw). These measurements were taken between 9:00 a.m. and 12 p.m. under field conditions at 1,860 µmol·m−2·s−1 photosynthetic photon flux density and ambient atmospheric CO2 levels (385 ± 23 µmol·mol−1). Gas exchange treatment effects were analyzed using full factorial analysis of variance (ANOVA) using PROC GLM procedure followed by a multiple comparison of means using Tukey's protected honestly significant difference at P = 0.05 (SAS Institute Inc., Cary, NC). Leaf chlorophyll content was determined on attached leaves by using a portable SPAD-502Plus meter (Konica Minolta, Tokyo, Japan) on three leaflets for each of three compound leaves with and without pecan leafroll mite injury. Additional compound leaves with and without pecan leafroll mite injury were collected and taken to the lab for leaf area analysis. On three trees, three compound leaves with pecan leafroll mite injury were collected from three terminals having compound leaves with pecan leafroll mite injury (n = 27 leaves). On the same three trees, compound leaves without pecan leafroll mite injury were similarly collected from terminals without pecan leafroll mite injury (n = 27 leaves). The total number of leaflets per compound leaf was recorded because the number of leaflets per compound leaf varies. Because all leaflets on a compound leaf may not exhibit mite injury, the number of leaflets with pecan leafroll mite damage on those compound leaves with pecan leafroll mite injury was documented. The area of each leaflet on all compound leaves was measured using image analysis software (Image-Pro Premier v.9.3.1, Media Cybernetics, Rockville, MD). Leaflet area for compound leaves with and without pecan leafroll mite injury was analyzed using a one-way ANOVA (JMP 1989–2021). On compound leaves with pecan leafroll mite injury, leaflets with and without injury were analyzed using one-way ANOVA (JMP 1989–2021).SPAD readings are a nondestructive measure of leaf chlorophyll concentrations in which the value is proportional to amount of chlorophyll in the leaf. In this study, leaves with pecan leafroll mite damage had higher SPAD values, but no significant differences in chlorophyll content were observed between healthy leaflets and leaflets with mite damage (P = 0.2146). Differences in net carbon A were not observed between treatments among the three sampling periods. However, significance was observed among dates and treatments for E and gsw (Table 1). Because gsw is a measure of the degree of stomatal opening, it can be used as an indicator of plant water status. A reduced gsw on leaves with pecan leafroll mite damage may indicate water stress and hence lower E, or water movement through the plant as the stomates close to preserve water.Upon visual inspection, pecan leaf roll mite damage on individual leaflets appears to decrease leaflet area, which could affect net photosynthesis and in turn nut development, quality, and yield (Lombardini 2006, HortScience 41: 1469–1473). A comparison of mean leaflet area from compound leaves with pecan leafroll mite injury compared with compound leaves without this injury did not reveal a significant difference in leaflet area for 28 July (F = 12.31; df = 1, 5; P = 0.0725), 29 August (F = 11.69; df = 1, 5; P = 0.0759), or 27 September (F = 1.47; df = 1, 5; P = 0.3487). However, on compound leaves with mite injury, those leaflets with mite injury had lower leaflet area than those leaflets without mite injury and the difference was significant on 28 July (F = 123.68; df = 1, 5; P = 0.0080) and 27 September (F = 51.58; df = 1, 5; P = 0.0188) (Fig. 1).Pecan leafroll mite-damaged compound leaves remain on trees through the season. These damaged leaves are photosynthetically active, and the overall reduction in leaflet area is not different between compound leaves with or without pecan leafroll mite injury. Thus, the leaf parameters measured during this study indicated that the level of damage was cosmetic and would not require treatment. These results suggest, however, that pecan leafroll mite damage may increase leaflet water stress. Severe outbreaks of pecan leafroll mite may cause injury at an economic level and so future studies should investigate the relationship of irrigation on tree health and incidence of pecan leafroll mites on pecan canopies.We thank K. Moncrief, R. Hartley, S. Burrell, and M. Bacon (USDA-ARS, Southeastern Fruit and Tree Nut Research Laboratory) for technical assistance. The findings and conclusions in this publication are those of the authors and should not be construed to represent any official USDA or U.S. Government determination or policy.

