The following research are carried out in the molecular genetic lab of Breeding and Pomology department at Istituto Sperimentale per la Frutticoltura (ISF)

     A.     Mapping the peach genome with molecular markers

     B.     QTL identification

     C.     Fingerprinting of Prunus cultivars and accession

          A. Genome Mapping

 In collaboration with several Italian and foreign institutions the group has been involved in the last years in mapping the Prunus genome.

Within the European project “Prunus Mapping”, in collaboration with IRTA of Cabrils (Spain) and INRA of Bordeaux (France), we set up a linkage map using an F₂ segregating population obtained by selfing an F₁ interspecific hybrid between Texas (Almond) and Early Gold (Peach). The map (T x E) is composed of 246 codominat loci, 235 RFLPs and 11 isozymes that coalesced in 8 linkage groups. It covers 491 cM with an average distance of 2 cM. Owing to its saturation and to the liability of its markers the map is considered the reference map of the genus Prunus (Joobeur et al. 1998).

A peach linkage map was elaborated at ISF in order to map traits of agricultural interest. A BC₁ progeny [P. persica x (P. persica x P. ferganensis)] was used to construct the map. An accession of P. ferganensis, resistant to powdery mildew (Spaerotheca pannosa), was used as donor parent. The map (P x F) is composed of 109 markers (74 RFLPs, 17 SSRs, 16 RAPDs and 2 morphological traits) distributed in 10 linkage groups. It covers 521 cM of the peach genome with an average distance of 4.8 cM. Two morphological traits, flesh adhesion (F/f) and leaf gland (E/e), were placed on the map in group 4 and 7 respectively (Dettori et al. 2001). Recently several Prunus SSRs, obtained by different research group, were tested on the progeny and will be placed on the map in the near future.  Moreover in collaboration with the Istituto Sperimentale per la Cerealicoltura of Bergamo we are trying to saturate the map with AFLP markers.

The group collaborates with Clemson University in order to construct a physical map for peach. In particular RFLP markers from both linkage maps were anchored to the BAC library available at Clemson so that both physical and linkage maps will be aligned. Consequently SSRs were developed in specific region of the peach genome using the BAC library resource (Verde et al. 2003).

In order to map the gene responsible for the “stony  hard” trait a new linkage map is going to be elaborated using an F₂ segregating population, obtained by Dr. Liverani in Forlì, selfing an F₁ tree from Yumyeong’ x ‘O’Henry’.

 B.     QTL identification

 Data on quantitative traits were collected in the BC₁ progeny in order to identify molecular markers linked to important agricultural characters. Then the genome was scanned using the software MAPMAKER QTL 1.1. Ten QTLs were identified: 2 for the traits “powdery mildew resistance”, 2 for “soluble solids content”, 2 for “skin color”, 2 for “ripening time” and one each for “blooming time” and “internode length” (Verde et al. 2002). We are increasing the number of individuals analyzed for a better definition of the detected QTL.

 C.     Fingerprinting

Molecular markers (RFLPs, RAPDs and SSRs) were also used for characterizing peach varieties and accessions. 

RAPDs and RFLPs were used to test 52 peach genotypes, 9 nectarines, 1 almond cultivars (‘Ferragnes’) e 4 peach x almond hybrids. They were able to discriminate 39 accessions. Most of the indiscriminate accessions were natural mutations, as ‘Redhaven’ and ‘Compact Redhaven’. None of the sport mutations included in the study were separated using this kind of markers (Quarta et al. 2001)

In collaboration with the University of Udine e Bologna 50 peach and nectarines varieties  were tested using 26 SSRs primers developed by Prof. Testolin at University of Udine. Microsatellites showed a higher discrimination power than RAPDs and RFLPs. They were able to discriminates some sport mutations as ‘Armking’ vs.  ‘Maybelle’, and ‘Springcrest’ vs. ‘Maycrest’. The paternity of several cultivars was analysed in the study. In most cases the parenthood was confirmed while for few cultivars the pedigree could not be confirmed. This is the case of  ‘Starlite’, ‘Elegant Lady’ and ‘Caldesi 2000’ whose analyses do not confirm the declared pedigrees (Testolin et al. 2000).

We are currently involved in the molecular characterization of the peach ecotype ‘Percoco di Tursi’ in order to valorise this important local production of south Italy.