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Successful disease management has always been vital in Florida tomato production, given the generally ideal environmental conditions for most plant diseases. An integrated disease management program is a successful approach.

ABSTRACT Type VI secretion system (T6SS) is a versatile, contact-dependent contractile nano-weapon in Gram-negative bacteria that fires proteinaceous effector molecules directly into prokaryotic and eukaryotic cells aiding in manipulation of the host and killing of competitors in complex niches. In plant pathogenic xanthomonads, T6SS has been demonstrated to play these diverse roles in individual pathosystems. However, the molecular network underlying the regulation of T6SS is still elusive in Xanthomonas spp. To bridge this knowledge gap, we conducted an in vitro transcriptome screen using plant apoplast mimicking minimal medium, XVM2 medium, to decipher the effect of tssM deletion, a core gene belonging to T6SS-cluster i3*, on the regulation of gene expression in Xanthomonas perforans strain AL65. Transcriptomic data revealed that a total of 277 and 525 genes were upregulated, while 307 and 392 genes were downregulated in the mutant strain after 8 and 16 hours of growth in XVM2 medium. The transcript abundance of several genes associated with flagellum and pilus biogenesis as well as type III secretion system was downregulated in the mutant strain. Deletion of tssM of cluster-i3* resulted in upregulation of several T6SS genes belonging to cluster-i3*** and genes involved in biofilm and cell wall biogenesis. Similarly, transcription regulators like rpoN, Pho regulon, rpoE, and csrA were identified to be upregulated in the mutant strain. Our results suggest that T6SS modulates the expression of global regulators like csrA, rpoN, and pho regulons, triggering a signaling cascade, and co-ordinates the expression of suite of virulence factors, stress response genes, and metabolic genes. IMPORTANCE T6SS has received attention due to its significance in mediating interorganismal competition through contact-dependent release of effector molecules into prokaryotic and eukaryotic cells. Reverse-genetic studies have indicated the role of T6SS in virulence in a variety of plant pathogenic bacteria, including the one studied here, Xanthomonas. However, it is not clear whether such effect on virulence is merely due to a shift in the microbiome-mediated protection or if T6SS is involved in a complex virulence regulatory network. In this study, we conducted in vitro transcriptome profiling in minimal medium to decipher the signaling pathways regulated by tssM-i3* in X. perforans AL65. We show that TssM-i3* regulates the expression of a suite of genes associated with virulence and metabolism either directly or indirectly by altering the transcription of several regulators. These findings further expand our knowledge on the intricate molecular circuits regulated by T6SS in phytopathogenic bacteria.

Ginger, galangal, and turmeric (Figure 1) are emerging crops for Florida production. All of these plants are in the Zingiberaceae family and share most aspects of their production. This bulletin describes production in containers or the field under Florida conditions to help guide growers interested in ginger, turmeric, and galangal production or expanding their market. All species have been evaluated by the UF/IFAS Assessment of Non-native Plants in Florida’s Natural Areas (UF/IFAS Assessment) using the Predictive Tool (an invasion risk assessment) and all present a low risk of invasion in Florida (https://assessment.ifas.ufl.edu).

Watermelon (Citrullus lanatus), cantaloupe or muskmelon (Cucumis melo), squash (Cucurbita pepo), bitter gourd (Momordica charantia), and cucumber (Cucumis sativa) are commonly grown throughout Florida on both commercial farms and home gardens, while pumpkin (Cucurbita maxima) production is largely limited to north Florida. Anthracnose on cucurbits, caused by the fungus Colletotrichum orbiculare, is a common disease that occurs worldwide and throughout Florida. While all cucurbits are susceptible to the disease, cucumber, cantaloupe, and watermelon are most frequently affected. This EDIS document provides information regarding the pathogen, disease cycle, diagnostics and symptoms, and an overview of management of this disease on cucucurbits.

