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Title: IN VITRO EVALUATION OF THE RESPONSE OF THREE PEACH CULTIVARS TO PRUNUS NECROTIC RINGSPOT VIRUS AFTER MICROGRAFTING

Author
item HEUSS, KATHY - CONTRACT EMPLOYEE, USDA
item Hammerschlag, Freddi
item QINGZHONG, LIU - CONTRACT EMPLOYEE, USDA
item Hammond, Rosemarie

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Prunus necrotic ringspot virus (PNRSV), a pollen-spread virus common in Prunus species can cause substantial reductions in the growth and yield of peach. A possible control strategy is the development of virus resistant peach cultivars through genetic engineering. Development of transgenic peaches with resistance to PNRSV will require a reliable method of screening for resistance. Resistance to PNRSV has been tested by grafting infected buds onto greenhouse trees, but such testing is limited to those months of the year when peach tissues are actively growing. In this study, we describe the use of in vitro micrografting as an inoculation method. Because PNRSV-infected peach does not always show symptoms, we used nucleic acid hybridization with a virus-derived probe as the method for detection of virus infection. This technique will be of value to scientists interested in year-round screening for resistance to PNRSV and for evaluation of peach transformants containing introduced genes for resistance to PNRSV.

Technical Abstract: As part of a program to develop transgenic peach cultivars with resistance to Prunus necrotic ringspot virus (PNRSV), we are testing a system for measuring virus in peach shoot cultures using in vitro micrografting as a method for inoculation and slot-blot hybridization, with a digoxigenin (DIG)-labeled cRNA probe derived from PNRSV RNA 3, for virus detection. In this study we investigated whether infected shoots maintain virus infection over long periods of culture at 4C and if PNRSV- infected 'Suncrest' shoot cultures can serve as graft bases to transmit this virus equally well into Nemaguard, Springcrest and Suncrest peach cultivars. RNA hybridization analysis showed that virus was present in extracts of leaf samples from 24-month-old PNRSV-infected 'Suncrest' shoots which had been subjected to varying lengths of incubation 4 degrees C in the dark, suggesting that infected shoots can be maintained for repeated use. Concentrations of PNRSV were similar in all three cultivars at two, four, and six weeks after grafting, suggesting that there is equal efficacy of graft inoculation from 'Suncrest' into these three cultivars and that no differences in resistance to PNRSV exist among these genotypes.