Identification of markers linked to major gene loci involved in determination of fruit shape index of apples (Malus domestica)

Abstract

Fruit shape index (FSI) is one of the most important traits in apple. In this study, the inheritance of a FSI (ratio between height and diameter at the widest point of the fruit) was analysed in a hybrid population derived from 'Jonathan' 9 'Golden Delicious' (Malus domestica Borkh) using frequency distribution and molecular marker analysis. A binary distribution pattern was observed which matched a 31:1 segregation ratio for small: large FSI scores. This ratio can be explained by the segregation of five independently inheriting single dose loci, whereby high FSI requires the simultaneous absence of all dominant alleles. The joined heritability of these major genes was estimated to be 75.00 and 75.

Candidate gene prediction via quantitative trait locus analysis of fruit shape index traits in apple

“…In our study, two yearstable loci associated with FSI (Locus 1 and Locus 2) were mapped to 4.4-6.7 Mb and 7.4-7.5 Mb, respectively, on chromosome 11 of 'Jonathan'. Locus 2 was located near the previously reported QTL region (8.9-10.8 Mb on LG 11) using SSR linkage maps (Chang et al 2014), and that location was also close to a major gene in a study using bulked segregant analysis with the same population (Sun et al 2012). Although the present study did not detect significant QTLs of FSI trait in 2010 or 2011, a peak LOD was present at 5.8 cM of LG 11 of the 'Jonathan' linkage map (data not shown).…”

“…Here, QTLs for fruit length were mapped at different LGs in 3 years, coinciding with weak correlations for the trait between 2008 or 2009 and 2014 (Table 1). However, FSI has high heritability in apple (Sun et al 2012) and a strong correlation among sampling years, as Diaz et al (2014) reported for melon. Huang et al (1997) suggested that stable QTLs of traits with high heritability are easy to detect under different environmental conditions.…”

“…We used a hybrid population of 'Jonathan' 9 'Golden Delicious' that consisted of 1733 seedlings (Sun et al 2012;Chang et al 2014). After preliminary selection for breeding in 2011, scions of all seedlings in the population were grafted onto Malus micromalus rootstock with a 30 cm 'SH40' dwarfing interstem and replanted at China Agricultural University (Beijing) for further genetic mapping.…”

“…In our study, fruit length was located on LG 7 of the 'Jonathan' linkage map in 2008 and on LG 11 in 2009. Fruit shape is a quantitative characteristic that is controlled by several genes (Sun et al 2012). King et al (2000) reported that QTL detection in a population is the result of single alleles derived from one parent, which must therefore be heterozygous for the locus underlying this trait.…”

“…In apple, the expression of two genes associated with cell proliferation, MdANT1 (MDP0000175309) and MdANT2 (MDP0000190889), was high from anthesis until 15 days after full bloom, a period coinciding with active cell division and rapid longitudinal fruit growth (Madhumita and Anish 2012). We previously identified five major gene loci involved in the regulation of FSI on four LGs (10, 11, 12, and 13) in a 'Jonathan' 9 'Golden Delicious' mapping population (Sun et al 2012). Recently, using the same population and simple sequence repeat (SSR) markers, the yearstable QTL for FSI, fsij08.11.2/fsij09.11 at 7.371 cM on chromosome 11 of the female parent, 'Jonathan', co-localised with a major gene locus, F11-1 (Chang et al 2014).…”