About

Dr. Kevin Ong is a professor and associate department head in the Department of Plant Pathology & Microbiology at Texas A&M University in College Station. His areas of expertise include plant disease diagnostics, diseases of ornamentals, and tree fruits. He joined Texas A&M in 2002 as the Extension Urban Plant Pathologist based at the Dallas Research & Extension Center. In 2008, he moved to College Station to direct the Texas Plant Disease Diagnostic Lab (TPDDL), which provides plant health support, education, and practical services to Texas and beyond. Dr. Ong works closely with the Texas Department of Agriculture and the USDA-APHIS on pest and pathogen management, quarantines, and biosecurity issues affecting plant health. His applied research interests include the development and optimization of pathogen detection methods and the development and implementation of best management practices in landscape and ornamental production areas.

Research topics

• Biology
• Horticulture
• Agroforestry
• Botany
• Ecology
• Molecular biology
• Virology
• Biochemistry
• Genetics

Selected publications

• Plumeria ampelovirus 1, a novel ampelovirus subgroup II member infecting Plumeria spp.

  Archives of Virology · 2026-02-19

  articleSenior author
  PublisherDOI

• Fruit Quality and Fusarium Wilt Race 2 Resistance in <scp> <i>Cucumis melo</i> </scp> Breeding Lines and Their F ₁ Hybrids

  Plant Breeding · 2025-07-23

  articleOpen access

  ABSTRACT Cucumis melo , a sweet‐tasting fruit from the Cucurbitaceae family, is popular in global markets. While some varieties of C. melo are used for pickling or salads, melons such as cantaloupes and honeydews are consumed as a dessert. Desirable appearance, shelf life and palatability are crucial in determining a variety's success. Specific traits are firmness (N), netting (HWC), abscission zone size (ABZ), seed cavity closedness (%), mesocarp colour, sugar content ( o Bx), size and shape. Besides quality, reducing yield losses from disease is a priority in plant breeding. A serious fungal disease is Fusarium wilt ( Fusarium oxysporum f. sp. melonis ). There are four known races. Thirty‐three F 1 hybrids were derived from 21 breeding lines. The parents and hybrids were evaluated at target locations: Uvalde and Weslaco, TX, during the summer of 2024. The objective was to estimate genotype by environment interactions, broad‐sense heritability and narrow‐sense heritability of nine quality traits. Traits with high broad‐sense heritability estimates were net height, width, ABZ and colour. Net height, width, ABZ and firmness were mostly heritable in the narrow sense. All genotypes were inoculated with Fusarium wilt, Race 2. Hybrids meriting further testing for quality were 3/70, 3/162 and 8/90. Breeding lines such as BL40 and BL70 lacked resistance.

  PublisherOA PDFDOI

• First Report of <i>Golovinomyces bolayi</i> Causing Powdery Mildew on Lettuce ( <i>Lactuca sativa</i> ) in Texas

