Mapping quantitative trait loci for fruit traits and powdery mildew resistance in melon (Cucumis melo).

Yu-Hua Wang,Hsiao-Feng Lo,Dong-Hong Wu,Jin-Hsing Huang,Shing-Jy Tsao,Kae-Kang Hwu

doi:10.1186/s40529-016-0130-1

Abstract

BackgroundFruit characters affect consumer preferences and the market value of melons is determined by fruit quality. Most fruit quality-related traits are controlled by multiple genes, and are influenced by environmental factors. Furthermore, powdery mildew is another limiting factor in melon production. To develop new melon cultivars with disease resistance and high quality fruits using the molecular marker-assisted breeding strategy, identification of quantitative trait loci for fruit quality and disease resistance is required.ResultsThe F2 populations from the cross of TARI-08874 (Cucumis melo ssp. melo) and ‘Bai-li-gua’ (C. melo ssp. agrestis) were used to map the quantitative trait loci (QTLs) for fruit-related traits and powdery mildew resistance in two trials. All traits were significantly different (P < 0.05) between parents. The generated linkage map consisted of twelve major linkage groups (LGs), spanning 626.1 cM in total, with an average distance of 8.3 cM between flanking markers. Nineteen QTLs were detected for seven melon traits, among which ten QTLs were localized to the same positions as the corresponding QTLs described in other studies. Four of these QTLs were detected in both trials. The results of identified QTLs in this study suggested that fruit size in the tested populations were mainly determined by fruit diameter and flesh thickness. All of the major QTLs for fruit diameter and flesh thickness were identified on LG5 and LG11. Four QTLs identified responsible for netting width of fruit rind were co-localized with the QTLs for netting density, suggesting similar genetic mechanisms affecting these two traits. Additionally, only one major QTL for powdery mildew resistance was detected on LG2, and it was closely linked to a simple sequence repeat (SSR) marker CMBR120 which was identified in a previous study.ConclusionBecause the netting feature is a crucial factor for external appearance of fruits in Asia market, we focus on mining the genetic information of fruit netting. This is the first report of QTL mapping to netting width. Furthermore, new QTLs were identified for netting density (qND4, qND6, and qND7) and netting width (qNW2, qNW4, qNW6, and qNW7) successfully. In addition, novel QTLs for fruit diameter (qFD5), flesh thickness (qFT11) were also detected.

Highlights

Fruit characters affect consumer preferences and the market value of melons is determined by fruit quality
Powdery mildew resistance, and correlation analysis In every aspects regarding to fruit size, which including diameter, length, flesh thickness, and the overall fruit weight, Taiwan Agricultural Research Institute (TARI)-08874 is significantly larger ‘Bai-li-gua’ (Table 1)
Four Quantitative trait loci (QTL) for fruit length, flesh thickness, and netting width were constantly detected in two independent trials, suggesting that they are less liable to environment changes

Summary

Introduction

Fruit characters affect consumer preferences and the market value of melons is determined by fruit quality. Cantalupensis, reticulatus, and makuwa are consumed as a dessert fruit because of its high sugar content and excellent external characters in Taiwan Many of these fruit quality characteristics are controlled by multiple genes and showed variable phenotypes under different environments and managements. A genetic map of C. melo was constructed using a recombinant inbred line (RIL) population derived from momordica and reticulatus botanical groups, and fourteen QTLs for five fruit-related traits including net cover, net density, fruit length, fruit width, and fruit weight were detected (Harel-Beja et al 2010). An F2 mapping population generated from crossing between the flexuosus and cantalupensis botanical groups was used to identify twelve QTLs related to four fruit traits, including fruit length, fruit width, netting density, and flesh thickness (Ramamurthy and Waters 2015)

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