PLUM VARIETIES USED AS PARENTS IN ROMANIAN BREEDING PROGRAM

Mădălina Butac

doi:10.33045/fgr.v37.2021.01

Abstract

There are about three thousand varieties belonging to Prunus domestica available at present worldwide that can be used as genitors in plum breeding activity. An analysis of the pedigrees of plum cvs. developed in Romanian breeding programs shows that the most are descended from ‘Tuleu gras’, ‘Renclod Althan’, ‘Anna Späth’, ‘Stanley’ and ‘Early Rivers’, called 'ancestors'. That means the majority of plum cvs. have at least one of the ancestors as parent or grandparent. For those 40 plum cvs. registered in Romania in 60 years an increased number of crosses with these 'ancestors' has led to what we call 'inbreeding'. According to data presented in this paper, ‘Tuleu gras’ cv. was the most frequently used parent in the cross combinations, giving origin to 23 cvs. Among the other frequently used genitors were: ‘Renclod Althan’ (7 cvs.), ‘Anna Späth’ (3 cvs.) and ‘Stanley’ (1 cv.). Many of the cultivars – 32 altogether (80%) have originated from hybridization, whereas 4 cvs. have originated from open pollination, others 3 cvs. from mutagenesis and 1 cv. from clonal selection. The goal of this work is to measure genetic diversity presently use in Romanian plum breeding. Pedigrees of each cv. were used to study the genetic contributions of ancestor. Of the 40 cvs. analyzed, 33 had an inbreeding coefficient other than zero. The overall mean inbreeding coefficient was 0.419 for all cvs., where their parentages were known. For cvs. with unknown parentage (nonrelated with known parentage) the inbreeding coefficient is zero. The mean coefficient of coancestry of 40 plum cvs. are 0.081 with ‘Tuleu gras’ cv., 0.019 with ‘Renclod Althan’ and ‘Anna Späth’ cvs., 0.017 with ‘Early Rivers’ cv., 0.014 with ‘d’Agen’ and ‘Renclod Violet’ cvs. and 0.005 with Stanley cv. In conclusion, plum breeders have worked with populations of greatly reduced genetic diversity and this strategy becomes a problem because it leads to genetic impoverishment, and, also, the loss of the genetic resistance to different diseases.

Highlights

European plum (Prunus domestica L.) is one of the most widespread species in the temperate regions, after the apple, pear and peach (Butac, 2020)
The goal of this work is to measure genetic diversity presently use in Romanian plum breeding
The inbreeding problem and potential genetic limitation have been raised for numerous other fruit species (Choi and Kappel, 2004; Lansari et al, 1994; Noiton and Alspach, 1996; Scorza et al, 1988)

Summary

Introduction

European plum (Prunus domestica L.) is one of the most widespread species in the temperate regions, after the apple, pear and peach (Butac, 2020). The origin place of this species is Caucasus Mountains near the Caspian Sea (Milosevič and Milosevič, 2018). This species grown in cooler areas can be divided in several groups considering the fruit characters: plumes, prunes, greengages (Reineclaudes) and mirabelles (Butac, 2020, Hartmann and Neumüller, 2009). 2n =2x = 16, genome formula CC) and tetraploid sloe or blackthorn (Prunus spinosa L., 2n = 4x = 32, genome formula SSSS) based on the fact that these species grow together in the Caucasian forests and can naturally hybridize with each other (Butac et al, 2019; Butac, 2020; Crane and Lawrence, 1934; Milosevič and Milosevič, 2018; Neumüller, 2011). There are three subspecies within Prunus domestica: ssp. insititia (mirabelles and so called “Spilinge”), ssp. oeconomica (prunes) and ssp. italica (plums, Reineclaudes and all other kinds of plum fruits) (Butac, 2010; Neumüller, 2011)

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