IntroductionOriginally regarded as garnish greens, microgreens are increasingly valued for their nutritional profile, including their mineral content. MethodsA study was conducted under controlled environmental conditions utilizing a selection of seventeen microgreen species belonging to seven different botanical families to investigate the genetic variation of macro- and micro-minerals and nitrate (NO3-) content. Plants were grown in a soilless system using a natural fiber mat as the substrate. After germination, microgreens were fertigated with a modified half-strength Hoagland solution prepared using deionized water and without adding microelements. At harvest (10 to 19 days after sowing, based on the species), yield components were measured and dry tissue samples were analyzed for the concentration of total nitrogen (N), NO3-, P, K, Ca, Mg, S, Na, Fe, Zn, Mn, Cu, and B. Results and discussionGenotypic variations were observed for all of the examined parameters. Nitrogen and K were the principal macronutrients accounting for 38.4% and 33.8% of the total macro-minerals concentration, respectively, followed in order by Ca, P, S, and Mg. Except for sunflower (Helianthus annuus L.), all the tested species accumulated high (1,000-2,500 mg kg(-1) FW) or very high (>2,500 mg kg(-1) FW) NO3- levels. Eight of the studied species had a K concentration above 300 mg 100 g(-1) FW and could be considered as a good dietary source of K. On the other hand, scallion (Allium fistulosum L.), red cabbage (Brassica oleracea L. var. capitata), amaranth (Amaranthus tricolor L.), and Genovese basil (Ocinum basilicum L.) microgreens were a good source of Ca. Among micro-minerals, the most abundant was Fe followed by Zn, Mn, B, and Cu. Sunflower, scallion, and shiso (Perilla frutescens (L.) Britton) were a good source of Cu. Moreover, sunflower was a good source of Zn, whereas none of the other species examined could be considered a good source of Fe and Zn, suggesting that supplementary fertilization may be required to biofortify microgreens with essential microminerals. In conclusion, the tested microgreens can be a good source of minerals showing a high potential to address different dietary needs; however, their yield potential and mineral profile are largely determined by the genotype.

A collection representing the native range of pecan was planted at the USDA − ARS Southeastern Fruit and Tree Nut Research Station, Byron, GA. The collection (867 trees) is a valuable genetic resource for characterizing important horticultural traits. Canopy density during leaf fall is important as the seasonal canopy dynamics provides insights to environmental cues and breeding potential of germplasm. The ability of visual raters to estimate canopy density on a subset of the provenance collection (76 trees) as an indicator of leaf shed during autumn along with image analysis values was explored. Mean canopy density using the image analysis software was less compared to visual estimates (11.9% vs 18.4%, respectively). At higher canopy densities, the raters overestimated foliage density, but overall agreement between raters and measured values was good ( ρ c = 0.849 to 0.915), and inter-rater reliability was high ( R 2 = 0.910 to 0.953). The provenance from Missouri (MO-L), the northernmost provenance, had the lowest canopy density in November, and results show that the higher the latitude of the provenance, the lower the canopy density. Based on regression, the source provenance latitude explained 0.609 of the variation using image analysis, and 0.551 to 0.640 when based on the rater estimates of canopy density. Visual assessment of pecan canopy density due to late season leaf fall for comparing pecan genotypes provides accurate and reliable estimates and could be used in future studies of the whole provenance collection.

Carya illinoinensis (Wangenh.) K.Koch production has expanded beyond the native distribution as the genetic diversity of the species, in part, has allowed the trees to grow under broad geographic and climatic ranges. Research in other plant species has demonstrated that the phytobiome enhances their ability to survive and thrive in specific environments and, conversely, is influenced by the prevailing environment and plant genetics, among other factors. We sought to analyze the microbiota of pecan seedlings from the controlled cross ‘Lakota’ × ‘Oaxaca’ that were made in Georgia and Texas, respectively, to determine if the maternal geographical origin influences the microbiome of the resulting progeny. No significant differences in bacterial communities were observed between the seeds obtained from the two different states (p = 0.081). However, seed origin did induce significant differences in leaf fungal composition (p = 0.012). Results suggest that, in addition to some environmental, epigenetics, or host genetic components, ecological processes, such as dispersal mechanisms of the host, differentially impact the pecan microbiome, which may have ramifications for the health of trees grown in different environments. Future studies on the role of the microbiome in plant health and productivity will aid in the development of sustainable agriculture for improved food security.

