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Title: First report of Colletotrichum nigrum causing anthracnose disease on tomato fruit in New Jersey

item RIVERA, YAZMIN - Rutgers University
item Stommel, John
item Dumm, Judith
item Ismaiel, Ed - Ed
item WYENANDT, ANDREW - Rutgers University
item Crouch, Jo Anne

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2016
Publication Date: 5/23/2016
Citation: Rivera, Y., Stommel, J.R., Dumm, J.M., Ismaiel, A.A., Wyenandt, A.C., Crouch, J. 2016. First report of Colletotrichum nigrum causing anthracnose disease on tomato fruit in New Jersey. Plant Disease. 100(10): 2162.

Interpretive Summary: Anthracnose diseases cause significant damage to numerous fruit and vegetable crops in the United States and worldwide. This research describes an outbreak of anthracnose disease causing tomato fruit rot in New Jersey during 2013. The fruit rot disease was caused by a fungal pathogen that has not been seen in North America since 1891, and has never been identified from New Jersey. The fungal pathogen caused substantial damage to tomato, but did not harm pepper fruits. Knowledge of this new tomato fruit rot pathogen will be useful to growers, breeders and plant pathologists working to control anthracnose fruit rot diseases in the United States.

Technical Abstract: Anthracnose fruit rot is one of the most serious diseases affecting the production of tomato (Solanum lycopersicum L.) in the United States and is typically incited by Colletotrichum coccodes, C. gloeosporioides or C. dematium (Farr and Rossman 2016). During the summer of 2013, symptoms characteristic of anthracnose fruit rot were observed on tomato fruits during a field survey in Cumberland County, New Jersey. Small sunken circular tan lesions that became larger with age were observed on processing tomato ‘5108’ mature (red) fruit. Black fruiting bodies and orange conidial masses were observed in mature lesions. Small pieces of infected fruit tissue were transferred to clarified V8 agar media and incubated at 25°C. On clarified V8 agar, colonies were initially pink, becoming black after two weeks with abundant acervuli and light orange conidial masses; conidia were hyaline, cylindrical with acute to sub-acute apex, guttulate, and aseptate; setae were brown, straight, gradually tapering at the tip; conidia measured 20.8 to 27.7 x 3.4 to 5.0 µm (mean 23.9 x 4.2 µm; n = 50); setae were 87 to 275 µm long (mean 166.4 µm; n = 20). DNA was extracted from fungal biomass using the DNeasy Plant Mini kit (QIAGEN, Gaithersburg, MD). DNA sequences were generated for actin, chitin synthase 1, rDNA internal transcribed spacer and ß-tubulin 2 marker regions (Liu et al. 2013; NCBI GenBank KU317767-70). Phylogenetic analysis alongside exemplar Colletotrichum isolates (Cannon et al. 2012) identified isolate RT1 as C. nigrum (BPI893331; Fig. 1). Pairwise nucleotide comparisons between RT1 and C. nigrum ex-epitype strain CBS 169.49 showed 100% sequence identity across these four loci (1573 bp). Together, the combined morphological (Liu et al. 2013) and molecular data identified the pathogen as C. nigrum. Pathogenicity tests were performed on three red tomatoes by inoculating them with 10 µl of a 1 x 106 conidia/mL suspension at needle puncture wound sites. Negative control tomato fruits (n=3) were inoculated with 0.1x potato dextrose broth. Fruits were maintained at 22-25°C in a closed container at high humidity for the first 24 h, after which lids were removed. After seven days, all tomato fruits exhibited symptoms characteristic of anthracnose infection, whereas negative controls remained asymptomatic. Morphological and molecular evaluation as described above identified the pathogen reisolated from infected tissue as C. nigrum. Anthracnose fruit rot on tomato caused by C. nigrum has been previously reported in the United States (Delaware, Hawaii, Ohio and Washington), New Zealand and China (Farr and Rossman, 2016). However, to our knowledge, this is the first report of C. nigrum infecting tomato fruits in New Jersey, and the first report of this pathogen infecting tomato in the continental United States since 1921. Colletotrichum spp. pose an ongoing threat to tomato and pepper production in the state of New Jersey, with significant losses experienced in recent years. Understanding which species are present in fields and farms where tomato and pepper are grown together or in rotation may greatly affect control strategies in New Jersey and elsewhere.