Volume 60 - Tomato Genetics Cooperative - University of Florida

was evaluated in relation to the parental genotypes. The genotype of the F1 families
was determined and subsequently transplanted in the field for the evaluation of their
phenotype of resistance. The hybrid (Gc21-a X Gh13), both parental lines, and a
susceptible control were planted in with three replications of five plants each. Plants
were scored for their DSIs in October 2009.
Results and Discussion:
Natural inoculation with begomoviruses in a field in Guatemala with high
populations of the whitefly vector was used to evaluate various combinations of
begomovirus-resistance introgressions for their effectiveness to provide resistance to
multiple begomoviruses.
Evaluations of the introgressions Ty3a and Ty4: The highly resistant inbred line,
Gc171 (Ty3a/Ty3a, Ty4/Ty4), was crossed with a slightly resistant genotype (Gh44,
ty3/ty3, ty4/ty4) (Garcia, et al., 2008a). Among the 77 F2 plants analyzed, 17 were
found to be homozygous Ty3a/Ty3a, 12 homozygous ty3a/ty3a, and 48 heterozygous
Ty3a/ty3a. With relation to Ty4 introgression, 10 plants were found to be
homozygous Ty4/Ty4, 42 homozygous ty4/ty4, and 25 heterozygous Ty4/ty4. Seven
F3 families were evaluated: three with genotype ty3/ty3, Ty4/Ty4 (SR), and four with
genotype Ty3a/Ty3a, ty4/ty4 (RS) (Fig. 1).
DSI
7
6
5
4
3
2
1
0
RR RS SR R-RR S-SS C-SS
F3 Families and Parents
Fig. 1. Disease severity index (DSI) and standard errors for F3 families of genotypes
RR (4 families Ty3a/Ty3a, Ty4/Ty4), RS (4 families, Ty3a/Ty3a, ty4/ty4), SR (4
families, ty3/ty3, Ty4/Ty4), C-SS (commercial susceptible control), R-RR (parent,
Gc171), S-SS (Gh44).
44