  Plant Disease · 2025-07-14

  articleOpen access

  Greenhouse lettuce is a growing industry valued at 2.5 billion in the world. Powdery mildew is one of the major fungal diseases in lettuce in controlled environment agriculture (CEA) (Hernandez 2025). Lettuce production in CEA in Texas is increasing with the establishment of the most extensive greenhouse production facilities (KXAN 2023). In May 2024, typical powdery mildew symptoms were observed on multiple lettuce varieties, with 40% disease incidence, grown on a nutrient film technique hydroponic system at the Texas A&M Research and Extension Center in Dallas. Powdery mildew covered 50% of the leaf surface. Ten diseased plants were collected using a randomized sampling method from different areas of the facility and analyzed at the Texas Plant Disease Diagnostic Laboratory in College Station, TX. Morphological examination revealed abundant hyphae and conidia on the upper and lower leaf surfaces. Hyphal appressoria were indistinct or nipple-shaped and solitary. Conidiophores (n=30) were hyaline, erect, and 78 to 110 μm long, arising from the upper surface of hyphal mother cells or the lateral surface. Foot cells were cylindrical, measuring 40 to 52 × 8 to 15 μm, followed by 1 to 3 shorter cells, and formed conidia in chains. Conidia (n=87) were hyaline, ellipsoid to ovoid, doliiform or subcylindrical, and 22 to 35 × 10 to 12 µm. Conidiogenesis was formed in the Euoidium-type. Chasmothecia were not observed. The morphological characteristics were consistent with those of Golovinomyces bolayi (Braun et al. 2019). Previously, G. bolayi was named Erysiphe cichoracearum f. intybi and is now considered synonymous, belonging to the G. orontii complex (Braun et al. 2019). The identity of the pathogen was further confirmed through sequence analysis. DNA was extracted from conidia and mycelia using Zymo Fungal Bacterial Kit (Zymo Research Corporation, Irvine, CA. The internal transcribed spacer (ITS) region was amplified using primers ITS5 and ITS4 (White et al. 1990), and the 28S region was amplified using nested PCR with primers ITS1/TW14 and PM28/PM28R (Bradshaw et al. 2020). BLASTn analysis of the 517-bp ITS sequence showed more than 99% identity to G. bolayi accessions AB427188.1 (516/517), AB769463.1 (516/517), AB769447.1 (517/517) (Uchida et al., 2009; Braun et al. 2019; Takamatsu et al. 2013) and the 554-bp 28S large subunit regions showed 100% identity with G. bolayi accessions MT060301.1 (554/554), AB769446.1 (554/554), and NG075340.1 (554/554) (Mieslerová et al. 2020; Takamatsu et al. 2013). The ITS and 28S region sequences were deposited in GenBank under accession numbers PV041439 and PV041440, respectively. Based on morphological data and sequence analysis, the fungus was identified as G. bolayi. Pathogenicity tests were performed and repeated two times on six 14-day-old plants of L. sativa cultivar ‘Green Sweet Crisp’ by gently shaking infected leaves from diseased plants above more than 20 leaves of the healthy plants to let conidia fall. Six additional control plants were not inoculated. The plants were maintained in a growth chamber at 22 ± 1°C with a 16/8 h day/night period with 40 ± 5% relative humidity. Signs similar to those observed on initial disease plants were observed 8-10 days post-inoculation. The pathogen was confirmed using morphological and molecular methods as described above. All non-inoculated controls remained symptom-free, fulfilling Koch’s postulates. G. bolayi is widespread on L. sativa and has been reported in many countries, including the USA (Braun et al. 2019; Mieslerová et al. 2020). To our knowledge, this is the first report of G. bolayi causing powdery mildew on lettuce in a greenhouse production system in Texas. The discovery of this species may necessitate a re-evaluation and refinement of current powdery mildew management practices, especially in a closed agriculture environment.

  PublisherOA PDFDOI

• Distinct gene reprogramming in rosetted and symptomless shoots from the same mature rose plants infected with rose rosette virus

  Frontiers in Plant Science · 2025-08-28

  articleOpen access

  Rose rosette virus (RRV) causes disease in rose shrubs manifesting as abnormal branch growth, stem thickening, increased thorniness, as well as malformed, discolored leaves and flowers. The uneven and strange development near apical regions and only in parts of the plant led us to investigate how RRV influences growth promoters to alter internal developmental programs. Leaf samples were collected from symptomatic (rosetted) and asymptomatic shoots of the same rose plants. We quantified viral RNA levels and analyzed the concentrations of some key hormones (abscisic acid [ABA], caffeic acid [CFA], indole acetic acid [IAA], and gibberellin [GA]). Additionally, gene expression profiling was performed, focusing on genes involved in hormone synthesis and signaling, auxin transport, and plant development. Viral RNA levels were unevenly distributed between rosetted and non-rosetted tissues. The ABA and IAA levels were similar between tissue types, whereas CFA and GA exhibited marked differences. We identified 39 genes with distinct or opposite expression in rosetted versus asymptomatic tissues, including PILS3, PIN1 , and two SAUR genes related to auxin transport and response. Expression of key regulators of ABA and GA synthesis and signaling, including YUCCA and AUX/IAA genes, were altered. Notably, Lonely Guy 3 (LOG3), which encodes a cytokinin-acitvating enzyme implicated in leaf patterning was significantly reduced in rosetted leaves, suggesting leaf-specific hormone imbalances. Several WOX transcription factors were suppressed indicating a potential role in antiviral responses. Our findings demonstrate that RRV selectively alters hormonal profiles and gene expression involved in plant growth and development. This study identified precise incursions of RRV into host molecular mechanisms controlling plant development and growth.

  PublisherOA PDFDOI

• Pilot for Harmonization of Diagnostic Protocols for Tomato Brown Rugose Fruit Virus (ToBRFV) in Tomato and Pepper Seeds

  PhytoFrontiers™ · 2025-01-03 · 2 citations

  articleOpen access

  Global seed trade is subject to various national, regional, and international regulations to prevent the introduction and spread of harmful seed-borne and seed-transmitted pathogens. When the plant health regulatory agencies of trading partners employ different diagnostic protocols for the same pathogen, contradictory test results may require additional testing that can cause delays in trade. Establishing equivalency of diagnostic protocols may expedite trade by adding confidence to diagnostic test results. The member countries of the North American Plant Protection Organization (NAPPO) conducted a project evaluating several diagnostic protocols for a seed-transmitted virus, tomato brown rugose fruit virus (ToBRFV), an emerging pathogen that has severely affected tomato and pepper fruit and seed production and trade globally. The objective of the study was to find protocols that could be harmonized among NAPPO member countries, thereby avoiding retesting of samples at different border points. The project was a collaboration between academia, industry, trade organizations, and national plant protection organizations (NPPOs). Three end-point PCR and two real-time PCR protocols were evaluated via a ring test. Nine laboratories from Canada, the United States, and Mexico participated in the ring test, which generated 3,680 data points from analytical, diagnostic, and calibrator samples. Four out of five diagnostic protocols were found to be fully transferable, and three protocols demonstrated optimal performance for accurate, reproducible, and user-friendly detection. The results of this regional effort will simplify the detection of ToBRFV-infected seeds in NAPPO member countries and demonstrate a way to establish equivalency of testing methods between the NPPOs. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

  PublisherDOI

• Novel resistance to tobacco etch virus in peppers (Capsicum spp.)

