Resistance to Downy Mildew in Lettuce 'La Brillante' is Conferred by Dm50 Gene and Multiple QTL.
Many cultivars of lettuce (Lactuca sativa L.) are susceptible to downy mildew, a nearly globally ubiquitous disease caused by Bremia lactucae. We previously determined that Batavia type cultivar 'La Brillante' has a high level of field resistance to the disease in California. Testing of a mapping population developed from a cross between 'Salinas 88' and La Brillante in multiple field and laboratory experiments revealed that at least five loci conferred resistance in La Brillante. The presence of a new dominant resistance gene (designated Dm50) that confers complete resistance to specific isolates was detected in laboratory tests of seedlings inoculated with multiple diverse isolates. Dm50 is located in the major resistance cluster on linkage group 2 that contains at least eight major, dominant Dm genes conferring resistance to downy mildew. However, this Dm gene is ineffective against the isolates of B. lactucae prevalent in the field in California and the Netherlands. A quantitative trait locus (QTL) located at the Dm50 chromosomal region (qDM2.2) was detected, though, when the amount of disease was evaluated a month before plants reached harvest maturity. Four additional QTL for resistance to B. lactucae were identified on linkage groups 4 (qDM4.1 and qDM4.2), 7 (qDM7.1), and 9 (qDM9.2). The largest effect was associated with qDM7.1 (up to 32.9% of the total phenotypic variance) that determined resistance in multiple field experiments. Markers identified in the present study will facilitate introduction of these resistance loci into commercial cultivars of lettuce.
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Ivan
I
Simko
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Oswaldo E
OE
Ochoa
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Mathieu A
MA
Pel
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Cayla
C
Tsuchida
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Carolina
C
Font I Forcada
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Ryan J
RJ
Hayes
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Maria-Jose
MJ
Truco
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Rudie
R
Antonise
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Carlos H
CH
Galeano
First, sixth, and ninth authors: United States Department of Agriculture-Agricultural Research Service, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905; second, fourth, fifth, seventh, and tenth authors: The Genome Center and Department of Plant Sciences, University of California, Davis 95616; third author: Enza Zaden BV, Haling 1-E, 1602 DB Enkhuizen, The Netherlands; and eighth author: KeyGene N.V., P.O. Box 216 6700 AE Wageningen, The Netherlands.
Richard W
RW
Michelmore
D002874:Chromosome Mapping; D060467:Disease Resistance / Q000235:genetics*; D008040:Genetic Linkage; D056426:Genetic Loci; D018545:Lactuca / Q000235:genetics* / Q000276:immunology; D009868:Oomycetes / Q000502:physiology*; D010935:Plant Diseases / Q000276:immunology*; D010940:Plant Proteins / Q000235:genetics*; D040641:Quantitative Trait Loci / Q000235:genetics*
D010940:Plant Proteins