Mealybug wilt of pineapple (MWP) is a disease of pineapple that has a long history in Hawaii, but is present throughout the world where pineapples are grown in tropical regions. The disease has an interesting etiology that is poorly understood but involves an association with virus particles, mealybug vectors, and ants which spread the mealybug vectors. Several distinct pineapple mealybug wilt-associated virus (PMWaV) species have been identified thus far with potential further member species yet to be characterized. Pineapple mealybug wilt-associated viruses are member species of the Ampelovirus genus of the Closteroviridae family. Ampeloviruses are split into two subgroups, subgroup I and subgroup II. PMWaV-2 is a subgroup II member, and these have a longer and more complex genome with additional genes on the 3’ terminus of the RNA genome compared to subgroup I ampeloviruses. PMWaV-2, along with the presence of mealybug vectors, have been shown to be necessary factors in symptom development in Hawaii. Some of these extra genes in the 3’ of PMWaV-2 have recently been shown to function as silencing suppressors, and may play a role in the virulence of PMWaV-2 and symptom development. In other regions of the world, reports of symptomatic plants without PMWaV-2 infection, but with PMWaV-1, -3 or some combination, contradict the requirement of PMWaV-2 for symptom development in MWP. It is possible that further, uncharacterized PMWaVs may be present in symptomatic pineapple plants that test negative for PMWaV-2, explaining the inconsistency in symptom development. More research is necessary to explore the confusing etiology of the MWP disease, and to perhaps shed light upon the symptom development.

Cotton leafroll dwarf disease (CLRDD) caused by the Cotton leafroll dwarf virus (CLRDV), is an emerging disease of cotton (Gossypium hirsutum L.) in the United States. It was previously reported in...

The 16SrIV-D phytoplasma was first identified in Florida in 2006. Since its discovery, it has spread throughout most of the state. It is most prevalent in the central part of Florida, from Hillsborough County on the west coast to St. Lucie County on the east coast. The 16SrIV-D phytoplasma is the causal agent of lethal bronzing disease (LBD), which is also known as Texas Phoenix palm decline (TPPD). It affects a variety of common and economically important ornamental palm species as well as the native and ecologically important species, Sabal palmetto. It has spread into the southern portions of Florida, where the palm species diversity is higher. The aims of this survey were to document the spread of disease in terms of geographic and host range one decade after its introduction into Florida, and to assess the risk that LBD poses to the nursery and landscaping industries. The survey included samples received from stakeholders throughout the state, covering 18 counties, as well as a systematic sampling of palms at the Fort Lauderdale Research and Education Center (FLREC), where the disease is spreading actively. The findings of this survey resulted in the detection of LBD in eight new counties, including Collier, Hernando, Jefferson, Martin, Miami-Dade, Monroe, Seminole, and St. Johns, and the expansion of LBD into four new host species, Cocos nucifera, Livistona chinensis, Butia capitata, and Carpentaria acuminata. These findings are crucial for stakeholders because they highlight new hosts of 16SrIV-D phytoplasma and the geographic expansion of the disease, indicating that vigilance is needed when surveying declining palms.

Watermelon (Citrullus lanatus) is a high nutrient crop, high in vitamins and very popular in the U.S and globally. The crop was harvested from 101,800 acres with a value of $560 million in the U.S (USDA-NASS, 2020). California, Florida, Georgia and Texas are the four-leading watermelon-producing states in the U.S. During the fall season of 2020, plants in two North Florida watermelon fields, one in Levy County (~20 acres) and one in Suwannee County (~80 acres) with varieties Talca and Troubadour, respectively, exhibited viral-like symptoms. The fields had 100% disease incidence that led to fruit quality issues and yield losses of 80% and above. Symptoms observed in the watermelon samples included leaf crumpling, yellowing and curling, and vein yellowing similar to that of single/and or mixed infection of cucurbit leaf crumple virus (CuLCrV; genus: Begomovirus, family: Geminiviridae), cucurbit yellow stunting disorder virus (CYSDV; genus: Crinivirus, family: Closteroviridae) and squash vein yellowing virus (SqVYV; genus: Ipomovirus, family: Potyviridae), although the vine decline symptoms often associated with SqVYV infection of watermelon were not observed. All three viruses are vectored by whiteflies and previously described in Florida (Akad et al., 2008; Polston et al., 2008; Adkins et al., 2009). To confirm the presence of these viruses, RNA was isolated from 20 symptomatic samples using the RNeasy Plant Mini Kit (Qiagen, USA) as per protocol. This was followed by RT-PCR (NEB, USA) using gene-specific primers described for CuLCrV, CYSDV and SqVYV (Adkins et al., 2009). Amplicons of expected sizes were obtained for all the viruses with the infection of CuLCrV in 17/20, CYSDV in 16/20, and SqVYV in 8/20 samples. In addition, the presence of cucurbit chlorotic yellows virus (CCYV; genus: Crinivirus, family: Closteroviridae) in mixed infection was confirmed in 4/20 samples (3 leaves and 1 fruit) by RT-PCR with primers specific to the CCYV coat protein (CP), heat shock protein 70 homolog (HSP70h) and RNA dependent RNA polymerase (RdRp) designed based on the available CCYV sequences (Sup Table. 1). The RT-PCR amplification was performed using a symptomatic watermelon sample and the amplicons of RdRp, HSP70h and CP were directly sequenced by Sanger method, and the sequences of the amplicons were deposited in GenBank under the accession number: MW527462 (RdRp, 952 bp), MW527461 (HSP70h, 583 bp) and MW527460 (CP, 852 bp). BLASTn analysis demonstrated that the sequences exhibited an identity of 99% to 100% (RdRp and HSP70h, 100%; and CP, 99%) with the corresponding regions of the CCYV isolate Shanghai from China (accession number: KY400636 and KY400633). The presence of CCYV was further confirmed in the watermelon samples by ELISA (Loewe, Germany) using crude sap extracted from the RT-PCR-positive, symptomatic watermelon samples. CCYV was first identified in Kumamoto, Japan in 2004 on melon plants (Gyoutoku et al. 2009). The CCYV was previously reported on melon from Imperial Valley, California (Wintermantel et al., 2019), and more recently on squash in Tifton, Georgia (Kavalappara et al., 2021) and cantaloupe in Cameron, Texas (Hernandez et al., 2021). To our knowledge, this is the first report of CCYV on field watermelon production in the U.S. Continued monitoring of the CCYV in spring and fall watermelon crop, and cucurbit volunteers and weeds will be critical toward understanding the spread of this virus and its potential risk to watermelon in Florida and other regions of the U.S.

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