  Euphytica · 2025-08-27

  articleOpen access

  Abstract Tobacco etch virus (TEV) is a pathogen that affects peppers all over the world. It causes serious losses, and it is difficult to control since it has many aphid vectors. Because these aphids move around, and transmit TEV in a non-persistent manner, many applications of pesticides would be necessary to reduce TEV incidence, leading to more environmental pollution and destruction of beneficial predator insects. Therefore, host plant resistance is the best solution for TEV. Peppers ( Capsicum spp.) exhibit ample genetic variability. Numerous resistance genes against TEV have been documented over the past 70 years. However, these are all recessive in nature. This has made deployment in hybrids more difficult and therefore, not many TEV resistant pepper cultivars have been released. The pepper breeding project at Texas A&amp;M AgriLife Research screened over 200 USDA plant introductions from 6 species for resistance to TEV with both natural field infection and controlled inoculations at Weslaco. ELISA tests and visual assessments of symptoms of the virus in the plants were performed. Four accessions not previously characterized as resistant were identified with mild or no symptoms. These included two C. chinense and two C. baccatum accessions. An interspecific population of C. annuum ‘serrano’ x C. baccatum var. baccatum was developed to study the resistance from that wild type. Chi-square analysis indicated that resistance is controlled by a single, dominant gene, which will facilitate the development of resistant varieties using traditional breeding procedures such as backcrossing.

  PublisherOA PDFDOI

• First Report of a ‘<i>Candidatus</i> Phytoplasma sacchari’-Related Strain Associated with Yellowing and Decline of Silver Bluestem in Texas, U.S.A.

  Plant Disease · 2024-04-30 · 1 citations

  articleOpen access

  Silver bluestem [Bothriochloa laguroides (DC.) Herter] is a warm-season grass native to Texas. This perennial grass plays a crucial role in maintaining ecological balance and supporting wildlife in the region. In September 2022, while investigating the ecological impact of invasive grass species on a grassland located near Pipe Creek (TX), B. laguroides plants were observed showing symptoms that included yellowing of the blades and occasionally brown discoloration of the midveins and stems (Fig. S1). Disease incidence was estimated as 2% of silver bluestem plants in the 2 hectares surveyed. To investigate the possibility of a phytoplasma association with the symptoms, four symptomatic and four asymptomatic leaf samples were collected for further study. Total DNA was extracted from leaf midribs using a DNeasy Plant Mini Kit (Qiagen). The DNA extracts were tested using a phytoplasma-specific quantitative PCR assay (Hodgetts et al. 2009), which identified two out of the four symptomatic B. laguroides samples as positive for phytoplasmas. A semi-nested PCR assay for amplification of the 16S rRNA gene fragment was then performed on these samples with primers P1/16S-SR followed by P1A/16S-SR (Deng, and Hiruki 1991; Lee et al. 2004), and two additional housekeeping genes (tuf and secA) were amplified as previously described (Makarova et al. 2012; Hodgetts et al. 2008; Bekele et al. 2011). All amplicons of the expected size, 1.5 kb (16S rRNA), 0.4 kb (tuf) and 0.6 kb (secA), were purified and bi-directionally sequenced using primers from each gene second round PCR amplification. Analysis of the sequences derived from the three gene fragments revealed no variation between the two plant samples and confirmed they originated from a phytoplasma, termed strain TXSB-2 (Texas Silver Bluestem). Sequences from a single B. laguroides plant DNA extract were deposited in GenBank with accession numbers OR711913 (16S rRNA), OR709687 (tuf) and OR709688 (secA). A BLAST search of the 16S rRNA gene sequence from TXSB-2 against the NCBI nucleotide database, showed 99.58% sequence identity with an unclassified phytoplasma clone 139-1 from a leafhopper collected in Australia (MW281491) (Fig. S2). The partial nucleotide sequence of the tuf and secA genes showed 90.60% and 89.78% similarity, respectively, to the corresponding genes in ‘Ca. P. sacchari’ strain SCWL1 (CP115156) associated with sugarcane in China. The iPhyClassifier, an interactive online tool for phytoplasma identification and classification (Zhao et al. 2009), was used to determine the ‘Candidatus Phytoplasma’ species affiliation and group/subgroup classification status of this phytoplasma strain. The result showed that the TXSB-2 16S rDNA shared 98.94% sequence identity with that of the 'Ca. P. sacchari' reference strain (GenBank accession: MN889545), indicating TXSB-2 is a 'Ca. P. sacchari'-related strain. The result from virtual restriction fragment length polymorphism (RFLP) analysis of the 16S rDNA F2nR2 fragment revealed that TXSB-2 possessed a collective RFLP pattern that is distinct from the reference patterns of all established phytoplasma ribosomal subgroups and is proposed as the representative strain of a new subgroup designated as 16SrXI-H. ‘Candidatus Phytoplasma sacchari’ has been reported associated with sugarcane grassy shoot disease, which is considered among the most damaging diseases of sugarcane across parts of Southeast Asia and India (Kirdat et al. 2021). The same phytoplasma was recently confirmed infecting sorghum in India (Nithya et al. 2024). To our knowledge, this is the first report of a ‘Ca. P. sacchari’-related strain infecting B. laguroides in the United States. Moreover, B. laguroides is a new host for strains related to ‘Ca. P. sacchari’. Further investigation is required to elucidate the prevalence of this disease in the area, its natural vectors, and the potential consequences arising from this novel phytoplasma strain within its ecosystem in Texas.

