Based on these result, we conclude that Pto (or linked genes) does not have a major impact on most
processing traits. It would also appear that Pto can be used in either the homozygous or heterozygous state with
similar effect. This result is different than that obtained for Mi (Tanksley et al 1997b, this issue of TGC) and Tm-2a
(Tanksley et al, 1997x) for many trait were affected and for which the heterozygous types have a clear yield over
either homozygous susceptible or homozygous resistant genotype. The main effect of the Pto locus (other than
providing resistance to P.s.) appears to be in lowering fruit pH and increasing venation and puffiness (in the
heterozygous state only).
Literature cited:
Martin et al. (1993) High-resolution analysis and physical characterization of the Pto bacterial resistance locus in
tomato. MPMI 6:26-34
Pitblado RE, MacNeill BH (1983) Genetic basis of resistance to Pseudomonas syringae pv. tomato in field
tomatoes. Can J Plant Pathol 5:251-255
Tanksley et al. (1997) Yield and Quality Evaluations on a Pair of Processing Tomato Lines Nearly Isogenic for the
Tm2a Gene for Resistance to the Tobacco Mosaic Virus. Euphytica (submitted)
Comparing the performance of a pair of processing lines nearly isogenic for Sw-5, a gene conferring resistance to
tomato spotted wilt virus.
Tanksley, S.1, Bernacchi, D.1, Fulton, T.1, Beck-Bunn, T.2, Emmatty, D.3, Eshed, Y4, Inai, S.5, Lopez, J 6,
Petiard, V.7 , Sayama, H.5, Uhlig, J.2, & Zamir, D .4
1 Department of Plant Breeding and Biometry, Cornell University, Ithaca, NY 14853
2 Seminis Vegetable Seeds, Woodland, CA 95695, U.S.A.
3 Heinz U.S.A., Stockton, CA 95201
4 Hebrew University,Rehovot 76-100, Israel
5 Nippon Del Monte,Numata, Gumma 378 Japan
6 Nestle R & D Center S.A., Apartado 435, E-06080, Badajoz, Spain
7 Centre Recherche Nestle, 101 av. G. Eiffel, 37390 NOTRE DAME D'OE, Tours Cedex, France
The Sw-5 gene was introgressed into cultivated tomato (Lycopersicon esculentum) from the wild species
L. peruvianum and provides resistance against the tomato spotted wilt virus as well as against two other
tospovirus species, tomato chlorotic spot virus (TCSV) and groundnut ring spot virus (GRSV) (Boiteux and
Giordano, 1993). The gene is located on the long arm of chromosome 9 near the RFLP marker CT220 (fig 1).
Figure 1. Molecular map of chromosome 9 showing position of Sw-5. Black area represents portion of
chromosome from L. peruvianum in the E6203 NIL.
To test the effect of Sw-5 on the performance of processing tomatoes, we transferred the gene from the
variety Stevens, through 6 sequential backcross generations, using marker assisted selection, into the open
pollinated, processing variety E6203. A resistant BC6 plant was
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