Abstract
Chinese chestnut is a wildly distributed nut species with importantly economic value. The nut size and ripening period are mainly desired breeding objectives in Chinese chestnut. However, high-density linkage maps and quantitative trait loci (QTL) analyses related to nut traits are less than satisfactory, which hinders progress in the breeding of Chinese chestnut. Here, a single nucleotide polymorphism (SNP)-based high-density linkage map was constructed through genotyping-by-sequencing (GBS) of an F1 cross between the two widely grown Chinese chestnut cultivars ‘Yanshanzaofeng’ and ‘Guanting No. 10’. The genetic linkage map consists of 2,620 SNP markers with a total length of 1078.06 cM in 12 linkage groups (LGs) and an average marker distance of 0.41 cM. 17 QTLs were identified for five nut traits, specifically single-nut weight (SNW), nut width (NW), nut thickness (NT), nut height (NH), and ripening period (RP), based on phenotypic data from two successive years. Of the 17 QTLs, two major QTLs, i.e., qNT-I-1 and qRP-B-1 related to the NT and RP traits, respectively, were exploited. Moreover, the data revealed one pleiotropic QTL at 23.97 cM on LG I, which might simultaneously control SNW, NT, and NW. This study provides useful benchmark information concerning high-density genetic mapping and QTLs identification related to nut size and ripening period, and will accelerate genetic improvements for nuts in the marker-assisted selection (MAS) breeding of Chinese chestnut.
Highlights
Castanea is one of the most economically and ecologically important genera in the Fagaceae family
The 2,620 single nucleotide polymorphism (SNP) markers were assigned to 12 linkage groups (LGs) (LG A–LG L) spanning a length of 1078.06 cM, with an average distance of 0.41 cM between adjacent markers in the integrated map (Figure 1 and Table 2)
The average distance between adjacent markers in each LG ranged from 0.28 cM (LG C) to 0.69 cM (LG L) (Table 3)
Summary
Castanea is one of the most economically and ecologically important genera in the Fagaceae family. Three Castanea species, i.e., the Chinese chestnut (C. mollissima), Japanese chestnut (C. crenata) and European chestnut (C. sativa), are widely cultivated for commercial nut production (Huang, 1998). Due to the high nutritional value of edible nuts, the chestnut, which is generally considered a woody grain, plays a significant role in human famine history. The chestnut plays an important ecological role in afforestation and ecosystem services (Martin et al, 2012; Zou et al, 2014). There are diverse germplasm resources for Chinese chestnut, and this plant has a long history of cultivation. The nut yield of Chinese chestnut ranks first worldwide, with an annual production of 1,650,000 tons, accounting for 82% of the total chestnut production (Barreira et al, 2008; Liang et al, 2009; Zhang et al, 2014)
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