  PublisherOA PDFDOI

• Biochar reduces containerized pepper blight caused by Phytophthora Capsici

  Scientific Reports · 2024-12-27 · 5 citations

  articleOpen access

  Phytophthora blight caused by Phytophthora capsici is a serious disease affecting a wide range of plants. Biochar as a soil amendment could partially replace peat moss and has the potential to suppress plant diseases, but its effects on controlling phytophthora blight of container-grown peppers have less been explored, especially in combination of biological control using Trichoderma. In vitro (petri dish) and in vivo (greenhouse) studies were conducted to test sugarcane bagasse biochar (SBB) and mixed hardwood biochar (HB) controlling effects on pepper phytophthora blight disease with and without Trichoderma. Sugarcane bagasse biochar and HB were blended with the commercial substrate (CS, peat-based) at 10% (SBB10, by volume), and 10%, 30%, 50%, 70% (HB10, HB30, HB50, and HB70, by volume), respectively, and CS (CS100) was used as the control. Both in vitro and in vivo studies used randomized complete block design with three treatment factors: pathogen (without or with inoculation of P. capsici), biochar (different biochar treatments), and Trichoderma (without or with inoculation). In vitro results showed that Trichoderma inhibited P. capsici growth while biochar did not have significant beneficial effects. In vivo results showed that plants grown in HB30 and HB50 had similar or higher plant growth index and shoot dry weight than the control regardless of pathogen presence. In the presence of the pathogen, plants grown in HB30, HB50, and HB70 had significantly lower disease severity, and disease incidence ratings than the control, while Trichoderma did not show beneficial effects on controlling the disease. In conclusion, HB replacing 30% and 50% peat moss in substrate could reduce pepper blight disease caused by P. capsici without negatively affecting plant growth.

  PublisherOA PDFDOI

• Biochar reduces containerized pepper blight caused by Phytophthora capsici

  Research Square · 2024-04-25

  preprintOpen access
  PublisherOA PDFDOI

• First Report of Nerine Yellow Stripe Virus Infecting Crinum Lily (<i>Crinum</i> sp.) in Texas

  Plant Disease · 2023-07-14

  articleOpen accessSenior author

  in California (Guaragna et al. 2013). To the best of our knowledge, this is the first report of NeYSV in Texas, thus expanding the geographical range of the virus in the USA. Anecdotal information from the sample submitter implicated infected crinum lily bulbs as the likely source of NeYSV introduction into the property, with subsequent vegetative propagation of plants resulting in 100% incidence of symptomatic lilies (n>100) over time. Thus, the results underscore the importance of ensuring that only virus-free vegetative plant materials are distributed and propagated by florists to curtail virus spread.

  PublisherOA PDFDOI

Frequent coauthors

• David Byrne

  Texas A&M University

  44 shared

• Jennifer Olson

  Oklahoma State University

  35 shared

• Mark T. Windham

  University of Tennessee at Knoxville

  34 shared

• Patricia E. Klein

  Texas A&M University

  18 shared

• Madalyn Shires

  Texas A&M University

  18 shared

• H. Brent Pemberton

  18 shared

• Jeekin Lau

  Texas A&M University

  17 shared

• Muqing Yan

  Texas A&M University

  16 shared

Labs

• Texas Plant Disease Diagnostic LabPI

Education

• B.S., Biology

  Pennsylvania State University

• M.A., Biology

  Temple University

• Ph.D., Plant Pathology

  Clemson University