Hop Stunt Viroid in Cannabis

OAKLAND, Calif., (March 4, 2019) — Dark Heart Nursery (DHN) proudly announced today that it is the first organization to positively identify hop latent viroid (HpLVd), previously identified as Putative Cannabis Infectious Agent (PCIA), as the cause of “dudding” in cannabis.

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• Stunting / dwarving, no big leaves
• Lack of vigor
• Glossy leaves
• Horizontal branching
• Leaf epinasty and distortion
• Lack of trichomes
• Lack of essential oils
• Fruit distortion and color break
• Stem and leaf necrosis
• Rubbery growth that peels off easily
• Poor root development
• White crust at meristem base (may be a secondary infection, only reported in some cases)

Chrysanthemum stunt viroid (CSVd) can infect Argyranthemum and cause serious economic loss. Low temperature treatment combined with meristem culture has been applied to eradicate viroids from their hosts, but without success in eliminating CSVd from diseased Argyranthemum. The objectives of this work were to investigate (1) the effect of low temperature treatment combined with meristem culture on elimination of CSVd, (2) the effect of low temperature treatment on CSVd distribution pattern in shoot apical meristem (SAM), and (3) CSVd distribution in flowers and stems of two infected Argyranthemum cultivars. After treatment with low temperature combined with meristem tip culture, two CSVd-free plants were found in ‘Border Dark Red’, but none in ‘Yellow Empire’. With the help of in situ hybridization, we found that CSVd distribution patterns in the SAM showed no changes in diseased ‘Yellow Empire’ following 5°C treatment, compared with non-treated plants. However, the CSVd-free area in SAM was enlarged in diseased ‘Border Dark Red’ following prolonged 5°C treatment. Localization of CSVd in the flowers and stems of infected ‘Border Dark Red’ and ‘Yellow Empire’ indicated that seeds could not transmit CSVd in these two cultivars, and CSVd existed in phloem. Results obtained in the study contributed to better understanding of the distribution of CSVd in systemically infected plants and the combination of low temperature treatment and meristem tip culture for production of viroid-free plants.

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Viroids are single-stranded, covalently closed, circular, highly structured noncoding RNAs that cause disease in several economically important crop plants. They replicate autonomously and move systemically in host plants with the aid of the host machinery. In addition to symptomatic infections, viroids also cause latent infections where there is no visual evidence of infection in the host; however, transfer to a susceptible host can result in devastating disease. While there are non-hosts for viroids, no naturally occurring durable resistance has been observed in most host species. Current effective control methods for viroid diseases include detection and eradication, and cultural controls. In addition, heat or cold therapy combined with meristem tip culture has been shown to be effective for elimination of viroids for some viroid–host combinations. An understanding of viroid–host interactions, host susceptibility, and non-host resistance could provide guidance for the design of viroid-resistant plants. Efforts to engineer viroid resistance into host species have been underway for several years, and include the use of antisense RNA, antisense RNA plus ribozymes, a dsRNase, and siRNAs, among others. The results of those efforts and the challenges associated with creating viroid resistant plants are summarized in this review.

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Two aspects of hop latent viroid (HLVd) relevant to control were examined: the production of viroid‐free plants from infected material and transmission of HLVd in the field. Plants free from HLVd were obtained by a combination of storing infected source plants at low temperature (2–4oC in the dark) for several months followed by meristem culture using small explants. A total of 77 plants of six cultivars and male pollinator clones were grown from meristems and 28 of these were free from HLVd. Tests showed that the cutting of stems (mimicking the use of tools) was more effective than abrasion (mimicking natural plant to plant contact) for the mechanical transmission of HLVd between hop plants. When field‐grown test plants were inoculated, infection occurred more commonly in May before plants had grown large enough for significant contact between neighbouring plants than later in the season. The aphid Phorodon humuli could not be shown to transmit HLVd.

These results indicate that all hop varieties and pollinator clones can be made available to the industry free from HLVd and that the chances of infection can be reduced by avoiding early‐season cultural operations that cut into hop shoots.

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One of the most intriguing classes of plant pathogens are the viroids, subviral
pathogens that have been isolated from higher plants afflicted with specific diseases.
Viroid hosts include both herbaceous and woody species — agronomic as well as
ornamental. Identification of viroid-infected plants can be accomplished by either
symptomatology on indicator hosts, a classical method still used in many certification
programs, or by molecular methods such as nucleic acid hybridization or polymerase
chain reaction.
Several viroid-incited diseases are of considerable economic importance. For
example, yield losses can be high in potatoes infected with Potato spindle tuber
viroid (PSTVd) (Fig. 1), chrysanthemum infected with Chrysanthemum stunt viroid
(CSVd), citrus infected with Citrus exocortis viroid (CEVd), coconut palms infected
with Coconut cadang-cadang viroid (CCCVd), and avocado infected with Avocado
sunblotch viroid (ASBVd). Exclusion or eradication of infected materials is the most
effective means of controlling viroid diseases, but routine diagnosis of viroid
diseases based on symptom expression in their natural hosts is often difficult.

