No virus was detected in the upper leaves and no symptoms were checked both in the inoculated leaves
and non inoculated leaves of all the F1, cross combinations. The two different F2 progenies segregated into
resistant and susceptible classes which fit a 3:1 ratio. Finally the backcross generation tested segregated into
resistant and susceptible classes which fit a 1:1 ratio. All the segregation ratios indicated that resistance is
controlled by a single dominant gene. We propose tentatively to name this gene "Am".
Literature cited
Parrella G., Legnani R., Cohen S., Gebre-Selassie K., Laterrot H., Marchoux G., 1996. TGC REPORT No. 46, p.
22.
Parrella G., Laterrot H., Marchoux G., Gebre-Selassie K., 1996. XL SIGA, Perugia 18-21 settembre.
A method for isolating milligram quantities of "polyphenol-free" nuclear DNA from tomato
Peterson, D.G. and Stack, S.M.
Department of Biology, Colorado State University, Fort Collins, CO 80523-1878
Tannins and other polyphenolic compounds are present in the tissues of many plants including tomato. If
cells are disrupted, oxidized polyphenols can contact and bind to DNA giving it a brown color and making it
useless for most research applications (e.g., Katterman and Shattuck 1983; Couch and Fritz 1990; Guillemaut and
Marechal-Drouard 1992; our observations). To avoid interaction between DNA and polyphenols, many DNA
isolation techniques involve freezing tissue in dry ice or liquid nitrogen during or prior to homogenization.
However, if one is interested in isolating pure nuclear DNA, homogenization of frozen tissue is not desirable as it
results in isolation of a mixture of nuclear, chloroplast, and mitochondrial DNAs. We have developed a relatively
inexpensive protocol for isolating milligram quantities of "polyphenol-free"
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