Nabil Killiny

University of Florida | UF · Department of Plant Pathology

Photosynthesis, the remarkable process by which green plants synthesize nutrients using light energy, plays a crucial role in sustaining life on Earth. However, the effects of pathogens on photosynthesis are not widely understood. In general, a reduction of photosynthesis occurs upon the infection with pathogens. Two main scenarios are responsible...

The vector-borne disease Huanglongbing (HLB) causes severe economic losses to citrus production worldwide with no available cure. Herein, we applied virus-induced gene silencing technology to engineer citrus that preferentially attracted and specifically killed Diaphorina citri, the vector associated with HLB. We engineered the infectious citrus tr...

Main conclusion Overexpression of VvmybA1 transcription factor in ‘Hamlin’ citrus enhances cold tolerance by increasing anthocyanin accumulation. This results in improved ROS scavenging, altered gene expression, and stomatal regulation, highlighting anthocyanins’ essential role in citrus cold acclimation. Abstract Cold stress is a significant thre...

Polyploidy induction is a promising strategy for enhancing stress tolerance and physiological resilience in crop plants. In this study, we investigated the efficacy of oryzalin treatment in inducing autoploidy in the finger lime hybrid 'UF SunLime' and examined its implication for cold tolerance and physiological responses to stress. Murashige and...

‘Candidatus Liberibacter asiaticus’, the putative causal agent of citrus greening disease is transmitted by the Asian citrus psyllid, Diaphorina citri in a propagative, circulative, and persistent manner. Unfortunately, ‘Ca. L. asiaticus’ is not yet available in pure culture to carry out Koch’s postulates and to confirm its etiology. When a pure cu...

BACKGROUND Asian citrus psyllid, Diaphorina citri, is a hemipteran that vectors the causal pathogen of citrus greening disease, or huanglongbing (HLB). HLB is a tree killing disease that has severely limited citrus production globally. Unfortunately, there is no cure for this disease, and mitigation depends on multiple insecticide applications to r...

Enzymatic browning poses a significant challenge that limits in vitro propagation and genetic transformation of plant tissues. This research focuses on investigating how adding antioxidant substances can suppress browning, leading to improved efficiency in transforming plant tissues using Agrobacterium and subsequent plant regeneration from rough l...

Anthocyanins are a class of natural pigments that accumulate transiently or permanently in plant tissues, often in response to abiotic and biotic stresses. They play a photoprotective role by attenuating the irradiance incident on the photochemical apparatus and quenching oxyradicals through their powerful anti-oxidative function. The objective of...

Resistance and cultural control strategies are usually sufåcient for managing sorghum diseases. The majority of the issues associated with sorghum diseases can be prevented by taking one or more of the following practical measures: • It is recommended to use locally adapted, disease-resistant germplasm if it is available. • Grow healthy plants from...

Somatic hybridization has emerged as a valuable tool for developing novel genetic combinations in citrus breeding programs, including the creation of salt-tolerant rootstocks. In this study, the performance of a tetraploid somatic hybrid, obtained by fusing protoplasts derived from salt-tolerant Cleopatra mandarin (Citrus reshni hort. ex Tanaka) an...

Huanglongbing (HLB; also known as citrus greening) is the most destructive bacterial disease of citrus worldwide with no known sustainable cure yet. Herein, we used non-targeted metabolomics and transcriptomics to prove that γ-aminobutyric acid (GABA) accumulation might influence the homeostasis of several metabolic pathways, as well as antioxidant...

The devastating citrus disease, Huanglongbing (HLB), is associated with ‘Candidatus Liberibacter sp.’ and transmitted by citrus psyllids. Unfortunately, HLB has no known sustainable cure yet. Herein, we proposed γ-aminobutyric acid (GABA) as a potential eco-friendly therapeutic solution to HLB. Herein, we used GC/MS-based targeted metabolomics comb...

Anthocyanin accumulation naturally occurs in the ‘blood orange’ (Citrus sinensis (L.) Osbeck) and is controlled by a retrotransposon that is inserted in the promoter of the Ruby transcription factor upon cold stress. Several enzymes work sequentially for anthocyanin biosynthesis following the activation of Ruby. We analyzed the juice vesicles of no...

Most Citrus cultivars are cold sensitive, and the low temperature can be a major limiting factor during the cultivation of many commercially important citrus cultivars. In contrast with Citrus, Poncirus trifoliata, a related species, is extremely cold tolerant with high survival rate under freezing at −20 °C ( −4 °F). Cold induction of genes encodi...

