29Background. The identification of genomic regions involved in agronomic traits is the 30 primary concern for sugarcane breeders. Genome-wide association studies (GWAS) leverage 31 the sequence variations to bridge phenotypes and genotypes. However, their effectiveness is 32 limited in species with high ploidy and large genomes, such as sugarcane. As an alternative, a 33 regional heritability mapping (RHM) method can be used to capture genetic signals that may 34 be missed by GWAS by combining genetic variance from neighboring regions. We used 35 RHM to screen the sugarcane genome aiming to identify regions with higher heritability 36 associated with agronomic traits. We considered percentage of fiber in sugarcane bagasse 37 (FB), apparent percentage of sugarcane sucrose (PC), tonnes of pol per hectare (TPH), and 38 tonnes of stalks per hectare (TSH). 39 Methods. Sequence-capture data of 508 sugarcane (Saccharum spp.) clones from a breeding 40 population under selection were processed for variant calling analysis using the sugarcane 41 genome cultivar R570 as a reference. A set of 375,195 single nucleotide polymorphisms were 42 selected after quality control. RHM was conducted by splitting the sugarcane genome into 43 windows of 2 Mb length.44Results. We selected the windows explaining > 20% of the total genomic heritability for TPH 45 (64 windows -5,654 genes) and TSH (72 windows -6,050 genes), and > 15% for PC (16 46 windows -1,517 genes) and FB (17 windows -1,615 genes). The top five windows that 47 explained the highest genomic heritability ranged from 20.8 to 24.6% for FB (629 genes), 48 18.0 to 22.0% for PC (452 genes), 53.8 to 66.0% for TPH (705 genes), and 59.5 to 67.4% for 49 TSH (413 genes). The functional annotation of genes included in those top five windows 50 revealed a set of genes that encode enzymes that integrate carbon metabolism, starch and 51 sucrose metabolism, and phenylpropanoid biosynthesis pathways.
52Conclusions. The selection of windows that explained the large proportions of genomic 53 heritability allowed us to identify genomic regions containing a set of genes that are related to 54 the agronomic traits in sugarcane. These windows spanned a region of 58.38Mb, which 55 corresponds to 14.28% of the reference assembly in the sugarcane genome. We contend that 56 RHM can be used as an alternative method for sugarcane breeders to reduce the complexity of 57 the sugarcane genome.
59 60Loci underlying Complex Trait Variation Using Regional Genomic Relationship 595 Mapping. PLoS ONE 7:e46501.