The apple scar skin disease was first re- ported 60 years ago in China ( Manchuria) with the name “Manshu-sabika-byo” (19). Twenty years later, two apple. Cause These diseases are caused by Apple scar skin viroid. Many infected cultivars of apple or pear do not express symptoms of disease. Apple scar skin viroid(ASSVd), a pathogenic RNA viroid, infects apple and pear trees. To determine if ASSVd can also infect apricot, we performed reverse.
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Natural infection of wild and cultivated pears with Apple scar skin viroid in Greece. Potato leafroll virus-assisted aphid transmission of potato spindle tuber viroid to potato leafroll virus-resistant potato.
Bar graph shows the percentage of infected cucumber plants which were inoculated through whiteflies. Nucleic acid transfer between plants is a phenomenon which is likely to occur in many ways in nature. Thomas Hohn, University of Basel, Switzerland for critically reading and editing the manuscript and Dr. Aple JA, Flores R. None of the known whitefly-transmitted viruses mentioned above were identified data not shown.
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Spread of Tomato apical aople viroid TASVd in greenhouse tomato crops is associated with seed transmission and bumble bee activity. Most commercial pear cultivars show no symptoms when applee with ASSVd.
However, in Hebei, China, the Chinese pear P. J Virol ; To screen for the presence of viroid in the viroidliferous whiteflies, we analyzed monomeric circular and linear RNAs. However, the role of plant host factors in determining the transmission efficiency cannot be overlooked. The twenty whiteflies were then allowed access to groups of 5 healthy cucumber seedlings at the one-true-leaf stage. In addition to the monomeric circular and monomeric linear bands, another band was observed in the whiteflies, which may correspond to replicative intermediates of viroid RNA.
Transmission to apple seedling of low molecular weight RNA from apple scar skin-diseased trees. Abstract Nucleic acid transfer between plants is a phenomenon which is likely to occur in many ways vigoid nature. Archives of Virology ; Dapple symptoms, which develop nearer to harvest, usually appear on the red-skinned cultivars e. Sundararaj, Institute of Wood Science and Technology, Bengaluru, Karnataka, India for his help in identification of the whitefly species as Trialeurodes vaporariorum.
Natural infection by the viroid has been observed not only in apple but also in Himalayan wild cherry, 19 monocots and flower crops such as gerbera unpublished data. A faint band corresponding to the ubiquitin ligase mRNA was also observed when using healthy cucumber phloem. Ralls Janet, water-soaked blotches appear first, followed by scar tissue, sacr then cracking. Go to distribution map Plant Pathology ; Results and Discussion A healthy Tv colony was maintained on seed-grown eggplant Solanum melongena.
The causal agent is controlled through the use of healthy propagation materials indexing programmes and, if necessary, the removal of diseased trees. Dot blot hybridization of the various plants inoculated through whitefly: The healthy control plants tissue culture-grown cucumber and bean and healthy whiteflies did not react with the ASSVd probe in the hybridization experiment and also yielded negative RT-PCR results.
Several workers have observed that the disease spread naturally to neighboring trees, 20,21 and ASSVd has been reported to be seed-borne but not seed-transmitted in apple.
A serious threat to crop production. The tips were placed on racks below a tube light in temperate-controlled chambers, and groups of 20 whiteflies fed on the solution. A proposed scheme for viroid classification and nomenclature. In sensitive cultivars, infection with the viroid causes significant reductions in fruit size and quality. Whiteflies directly damage plants by sucking sap from leaves, inducing physiological disorders.
Apple scar skin viroid ASSVdthe type member of the genus Apscaviroid within the family Pospiviroidaecauses scarring and dappling on apple fruits.
Enhanced resolution of circular and linear molecular forms of viroid and viroid-like RNA by electrophoresis in a discontinuous-pH system. Sequence alignment between the ubiquitin ligase mRNA and ASSVd primers indicated high sequence similarity between the 2, applf explaining why this amplicon was obtained Fig. In wcar study, ASSVd was found to be directly transmitted by a whitefly Tv that was otherwise free of whitefly-transmitted viruses. Plant Dis ; To explore the identity of this DNA form, rolling circle amplification RCA was performed using viroidliferous and healthy whiteflies.
The same band was observed in non-viroidliferous whiteflies, but its intensity was comparatively quite low.
Apple scar skin viroid
Thus, the efficiency of viroid transmission increased after feeding on phloem exudate and purified recombinant CsPP2, thereby indicating that this complex facilitates acquisition and transmission by the whitefly, most likely after associating with other insect proteins.
Although symptoms of ASSVd are usually confined to the fruit, under certain conditions, some apple cultivars may develop leaf roll or leaf epinasty symptoms Ito and Yoshida, ; Koganezawa et al. The whitefly-mediated transmission of ASSVd may enhance the efficiency of viroid transfer to a large number of plants and widen the host range. Disclosure of Potential Conflicts of Interest No potential conflicts of interest were disclosed.
Because some insects are known to possess endogenous reverse transcription activity, 18 total DNA of the whitefly was isolated and tested for a possible DNA form of the viroid using PCR. Side box indicates size of the different fragments bp, bp, bp, bp and bp obtained after digestion of RCA product in case of viroidliferous whitefly.
A high incidence of ASSVd in commercial apple orchards has been observed, and this situation was thought to be related to the transmission of the viroid by razor blades in the field.