Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA.
Department of Horticulture and Crop Science, The Ohio State University, Wooster, OH, 44691, USA.
Theor Appl Genet. 2021 Aug;134(8):2561-2575. doi: 10.1007/s00122-021-03842-x. Epub 2021 May 13.
We identified cryptic early blight resistance introgressions in tomato breeding lines and demonstrated efficient genotypic selection for resistance in the context of a tomato breeding program. Early blight is a widespread and problematic disease affecting tomatoes (Solanum lycopersicum). Caused by the fungal pathogen Alternaria linariae (syn. A. tomatophila), symptoms include lesions on tomato stems, fruit, and foliage, often resulting in yield losses. Breeding tomatoes with genetic resistance would enhance production sustainability. Using cross-market breeding populations, we identified several quantitative trait loci (QTL) associated with early blight resistance. Early blight resistance putatively derived from 'Campbell 1943' was confirmed in modern fresh market tomato breeding lines. This resistance offered substantial protection against early blight stem lesions (collar rot) and moderate protection from defoliation. A distinctive and potentially novel form of early blight foliar resistance was discovered in a processing tomato breeding line and is probably derived from S. pimpinellifolium via 'Hawaii 7998'. Additional field trials validated the three most promising large-effect QTL, EB-1.2, EB-5, and EB-9. Resistance effects for EB-5 and EB-9 were consistent across breeding populations and environments, while EB-1.2's effect was population specific. Using genome-wide marker-assisted backcrossing, we developed fresh market tomato lines that were near-isogenic for early blight QTL. Resistance in these lines was largely mediated by just two QTL, EB-5 and EB-9, that together captured 49.0 and 68.7% of the defoliation and stem lesion variance, respectively. Our work showcases the value of mining cryptic introgressions in tomato lines, and across market classes, for use as additional sources of disease resistance.
我们在番茄育种系中鉴定了隐性早疫病抗性的渐渗片段，并在番茄育种计划的背景下展示了对抗性的有效基因型选择。早疫病是一种广泛存在且成问题的番茄病害（Solanum lycopersicum）。由真菌病原体Alternaria linariae（同义词 A. tomatophila）引起，症状包括番茄茎、果实和叶片上的病斑，常导致产量损失。培育具有遗传抗性的番茄将提高生产的可持续性。使用跨市场的育种群体，我们鉴定了几个与早疫病抗性相关的数量性状位点（QTL）。早疫病抗性源自“Campbell 1943”，在现代新鲜市场番茄育种系中得到了证实。这种抗性对早疫病茎部病斑（衣领腐烂）提供了大量保护，对落叶有适度保护。在一个加工番茄育种系中发现了一种独特的、可能是新的早疫病叶片抗性形式，可能源自 S. pimpinellifolium 通过“夏威夷 7998”。另外的田间试验验证了三个最有前途的大效应 QTL，EB-1.2、EB-5 和 EB-9。EB-5 和 EB-9 的抗性效果在不同的育种群体和环境中是一致的，而 EB-1.2 的效果是群体特异性的。利用全基因组标记辅助回交，我们开发了接近早疫病 QTL 的新鲜市场番茄系。这些系的抗性主要由两个 QTL 介导，EB-5 和 EB-9，它们分别解释了 49.0%和 68.7%的落叶和茎部病斑方差。我们的工作展示了在番茄系中挖掘隐性渐渗片段的价值，以及在不同市场类别中，将其作为额外的抗病性来源的价值。
