Abstract
The candidate recessive gene AhRt2 responsible for red testa of peanut was identified through combined BSA-seq and linkage mapping approaches. The testa colorof peanuts (Arachis hypogaea L.) is an important trait, and those with red testa are particularly popular owing to the high-anthocyanin content. However, the identification of genes underlying the regulation of the red testa trait in peanut are rarely reported. In order to fine map red testa gene, two F2:4 populations were constructed through the cross of YZ9102 (pink testa) with ZH12 (red testa) and ZH2 (red testa). Genetic analysis indicated that red testa was controlled by a single recessive gene named as AhRt2 (Red testa gene 2). Using BSA-seq approach, AhRt2 was preliminary identified on chromosome 12, which was further mapped to a 530-kb interval using 220 recombinant lines through linkage mapping. Furthermore, functional annotation, expression profiling, and the analyses of sequence variation confirmed that the anthocyanin reductase namely (Arahy.IK60LM) was the most likely candidate gene for AhRt2. It was found that a SNP in the third exon of AhRt2 altered the encoding amino acids, and was associated with red testa in peanut. In addition, a closely linked molecular marker linked with red testa trait in peanut was also developed for future studies. Our results provide valuable insight into the molecular mechanism underlying peanut testa color and present significant diagnostic marker resources for marker-assisted selected breeding in peanut.
Highlights
Peanut (Arachis hypogaea L.) is widely grown in more than 100 countries, with a total production of approximately 48.8 million tons in 2019
Peanut is superior in nutrition because it is enriched in many nutritional ingredients, such as vitamin B1, B3, B9 and E, biotin, resveratrol, isoflavones, phytic acid, anthocyanin and procyanidins, and many of which are accumulated in the testa (Pandey et al, 2012, Zhao et al, 2012, Zhao et al, 2020)
In order to gain insights into the genetic inheritance of red testa in peanut, the pink testa Yuanza 9102 (YZ9102) was crossed with the red testa Zhonghua[12] (ZH12) and Zhanhong[2] (ZH2) and two segregating populations, YZZH12 and YZZH2, were developed respectively (Table 1)
Summary
Peanut (Arachis hypogaea L.) is widely grown in more than 100 countries, with a total production of approximately 48.8 million tons in 2019 (http://www.fao.org/faostat/en/#data/QC). The testa color is an important trait of peanut and with a lot of variations, such as white, pink, red and black (or deep purple). There are six kinds of anthocyanins including delphinidin, cyanidin, pelargonidin, peonidin, petunidin and malvidin. The metabolome comparison results suggested that the accumulation of petunidin and cyanidin was higher in red testa than that in the pink testa of peanut (Xue et al, 2021). High-anthocyanin varieties have become one of the important directions of rice and wheat breeding (Giordano et al, 2017, Ito & Lacerda, 2019). The testa was developed from the integument and with the same genotype as its maternal plant, the phenotype of testa color appears one generation late than other traits (Chen et al, 2021, Zhao et al, 2020). For MAS approach, revealing the genetics and developing DNA markers tightly linked the traits are required
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