Simko Ivan, Ochoa Oswaldo E, Pel Mathieu A, Tsuchida Cayla, Font I Forcada Carolina, Hayes Ryan J, Truco Maria-Jose, Antonise Rudie, Galeano Carlos H, Michelmore Richard W
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.
Phytopathology. 2015 Sep;105(9):1220-8. doi: 10.1094/PHYTO-02-15-0057-R. Epub 2015 Aug 24.
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.
许多生菜（Lactuca sativa L.）品种对霜霉病敏感，霜霉病是一种几乎在全球普遍存在的由莴苣盘梗霉（Bremia lactucae）引起的病害。我们之前确定，巴达维亚类型品种“La Brillante”在加利福尼亚州对该病具有高水平的田间抗性。对由“萨利纳斯88”和“La Brillante”杂交产生的作图群体在多个田间和实验室试验中的测试表明，“La Brillante”中至少有五个基因座赋予了抗性。在用多种不同分离株接种的幼苗实验室试验中，检测到一个新的显性抗性基因（命名为Dm50），该基因对特定分离株具有完全抗性。Dm50位于连锁群2上的主要抗性簇中，该簇包含至少八个赋予霜霉病抗性的主要显性Dm基因。然而，这个Dm基因对加利福尼亚州和荷兰田间流行的莴苣盘梗霉分离株无效。不过，当在植株达到收获成熟前一个月评估病害量时，在Dm50染色体区域（qDM2.2）检测到一个数量性状基因座（QTL）。在连锁群4（qDM4.1和qDM4.2）、7（qDM7.1）和9（qDM9.2）上还鉴定出另外四个抗莴苣盘梗霉的QTL。最大的效应与qDM7.1相关（高达总表型变异的32.9%），该基因座在多个田间试验中决定抗性。本研究中鉴定的标记将有助于将这些抗性基因座导入生菜商业品种中。
