Simpson, C.G., Cullen, D.W., Hackett, C.A., Smith, K., Hallett, P., McNicol, J.W., Woodhead, M. and Graham, J.
Theoretical and Applied Genetics 130, 557-572.
||Fruit softening is an important agronomical trait that involves a complex interaction of plant cell processes. We have used both qualitative and quantitative scoring of fruit firmness, length, mass and resistance to applied force to identify QTL in a raspberry mapping population. QTLs were located primarily on linkage group (LG) 3 with other significant loci on LG 1 and LG 5 and showed mostly additive effects between the two parents. The expression of key genes that underly these QTLs, with roles in cell wall solubility, water uptake, ethylene synthesis, polyamine synthesis, transcription and cell respiration were tested across five stages of fruit development, from immature green to red ripe fruit, using real time RT-qPCR. Gene expression patterns showed variable expression patterns across fruit development with highly significant positive and negative correlation between genes, supporting precise regulation of expression of different cell processes throughout raspberry fruit development. Variable timing in expression was also found in some genes at different fruit development stages between soft and firm cultivars. Multiple processes have a role to play in the fruit softening and this will require development of multiple marker combinations to different genes to characterise raspberry fruit softening.