Soilborne pests are a major obstacle that must be overcome for the production of horticultural crops. Methyl bromide (MBr) was an effective preplanting soil broad-spectrum biocide, but its use has been banned due to its role in depleting the ozone layer. As a result, sustainable alternative methods for controlling soilborne pathogens and pests are needed. Nitrous oxide (N2 O) emissions are of concern in crop production due to the role of N2 O as a greenhouse gas. Agricultural lands are known sources for emission of N2 O into the atmosphere. Emissions are related to many environmental factors as well as fertilization and fumigation practices. This study evaluated the influence of different alternatives to MBr on N2 O emissions throughout a tomato production season in two locations representative of southern and northern Florida. We evaluated eight soil management practices, including (a) untreated controls; (b) chemical soil fumigation; (c) anaerobic soil disinfestation using molasses (M) + composted poultry litter and (d and e) M + composted yard waste (CYW, at two rates); (f) Soil Symphony Amendment (SSA), a commercially available mix of microbes and nutrients; (g) CYW alone; and (h) CYW + SSA. Nitrous oxide emissions were measured throughout the cropping season. Emissions were highest on the day of planting (Day 21), ranging from 213 to 1,878 μg m-2 h-1 , likely due to the release of N2 O that had accumulated under the totally impermeable film when it was punctured for planting. However, statistical significance varied between sites. Estimated cumulative emissions of N2 O throughout the production season ranged from 1.3 to 4.8 kg N2 O-N ha-1 .

Genome-enabled biotechnologies have the potential to accelerate breeding efforts in long-lived perennial crop species. Despite the transformative potential of molecular tools in pecan and other outcrossing tree species, highly heterozygous genomes, significant presence-absence gene content variation, and histories of interspecific hybridization have constrained breeding efforts. To overcome these challenges, here, we present diploid genome assemblies and annotations of four outbred pecan genotypes, including a PacBio HiFi chromosome-scale assembly of both haplotypes of the 'Pawnee' cultivar. Comparative analysis and pan-genome integration reveal substantial and likely adaptive interspecific genomic introgressions, including an over-retained haplotype introgressed from bitternut hickory into pecan breeding pedigrees. Further, by leveraging our pan-genome presence-absence and functional annotation database among genomes and within the two outbred haplotypes of the 'Lakota' genome, we identify candidate genes for pest and pathogen resistance. Combined, these analyses and resources highlight significant progress towards functional and quantitative genomics in highly diverse and outbred crops.

Wilt and vine decline symptoms were observed on watermelon plants in Glades and Hardee Counties in Florida in spring 2017 that resembled viral watermelon vine decline caused by squash vein yellowing virus (SqVYV). When no SqVYV was detected, greenhouse studies and morphological and molecular analyses revealed three fungal pathogens, Macrophomina phaseolina, Fusarium brachygibbosum, and Lasiodiplodia theobromae, that were not previously reported on watermelon in Florida. A previously reported oomycete, Pythium spinosum, was also detected in some, but not all, isolations and when applied independently resulted in disease incidence that was comparable to the untreated check, ruling it out as a primary causal agent of the symptoms observed in the field. In one of three experiments, seedlings inoculated with a combination of M. phaseolina, F. brachygibbosum, and P. spinosum suffered the highest disease severity based on AUDPC values. In another experiment, seedlings inoculated with F. brachygibbosum exhibited the most severe symptoms and rapid disease development following inoculation. When seeds were inoculated with either a single or a combination of the isolated fungi, those inoculated with L. theobromae resulted in seedlings with the greatest disease severity. This is the first report of these three fungal pathogens on watermelon in Florida.

