Inheritance And QTL Mapping For Fruit Shape And Size In Apple

Fruit size and shape are important external quality traits in commercial crops, in this study, The progeny of cross between the apple cultivars ’Jonathan’ and ’Golden Delicious’ were used to analyse the inheritance of fruit length and diameter, correlation of fruit size, shape, length and diameter in two successive years.. We also dected the QTLs for fuit size, length, diameter, shape index by a SSR and SNP linkage maps, then the candidate genes predicted according to the QTL interval.Fruit size, length, diameter are followed a normal distribution in2008and2009, indicated they are controlled by polygenes without major gene segregation.The broad-sense heritability of fruit length and diameter were estimated as91%and93%, respectively in2008; and as82%and85%in2009. These values indicated that fruit length and diameter were easily affected by environmental in2009.Fruit length and diameter were significantly correlated in both2008and2009(r>0.75). FSI was positively correlated with fruit length (r=0.48; r=0.42), and negatively correlated with fruit diameter (r=-0.19; r=-0.17). The absolute values of correlation coefficients between FSI and fruit length were larger than those between FSI and fruit diameter, suggesting that length was a more pronounced trait than diameter. Both length (r=0.76; r=0.78) and diameter (r=0.87; r=0.89) were positively correlated with fruit size, though the correlation was stronger for diameter, indicating that fruit size (weight) was more a function of diameter than of length. No significant correlation was detected between FSI and fruit size (r=-0.033; r=-0.084).By the SSR linkage map19QTLs for fruit size, shape, length, and diameter were identified at the whole-genome level based on a LOD threshold≥2.80in both sampling years and16QTLs detected by SNPs linkage maps at the LOD≥3.50.In SSRs linkage map,4QTLs and6QTLs for fruit size were overlapped or closely associated with QTLs for fruit length and diameter, respectively,2QTLs and1QTL for fruit shape index were linked the QTLs for fruit size and diameter. Meanwhile, by SNPs linkage map, there are1QTL for fruit size coincided with the QTL for fruit diameter and1QTL for fruit shape index tightly linked the QTL for fruit length.No significant correlation was detected between FSI and fruit size and none of the QTLs for fruit size mapped to the same region as QTLs for fruit shape, implying that fruit size and shape are under independent genetic control.We predicted the interval genes for QTLs which dectected at the LOD≥3.50by the SNPs linkage map and3candidate genes (located on LG3) for fruit diameter and size,2genes (located on LG7) for fruit length, and14genes (on LG11) for fruit shape index obtained which may be controlled the trait.