Functional genetic map construction and QTL of economic importance detection in a derived bi-parental cross between two commercial sugarcane varieties

Author(s)

Melina Cristina Mancini

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2014-04-07

Examining board members

Anete Pereira de Souza; Gabriel Rodrigues Alves; Mariângela Cristofani Yaly; Eugenio Cesar Ulian; Jurandir Vieira de Magalhães

• Advisor: Anete Pereira de Souza; Antonio Augusto Franco Garcia

Abstract

The increasing search for sugarcane varieties with higher productivity and resistant to major diseases is an important goal for the success of Sugarcane Breeding Program. Thus, molecular markers can be used to identify Quantitative Trait Loci (QTLs) and have become a powerful tool in Breeding Programs. This thesis aimed to contribute for the basic knowledge of genetics and molecular biology in sugarcane through detection of markers linked to quantitative traits. Was used a sugarcane population consisted of 240 F1 individuals derived from a cross between SP81-3250 and RB925345. To detect the QTLs it was necessary to perform phenotypic and genotypic studies. The phenotypic data were made for cane yield (stalk diameter, stalk height, stalk number, stalk weight and tons of cane per hectare) and quality traits (soluble solid content, sucrose content, juice sucrose content, purity, fiber and tons of Pol per hectare) for three harvest years (2011, 2012 and 2013) in Araras and Ipaussu cities, located in the state of São Paulo. The average, variance and covariance matrix (VCOV), heritability and phenotypic correlation was estimated via mixed models. All results showed a great environmental control, the lowest heritability was purity (0.77), besides 30 significant phenotypic correlations. confirming that these data can be used for QTLs detection. The genotypic data were obtained analyzing the regions containing microsatellites and single nucleotide genetic variants, by the markers SSR (Simple Sequence Repeat) and SNP (Single Nucleotide Polymorphism), respectively. The SNPs genotyping were performed via mass spectrometry by Sequenom MassARRAY® platform (Sequenom Inc., San Diego, California, USA). The analysis was performed using the SuperMASSA software allowing to estimate the loci ploidy. The SNPs markers were used for QTL detection for cane yield and quality traits. By linear regression 17 QTL association evidences were found for stalk diameter (four evidences), stalk number (one evidence), stalk weight (one evidence), soluble solid content (two evidences), juice sucrose content (three evidences), purity (two evidences), tons of cane per hectare (two evidences) and tons of Pol per hectare (two evidences). The phenotypic variation explained by genotype ranged from 1.6% to 11.1%. The SNPs associated with the traits mentioned had ploidy levels ranging from hexaploid to dodecaploide. Via genotypic-phenotypic correlation, it was detected seven QTL evidence of association for stalk diameter (one evidence), soluble solid content (two evidences), sucrose content (one evidence), juice sucrose content (two evidences) and purity (one evidence). The SNPs detected significant genotypic-phenotypic correlations showed ploidy levels ranging from tetradecaploide to icosaploide. The different ploidies allowed the detection of QTLs in multi-dose and can be used as prior information about QTL mapping, contributing to the advancement of the sugarcane genetics knowledge (AU)