Volume 60 - Tomato Genetics Cooperative - University of Florida

The average DSI for the RS F3 families with the Ty3a introgression was 2.1,
while the SR F3 families with the Ty4 introgression was 3.6, which is similar to the
slightly resistant parent, Gh44 (S-SS). These results indicate that there is a larger
effect on resistance by Ty3a than by Ty4 to the multiple bipartite begomoviruses
present in this area. This is consistent with the report by Ji et al. (2008) where the
Ty4 introgression had a lesser effect on resistance to Tomato yellow leaf curl virus
than the Ty3a introgression.
Combinations of introgression Ty2 and Ty3: Seventeen F3 families were
obtained from individual F2 plants arising from the cross of Gh13 X CLN2116 (F1,
Ty3/ty3, Ty2/ty2). The F3 families were evaluated for symptom development 36 days
after transplanting (Fig. 2).
DSI
6
5
4
3
2
1
0
RR SR RS SS SR-C RS-C SS-C
F3 Families and Parents
Fig. 2. Disease severity index (DSI) with standard errors for the F3 families of
genotypes RR (6 families, Ty3/Ty3, Ty2/Ty2), SR (5 families, ty3/ty3, Ty2/Ty2), RS (3
families, Ty3/Ty3, ty2/ty2), SS (3 families, ty3/ty3, ty2/ty2), SR-C (CLN2116, ty3/ty3,
Ty2/Ty2), RS-C (Gh13, Ty3/Ty3, ty2/ty2) and SS-C (susceptible commercial hybrid
control, ty3/ty3, ty2/ty2).
45