Plant Pathology

Team

• Yuan Zeng - Principal Investigator
• Priyanka Gangwar - Postdoctoral Fellow
• Ayodeji Bello - Presidential Postdoctoral Fellow
• Kamal Chhetri - Ph.D. student
• Jiayu Dong - Ph.D. student 
• Emma Raimondi - M.S. student

Lab Alumni

• Samatha Ferrer, Hollins University, Undergraduate research assistant, Summer 2024
• Liv Erickson, Virginia Tech, Undergraduate research assistant, Summer 2024
• Denis Sarisoy, New Jersey Institute of Technology, Summer 2024
• Caroline Taylor, Virginia Tech, Undergraduate research assistant, Summer 2023
• Sarah Hingst, Virginia Tech, Undergraduate research assistant, Summer 2023
• Xueming Xu, Virginia Tech, Undergraduate research assistant, Summer & Fall 2023

Disease Management and Diagnosis

Black Shank

Black shank is caused by an oomycete pathogen, Phytophthora nicotianae, that lives in the soil and attacks tobacco roots and stalks. Widespread continuous planting of flue-cured tobacco cultivars possessing single-gene (designated Ph) resistance to black shank enabled tobacco producers to dramatically reduce the application of soil fungicides beginning in 1996. However, this has led to the breakdown in the efficacy of this resistance by shifting the distribution of the pathogen populations from host race 0 to race 1.

Granville (Bacterial) wilt

Granville (Bacterial) wilt is caused by a soil-inhabiting bacterium, Ralstonia solanacearum, invading tobacco plants mainly through roots. The pathogen can also invade tobacco plants through wounds, so early and shallow cultivation and hand-topping can help reduce the spread in infested fields. Although symptoms are somewhat similar to those for black shank, intermediate symptoms of Granville wilt involve wilting on only one side, and wilted leaves may retain their normal green color rather than yellow. 

Fusarium wilt

Fusarium oxysporum f. sp. nicotianae mainly causes Fusarium wilt. We recently demonstrated that other Fusarium species are also associated with the disease. Fusarium wilt can become a serious problem when tobacco plants are stressed by abiotic (e.g., drought, warm) and other biotic factors (e.g., nematode). Infected plants are often wilted on one side, and leaves or parts of leaves are significantly yellowed or chlorotic. Early destruction of tobacco stalks and roots and crop rotation (for as long as possible, but not with cotton or sweet potato) will also help reduce problems with Fusarium wilt.

Soil Test Service

We offer a soil test (e.g., real-time polymerase chain reaction assay) to quantify DNA concentrations of the black shank pathogen in your field soil. Please contact Dr. Yuan Zeng for instructions on soil sampling and sample submission.

2025 Flue-Cured Tobacco Production Guide

Tar Spot Disease Management

• Evaluate fungicide efficacy and corn hybrid susceptibility
• Link fungal pathogen monitoring and observations of environmental conditions to predict foliar disease occurrence and severity

Tar spot of corn, caused by the fungal pathogen Phyllachora maydis, has resulted in significant yield losses in corn-producing areas, with approximately 241 million bushels in the United States. Phyllachora maydis was first reported in the U.S. in 2015 and now has spread to at least 18 states, including Virginia. A risk assessment tool uses weather data to predict tar spot disease severity and recommends corn growers with fungicide applications. However, it neglects the presence and population density of P. maydis in an environment and the susceptibility of corn hybrids, leading to incorrect decision-making recommendations in several corn-growing regions (e.g., spray without the presence of pathogen) and potential risks for the pathogen to develop fungicide resistance.

Soil microbiota variations in soybean fields infested with Fusarium virguliformae

Soil harbors the most diverse and abundant microbiome on Earth, including bacteria, fungi, protists, archaea, and viruses, which plays a vital role in nitrogen, phosphorus, iron, and sulfur cycling, organic matter dynamics, mycotoxin reduction, stress tolerance, and carbon sequestration and transformations. Soil microbiome also drives plant productivity because it is the main microbial source for plant microbiota. Our lab aims to explore the dynamic interactions between Fusarium virguliformae, native soil microbiome, and soil properties during soybean Sudden Death Syndrome disease development and how the interactions influence disease incidence and severity.

Disease Diagnosis Service

• Neopestalotiopsis diseases (https://www.pubs.ext.vt.edu/SPES/spes-627/spes-627.html)
• Phytophthora crown and root rot
• Anthracnose crown and fruit rot
• Fusarium wilt