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Virus-free Plants (virus-free + plant)
Selected AbstractsMovement of aphid-transmitted Sugarcane yellow leaf virus (ScYLV) within and between sugarcane plantsPLANT PATHOLOGY, Issue 4 2007A. T. Lehrer Sugarcane yellow leaf virus (ScYLV) is distributed worldwide and has been shown to be the cause of the disease sugarcane yellow leaf syndrome (YLS). This study was an investigation of the transmission and spread of ScYLV in Hawaii. Several aphids are known to transmit the virus, but investigation of infestation and transmission efficiency showed Melanaphis sacchari to be the only vector important for field spread of the disease. The initial multiplication of ScYLV in a virus-free plant occurred exclusively in very young sink tissues. When a single leaf was inoculated on a plant, that leaf and all older leaves remained virus-free, based on tissue-blot immunoassay, whereas meristems and all subsequently formed new leaves became infected. Therefore, only after those leaves which had already developed before inoculation had been shed, did the complete plant contain ScYLV. Spread of the viral infection to neighbouring plants in the plantation fields via aphids was relatively slow and in the range of a few metres per year. No indication of long-distance transfer could be seen. This indicates that it may be possible to produce and use virus-free seed cane for planting of high-yielding but YLS-susceptible cultivars. [source] Ultrastructural and Immunocytochemical Studies on Effects of Barley Yellow Dwarf Virus , Infection on Fusarium Head Blight, Caused by Fusarium graminearum, in Wheat PlantsJOURNAL OF PHYTOPATHOLOGY, Issue 1 2006Y. Liu Abstract The interactions between barley yellow dwarf virus (BYDV) and Fusarium head blight (FHB), caused by Fusarium graminearum, were studied in the two winter wheat cultivars (cvs.), Agent (susceptible to FHB) and Petrus (moderately resistant to FHB), using ultrastructural and immunocytochemical methods. Infections of wheat plants of both cvs. by BYDV increased susceptibility to FHB. BYDV infection caused numerous cytological changes in lemma tissue of both cvs. such as formation of vesicles in the cytoplasm, degradation of fine structures of chloroplasts of both cvs. and accumulation of large starch grains in the chloroplasts. Electron microscopical studies showed that the development of F. graminearum on spike surfaces was not affected in BYDV-infected plants. After penetration and intercellular growth in lemma tissue, defence responses to Fusarium infections were markedly reduced in BYDV-diseased plants compared to the tissue of virus-free plants. At sites of contact of fungal cells with host tissue, depositions of cell wall material were distinctly less pronounced than in tissues of virus-free plants of cv. Petrus. Detection of , -1,3-glucanases and chitinases in lemma tissue of cv. Agent revealed no appreciably increased accumulation of both defence enzymes in F. graminearum -infected virus-free and BYDV-infected tissues compared to the non-infected control tissue. On the other hand, in cv. Petrus, infection with F. graminearum induced a markedly enhanced activity of both enzymes 3 days after inoculation. The increase of both enzyme activities was less pronounced in BYDV-infected plants than in tissue exclusively infected with F. graminearum. Cytological studies suggest that in contrast to the susceptible cv. Agent postinfectional defence responses may play still an important role in the resistance of the moderately resistant cv. Petrus to FHB. [source] Combined thermotherapy and cryotherapy for efficient virus eradication: relation of virus distribution, subcellular changes, cell survival and viral RNA degradation in shoot tipsMOLECULAR PLANT PATHOLOGY, Issue 2 2008QIAOCHUN WANG SUMMARY Accumulation of viruses in vegetatively propagated plants causes heavy yield losses. Therefore, supply of virus-free planting materials is pivotal to sustainable crop production. In previous studies, Raspberry bushy dwarf virus (RBDV) was difficult to eradicate from raspberry (Rubus idaeus) using the conventional means of meristem tip culture. As shown in the present study, it was probably because this pollen-transmitted virus efficiently invades leaf primordia and all meristematic tissues