The CRISPR/Cas9 system is a promising technology for genome editing in plants. Protoplasts, which are plant cells with the cell wall enzymatically removed are often utilized for the development of genetically modified plants by the in vitro integration of recombinant DNA (either plasmid-based or linear) into the plant genome. Various methods such a...

‘UF SunLime’, a distinct diploid and monoembryonic Finger lime hybrid cultivar, is a precocious bearing tree that produces deep red, seedy fruits. This unique cultivar has excellent potential as a breeding parent for the development of the next generation of newer finger lime hybrids. In this study, oryzalin was used to develop autotetraploid plant...

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae) transmits the Gram-negative bacterium 'Candidatus Liberibacter asiaticus' that causes citrus greening disease. While chemical control has been the main management strategy for limiting D. citri, the widespread usage of chemical sprays has decreased the susceptibility of D. ci...

Somatic hybridization is an efficient tool for the development of novel genotypes and are used in citrus breeding programs. Somatic hybrids can lead to the direct development of tetraploid rootstocks or be used as breeding parents for the development of triploid scion cultivars. The Cleopatra mandarin is a salt-tolerant rootstock, while the Carrizo...

Plant bacterial pathogens transmitted by Hemipteran vectors pose a large threat to the agricultural industry worldwide. While virus-vector relationships have been widely investigated, a significant gap exists in our understanding of the molecular interactions between circulative bacteria and their insect vectors, mainly leafhoppers and psyllids. In...

Citrus greening disease is now completely endemic to Florida citrus trees, having spread rapidly across all counties in the past 20 years and causing devastating economic losses. The disease’s etiological agent is the phloem-restricted bacterium, Candidatus Liberibacter asiaticus (CLas). Liberibacter crescens, the closest culturable relative, was d...

DNA microarrays are a powerful technology that has great implications in plant sciences, biomedical sciences, veterinary, and pharmacological research. It can deal with large numbers of samples for the detection of microbes, clinical diagnosis, gene expression analysis, host–pathogen interactions, food safety testing, and environmental monitoring....

The Asian citrus psyllid, Diaphorina citri is the main vector of citrus greening disease, also known as Huanglongbing (HLB). Currently, mitigating HLB depends on the control of D. citri using insecticides. To design innovative control strategies, we should investigate various biological aspects of D. citri at the molecular level. Herein we explored...

Huanglongbing (HLB), which is caused by the phloem-limited bacterium 'Candidatus Liberibacter asiaticus,' is an economically important disease of citrus in many regions of the world. Due to the significant damage caused by the HLB disease in recent years, the use of antibiotics was recommended for the therapy of this destructive disease. Products w...

Dissecting the heads of small insects belonging to the order Hemiptera for detailed anatomical investigation with light or scanning electron microscopy is difficult, time-consuming, and destructive, often resulting in sample preparation artifacts. Nevertheless, the structural details of these insects often hold critical information regarding their...

Virus-induced gene silencing is a promising technique for functional genomics studies. Citrus tristeza virus was employed successfully to create an infectious clone that was used to silence endogenous citrus genes. Phytoene desaturase (PDS) and delta (δ)-aminolevulinic acid dehydratase (ALAD) were targeted successfully in citrus. Silencing PDS usua...

Citrus is a major fruit crop cultivated on a global scale. Citrus trees are long lived perennials with a large canopy. Understanding the genetic control of tree architecture could provide tools for breeding and selection of citrus cultivars suitable for high density planting with improved light exposure. Tree architecture is modulated by the TILLER...

The curry leaf tree, Bergera koenigii, is highly attractive to the Asian citrus psyllid, Diaphorina citri, which vectors the bacterial causative agent of citrus greening or huanglongbing disease. This disease has decimated citrus production in Florida and in other citrus-producing countries. As D. citri exhibits high affinity for feeding on young l...

Volatile organic compounds (VOCs) are a large group of lipophilic hydrocarbon compounds derived from different biosynthetic pathways in plants. VOCs are produced and released from plants as a defense mechanism against biotic and abiotic stresses. They are involved in communication with the surrounding environment including plant-to-plant interactio...

The δ-aminolevulinic acid dehydratase (ALAD) enzyme is an intermediate in the biosynthetic pathway of tetrapyrroles. It combines two δ‐aminolevulinic acid (δ‐ALA) molecules to form the pyrrole, porphobilinogen, an important precursor for plant pigments involved in photosynthesis, respiration, light-sensing, and nutrient uptake. Our recent efforts s...

