First report of tomato yellow leaf curl virus infecting upland cotton (Gossypium hirsutum) 2 in Alabama, USA

Authors: MCLAUGHLIN, AUTUMN - Auburn University; HEILSNIS, BRIANNA - Auburn University; KOEBERNICK, JENNY - Auburn University; CONNER, KASSIE - Auburn University; JACOBSON, ALANA - Auburn University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2022
Publication Date: 4/12/2023
Citation: Mclaughlin, A., Heilsnis, B., Koebernick, J., Conner, K., Jacobson, A. 2023. First report of tomato yellow leaf curl virus infecting upland cotton (Gossypium hirsutum) 2 in Alabama, USA. Plant Disease. 106(11):2773-3007. https://doi.org/10.1094/PDIS-09-20-2041-PDN.
DOI: https://doi.org/10.1094/PDIS-09-20-2041-PDN

Interpretive Summary: Cotton is commonly used as a non-host for tomato yellow leaf curl virus (TYLCV) in many research studies. During CLRDV surveys in 2018, samples were also screened for begomoviruses because the whitefly vector was present in abundance. Five out of 200 cotton samples tested positive and were confirmed as TYLCV. To confirm that TYLCV can infect cotton, seedlings were agroinoculated with a TYLCV-Isreal clone. 2/18 inoculated cotton plants tested positive for TYLCV. Whitefly transmission of TYLCV to cotton was confirmed using a leaf-disc bioassay for rapid testing. TYLCV-infection was confirmed in (9/20) cotton leaf discs. No obvious begomovirus symptoms were observed on cotton plants in the field or laboratory. TYLCV infection of cotton does not appear to be of economic importance.

Technical Abstract: Cotton is used as a non-host of tomato yellow leaf curl virus (TYLCV) in many studies, but only one reports methods used to determine host-status, and there is one contradictory report from China stating cotton is a host of TYLCV. In October 2018, cotton was screened for the presence of begomoviruses in Elmore, Escambia and Macon Counties, AL, where infestations of its whitefly vector occurred in August. DNA was extracted from fully expanded leaves from the upper 1/3 of the canopy using a DNeasy® Plant Mini Kit and amplified with primers V324/C889 targeting a 575 bp coat protein fragment of begomoviruses. Five out of 200 cotton samples tested positive, and sequences recovered from three samples revealed 98-99% identity to TYLCV isolates in NCBI; sequences from the other two samples were of low quality and inconclusive. These samples were not available for additional tests, therefore, we proceeded to confirm host status using a monopartite clone of TYLCV-Israel reported in the US. All experiments were conducted in growth chambers with 16:8 light:dark cycle at 25.0' and 50% RH. Cotton seedlings at the 2-3 true leaf stage and tomatoes at the 4 true leaf stage were agroinoculated at the stem tissue between the apical meristem and the first node. Tomato served as a positive control; tomato and cotton mock inoculated with an empty vector were negative controls. A hole-punch was used to collect 4 leaf discs along midveins of the three, uppermost fully expanded leaves. DNA was extracted 28 days after inoculation as described above. A 390 bp segment of the intergenic region of TYLCV-A was amplified using primers PTYIRc287/PTYIRv21. PCR results from agroinoculated plants confirmed (2/18) cotton plants, (5/5) tomatoes and (0/10) mock inoculated controls were infected with TYLCV. Whitefly transmission to cotton was confirmed using a leaf-disc bioassay for rapid testing. Bemisia tabaci MEAM-1 reared on eggplant (non-host of TYLCV) were placed on agroinoculated TYLCV-infected tomato plants for a 96-h acquisition access period. Cohorts of 10 viruliferous B. tabaci were aspirated into 30mL cups each containing a 2.5cm healthy cotton leaf disc set in plant agar. After a 48-h inoculation access period, adults and their eggs were removed from the leaf discs. Leaf discs were held another 96-h before they were tested for TYLCV using the methods described above. TYLCV-infection was confirmed in (9/20) cotton leaf discs, demonstrating the viral load delivered by whiteflies was high enough to initiate local infection in cotton. No obvious begomovirus symptoms were observed on cotton plants in the field or laboratory. Field collection of samples was prompted by symptoms attributed to cotton leafroll dwarf virus. TYLCV infection of cotton does not appear to be of economic importance. Additional information is needed to determine the frequency of infection in the field, specificity of TYLCV isolate x cotton genotype interactions leading to successful infection, and underlying causes of conflicting host-status reports in previously published studies.