A Citrus volkameriana tree displaying symptoms similar to citrus leprosis on its leaves and bark was found in Hawaii. Citrus leprosis virus C (CiLV-C)-specific detection assays, however, were ...negative for all tissues tested. Short, bacilliform virus-like particles were observed by transmission electron microscopy in the cytoplasm of symptomatic leaves but not in healthy controls. Double-stranded (ds) RNAs ≈8 and 3 kbp in size were present in symptomatic leaf tissue but not in healthy controls. Excluding poly(A) tails, the largest molecule, RNA1, was 8,354 bp in length. The ≈3 kbp dsRNA band was found to be composed of two distinct molecules, RNA2 and RNA3, which were 3,169 and 3,113 bp, respectively. Phylogenetic analyses indicated that the RNA-dependent RNA polymerase (RdRp) domain located in RNA1 was most closely related to the RdRp domain of CiLV-C. A reverse-transcription polymerase chain reaction assay developed for the detection of this virus was used to screen nearby citrus trees as well as Hibiscus arnottianus plants with symptoms of hibiscus green spot, a disease associated with infection by Hibiscus green spot virus (HGSV). All nearby citrus trees tested negative with the assay; however, symptomatic H. arnottianus plants were positive. All three RNAs were present in symptomatic H. arnottianus and were >98% identical to the RNAs isolated from C. volkameriana. We contend that the virus described in this study is HGSV, and propose that it be the type member of a new virus genus, Higrevirus.
Canna yellow mottle virus (CaYMV) is an important badnavirus infecting Canna spp. worldwide. This is the first report of CaYMV in flowering ginger (Alpinia purpurata) in Hawaii, where it is ...associated with yellow mottling and necrosis of leaves, vein streaking, and stunted plants. We have sequenced CaYMV in A. purpurata (CaYMV-Ap) using a combination of next-generation sequencing and traditional Sanger sequencing techniques. The complete genome of CaYMV-Ap was 7,120 bp with an organization typical of other Badnavirus species. Our results indicated that CaYMV-Ap was present in the episomal form in infected flowering ginger. We determined that this virus disease is prevalent in Hawaii and could potentially have significant economic impact on the marketing of A. purpurata as cut flowers. There is a potential concern that the host range of CaYMV-Ap may expand to include other important tropical plants.
The Hawaiian Islands are home to a widespread and diverse population of Citrus tristeza virus (CTV), an economically important pathogen of citrus. In this study, we quantified the genetic diversity ...of two CTV genes and determined the complete genomic sequence for two strains of Hawaiian CTV. The nucleotide diversity was estimated to be 0.0565 ± 0.0022 for the coat protein (CP) gene (n = 137) and 0.0822 ± 0.0033 for the p23 gene (n = 30). The genome size and organization of CTV strains HA18-9 and HA16-5 were similar to other fully sequenced strains of CTV. The 3′-terminal halves of their genomes were nearly identical (98.5% nucleotide identity), whereas the 5′-terminal halves were more distantly related (72.3% nucleotide identity), suggesting a possible recombination event. Closer examination of strain HA16-5 indicated that it arose through recent recombination between the movement module of an HA18-9 genotype, and the replication module of an undescribed CTV genotype.
Tomato spotted wilt virus (TSWV) has a very wide host range, and is transmitted in a persistent manner by several species of thrips. These characteristics make this virus difficult to control. We ...show here that the over-expression of the mitochondrial alternative oxidase (AOX) in tomato and petunia is related to TSWV resistance.
The open reading frame and full-length sequence of the tomato AOX gene LeAox1au were cloned and introduced into tomato 'Healani' and petunia 'Sheer Madness' using Agrobacterium-mediated transformation. Highly expressed AOX transgenic tomato and petunia plants were selfed and transgenic R1 seedlings from 10 tomato lines and 12 petunia lines were used for bioassay. For each assayed line, 22 to 32 tomato R1 progeny in three replications and 39 to 128 petunia progeny in 13 replications were challenged with TSWV. Enzyme-Linked Immunosorbent Assays showed that the TSWV levels in transgenic tomato line FKT4-1 was significantly lower than that of wild-type controls after challenge with TSWV. In addition, transgenic petunia line FKP10 showed significantly less lesion number and smaller lesion size than non-transgenic controls after inoculation by TSWV.
In all assayed transgenic tomato lines, a higher percentage of transgenic progeny had lower TSWV levels than non-transgenic plants after challenge with TSWV, and the significantly increased resistant levels of tomato and petunia lines identified in this study indicate that altered expression levels of AOX in tomato and petunia can affect the levels of TSWV resistance.
The ti plant (Cordyline fruticosa L.) is culturally important throughout most of Polynesia and has considerable economic importance in Hawai'i where the foliage is commonly used in cultural ...ceremonies as well as food and ornamental industries. In Hawai'i, ringspot symptoms were recently observed on leaves of the common green variety of ti growing in Kahalu'u on the island of O'ahu, and Wailuku and Hana on the island of Maui. High molecular weight double-stranded (ds)RNAs were isolated from the leaves of symptomatic plants as well as plants without symptoms. A cDNA library derived from the dsRNAs present in symptomatic plants was generated and sequenced. These sequences indicated at least four distinct clostero-like viruses were present in the plants, and phylogenetic analyses suggested they were most closely related to Little cherry virus 1, an unassigned member of the family Closteroviridae. The 16,883 nucleotide genome of one of these viruses was determined and predicted to contain ten open reading frames with an organization typical of closteroviruses. Reverse-transcription PCR revealed this virus was present in both symptomatic and asymptomatic ti plants, making it unlikely to be responsible for the observed ringspot symptoms. We propose the name Cordyline virus 1 (CoV-1) for this virus and include it as a new, unassigned member of the family Closteroviridae.
