CORESTA Congress, New Orleans, 2002, APPOST 22

Pathogenesis related protein expression and resistance to tomato spotted wilt virus in tobacco by acibenzolar-S-methyl

University of Georgia, Dept. of Plant Pathology, Tifton, GA, USA.
Tomato spotted wilt virus (TSWV) is the most important viral pathogen of tobacco in Georgia. We have demonstrated that application of acibenzolar-S-methyl (ASM) protected tobacco in the field against TSWV. In this study, tobacco seedlings were treated with ASM (2 g a.i.or 4 g a.i/7000 plants) in the greenhouse and subsequently challenged with TSWV at every 24 h for seven days. Treated plants showed reduction of number of local lesions caused by TSWV as time increased post treatment (pt). At four to five days pt treated plants had few lesions whereas, non-treated plants had a large number of lesions causing withering of inoculated leaves. Plants treated with 2 g a.i. ASM/7000 plants were collected every 24 h for 10 days pt and leaf samples of 1.5 g from five plants at each time point were analyzed for pathogenesis related protein (PRP). Polyacrylamide gel electrophoresis analysis of total protein from ASM treated plants showed the induction of various protein bands. Quantitization of total protein revealed a significant increase of protein level in plants at 24 h after treatment with ASM. Northern blot analysis using PR3 probe showed expression of PR3 genes in treated plants only. Western blot analysis showed expression of various classes (PR1, PR3 and PR5) of PRP due to ASM treatment. Relatively higher level of PRP expression was noted at two days after treatment with ASM, while the number of TSWV local lesions per plant was significantly reduced. The data suggest that the resistance observed against TSWV may be due to the ASM-induced expression of host defense genes.