Expression of commonly observed symptoms of viroid infection — stunting, leaf
epinasty and distortion, fruit distortion and color break, stem and leaf necrosis, and
even death of the whole plant — is often dependent upon environmental conditions.
Also, many viruses can cause very similar symptoms. While viroids were initially identified by their association with specific diseases, we now know that not all viroid infected plants exhibit obvious signs of disease. In some cases, a viroid may be
latent in one host yet cause severe symptoms in another host. One example is
Columnea latent viroid (CLVd), which was isolated from healthy-looking plants of the
ornamental Columnea erythrophae but causes a disease similar to, but more severe
than that caused by PSTVd in potato.
Recent outbreaks of diseases caused by viroids suggest that either current control
measures are inadequate or that growers may be unaware of the risks that viroid
infection pose to their crops. Viroids are also being detected in crop species where
they were not previously known to occur. In some cases, these infections are latent,
but in others, severe disease symptoms develop. These observations raise several
intriguing questions: Why are viroid diseases recurring in certain crops where they
were previously assumed to be under control? Are viroid infections more common
than we know; if so, do they pose a serious threat to modern agriculture?
Our review of the literature attempts to address these questions.

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Storm Shadow said:

This is a new virus that hit the scene over the last few years... its not the original DUD that was destroying everyone ...

WHITE FLAGGING ... one of the most obvious signs of DUDs ... Viroids arent responsible for that... Google ALFALFA STEM NEMATODES and WHITE FLAGGING.. along with Witches BROOM ETC ...

Ive picked up the new Viroid virus from DARK HEAR NURSERY ....its totally different... Ill take pics later today ... Id take the Viroid all day/night over ASM

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Effect of HpSVd on yield and levels of brewing organic acids.

Plants infected by HpSVd produced fewer and smaller cones with yields 50% lower, and alpha and beta acid levels 50 to 70% lower than in viroid free plants (164,201). The proportions of the brewing organic acids are also altered by HpSVd. Ratios of beta to alpha acids less than 1:20 are characteristic of healthy plants, whereas ratios greater than 1:44 are typical of HpSVd infection (164). Momma and Takahashi (110) reported that the number of lupulin glands was reduced by more than 60% in cones.

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Season-dependent fluctuation of hop latent viroid in meristem tips enabled selection of viroid-free cultures from Osvald's clone 31, 72, 114, and cv. Premiant. These mericlones were used to evaluate effect of viroid infection on the composition of hop resins and essential oils in the first production year. Healthy plants were compared with naturally re-infected individuals under field conditions. On average, viroid infection decreased content of α-bitter acids by 40 %. The content of β-bitter acids, as well as the ratios of humulone/cohumulone and lupulone/colupulone was not influenced by viroid infection. The content of all monoterpenes was for 29, 37.4 and 41.6 % higher for myrcene, α- and β-pinene, respectively, in infected plants compared with the healthy controls. The contents of sesquiterpenes like β-caryophyllen α-humulene, α-copaene, γ-muurolene, β-bisabolene, γ-cadinene, and δ-cadinene decreased by 13.7, 13, 14, 18.5, 29, 21.7 and 18.5 %, respectively, due to viroid infection. The possible influence of some oxidative-reduction processes activated by viroid-caused pathogenesis was assumed to be involved in the accumulation of terpenes alcohols like geraniol and methylgeranate, and in the reduction of the contents of the majority of ketones detected in the spectra of essential oils.

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palmeezy said:

storm shadow, thanks for sharing. following the advice you've posted (which few others seem to be willing to share) i've turned things around after a miserable period.

i'm guessing kontos and pylon are effective against ASM.

do you think ASM is the cause of the witches brooming?

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Azaghal said:

Thank you very much for sharing, beta !


Found this paper, the lead author is Jeremy warren who



"recently accepted a position at Dark Heart Nursery as Director of Plant Health"


according to Dark Heart Nursery (first Link of the first Post in this Thread).


https://apsjournals.apsnet.org/doi/10.1094/PDIS-03-19-0530-PDN


("The occurrence of Hop latent viroid causing disease in Cannabis sativa in California.")



Just want to say that viroids are very interesting because


"Viroids are the smallest infectious pathogens known",
"eighty times smaller than the smallest viruses"


and they are


"single-stranded, covalently closed, circular RNA molecule(s), existing as highly base-paired rod-like structure(s)"



without having any protein coat themselves or coding for any proteins.
Also could they represent remnants of the early evolutionary history of live on this planet

(see paragraph "RNA world hypothesis" in the link below),

and if that is not interesting, then I do not know what really is ... .



https://en.wikipedia.org/wiki/Viroid


and the plant pathologist who discovered Viroids


https://en.wikipedia.org/wiki/Theodor_Otto_Diener


Cheers

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