Inheritance of chilling and heat requirements for flowering in almond and QTL analysis

The chilling and heat requirements and flowering time were studied, for 2 years, in an almond progeny from the cross between the late-flowering French selection R1000 and the early-flowering Spanish Desmayo Largueta. These three temperature-dependent traits showed quantitative inheritance, although for chilling requirements and flowering time a major gene could be involved, modified by other minor genes. The results indicate that flowering time is mainly a consequence of the chilling requirements; heat requirements having a smaller effect. In agreement with the genetic findings, a significant Quantitative Trait Loci (QTL) for chilling requirements was found in G4 together with other minor QTLs in G1, G3, and G7. For heat requirements, two QTLs in G2 and G7 were identified. The results also show the high influence of temperature in the expression of the three traits and their QTL analyses. In addition, QTL analysis for flowering time allowed the identification of one significant QTL in linkage group 4 (G4) that explained most of the phenotypic variation together with other minor QTLs located in G1, G6, and G7.