Analysis of intra-plant Tomato spotted wilt virus infection distribution of Nicotiana tabacum L
Connell S1, Wright S1, Csinos A1, Gitaitis R1, Nischwitz C1, Stephenson M2, Mullis S1
1Department of Plant Pathology, University of Georgia, P.O.Box 748, Tifton GA 31793.
2Crop and Soil Sciences, University of Georgia, P.O. Box 748, Tifton, GA 31793
Correspondence: spotwilt@uga.edu
Tomato spotted wilt virus (TSWV) has caused severe losses in tobacco in Georgia for approximately 15 years. Although much has been learned in that time, one aspect not clearly documented was the intra-plant distribution of TSWV. In previous studies, virus detected in roots was thought to be redistributed throughout the plant. This study presents a further evaluation of virus distribution in individual tobacco plants. At 8 weeks post transplanting during the 2005 growing season, root tissues from ninety non-symptomatic N. tabacum L. variety K-326 plants were tested for TSWV by DAS-ELISA (Agdia Inc., Elkhart, IN). Ten infected and 10 healthy plants were flagged for further analysis. Leaves were numbered sequentially from oldest to youngest on each plant and 100 mg tissue samples were collected bi-weekly for 3 wks and tested by DAS-ELISA. Within this period, TSWV was found more frequently in the oldest and youngest leaves. Plants with roots testing positive initially had the highest frequency of old and new leaf infections, whereas, plants initially testing negative primarily had TSWV in younger leaves with a subsequent lower frequency of TSWV in roots. Symptom expression did not necessarily follow this infection observation. It is not known if two separate inoculation periods, plant physiology, leaf size, virus titer or some other factor is responsible for this pattern. These data suggest that when testing for TSWV in tobacco, samples should be taken from multiple sources (leaves of various ages as well as roots) to increase the probability of detecting an infected plant.
