Inheritance of shell and kernel shape in almond (Prunus dulcis)

Shape of almond kernel has an important impact in the final commercial value. Elliptic shapes are more common while round shapes, 'Marcona' types, are scarce and very appreciated. In order to increase the efficiency of the breeding programs for specific shape is important to know the genetic control of this trait. In this work, heritability of length, width, thickness, roundness and globosity, of shell and kernel, was estimated by midparent-offspring regression (narrow sense, h2) and by variance components analysis (broad sense, H2) for three years, using full-sib and half-sib offsprings coming from four crosses designed only for this objective. Length and roundness of shell and kernel showed the highest heritability by both methods every year, being intermediate or very low for the other traits. Kernels were usually less rounded than their shells. Values near one of the ratio h2/H2 were observed for length and roundness, showing an absence of non-additive effects for these two traits. In general, a normal phenotypic distribution was observed for all the traits and certain transgressive segregation was observed in the descendants. The results confirmed the complex architecture of this trait transmitted quantitatively, where additive effects play the mayor role.