Linkage map construction and analysis of fruit size in sweet (Prunus avium L.) and sour (Prunus cerasus L.) cherry

Maximizing fruit size is critical for profitable sweet (Prunes avium L.) and sour (Prunes cerasus L.) cherry production, yet little is known about the genetic control of this trait. Fruit size varies widely between cherry cultivars, and significant variation exists among genetically identical fruit due to environmental and cultural differences. A more thorough understanding of the genetic control of fruit size may be used to design future management and genetic improvement strategies to increase cherry fruit size.; This research examined the mesocarp cellular differences between five cultivars representing a broad range of fruit size in sweet cherry. Both cell number and cell size were significantly different (P < 0.05) between cultivars. However, the relationship of cell number with fruit weight and diameter was significantly and positively correlated while cell size was not correlated with either measure of fruit size. Cell number was stable during the three years of this study and in two different locations. Differences in cell number due to environmental variation were examined in fruit from three of the same cultivars that were significantly different ( P < 0.001) in fruit size. In this case, fruit size differences were attributed to a difference in cell size rather than cell number, confirming the identification of cell number as the primary genetic component resulting in fruit size differences between cultivars.; To study the genetic control of fruit size in cherry, linkage maps were constructed for reciprocal crosses between the sweet cherry cultivars 'NY 54' and 'EF'. The linkage maps consist of 8 linkage groups (LG) for the 'EF' parent (479.1 cM) and 10 LG for the 'NY 54' parent (308.9 cM). The average distance between marker loci and largest gaps are 7 cM and 29 cM for 'EF' and 8 cM and 34 cM for 'NY 54', respectively. Fourteen of the sweet cherry linkage groups could be aligned with the reference Prunus map based on shared SSR markers.; QTL analysis of fruit size traits was performed using the 'NY 54' x 'EF' population. For mesocarp length, one QTL (mlength1) was identified on 'EF' linkage group 6 (LG 6) and one on 'NY 54' LG (y) ( mlength2), explaining 18.3% and 37.4% of the total phenotypic variance, respectively. Three QTL were identified for mesocarp cell length, on 'EF' LG 6 (clength1) and 'NY 54' LG 6 (clength2) and LG (y) (clength3). The QTL explained 17.4, 16.8, and 16.8% of the phenotypic variation, respectively.; A targeted mapping approach, using SSR loci previously mapped to LG 6 in other Prunus species was used to develop a linkage map for the 'UF' x 'Surefire' sour cherry population. A QTL three cM from the S locus explaining 26.4% of the phenotypic variation was identified in the 'UF' x 'Surefire' population. Additionally, a fruit shape QTL was also located on LG 6, co-segregating with the CPSCT012 marker and explaining up to 22.6% of the phenotypic variation for fruit shape.