Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: MAPPING QUANTITATIVE TRAIT LOCI ASSOCIATED WITH RESISTANCE TO
WATERMOLD (Pythium ultimum) AND BLACKMOLD (Alternaria alternata)
IN TOMATO
MAPPING QUANTITATIVE TRAIT LOCI ASSOCIATED WITH RESISTANCE TO
WATERMOLD (Pythium ultimum) AND BLACKMOLD (Alternaria alternata)
IN TOMATO.
K. Aitken, D. Francis, M. Bongue Bartlesman, T. Cassol, D.A. St.
Clair, Department of Vegetable Crops, University of California,
Davis, CA 95616-8746 USA.
Blackmold and watermold are both ripe fruit diseases that
can cause significant losses of processing tomatoes in the field.
The parental, F1, F2, F3 and BC1 generations of a cross between
the susceptible Lycopersicon esculentum cultivar VF 145B-7879 and
the resistant wild relative L. cheesmanii f. typicum accession
LA422 were used for the disease evaluation. Data analysis
revealed that the inheritance of resistance to blackmold has low
heritability (9-16%), is environmentally afflicted, and is
controlled by a minimum of two genes (T. Cassol and D. St.
Clair, Theor. Appl. Genetics, in press). The inheritance of
resistance to watermold has a higher heritability (68%) in this
same cross and appears to be controlled by a minimum of 2 to 4
genes. F3 plants were used to reconstruct the F2 generation of
the above cross to map QTL for resistance. RFLP markers (from S.
Tanksley, Cornell University) have been screened on the two
parent lines to determine polymorphic clones for mapping.
Polymorphic markers spaced 10-20 cM along the chromosomes were
chosen to cover the entire tomato genome. Data will be
presented, using analysis of variance at each marker, on the
location and effect of QTL governing disease resistance. This
method will be compared to interval mapping using Mapmaker/QTL
(Lander et al 1987, Genomics 1:174-181). This population is also
segregating for fruit size, fruit color, plant determinancy,
leaflet number and trichome density and these traits will also be
mapped. In addition, methods to quickly identify QTL linked to
these traits using RAPD markers have been developed using a BC1
population derived from the same cross. Recombinant inbred lines
have been developed from the F2 progeny and these will be used to
verify the QTL identified in both the F2 and BC1 mapping
populations.
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