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Stemphylium Gray Leaf Spot in Tomatoes

Stemphylium Gray Leaf Spot in Tomatoes Professor DeBacco Multiple Viewpoints of Stemphylium Description of the disease Actual images and video of a known case Comparison to a common lookalike Microscopic view Genetic investigation regarding virulence factor About Stemphylium While it may seem like a new problem Gray Leaf Spot of tomato was first reported in 1930. Four Stemphylium species, S. lycopersici, Stemphylium solani, Stemphylium vesicarium, and Stemphylium botryosum f. sp. lycopersici, are necrotrophic fungi that cause tomato (Solanum lycopersicum) gray leaf spot disease (GLS) High humidity or free water on leaf surfaces is required for spore germination and infection. Spots on leaves were small, light brown, and somewhat circular to irregular in shape. Some larger spots were cracked. Symptoms start to appear within two to five days of infection. Stemphylium Dispersal Via air currents (wind) and splashing water. Can also be seed-born Survives on crop debris as a saprophyte Upper and Lower Leaflet View Comparisons of Stemphylium Upper and Lower Leaflet View Comparisons of Stemphylium This represents more advanced progression which is evident by the large browning area and the larger lesions located on the under side of the leaf. Full Leaf View of Stemphylium These images show lower leaves (just above the pruning point) exhibiting more advanced symptoms. Stemphylium Symptoms on Rachis and Petioles When inspecting the rachis and petioles closely of the tomato leaf look for small rectangular shaped lesions. These can be difficult to find, but something else to be aware of. High Tunnel Video (Recorded and uploaded in 4k) This was an officially lab confirmed case of Stemphylium First symptoms occurred around mid-July about 4-weeks prior to the video being taken. Typically is starts in the older leaves and works it way up the plant. Different varieties will have different levels of severity. What to Look For While fact sheets tend to report that Cherry and grape tomatoes are more susceptible than other types based on grower observations it did show on all of the cheery varieties, but it did not seem to really have much negative impacts in regards to overall plant performance and yield. Most commonly occurs (or is first seen) in high tunnels with the higher temperatures and humidity being favorable for disease development. Look alike… Septoria Stemphylium is often mistaken as Septoria leaf spot. Stemphylium- has more irregular lesions with brown margins and tan centers. The leaves tend to remain green in areas unaffected. Septoria- tends to be more circular spots with an inner circle of a lighter shade of brown. In addition the leaf will typically yellow. Stemphylium: Under the Microscope Stemphylium: Conidiophore Conidiophore: a specialized hyphal branch of some fungi that produces conidia. Stemphylium: Conidia Conidia: an asexual spore produced on a conidiophore of certain fungi Research Article Lian, J., Han, H., Chen, X., Chen, Q., Zhao, J., & Li, C. (2022). Stemphylium lycopersici Nep1-like Protein (NLP) Is a Key Virulence Factor in Tomato Gray Leaf Spot Disease. Journal of Fungi, 8(5), 518. https://www.mdpi.com/2309-608X/8/5/518 NLP gene, which encodes a necrosis and ethylene inducing peptide 1 (Nep1)-like protein (NLP). NLP Is Required for Full Virulence of S. lycopersici in Tomato NLP is a key virulence factor of S. lycopersici during infection on tomato leaves. Study Findings… Through analysis of the NLP gene (which encodes a necrosis- and ethylene inducing peptide 1 (Nep1)-like protein (NLP)) it was found that targeted disruption of the NLP gene in Stemphylium lycopersici significantly compromised its virulence on tomato. NLP suppressed the production of reactive oxygen species (ROS) in tomato leaves during S. lycopersici infection. Expressing the fungal NLP in tomato resulted in constitutive transcription of immune-responsive genes and inhibited plant growth. Conclusions NLP might contribute to the virulence of S. lycopersici by suppressing ROS-mediated immunity in tomato. Large-scale functional genomic studies are required to further dissect the pathogenicity of Stemphylium spp. Link to Lecture Slides: https://drive.google.com/file/d/1QfE1... *Due to the description character limit the full work cited for "Stemphylium Gray Leaf Spot in Tomatoes" can be viewed at... https://docs.google.com/document/d/1x...