Dominus (R) (Isagro, USA), a newly registered biofumigant in the United States with active ingredient allylisothiocyanate (AITC), is currently under evaluation for use as a pre-plant soil treatment for both conventional and organic crop production. In recent field trials, Dominus provided root-knot nematode control in ornamental crops equivalent to that achieved with methyl bromide, but had inadequate weed control. A series of factorial field trials were conducted to evaluate weed and disease control in which Dominus was compared to an experimental formulation of organic acids and an untreated control. These treatments were applied with or without registered herbicides for tomato and bell pepper production. Application of the biofumigant (280 L ha(-1)) resulted in lower incidence of bacterial wilt (Ralstonia solanacearum) of tomato and soil populations of root-knot nematodes (Meloidogyne spp.). There was no improvement in nutsedge control with soil treatments, but both herbicides (fomesafen and halosulfuron) were effective in reducing nutsedge germination. Yields of both bell pepper and tomato were greatest in Dominus-treated plots, regardless of herbicide application. Combining Dominus with an herbicide provided broad-spectrum control of pathogens and weeds. The active ingredient AITC has well established potential as a biofumigant and the availability of a commercial formulation that can be combined with labeled herbicides provides a greatly needed pest control option.

Anaerobic soil disinfestation (ASD) is a pre-plant biological soil disinfestation technique proposed for the simultaneous control of soilborne pathogens, nematodes, and weeds in several horticultural crops grown in conventional and organic systems. The technique is applied by amending the soil with a labile carbon source, tarping the soil with totally impermeable film, and irrigating the soil to saturation. The rapid shift of redox potential stimulates the growth of anaerobic microorganisms and the anaerobic decomposition of the C source, with the consequent production of metabolites (organic acids, aldehydes, alcohols, ammonia, and volatile organic compounds), which results in the suppression of many soilborne pathogens and pests. The changes in the soil microbial population, redox potential, and pH that occur during ASD may also have an impact on nutrient cycling, thereby affecting soil fertility, availability of nutrients for the crop, and potential loss of nutrients into the environment. Understanding the nutrient dynamics and the factors that influence the availability and/or loss of nutrients during and after ASD treatment is critical for the sustainable application of this technique on a large scale. The objective of this work was to review the factors that govern the nutrient cycling in relation to ASD treatment, discuss potential solutions to optimize crop nutrient management and minimize the risks of nutrient loss, and identify future research priorities. While there are concerns about N2O emissions and nutrient leaching, the results of previous studies and of ongoing research activities conducted at multiple sites suggest that the risks of nutrient loss are not higher than those associated with standard chemical soil fumigation practices. Instead, there is clear evidence that ASD has both short- and long-term effects on the soil fertility and, excluding some risks of phytotoxicity at transplanting, ASD has been demonstrated to have positive effects on plant growth and crop yield.

In the search for alternative practices to chemical soil fumigation (CSF), anaerobic soil disinfestation (ASD) has proven to be a promising tool for soil-borne pest management and crop production improvement. The ASD treatment with composted poultry litter (CPL) and molasses (M, a labile carbon source) was identified as an effective approach for a biologically based soil disinfestation system in tomato (Solanum lycopersicumL.) production in Florida. However, environmental and food-safety concerns are associated with animal manure-based amendments, which led to the exploration of composted yard waste (CYW) as a potential substitute for CPL in ASD application. In this study, field trials were conducted in Citra and Immokalee, FL to examine the effects of ASD using CYW, CPL and M compared with a commercially available microbial amendment system on root-knot nematodes, weeds, fruit yield and quality of fresh-market tomato. Treatments included (1) ASD with CPL (11 Mg ha(-1)) and M (6.9 m(3)ha(-1)) (ASD0.5), (2) ASD with CYW (26.9 Mg ha(-1)) and M (CYW1 + M), (3) ASD with CYW (13.5 Mg ha(-1)) and M (CYW0.5 + M), (4) Soil Symphony Amendment (SSA), (5) CYW (26.9 Mg ha(-1)) alone (CYW1) and (6) a combination of CYW1 + SSA, in comparison with (7) untreated control and (8) CSF (Pic-Clor 60 at 224 kg ha(-1)). Cumulative soil anaerobiosis was greater in ASD0.5 compared with all the other treatments. The root-knot nematode gall index ratings on the tomato crop were significantly lower in CSF, ASD0.5, CYW1 + M and CYW0.5 + M than untreated control in Citra. Although CYW1 and SSA alone had a moderately suppressive effect on weed coverage and root-knot nematodes, their positive impact on crop performance was limited when used alone. ASD0.5, CYW1 + M and CSF had significantly higher marketable and total fruit yields than untreated control in both locations, while all treatments showed promising results in the Immokalee trial in comparison with untreated control. In general, few differences in major fruit quality attributes were found. Although using CYW in ASD was not as effective as CPL in creating soil anaerobic conditions, the enhanced crop performance in CYW1 + M and CYW0.5 + M suggests the potential of using CYW as an alternative source of organic amendment in combination with M to achieve benefits similar to those obtained with CPL-based ASD.