Although the mitochondria retain all required enzymes for an intact tricarboxylic acid (TCA) cycle, plants might shift the cyclic flux from the TCA cycle to an alternative noncyclic pathway via γ-aminobutyric acid (GABA) shunt under specific physiological conditions. We hypothesize that several genes may ease this noncyclic flux and contribute to t...

Under tropical and subtropical environments, citrus leaves are exposed to excess sunlight, inducing photoinhibition. Huanglongbing (HLB, citrus greening), a devastating phloem‐limited disease putatively caused by Candidatus Liberibacter asiaticus, exacerbates this challenge with additional photosynthetic loss and excessive starch accumulation. A co...

Nowadays, citrus greening or Huanglongbing is considered the most destructive disease in the citrus industry worldwide. In the Americas and Asia, the disease is caused by the putative pathogen, ‘Candidatus Liberibacter asiaticus’ and transmitted by the psyllid vector, Diaphorina citri. It has been shown that volatile organic compounds (VOC) that ar...

Nowadays, the Asian citrus psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Liviidae) is considered the most devastating pest of citrus because it transmits “Candidatus Liberibacter asiaticus”, the putative causal agent of huanglongbing (HLB) or citrus greening. Controlling the vector is the main strategy used to mitigate HLB. Targeting D. citri at...

The Asian citrus psyllid, Diaphorina citri Kuwayama is devastating the citrus industry worldwide. It transmits 'Candidatus Liberibacter asiaticus', the pathogen of Huanglongbing in citrus. RNA interference is an excellent tool for functional genomics and for screening target genes for pest control. Herein, we silenced the aquaporin (AQP) gene (DcAQ...

‛Candidatus Liberibacter asiaticus’, the putative causal agent of citrus greening is not available in pure culture yet. In addition to trees of citrus and citrus relatives, ‛Ca. L. asiaticus’ can grow in Madagascar periwinkle (Catharanthus roseus). Using GC-MS, we compared the phloem sap composition in sweet orange ‛Valencia’ (Citrus sinensis) and...

Oxytetracycline (OTC) has been used for the control of several plant diseases and was recently approved for the control of Huanglongbing, the citrus greening disease. Huanglongbing is caused by the phloem limited ‘Candidatus Liberibacter asiaticus’. Determination of OTC in the xylem and phloem of citrus plants is of great interest as they are the m...

Citrus greening, or Huanglongbing (HLB), currently is the most destructive disease of citrus. HLB disease is putatively caused by the phloem-restricted α-proteobacterium, ‛Candidatus Liberibacter asiaticus’. This bacterium is primarily transmitted by the Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae). Most animal pathogens are conside...

Key message Overstory shade enhances photochemical performance of feral citrus trees and reduces transmission of an invasive vectored pathogen. Abstract Feral citrus trees growing under forest overstory appeared healthy and showed no symptoms of huanglongbing (HLB; citrus greening disease), despite high infection rates and obvious symptoms in open...

Oxytetracycline (OTC) and streptomycin have been used for the control of several plant diseases and were recently permitted for the control of citrus greening disease, Huanglongbing. Consequently, sensitive and reliable methods are highly needed for the detection of OTC in citrus tissues. Herein, we studied the replacement of cetyltrimethylammonium...

Melatonin is synthesized from the amino acid L-tryptophan via the shikimic acid pathway and ubiquitously distributed in both prokaryotes and eukaryotes. Although most of melatonin biosynthesis genes were characterized in several plants and animal species including the insect model, Drosophila melanogaster, none of these enzymes have been identified...

Huanglongbing (HLB) is one of the most destructive diseases in citrus worldwide. Unfortunately, HLB has no cure and management relies on insecticides to reduce populations of the vector, Diaphorina citri Kuwayama (Hemiptera: Liviidae). We propose an attract-and-kill strategy using a trap crop as an alternative to vector control to reduce transmissi...

Antimicrobial compounds have been successfully used to control many plant and animal diseases. Recently, oxytetracycline (OTC) and streptomycin have been approved for the treatment of Huanglongbing in citrus. Since the application of OTC is under strict regulations, several methods have been developed to determine and monitor its levels in the envi...

The technology of transgenic plants is challenging and time consuming, especially for higher plants and trees such as citrus. Double-stranded RNA (dsRNA) delivery via a plant virus is an alternative method to create transgenic plants by suppressing the expression of plant endogenous genes. Citrus tristeza virus-based vector has been constructed spe...

