Ballén-Taborda Carolina, Chu Ye, Ozias-Akins Peggy, Holbrook C Corley, Timper Patricia, Jackson Scott A, Bertioli David J, Leal-Bertioli Soraya C M
Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Athens, GA, United States.
Department of Horticulture, University of Georgia, Tifton, GA, United States.
Front Plant Sci. 2022 Jan 17;12:785358. doi: 10.3389/fpls.2021.785358. eCollection 2021.
Crop wild species are increasingly important for crop improvement. Peanut ( L.) wild relatives comprise a diverse genetic pool that is being used to broaden its narrow genetic base. Peanut is an allotetraploid species extremely susceptible to peanut root-knot nematode (PRKN) . Current resistant cultivars rely on a single introgression for PRKN resistance incorporated from the wild relative , which could be overcome as a result of the emergence of virulent nematode populations. Therefore, new sources of resistance may be needed. Near-immunity has been found in the peanut wild relative . The two loci controlling the resistance, present on chromosomes A02 and A09, have been validated in tetraploid lines and have been shown to reduce nematode reproduction by up to 98%. To incorporate these new resistance QTL into cultivated peanut, we used a marker-assisted backcrossing approach, using PRKN -derived resistant lines as donor parents. Four cycles of backcrossing were completed, and SNP assays linked to the QTL were used for foreground selection. In each backcross generation seed weight, length, and width were measured, and based on a statistical analysis we observed that only one generation of backcrossing was required to recover the elite peanut's seed size. A populating of 271 BCF lines was genome-wide genotyped to characterize the introgressions across the genome. Phenotypic information for leaf spot incidence and domestication traits (seed size, fertility, plant architecture, and flower color) were recorded. Correlations between the wild introgressions in different chromosomes and the phenotypic data allowed us to identify candidate regions controlling these domestication traits. Finally, PRKN resistance was validated in BCF lines. We observed that the QTL in A02 and/or large introgression in A09 are needed for resistance. This present work represents an important step toward the development of new high-yielding and nematode-resistant peanut cultivars.
野生近缘种对于作物改良愈发重要。花生（Arachis hypogaea L.）的野生近缘种构成了一个多样的基因库，正被用于拓宽其狭窄的遗传基础。花生是一种异源四倍体物种，对花生根结线虫（PRKN）极为敏感。当前的抗性品种依赖于从野生近缘种导入的单一基因来抵抗PRKN，然而由于毒性线虫种群的出现，这种抗性可能会被克服。因此，可能需要新的抗性来源。在花生野生近缘种中发现了近乎免疫的情况。控制这种抗性的两个基因座位于A02和A09染色体上，已在四倍体系中得到验证，并显示可将线虫繁殖减少多达98%。为了将这些新的抗性QTL导入栽培花生，我们采用了标记辅助回交方法，使用源自PRKN抗性的品系作为供体亲本。完成了四个回交周期，并使用与QTL相关的SNP分析进行前景选择。在每个回交世代中，测量种子重量、长度和宽度，基于统计分析，我们观察到仅需一代回交就能恢复优良花生的种子大小。对271个BCF品系群体进行全基因组基因分型，以表征全基因组的渗入情况。记录叶斑病发病率和驯化性状（种子大小、育性、植株结构和花色）的表型信息。不同染色体上野生渗入与表型数据之间的相关性使我们能够识别控制这些驯化性状的候选区域。最后，在BCF品系中验证了PRKN抗性。我们观察到A02染色体上的QTL和/或A09染色体上的大片段渗入对于抗性是必需的。这项工作是朝着培育新的高产抗线虫花生品种迈出的重要一步。
