QTL Analysis for Fruit Traits in Citrus

QTL analysis for fruit traits in Citrus

Maiara Curtolo^1,2, Mariangela Cristofani-Yaly¹, Marco A. Takita¹, Marinês Bastianel¹, Valdenice Moreira Novelli¹, Rodrigo Gazaffi³, Andrzej Kilian⁴_, Antonio Vargas de Oliveira Figueira² and Marcos Antonio Machado¹, ⁽¹⁾Centro de Citricultura Sylvio Moreira, IAC, Cordeiropolis, SP, Brazil ⁽²⁾Centro de Energia Nuclear na Agricultura/USP, Piracicaba, SP, Brazil ⁽³⁾Universidade Federal de São Carlos, ⁽⁴⁾ Diversity Arrays, Technology Pty Ltd, PO Box 7141, Yarralumla, ACT 2600, Australia

This study aimed to construct an integrated genetic map of tangor Murcott and Pera sweet orange, using the DArT_seq^TM molecular markers and localize QTLs for twelve fruit traits. A total of 278 F₁ hybrids were genotyped using the DArT-seq^TM markers. To build the integrated map we used the OneMap program and considered all DArT loci that showed no segregation deviation. The likelihood ratio was used for formation of linkage groups besides the genomic information obtained from one of the available Citrus sinensis genome sequence (http://citrus.hzau.edu.cn/orange/index.php), then proceeded to the preliminary ordering of markers to remove redundancy. The integrated map was composed of 932 markers, 160 that segregated in the 3:1 ratio, 394 that segregated for  Murcott tangor and 378 that segregated for Pera sweet orange. The markers were linked in 9 groups with genomic coverage of 2,895.51 cM. The map is saturated and perfectly represent the number of chromosomes of the haploid species. According to the analyzes using the "Multiple QTL Mapping" (MQM) and the results of the permutation test,19 QTLs were identified in total, taking into account the fruits characteristics analyzed: diameter (mm), height (mm), ratio of H/D, weight (g),  rind thickness (mm),  segments per fruit, soluble solids (%), Acids (%), Juice content (%), number of seeds, ratio of solids/acids and number of fruits per box. The genome (pseudo chromosomes) of Citrus sinensis L. Osbeck was compared to the genetic maps and synteny were clearly identified. Further analysis of the regions with the highest LOD scores was carried and we verified the presence of genes that could be associated with the characteristics.

Financial support: FAPESP (08/57909-2) and CNPq (573848/08-4).