Finding of parthenocarpic fruit in Gymnocladus dioicus (L.) K. Koch in a plantation at Fruška gora (Serbia)

Abstract

The genus Gymnocladus (Fabaceae) consists of five species with reproductive system described as polygamous, monoecious and dioecious. The species Gymnocladus dioicus (L.) K. Koch has been present in Serbia for over 150 years. Its flower sexuality was described as dioecious, but there are references stating that there are flowers that are morphologically hermaphrodite and functionally monosexual having the sterile pollen. In the area of Belgrade, a sexually reproductive tree with morphologically hermaphrodite flowers was recorded, but it is still needed to be checked for functional androdioecy. In this paper, we point out the finding of parthenocarpic fruits in G. dioicus in a large number of adult trees in a plantation at Fruška Gora (Serbia). Considering that during a multiannual period a mass occurrence of parthenocarpic fruits with concurrent absence of pods with characteristic seeds for this species was recorded, there is a possibility that the plantation was raised by clonal selection. So far, the occurrence of parthenocarpic fruits in G. dioicus was recorded on one isolated tree in France. The analyzed parthenocarpic fruits have the characteristic shape, structure and size that are in compliance with parthenocarpic fruits from France. The pods are seedless, i.e. with undeveloped seed about 1 mm in size, with the characteristic curved tip pointed to the ventral suture, with a length of 4.6-8.9 cm (6.9 cm on average), and width of 1.8-3.6 cm (2.6 cm on average). Research of the sexual dimorphism of G. dioicus is important for silviculture of this allochthonous species in Serbia, because in plantations at favourable sites, the individuals of a certain sex may achieve growth that is desirable for timber production, but with limited ability of subspontaneous dispersal by vegetative means.