The nucleotide sequence of Pineapple mealybug wilt associated virus-3 (PMWaV-3) (Closteroviridae: Ampelovirus), spanning seven open reading frames (ORFs) and the untranslatable region of the 3' end ...was determined. Based on the amino acid identities with orthologous ORFs of PMWaV-1 (54%-73%) and PMWaV-2 (13%-35%), we propose PMWaV-3 is a new species in the PMWaV complex. PMWaV-3 lacks an intergenic region between ORF1b and ORF2, encodes a relatively small, 28.8 kDa, coat protein, and lacks a coat protein duplicate. Phylogenetic analyses were used to analyze seven different domains and ORFs from members of the family Closteroviridae. Two distinct clades within the recognized genus Ampelovirus were observed; one that includes PMWaV-3 and PMWaV-1 and several GLRaVs and another that includes PMWaV-2 and GLRaV-3, the type member of the genus Ampelovirus.
Mealybug wilt of pineapple (MWP) is a devastating disease worldwide, the etiology of which is unknown. Two closteroviruses, Pineapple mealybug wilt associated virus-1 (PMWaV-1) and PMWaV-2, were ...identified in pineapple from Hawaii and around the world. Both viruses are transmitted by pink pineapple mealybugs, Dysmicoccus brevipes, and grey pineapple mealybugs, D. neobrevipes. PMWaV-2 was shown to be an integral factor in MWP etiology. Typical MWP symptoms developed in pineapple plants infected with PMWaV-2 that were exposed to mealybugs. MWP did not develop in PMWaV-1-free or PMWaV-l-infected plants that were exposed to mealybugs or in plants infected with PMWaV-1, PMWaV-2, or both viruses if kept mealybug-free. MWP resulted in a 35% reduction in yield when compared to yields of PMWaV-free plants. Yield reductions were dependent on time of MWP symptom development; the earlier the expression of symptoms the greater the impact on plant crop fruit yield. Both PMWaV-1 and PMWaV-2 suppressed yield in the ratoon crop. Spatial analysis of PMWaV-2 spread and MWP symptom expression in mealybug-inoculated pineapple plots showed patterns of aggregation within rows and within beds but not between beds. Initial occurrence of MWP symptomatic plants showed underdispersed which was consistent with the random occurrence of PMWaV-2 plants. After six months of mealybug exposure, patterns of both PMWaV-2 incidence and MWP were overdispersed. PMWaV-1 and PMWaV-2 were detected in MWP symptomatic and healthy looking pineapple samples from around the world but PMWaV-2 infection was correlated with 100% of the MWP symptomatic samples that were PNIWaV-1-free. PMWaV-2 infection occurs at a lower frequency than PMWaV-1 infection in the Hawaiian grown pineapple selections and several hybrids. Infections of at least one PMWaV were found in 73% of the pineapple accessions maintained at the USDA-ARS National Clonal Germplasm Repository in Hilo, HI. No plants commonly found growing near or in pineapple fields were identified as hosts for PMWaV-1 and no pineapple germplasm was immune to PMWaV-1. PMWaV-1 was eliminated through bud propagation from infected crowns.
Peppermint, Mentha piperita 'Black Mitcham' was established as a host for tomato
spotted wilt virus-impatiens serotype (TSWV-I). TSWV-I infection of peppermint,
initially observed in a research ...greenhouse (Corvallis, OR), included stunting and
downward curling of leaves accompanied by bronzing, and occasionally tip necrosis.
Young leaves appeared either symptomless, deformed, or pale even under high nitrogen
conditions. Older leaves had sunken, brownish-grey lesions. Bright yellow mottling was
observed on newly mature deep green leaves. A begonia isolate of TSWV-I was
transmitted to peppermint both mechanically and by western flower thrips, Frankliniella
occidentalis (Pergande). Symptoms of TSWV-I infection were similar although only a
faint yellow mottling was produced and only under cool temperatures (15°C). ELISA
detection of virus distribution throughout the plant indicated infection was systemic.
Bulked groups of thrips (5 thrips/sample) also tested positive for TSWV-I using ELISA.
Transmission efficiency of 4, 6, 8, and 10 day old thrips adults given acquisition sources
during the entire nymphal stage varied from 0-40% for thrips tested in pairs and 0-20%
for single thrips (based on a 12 hour access feeding period). Adults 2 days old failed to
transmit the virus. Western flower thrips exposed to TSWV-I had reduced survival and
reproductive potential and slower development rates than unexposed thrips. Virusexposed
thrips were 1.4 times as likely to die than unexposed thrips on a given day. Both
individual and population reproductive potentials were significantly lower. Preoviposition
period was extended in virus-exposed thrips. Development time from second instar to
adult was 15% longer for virus-exposed thrips. This is the first report of altered
population parameters in western flower thrips exposed to TSWV-I.
Graduation date: 1992
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