Broad-Sense Heritability and QTL Mapping for Brown Rust and Pith in Sugarcane (Saccharum spp.) Commercial Cross

Energy security is one of the main challenges of this century. Cleaner and cheaper, energy from sugarcane is the second main source of primary energy in Brazil. New types of molecular markers and QTL mapping strategies can help us to explore with understanding the complex genome of sugarcane. The purpose of this project is identifying molecular markers associated with brown rust resistance and pith in sugarcane. The mapping population was derived from a bi-parental commercial cross (SP80-3280 x RB835486). The field experiment was conducted in two locations, and established in augmented Federer’s block design with three replications. In preliminary phenotypic analysis, generalized linear mixed models were employed to calculate the broad sense heritabilities (H²) of traits. Also as a preliminary analysis, single marker trait analysis based on simple linear regression was undertaken to detect QTLs. High heritabilities (H²) for traits evaluated were found: pith (H² = 0.74) and brown rust resistance (H² = 0.95). Linkage map is still under construction and until now 54 SSR loci and RGA were genotyped in 153 individuals of the mapping population. Of the 55 loci analyzed, 459 fragments were generated, being 404 polymorphic (88.01%). Of the 238 single dose markers (1:1 or 3:1), 19 (7.98%) were associated with putative QTLs involving 16 microsatellite (p-value ≤ 0.05). For resistance against brown rust and pith were found 12 and 7 marker-trait significant associations, respectively. This work shows a first reported on QTL mapping of pith in sugarcane commercial cross.