Summer squash (Cucurbita pepo L.) is a major vegetable crop produced in Georgia and Florida during the fall season. This production is vulnerable to whitefly (Bemisisia tabaci Genn.)-transmitted viruses that lead to severe yield losses. Over the past several years, whitefly populations have increased during the fall, thus leading to an increase in whitefly-transmitted viruses such as Cucurbit leaf crumple virus (CuLCrV) and Cucurbit yellow stunting disorder virus (CYSDV). Whitefly management for summer squash relies on the use of insecticides and can be costly without providing adequate management of the viruses. Deployment of host resistance to whiteflies and their transmitted viruses (CuLCrV and CYSDV) is the best strategy for mitigating yield loss of summer squash; however, no resistant cultivars are commercially available. In the current study, resistance or tolerance to whiteflies, CuLCrV, and CYSDV was determined for squash germplasm from the U.S. Department of Agriculture (USDA) Germplasm Resources Information Network (GRIN), university breeding programs, and commercial companies in Georgia and Florida across 2 years. In both locations and years, visual virus symptom severity scores were collected and a quantitative polymerase chain reaction (qPCR) was used to determine the CuLCrV viral load and CYSDV presence in Georgia. Whitefly-induced feeding damage was evaluated by directly assessing the intensity of silverleaf symptoms and visual counts of whitefly adults on the foliage in the field or in photographs. Virus symptom severity was lower in C. moschata Duchesne ex Poir. genotypes, namely, PI 550689, PI 550692, PI 550694, PI 653064, and Squash Betternut 900, than in other evaluated genotypes. Two C. pepo accessions were common between both locations for viral severity (PI 442294) or viral severity and viral load (PI 171625). Lower CuLCrV loads were identified in C. ecuadorensis Cutler & Whitaker (PI 540895), and C. okeechobeensis (Small) L.H.Bailey (PI 540900) than other evaluated genotypes. Four genotypes tested negative for CYSDV during both years: C. pepo (PI 507882), C. moschata (PI 483345), C. ecuadorensis (PI 390455), and C. okeechobeensis (PI 540900); they are potential sources of resistance. Six C. moschata accessions (PI 211999, PI 550690, PI 550692, PI 550694, PI 634982, and PI 653064) showed high tolerance to silverleaf disorder and had the lowest adult whitefly counts. Collectively, the accessions identified in the current study are potential sources of resistance or tolerance to whitefly and whitefly-transmitted viruses (CuLCrV and CYSDV).

This new 7-page article provides a concise overview of some influential high-tunnel tomato soilborne and foliar diseases and their cultural management techniques. Written by Zachary D. Eldred, Shufang Tian, Gary E. Vallad, Xin Zhao, Mathews Paret, and Nicholas S. Dufault and published by the UF/IFAS Plant Pathology Department. https://edis.ifas.ufl.edu/pp368

Chapter 4 of the Vegetable Production Handbook of Florida

This publication lists and describes common viruses spread in cucurbit crops by whiteflies. It includes strategies for managing whiteflies, most of them originally from a similar publication on managing whiteflies in tomatoes.

Chapter 4 of the Vegetable Production Handbook.

This study explores the development of Loop-mediated isothermal amplification (LAMP) for detection of rose rosette virus (RRV), a technique with the potential to be translated to rose nurseries. RRV is a negative-sense, single-stranded RNA virus which is a member of the genus Emaravirus (Family Fimoviridae) and the causal agent of the rose rosette disease (RRD). Although RRV symptoms are characteristics, early visual diagnosis of RRD can be misleading and confusing since it may appear like herbicide damage. Moreover, it may take incubation time for symptoms to appear after virus infection. Two sets of RRV gene sequences RNA3 and RNA4 were analyzed and two sets of four LAMP primers were designed. The direct antigen-capture method for direct trapping of RRV in plastic was used for RNA extraction followed by cDNA synthesis. RT-LAMP reactions were for 1 hour at 64°C (RRV-P3) and 66.5°C (RRV-P4) using either a thermocycler or a portable dry bath. RT-qLAMP was also optimized using DNA polymerase GspSSD LD using the same RRV sets of primers. RRV was detected in symptomatic and non-symptomatic RRD tissue from Oklahoma. The limit of detection (LoD) was 1pg/μL and 1 fg/μL using Bst 2.0 LAMP and GspSSD LD quantitative LAMP, respectively. In visual colorimetric pre- and post-reactions, the LoD was 10 pg/μL and 0.1 pg/μL using hydroxy naphthol blue (HNB, 120 μM) and SYBR green I (1:10 dilution), respectively. No cross-reactivity was detected in the RT-LAMP reaction testing cDNAs of eight commonly co-infecting rose viruses and one virus taxonomically related to RRV. Four different dyes were tested, and visible colorimetric reactions were obtained with RT-LAMP Bst 2.0 combined with SYBR I or HNB. RT-qLAMP with GspSSD2.0 offers LoD equal to RT-PCR and it is faster since it works with RNA directly.

This chapter covers production of cucurbits, such as cantaloupe, cucumber, squash, watermelon, and pumpkin.

