*1.1. Peanut Information*

Peanut or groundnut (*Arachis hypogaea* L.) is an important oil and cash crop of the world [1]. Peanut seeds are rich in oil (48–50%) and protein (25–28%) and they contain certain vitamins and minerals which allows them to be used as an energy source for humans [2,3]. In addition, peanuts contain rich functional elements, such as oleic acid, linoleic acid, resveratrol, fiber, and vitamins [4–6].

Since the beginning of agriculture, food grains have been subjected to selection and breeding for size and most of the grains have seeds far larger than their wild relatives [7]. In the United States, peanut seed size is one of the standards used to determine the grade of shelled peanuts and to evaluate the commercial potential of advanced peanut breeding lines prior to the release of varieties [8].

**Citation:** Zou, K.; Kim, K.; Kim, K.; Kang, D.; Park, Y.; Sun, H.; Ha, B.; Ha, J.; Jun, T. Genetic Diversity and Genome-Wide Association Study of Seed Aspect Ratio Using a High-Density SNP Array in Peanut (*Arachis hypogaea* L.). *Genes* **2021**, *12*, 2. https://dx.doi.org/ 10.3390/genes12010002

Received: 22 August 2020 Accepted: 17 December 2020 Published: 22 December 2020

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There have been some studies on seed size in peanut. Quantitative trait loci (QTL) study were conducted to identify loci controlling seed size using a 142 backcross population (87 BC3F1 and 55 BC2F2) with two parents under two water regimes in peanut, while several QTLs associated with increased seed width were detected under water-limited treatment [9]. Simple sequence repeat (SSR) marker PM375 associated with seed length was identified in a total of 88 F2:6 recombinant inbred lines (RILs), representing that increase in seed length may influence in an increase in the weight of a hundred seeds, or in the length of the pod [10]. Florida-07 by GP-NC WS 16. A major seed size QTL on chromosome A05 was identified in the US peanut mini core collection using RILs from a cross between Florida-07 and GP-NC WS 16 [8]. However, there are few studies on seed shape in peanuts so far.
