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Tree Genetics and Molecular Breeding 2014, Vol.4, No.2, 1
-
10
http://tgmb.biopublisher.ca
1
Research Report Open Access
Genetic and Physical Mapping of QTLs for Fruit Juice Browning and Fruit
Acidity on Linkage Group 16 in Apple
Takuya Morimoto
1
, Koki Yonemushi
2
, Hironori Ohnishi
2
, Kiyoshi Banno
3
1. Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
2. Graduate School of Agriculture, Shinshu University, Minami-minowa, Nagano 399-4598, Japan
3. Faculty of Agriculture, Shinshu University, Minami-minowa, Nagano 399-4598, Japan
Corresponding authors email:
morimoto30261915@gmail.com
Authors
Tree Genetics and Molecular Breeding, 2014, Vol.4, No.2 doi: 10.5376/tgmb.2014.04.0002
Received: 26 Nov., 2014
Accepted: 29 Dec., 2014
Published: 29 Dec., 2014
Copyright
©2014 Morimoto et al. This is an open access article published under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Morimoto et al., 2014, Genetic and Physical Mapping of QTLs for Fruit Juice Browning and Fruit Acidity on Linkage Group 16 in Apple, Tree Genetics and
Molecular Breeding, Vol.4, No.2 1
-
10 (doi: 10.5376/tgmb.2014.04.0002)
Abstract
Fruit juice browning and fruit acidity, which are important characteristics for the determination of marketability and
processability of apple fruit, are becoming major targets for apple breeding. To identify the genetic basis of these two traits,
quantitative trait locus (QTL) analysis was carried out using a 79 progenies of ‘Fuji’ × ‘Maypole’ F
1
population. The maternal parent
‘Fuji’ was characterized by low acidity and high browning, whereas the paternal parent ‘Maypole’ showed opposite
phenotypes—high acidity and low browning—resulting in an F
1
population with a wide range of phenotypes. QTL analysis identified
the major QTLs for both traits on the upper part of linkage group (LG) 16 of ‘Fuji’. The effects of these QTLs explained 57.5% and
49.7 % of observed variation in fruit juice browning and fruit acidity, respectively. These two QTLs co-segregated with each other,
with the allele for high acidity associated with the allele for low browning and vice versa in this population. To physically map the
QTL region, recombinant progeny were genotyped with newly designed DNA markers; both QTLs were delimited to a 514-kb region
including 105 annotated genes on apple chromosome 16. Several candidate genes were predicted in this region and their associations
with fruit juice browning and fruit acidity were considered
Keywords
DNA marker; Fruit quality; Genetic analysis;
Malus×domestica
; QTL analysis
Background
Because of its importance to the marketability of
apples (
Malus×domestica
Borkh.), fruit quality
improvement is a major goal of apple breeding
programs worldwide. Fruit quality is complex and
comprises many traits, including fruit size, texture,
fruit acidity, soluble solid contents, and fruit juice
browning. In addition, the high levels of
heterozygosity present in cultivated apple (Velasco et
al., 2010) hinder prediction of quantitative phenotypes
of progeny derived from controlled crosses. In
breeding programs, interest has increasingly focused
on the use of molecular markers linked to important
fruit characteristics. For these reasons, quantitative
trait locus (QTL) analysis to identify QTLs
co-segregating with fruit quality traits has become
popular as a means to develop marker-assisted
breeding programs and to unravel the mechanisms
underlying the genetic basis of important
characteristics in apple (Chagné et al., 2012; Guitton
et al., 2012; Kenis et al., 2008; Liebhard et al., 2003).
With respect to apple fruit quality, attention has
focused on two important characteristics: fruit acidity
and fruit juice browning. Organic acid levels greatly
affect the fruit taste and flavor of a given cultivar as
well as its suitability for dessert or processing
purposes (Kingston 1992). Fruit acidity also
determines whether or not fruit should be consumed
immediately and how long fruit can be stored: acidity
gradually decreases during storage, and an excessive
decrease in acidity reduces the eating quality of the
fruit (Iwanami et al., 2012). In mature apple fruit,
malic acid is the predominant organic acid, although
other organic acids such as citric acid, fumaric acid,
and quinic acid are also detectable (Zhang et al., 2010).
The major locus controlling apple fruit acidity has
been mapped to linkage group (LG) 16 and designated
as
Ma
(malic acid), where
Ma
corresponds to the