Bacterial wilt, caused by Ralstonia solanacearum, is an emerging constraint in amaranth production in Benin. Host resistance is the most sustainable disease control measure. Ten amaranth varieties including A2002, Bresil (B) -Sel, Madiira 2, AC-NL, GARE ES13-7, Madiira 1, UG-AMES13-2, AM-NKGN, IP-5-Sel and a local variety from Benin were screened for resistance to bacterial wilt. The study was conducted in a screen house and in the naturally contaminated open field during a consecutive rainy and dry season using a randomized complete block design with four and three replications, respectively. In the screen house, plants were inoculated by drenching a 40 mL of bacterial suspension containing 108 CFU/mL of R. solanacearum strain NCBI 5 GenBank N° MH397250 at the collar region. The bacterial wilt incidence (BWI) and the area under the disease progress curve (AUDPC) suggested differential reactions of amaranth varieties to the pathogen. BWI and AUDPC were low for UG-AMES13-2, moderate for Madiira 2, AM-NKGN and the local variety and very high for A2002, Bresil (B) -Sel, AC-NL, GARE ES13-7, Madiira 1 and IP-5-Sel. The World Vegetable Center’s UG-AMES13-2 can be considered as first choice, which is resistant to R. solanacearum, and should be scaled up for seed production towards supporting farmers.

Bacterial spot is one of the most detrimental diseases of tomato and is especially severe in the southeast United States when weather conditions (high temperature, high humidity, and rain) become conducive for disease development. This new 8-page publication of the UF/IFAS Plant Pathology Department presents updated information about the causal pathogen and management of bacterial spot on tomato in Florida. Written by Amanda Strayer-Scherer, Ying-Yu Liao, Peter Abrahamian, Sujan Timilsina, Mathews Paret, Tim Momol, Jeff Jones, and Gary Vallad. https://edis.ifas.ufl.edu/pp353

Fusarium wilt of watermelon is one of the most serious and difficult diseases to manage and occurs in most production regions worldwide. The fungus can be seedborne and has great longevity in the soil, allowing infested soil to also serve as a source of infection. This new 4-page publication of the UF/IFAS Plant Pathology Department signs, symptoms, and the disease cycle of Fusarium wilt and provides recommendations for cultural and chemical management. Written by Pamela Roberts, Nicholas Dufault, Robert Hochmuth, Gary Vallad, and Mathews Paret. https://edis.ifas.ufl.edu/pp352

This 28-page fact sheet is chapter 7 of the 2018 Vegetable Production Handbook. Written by Josh H. Freeman, Eugene J. McAvoy, Nathan S. Boyd, Monica Ozores-Hampton, Mathews Paret, Qingren Wang, Christian F. Miller, Johan Desaeger, Joseph W. Noling, and Xavier Martini, and published by the Horticultural Sciences Department, 2018. HS725/CV123: Chapter 7. Cucurbit Production (ufl.edu)

Rhizobium radiobacter (also known as Agrobacterium tumefaciens), has been reported to be found on more than 600 different plant species worldwide including many common vegetables, weeds, deciduous and evergreen trees and shrubs. This document discusses the biology, symptom expression, and management of this bacterium.

Snap bean is an important vegetable crop in Florida. It is produced in all regions of the state. Bush snap beans dominate commercial plantings, but pole beans are also produced, primarily in Miami-Dade County. Midwinter bean production, the most profitable for Florida, is centered in the Homestead, southwest Florida, and Belle Glade areas. Based on the 2012 US Census of Agriculture (NASS, USDA), snap bean is an economically important vegetable crop in Florida with a total of 33,338 acres harvested in 2012. Miami-Dade County ranked second in snap bean production in the United States with a total of 11,126 acres. Because of Florida's warm and wet weather, many diseases affect snap beans. Disease management is an important component in successful snap bean farming. Despite vigorous control efforts, substantial losses in yield and quality can still occur. This publication suggests a sequential disease control program for snap beans in Florida. Postharvest disease problems are addressed only to the extent that they are affected by field practices. The application of the following sequential control program should minimize yield losses for the majority of plantings. This revision is by Shouan Zhang, Nicholas Dufault, Mathews Paret, Pamela Roberts, Guodong Liu, and Qingren Wang.

Several invasive species of thrips have established in Florida and are causing serious economic losses to vegetable, ornamental, and agronomic crops. Damage to crops results from thrips feeding and egg-laying injury, by the thrips vectoring of plant diseases, the cost of using control tactics, and the loss of pesticides due to resistance. This updated fact sheet describes the biology and ecology of thrips and tomato spotted wilt virus, and recommends a management program. ENY859/IN895: Managing Thrips and Tospoviruses in Tomato (ufl.edu)

Roses are one of the most popular flowering shrubs in Florida and the United States. Valued for their beautiful and often fragrant blooms, roses have been cultivated in gardens for centuries as vines. Roses can grow and flower 9 months of the year in North Florida and year-round in the rest of Florida. Roses have become especially popular in recent years with the introduction of Knock Out® and other shrub roses. Unfortunately, increased use and misuse of roses have resulted in more reports of pest problems. This revised 9-page fact sheet was written by Gary W. Knox, Mathews Paret, and Russell F. Mizell, III, and published by the UF Department of Environmental Horticulture, January 2012. ENH1108/EP371: Rose Pests and Diseases in Florida (ufl.edu)