'Candidatus Liberibacter asiaticus' ('Ca. L. asiaticus'), the suspected causative agent of citrus greening disease, is one of many phloem-restricted plant pathogens that have not been isolated and grown in an axenic culture. In this study, infected Asian citrus psyllids were used to prepare a host-free source of 'Ca. L. asiaticus'. Host-free mixed...

The citrus industry at present is severely affected by huanglongbing disease (HLB). HLB is caused by the supposed bacterial pathogen “Candidatus Liberibacter asiaticus” and is transmitted by the insect vector, the Asian citrus psyllid, Diaphorina citri Kuwayama. Developing new citrus hybrids to improve HLB management is much needed. In this study,...

Citrus greening (Huanglongbing, HLB) is a destructive disease associated with the uncultivable, phloem‐limited, gram‐negative bacteria Candidatus Liberibacter spp., which affects citrus crops and other Rutaceae species. HLB is rapidly transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). We developed an artificia...

Antibiotics have been successfully used to control plant diseases for more than fifty years. Recently, oxytetracycline and streptomycin have been approved for the treatment of Huanglongbing, which is threatening the citrus industry in many regions. Because the efficiency of antibiotics in planta is highly affected by their movement and distribution...

Huanglongbing (HLB), formerly known as citrus greening disease, is one of the most devastating bacterial diseases in citrus worldwide. HLB is caused by ‘Candidatus Liberibacter asiaticus’ bacterium and transmitted by Diaphorina citri. Both ‘Ca. L. asiaticus’ and its vector manipulate the host metabolism to fulfill their nutritional needs and/or to...

Plant viruses are threatening many valuable crops, and Citrus tristeza virus (CTV) is considered one of the most economically important plant viruses. CTV has destroyed millions of citrus trees in many regions of the world. Consequently, understanding of the transmission mechanism of CTV by its main vector, the brown citrus aphid, Aphis (Toxoptera)...

Recently in Florida, foliar treatments using products with the antibiotics oxytetracycline and streptomycin have been approved for the treatment of citrus Huanglongbing (HLB), which is caused by the putative bacterial pathogen ‘Candidatus Liberibacter asiaticus’. Herein, we assessed the levels of oxytetracycline and ‘Ca. L. asiaticus’ titers in cit...

Huanglongbing (HLB) is a devastating citrus disease worldwide that is putatively caused by 'Candidatus Liberibacter asiaticus' and transmitted by Diaphorina citri. Melatonin is a ubiquitously distributed auxin-like metabolite found in both prokaryotes and eukaryotes. In this study, we used integrative metabolomic and transcriptomic approaches to in...

Huanglongbing (HLB) is the most destructive disease to the citrus industry. In North America, HLB is caused by Can-didatus Liberibacter asiaticus (CLas) and is transmitted by the Asian citrus psyllid, Diaphorina citri. Recent studies showed that antibiotics such as oxytetracycline and streptomycin were effective against the CLas pathogen in planta....

Huanglongbing (HLB) is the most destructive disease to the citrus industry. In North America, HLB is caused by Can-didatus Liberibacter asiaticus (CLas) and is transmitted by the Asian citrus psyllid, Diaphorina citri. Recent studies showed that antibiotics such as oxytetracycline and streptomycin were effective against the CLas pathogen in planta....

The δ-aminolevulinic acid (δ-ALA) is an intermediate in the biosynthetic pathway of tetrapyrroles. Tetrapyrroles play vital roles in many biological processes such as photosynthesis, respiration, and light-sensing. ALA-dehydratase (ALAD) combines two molecules of δ-ALA to form porphobilinogen. In citrus, the silencing of ALAD caused discrete yellow...

Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is the natural vector of the Huanglongbing (HLB) pathogen that presents an unparalleled challenge to citrus production. RNA interference (RNAi) has already shown great potential for insect pest management owing to its high specificity. RNAi technique relies on the delivery of ex...

Citrus plants are challenged by a broad diversity of abiotic and biotic stresses, which definitely alter their growth, development, and productivity. In order to survive the various stressful conditions, citrus plants relay on multi-layered adaptive strategies, among which is the accumulation of stress-associated metabolites that play vital and com...

Huanglongbing (HLB) is the most damaging disease in citrus. It is caused by the putative bacterium, “Candidatus Liberibacter asiaticus” and is transmitted by the Asian citrus psyllid, Diaphorina citri. Unfortunately, no cure has been found or effective control strategy established for the combat of this disease. Citrus tristeza virus (CTV) was empl...

Antibiotics have been successfully used for the control of several plant diseases for many years. Recently, streptomycin and oxytetracycline have been approved for the treatment of Huanglongbing (HLB) in Florida. The enzyme-linked immunosorbent assay (ELISA) is the most commonly used assay for the detection of these antibiotics because it is quick,...

