Inheritance of Chilling Requirement in Progenies of Apricot (Prunus armeniaca L.)

This research had the aim to study, under the Mediterranean climatic conditions, the genetic variation of the Chilling Requirement (CR) character in progenies originated from parents with low-medium and very high CR. Adult apricot seedlings of seven year old, growing under the climatic conditions of the Tuscan coastal area, Italy (lat. 43,02N, long. 10,36E), were randomly selected from two families obtained by crossing cultivars with different CR: 1) 30 genotypes from 'Portici' x 'Stark Early Orange' (medium and very high CR, respectively); 2) 24 genotypes from 'Sungold' x 'Moniqui' (medium and high CR, respectively). The following determinations were periodically performed on flower buds during the winter season: a) endo- and ecodormancy overcoming through biological observations (forcing method); b) changes on glutathione (GSH, GSSG) contents through biochemical analysis; c) blooming entity. The results confirm that the female parents ('Portici' and 'Sungold') need a medium CR, while the male parents ('Stark Early Orange' and 'Moniqui') are characterized by a high or a very high CR with a scantly flowering. Analysing the flower bud dormancy evolution of genotypes of the two progenies, a different distribution of character CR in relation to the cross combination was observed. From deep to the end of dormancy, the glutathione oxidised form GSSG was depleted and the active reduced form (GSH) increased, altering the GSH/GSSG ratio. Although, this behaviour was different in relation to the genotypes, glutathione is one of the putative key compounds inducing the resumption of flower bud growth.