Mapping a dominant negative mutation for triforine sensitivity in lettuce and its use as a selectable marker for detecting hybrids
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Some lettuce cultivars are highly sensitive to triforine, an inhibitor of sterol biosynthesis found in some commercial systemic fungicides. First symptoms of a sensitive reaction are usually observed within 24–48 h after treatment and include severe wilting, necrosis and rapid plant death. We mapped a single dominant gene (Tr) that confers sensitivity of lettuce to triforine to linkage group 1 of the integrated genetic map of lettuce. The occurrence of sensitivity is not uniform across horticultural types of lettuce. While over 80% of green-romaine lettuce cultivars tested were sensitive, most cultivars of all other lettuce types were insensitive to triforine. All accessions of wild Lactuca spp. were insensitive to triforine. Allelism tests using F1 and F2 progeny revealed that sensitive cultivars of all horticultural types likely carry the same Tr gene. The dominant allele for sensitivity found in cultivated lettuce probably had a monophyletic origin. The reaction to triforine can be used as a marker for detecting hybrids originating from a cross between phenotypically similar parents with different responses to triforine treatment. It also provides an indication of genotypes for which applications of triforine-containing fungicides are inappropriate.
KeywordsDominant mutation Lettuce Selectable marker Sterol biosynthesis inhibitor Triforine
- Tr gene
A dominant gene that confers sensitivity to triforine in lettuce
The authors thank Amy Atallah, Mario Estrada, and Amy Folck for technical assistance and Zahi Atallah for valuable discussion. Sharon Benzen and Todd Bunnell provided fungicides for trials and Nina Simkova made corrections to the manuscript. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.
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