except the least differentiated cells of the apical dome. Subjecting plants to thermotherapy prior to meristem tip culture heavily reduced viral RNA2, RNA3 and the coat protein in the shoot tips, but no virus-free plants were obtained. Therefore, a novel method including thermotherapy followed by cryotherapy was developed for efficient virus eradication. Heat treatment caused subcellular alterations such as enlargement of vacuoles in the more developed, virus-infected cells, which were largely eliminated following subsequent cryotherapy. Using this protocol, 20,36% of the treated shoot tips survived, 30,40% regenerated and up to 35% of the regenerated plants were virus-free, as tested by ELISA and reverse transcription loop-mediated isothermal amplification. Novel cellular and molecular insights into RBDV,host interactions and the factors influencing virus eradication were obtained, including invasion of shoot tips and meristematic tissues by RBDV, enhanced viral RNA degradation and increased sensitivity to freezing caused by thermotherapy, and subcellular changes and subsequent death of cells caused by cryotherapy. This novel procedure should be helpful with many virus,host combinations in which virus eradication by conventional means has proven difficult. [source] Tomato spotted wilt virus in peanut tissue types and physiological effects related to disease incidence and severity,PLANT PATHOLOGY, Issue 4 2005D. Rowland Three peanut cultivars, Georgia Green, NC-V11, and ANorden, were grown using production practices that encouraged the development of Tomato spotted wilt virus (TSWV). The progression of TSWV infection was examined through the season using enzyme-linked immunosorbent assay (ELISA) tests on different tissue types [roots, leaves, pegs (pod attachment stem structures) and pods] and the effect of TSWV infection on physiological functions was examined at three harvest dates. Plants were classed into three severity categories: (i) no TSWV symptoms or previous positive ELISA tests; (ii) less than 50% of leaf tissue exhibiting TSWV symptoms; and (iii) greater than 50% of leaf tissue affected. TSWV showed a slow rate of infection at the beginning of the season and a greater percentage of infection of the roots than in the leaves. Photosynthesis was reduced in virus-affected infected plants by an average of 30% at the mid-season harvest and 51% at the late season harvest compared with virus-free plants across all three cultivars. Leaf tissue with symptoms had lower photosynthetic rates than healthy leaves. There were small differences among cultivars, with cv. ANorden maintaining higher average photosynthetic levels than cv. Georgia Green and higher transpirational levels than cv. NC-V11. The ability to maintain high assimilation physiology in the presence of the virus may help cultivars withstand TSWV infection and maintain final yields. [source] Hydroxyproline-rich glycoprotein accumulation in tobacco leaves protected against Erysiphe cichoracearum by potato virus Y infectionPLANT PATHOLOGY, Issue 2 2000V. Raggi Tobacco cv. Havana 425 acquired resistance to a compatible isolate of Erysiphe cichoracearum after infection by a strain of potato virus Y (PVYN) that causes veinal necrosis; another common strain (PVYO) that does not cause necrosis gave less protection. Hydroxyproline-rich glycoproteins (HRGPs), believed to be involved in resistance, were determined by analysing hydroxyproline (Hyp) in purified cell walls. Hyp content increased significantly in PVYN -protected leaves, compared with untreated controls, 2,4 days after necrotic lesion symptoms developed. No further increase in Hyp was noted in PVYN -protected leaves after E. cichoracearum challenge. Hyp increases were significantly higher in protected leaves of plants showing symptoms on day 7 than on day 10. Infection with the PVYO strain caused significant decrease in Hyp content, compared with uninoculated controls. Inoculation of virus-free plants with E. cichoracearum induced moderate and transitory Hyp increases on day 2 or 3, followed by a quick decrease associated with a weak response by the compatible host. It is suggested that HRGP accumulation induced by PVYN (but not by PVYO) causes changes in the host cell wall that result in resistance to E. cichoracearum. [source] | ||||||||||