Background Pecan ( Carya illinoinensis ) is an important native nut crop in the southern USA. In the Southeast, scab (caused by Venturia effusa ) is a major constraint to production, and can result in significant yield losses. The breadth of sources of resistance are poorly defined, and the genetics of resistance has not been established. The aim of this study was to assess the severity of pecan scab on foliage and fruit of the trees in a collection at Georgia, USA, of 875 native pecan genotypes from 93 families in 19 provenances in various states in the USA and Mexico. Methods The scab responses on foliage and fruit on each pecan tree was visually assessed in 2018 and 2019. Both a most severe measure (most severely infected leaf or fruit), and an overall tree rating was taken. Scab severity data were analyzed using a mixed linear model with means separation to explore provenance and family within provenance scab susceptibilities. Results Significant differences in scab susceptibility between provenances and among families within provenances were detected. Trees from provenances in Illinois, Kansas, Kentucky, Missouri, Mississippi, Tennessee and Texas, USA, showed the greatest resistance (based on mean scab severity) for both foliar and fruit scab. Assessments of scab on foliage and fruit gave similar results, as did the values for the most severe scab in the tree and the overall scab severity score. Of the 875 trees assessed, 201 trees had no detectable scab symptoms on foliage or fruit in either year. An additional 116 trees were free of scab symptoms on foliage but did not produce fruit in either year. Those provenances, families within provenances and trees with greatest resistance to scab most often originated from provenance locations with higher rainfall and consequently would be under selection to adapt to scab. Conclusions Identifying populations with most diverse resistance, and those most consistently resistant trees can serve as a resource to develop a better understanding of the scab resistance mechanisms. These natural sources of scab resistance coupled with molecular and genomics tools will contribute to the accelerated development of new pecan cultivars with durable resistance to scab.

Anaerobic soil disinfestation (ASD) is a non-chemical alternative to soil fumigation based on the combined concepts of biofumigation, biosolarization, soil saturation, and forced shifts in the microbial community that are highly dependent upon soil temperature, moisture, and the availability of a labile carbon source. This method is currently being investigated in many countries, with its origins in the Netherlands and Japan. Different organic amendments are being evaluated as carbon sources for ASD, including rice bran in California and sugarcane molasses in Florida, USA. In Florida, composted poultry litter (CPL) and sugarcane molasses are applied with 5 cm of initial irrigation, and beds are then covered with totally impermeable film (TIF) and allowed to incubate for 3 weeks. Levels of anaerobicity are monitored throughout the treatment time with a cumulative Eh target of 50,000 mVh for control of some soilborne plant-pathogenic fungi. In order to address researchable issues related to the implementation and adoption of ASD, a regional project was initiated in the southeastern United States in which a multi -disciplinary team conducted ASD field trials to answer specific grower-driven questions concerning ASD. Using tomato as the target crop, field trials were established at multiple locations in order to determine whether ASD could be: conducted utilizing opaque TIF; established prior to a spring production system when soil temperatures are cooler than for fall production; and combined with herbicides without causing crop phytotoxicity. In addition, concerns over nitrogen loss to the atmosphere as well as issues regarding expense of effective labile carbon sources are addressed.