First report of potato (Solanum tuberosum L.) blackleg disease caused by Dickeya solani in Mayabeque, Cuba.

Blackleg, caused by Pectobacterium spp. and Dickeya spp., is an important disease of potatoes. During the period from November 20 and March 2021, stems of potato plants showing necrosis and rot symptoms, and chlorotic leaves, were collected from commercial production areas of the Mayabeque province of Cuba (Fig. 1A). After disinfestation of affected stems, small fragments of the stem were cut and macerated in a sterile 0.85% NaCl solution. Serial dilutions of bacterial suspension were prepared and streaked onto nutrient agar in Petri plates. Two colonies per sample showing the characteristic of "fried egg" were selected for further investigation, and an isolated was selected and named D7. The isolated bacterium was rod shaped, gram-negative, motile, oxidase and indole production negative, with anaerobic growth, and able to use lactose as carbon source in Mac Conkey Agar medium. One colony of the isolate D7 was selected and multiplied. Total DNA of the bacteria cells was extracted and used to amplify the genes pelADE (Nassar et al., 1996) and gapA (Cigna et al., 2017), to differentiate Dickeya from Pectobacterium. The sequence obtained showed 99.75% and 99.88% nucleotide identity with Dickeya solani for pelADE (Genbank accession number ON644347) and gapA (Genbank accession number ON644346), respectively. To confirm the pathogenicity of the isolate D7, four 15-day-old potato plants, including two plants of each 'Otolia' and 'Naima' potatoes were inoculated with a bacterial suspension of the isolate D7 (108 CFU/ml) in sterile water by stabbing. Control plants were stabbed with sterile water. Inoculated plants were maintained at 28°C, relative humidity of about 90%, and at 12 h light/12 h dark, as described by (Chen et al. 2014). After 3 to 5 days, typical blackleg disease symptoms (water-soaked lesions and necrosis) developed at the inoculated areas of plants (Fig. 1B). No symptom was observed in the control plants. Bacterium was re-isolated from symptomatic plants and the isolates had the same cultural, physiological, and biochemical characteristics to the isolate D7. To our knowledge, this is the first report of D. solani causing blackleg in potato fields in Cuba. Further studies to determine the spread of this pathogen in potato producing areas in Cuba is underway.

Complete genome sequences of two novel bipartite begomoviruses infecting common bean in Cuba.

The common bean is a host for a large number of begomoviruses (genus Begomovirus, family Geminiviridae) in the New World. Based on the current taxonomic criteria established for the genus Begomovirus, two new members of this genus infecting common bean (Phaseolus vulgaris) in Cuba are herein reported. The cloned bipartite genomes, composed of DNA-A and DNA-B, showed the typical organization of the New World begomoviruses. We propose the names common bean severe mosaic virus and common bean mottle virus for the new begomovirus species.

A novel class of DNA satellites associated with New World begomoviruses.

Begomoviruses (family Geminiviridae) are whitefly-transmitted plant DNA viruses that have been shown to be helper viruses for a number of distinct DNA satellites, including betasatellites and alphasatellites. Replication of the satellites interferes to some degree with replication of the helper and in some cases they affect the disease symptoms. To date, betasatellites and related molecules such as the satellite associated with Tomato leaf curl virus (ToLCV-sat), have only been associated with Old World begomoviruses. Here, we report the discovery and characterization of subviral molecules associated with bipartite begomoviruses from the New World, which constitute a novel class of DNA satellites, in two malvaceous plant species. These molecules, in addition to sharing some genetic features with betasatellites and ToLCV-sat, contain nucleotide stretches of begomoviral origin, presumably the remains of recombination events involved in their origin.

Begomoviruses infecting weeds in Cuba: increased host range and a novel virus infecting Sida rhombifolia.

As a result of surveys conducted during the last few years to search for wild reservoirs of begomoviruses in Cuba, we detected a novel bipartite begomovirus, sida yellow mottle virus (SiYMoV), infecting Sida rhombifolia plants. The complete genome sequence was obtained, showing that DNA-A was 2622 nucleotides (nt) in length and that it was most closely related (87.6% nucleotide identity) to DNA-A of an isolate of sida golden mosaic virus (SiGMV) that infects snap beans (Phaseolus vulgaris) in Florida. The DNA-B sequence was 2600 nt in length and shared the highest nucleotide identity (75.1%) with corchorus yellow spot virus (CoYSV). Phylogenetic relationship analysis showed that both DNA components of SiYMoV were grouped in the Abutilon clade, along with begomoviruses from Florida and the Caribbean islands. We also present here the complete nucleotide sequence of a novel strain of sida yellow vein virus found infecting Malvastrum coromandelianum and an isolate of euphorbia mosaic virus that was found for the first time infecting Euphorbia heterophylla in Cuba.

Two novel begomoviruses belonging to different lineages infecting Rhynchosia minima.

Rhynchosia minima is a host for several begomoviruses, both in the Old World and the New World. In Cuba, a whitefly-transmitted disease causing yellow mosaic symptoms, suggested to be of viral origin, was described more than 30 years ago in R. minima, but no information about the nature of the viruses infecting this weed in this country is available to date. Here, we report the detection of isolates of two novel begomovirus species infecting R. minima in Cuba, which we proposed be named Rhynchosia golden mosaic Havana virus (RhGMHaV) and Rhynchosia rugose golden mosaic virus (RhRGMV). The highest nucleotide sequence identities of RhGMHaV and RhRGMV DNA-A were with isolates of Rhynchosia golden mosaic virus (78.7%) and Sida golden mosaic virus (87.5%), respectively. Phylogenetic analysis demonstrated that these novel viruses belong to two different lineages of New World begomoviruses.

Complete nucleotide sequence of Sida golden mosaic Florida virus and phylogenetic relationships with other begomoviruses infecting malvaceous weeds in the Caribbean.

The complete genome sequence of two isolates of the bipartite begomovirus (genus Begomovirus, family Geminiviridae) Sida golden mosaic Florida virus (SiGMFV) is presented. We propose that both isolates, found infecting Malvastrum coromandelianum (family Malvaceae) in Cuba, belong to a new strain of SiGMFV. Phylogenetic analysis showed that SiGMFV DNA-A is located in a monophyletic cluster that includes begomoviruses infecting malvaceous weeds from the Caribbean.