Huanglongbing (HLB) is a highly destructive disease to the citrus industry in Florida caused by the bacterium, Candidatus Liberibacter asiaticus(CLas) and is transmitted by Diaphorina citri. It is hypothesized that plants with high phenolic contents show higher tolerance to certain plant pathogens. In this regard, different citrus varieties and pla...

Polyamines (PAs) are ubiquitous biogenic amines found in all living organisms from bacteria to Archaea, and Eukaryotes including plants and animals. Since the first description of putrescine conjugate, feruloyl-putrescine (originally called subaphylline), from grapefruit leaves and juice, many research studies have highlighted the importance of PAs...

Background: Exogenous application of gamma-aminobutyric acid (GABA) could relieve stress symptoms caused by abiotic stresses including anoxia, heat and cold shock, drought, and salt. However, studying translocation and metabolism of exogenous GABA is challenged by the presence of endogenous GABA. Results: Herein, we used D6-GABA in order to inve...

Candidatus Liberibacter asiaticus’ is a fastidious bacterium and a putative agent of citrus greening disease (a.k.a., huanglongbing, HLB), a significant agricultural disease that affects citrus fruit quality and tree health. In citrus, ‘Ca. L. asiaticus’ is phloem limited. Lack of culture tools to study ‘Ca. L. asiaticus’ complicates analysis of th...

Huánglóngbìng (HLB), citrus greening, is one of the most destructive diseases of citrus plants worldwide. In North America, HLB is caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus and is transmitted by the Asian citrus psyllid, Diaphorina citri. No cure exists at present, and the use of antibiotics for the control of HLB has...

Plant pathogenic bacteria interact with their insect host(s)/vector(s) at the cellular and molecular levels. This interaction may alter the physiology of their insect vector, which may also promote the growth and transmission of the bacterium. Here we studied the effect of “Candidatus Liberibacter asiaticus” (“Ca. L. asiaticus”) on physiochemical c...

Huanglongbing (HLB), or citrus greening, is the most destructive disease to the citrus industry. In Florida, it is caused by the bacterium, Candidatus Liberibacter asiaticus (CLas) and is transmitted by the Asian citrus psyllid, Diaphorina citri. Recent studies suggested that antibiotics could inhibit the growth of the CLas pathogen in planta. In t...

The attraction of entomopathogenic nematodes (EPNs) to herbivore injured plant roots has been documented recently to be a common tritrophic interaction. Belowground tritrophic interactions are especially subject to modulation by many abiotic factors including drought. In this study, complementary greenhouse experiments were conducted to understand...

Inability to culture the phloem-restricted alpha-proteobacterium “Candidatus Liberibacter asiaticus” (“Ca. L. asiaticus”) or the closely related species (“Candidatus Liberibacter americanus” and “Candidatus Liberibacter africanus”) that are associated with Huanglongbing (HLB) hampers the development of effective long-term control strategies for thi...

Key message In citrus, abscisic acid-deficiency was associated with a dwarfing phenotype, slow growth, small leaves, decreased fresh weight, and faster water loss. ABA supplementation reversed the dwarfing phenotype and enhanced growth. Abstract Abscisic acid (ABA) is a ubiquitously distributed phytohormone, which is almost produced by all living...

Phloem tissue is essential for the translocation of nutrients, water, energy, and signals in plants. In order to study the chemical composition of phloem sap, several methods have been used for its collection including the dipotassium ethylenediamine tetraacetic acid (K2-EDTA) exudation, incision, and the stylectomy by aphids. Each method has advan...

Virus-induced silencing gene technology has been increasingly used; however, a controversy exists among researchers about whether using the sense or antisense orientation of the gene target is more efficient. Herein, instead of using the entire citrus tree, a reduced system consisting of a single leaf, 5 cm of the stem and a few roots was establish...

In this study, phytoene desaturase (PDS) in citrus and green fluorescent protein (GFP) in Nicotiana benthamiana (line 16c) were silenced by virus-induced gene silencing (VIGS) with Citrus tristeza virus (CTV), using the sense and antisense orientations. The antisense orientation showed a stronger reduction of GFP expression in N. benthamiana compar...

To prevent the spread of diseases in humans, animals or plants, determining whether potential vectors are infected is crucial. For example, early detection of the citrus disease Huanglongbing, which has been a scourge on the citrus industries around the world, is a critical need. This vector-borne disease is transmitted by Diaphorina citri, the Asi...