RESUMO
Melon (Cucumis melo L.) is an economically important Cucurbitaceae crop grown around the globe. The sweetness of melon is a significant factor in fruit quality and consumer appeal, and the soluble solids content (SSC) is a key index of melon sweetness. In this study, 146 recombinant inbred lines (RILs) derived from two oriental melon materials with different levels of sweetness containing 1427 bin markers, and 213 melon accessions containing 1,681,775 single nucleotide polymorphism (SNP) markers were used to identify genomic regions influencing SSC. Linkage mapping detected 10 quantitative trait loci (QTLs) distributed on six chromosomes, seven of which were overlapped with the reported QTLs. A total of 211 significant SNPs were identified by genome-wide association study (GWAS), 138 of which overlapped with the reported QTLs. Two new stable, co-localized regions on chromosome 3 were identified by QTL mapping and GWAS across multiple environments, which explained large phenotypic variance. Five candidate genes related to SSC were identified by QTL mapping, GWAS, and qRT-PCR, two of which were involved in hydrolysis of raffinose and sucrose located in the new stable loci. The other three candidate genes were involved in raffinose synthesis, sugar transport, and production of substrate for sugar synthesis. The genomic regions and candidate genes will be helpful for molecular breeding programs and elucidating the mechanisms of sugar accumulation.
RESUMO
Soybean mosaic virus (SMV) disease is one of the most serious and broadly distributed soybean (Glycine max (L.) Merr.) diseases. Here, we combine the advantages of association and linkage analysis to identify and fine-map the soybean genes associated with resistance to SMV strain SC7. A set of 191 soybean accessions from different geographic origins and 184 recombinant inbred lines (RILs) derived from Kefeng No.1 (resistant) × Nannong 1138-2 (susceptible) were used in this study. The SC7 resistance genes were previously mapped to a 2.65 Mb region on chromosome 2 and a 380 kb region on chromosome 13. Among 19 single nucleotide polymorphisms (SNPs) detected via association analysis in the study, the SNP BARC-021625-04157 was located in the 2.65 Mb region, and the SNP BARC-041671-08065 was located near the 380 kb region; three genes harboring the SNPs were probably related to SC7 resistance. The resistance gene associated with BARC-021625-04157 was then fine-mapped to a region of approximately 158 kb on chromosome 2 using 184 RILs. Among the 15 genes within this region, one NBS-LRR type gene, one HSP40 gene and one serine carboxypeptidase-type gene might be candidate SC7 resistance genes. These results will be useful for map-based cloning and marker-assisted selection in soybean breeding programs.
Assuntos
Resistência à Doença/genética , Genes de Plantas , Estudos de Associação Genética , Ligação Genética , Glycine max/genética , Mapeamento Físico do Cromossomo/métodos , Doenças das Plantas/genética , Análise de Variância , Cromossomos de Plantas , Padrões de Herança/genética , Anotação de Sequência Molecular , Vírus do Mosaico/fisiologia , Fenótipo , Doenças das Plantas/virologia , Polimorfismo de Nucleotídeo Único , Recombinação Genética/genética , Glycine max/virologiaRESUMO
Soybean isoflavone synthase (IFS) and flavanone 3-hydroxylase (F3H) are two key enzymes catalyzing the biosynthesis of isoflavonoids and flavonoids, both of which play diverse roles in stress responses. However, little is known about the evolutionary pattern of these genes in cultivated soybean and its wild progenitors. Herein, we investigated the nucleotide polymorphisms in Isoflavone synthase (IFS1, IFS2) and Flavanone 3-hydroxylase (F3H2) genes from 33 soybean accessions, including 17 cultivars (Glycine max) and 16 their wild progenitors (Glycine soja). Our data showed that the target genes shared the levels of nucleotide polymorphism with three reference genes involved in plant-microbe interactions, but possessed a much higher nucleotide polymorphism than other reference genes. Moreover, no significant genetic differentiation was found between cultivated soybean and its wild relatives in three target genes, despite of considering bottleneck and founder effect during domestication. These results indicate that IFS and F3H genes could have experienced gene introgressions or diversifying selection events during domestication process. Especially, F3H2 gene appears to evolve under positive selection and enjoy a faster evolutionary rate than IFS1 and IFS2 genes.