W224 Identification and validation of QTL modifying melon (Cucumis melo L.) fruit morphology in a ‘Piel de Sapo'×PI124112 cross

Date: Sunday, January 15, 2012
Time: 5:30 PM
Room: Pacific Salon 1
Aurora Díaz Bermúdez , IBMCP Instituto de Biologia Molecular y Celular de Plantas, Valencia, Spain
Belkacem Zaouri , Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA)
Mohamed Fergany , Agronomy Department Faculty of Agriculture Ain Shams University
Maria Belen Pico , Institute for the Conservation and Breeding of Agricultural Biodiversity (COMAV-UPV)
Antonio J. Monforte , Instituto de Biología Molecular y Celular de Plantas (IBMCP)
Modern market trends demand small round melons. In this scenario, a F2 population from the cross inodorus ‘Piel de Sapo’× momordica PI124112 (Indian accession) was generated for studying the genetic control of fruit shape (FS) by QTL analysis. Two hundred and ninety F2 plants from two locations were phenotyped for FS. Eighty-three individuals showing extreme phenotypes (round and elongated) were selected for genotyping with 150 markers (CAPS, microsatellites and SNPs) evenly distributed throughout the genome. Two major QTL were detected on linkage groups (LG) II and VIII, whereas QTL with minor effects were also detected on LGIII and XII. The QTL on LGII (fs2.1) cosegregated with gen a (andromonoecious) in LGII, which is responsible for sex determination in flowers and has pleiotropic effects on FS. The QTL on LGVIII explained the 38% of the phenotypic variation in FS and probably is an alternative allele of fs8.3 detected previously in a ‘Piel de Sapo’× conomon PI161375 cross. Surprisingly, unlike the PI161375 allele, the PI124112 allele of f8.3 induces rounder fruits, even though PI124112 produces elongated-shaped fruit. The PI124112 allele of fs8.3 interacts epistatically with fs2.1, masking the pleiotropic effects of a on FS. Time course assays showed that fs8.3 effects are patent at very early stages of fruit development. The fs8.3 PI124112 allele has been introgressed in a ‘Piel de Sapo’ background after several rounds of Marker-Assisted Selection. The fs8.3-NIL (Near Isogenic Line) displays a consistent round fruit, confirming the QTL effects and setting the basis for their future molecular isolation.