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The germplasm with exotic genomic components especially from Sea Island cotton (Gossypium barbadense L. Gb) is the dominant genetic resources to enhance fiber quality of upland cotton (G. hirsutum L., Gh). Due to low efficiency of phenotypic evaluation and selection on fiber quality, genetic dissection of favorable alleles using molecular markers is essential. Genetic dissection on putative Gb introgressions related to fiber traits were conducted by SSR markers with mapping populations derived from a cross between Luyuan343 (LY343), a superior fiber quality introgression line (IL) with genomic components from Gb, and an elite Upland cotton cv. Lumianyan#22 (LMY22). Among 82 polymorphic loci screened out from 4050 SSRs, 42 were identified as putative introgression alleles. A total of 29 fiber-related QTLs (23 for fiber quality and six for lint percentage) were detected and most of which clustered on the putative Gb introgression chromosomal segments of Chr.2, Chr.16, Chr.23 and Chr.25. As expected, a majority of favorable alleles of fiber quality QTLs (12/17, not considering the QTLs for fiber fineness) came from the IL parent and most of which (11/12) were conferred by the introgression genomic components while three of the six (3/6) favorable alleles for lint percentage came from the Gh parent. Validation of these QTLs using an F 8 breeding population from the same cross made previously indicated that 13 out of 29 QTLs showed considerable stability. The results suggest that fiber quality improvement using the introgression components could be facilitated by marker-assisted selection in cotton breeding program.

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In this article, we carried out genome resequencing and SNP mining for cultivated apples in Shandong Province for the sake of the rapid identification of apple varieties, germplasm evaluation, and utilization. Genomic DNA was extracted immediately from leaves of each sample, and Paired-end Illumina genomic libraries were prepared and sequenced on an Illumina Hiseq 4 000 platform following the manufacturer's instructions. Resequencing of the 31 apple genomes generated a total of 363 Gb high-quality cleaned sequences, with an average of 12.5 Gb per accession that represented approximately 15.9x coverage of the apple genome. The data volume fully meets the needs of downstream analysis and SNP mining. When we used the nucleotide mismatch parameter from 1~12, the mapping rate gradually increased to saturation. There was a highly significant correlation (p<0.0001) between the total mapping rate, mapping rate of pair-end data, and mismatch parameter. Univariate fourth-order equation (regression coefficient r>0.99) were predicted. As the mismatch rate increases, the accuracy of mapping decreases; the genome coverage gradually increases, and heterozygous sites' accuracy gradually increases. In this study, two algorithms were used in SNP mining. The intersection was further taken based on the 'chromosome+site information' as the eigenvalues to obtain a highly reliable single nucleotide variant dataset. A total of 374 404 SNP locus were detected. On average, one variation can be identified from 1 896 bp. The accuracy of the Sanger verification test is as high as 98.1%. Annotation analysis shows that among the 373 763 SNPs, 25 047 (6.7%) are located in the gene coding region, 143 269 (38.27%) are located in the intergenic region, and 179 426 (47.92%) are located in the 2 kb region upstream or downstream of the corresponding genes. Among the coding region SNPs, 13 422 are non-synonymous, while 11 625 are synonymous variations. The ratio of non-synonymous to synonymous SNP is 1.15: 1. Using the filtered 4DTV sites, population clustering analysis results constructed using neighbor-joining algorithms are in line with the trend of the classification of cultivated apples in Shandong province. Keywords Cultivated apple; Genome resequencing; Development of SNP markers Apple is one of the most important fruits in the forefront of production. Global apple yealid in 2019 exceeded 8.314×10 10 kg, of which China's output was 4.139×10 10 kg (data from the FAO database, http://www.fao.org/ faostat/zh/#search/apple), accounting for 50% the above. For many years, apple production of Shandong province has been at the forefront of China (accounting for more than 25%). Simultaneously, it is also a province with extensive apple germplasm resources, leading the country in apple germplasm resource collection, innovation, and new varieties selection.