Trials were established at Aula Dei Experimental Station (EEAD-CSIC, Zaragoza, Spain) to assess graft compatibility between peach cultivars [Prunus persica (L.) Batsch] and new Prunus spp. rootstocks or selections. Peach cvs. `Catherina' and `Tebana' and nectarine cvs. `Big Top' and `Summergrand' were grafted on peach seedlings, plum rootstocks, almond × peach hybrids, and other interspecific rootstocks. Part of the evaluated material belongs to the EEAD-CSIC selection program, which has showed good adaptation to Mediterranean growing conditions. Other rootstocks such as Bruce, Evrica, Hiawatha, Ishtara, Tetra, and Krymsk-1 have been recently introduced in Spain. A peach and a plum source, GF 677 and Adesoto 101, respectively, were used as compatible reference rootstocks. Both are widely used for peach and nectarine production in the Mediterranean area.
Olfa Zarrouk, Yolanda Gogorcena, Maria Angeles Moreno and Jorge Pinochet
Olfa Zarrouk, Pilar S. Testillano, María Carmen Risueño, María Ángeles Moreno and Yolanda Gogorcena
Changes in cell and tissue organization and in peroxidase activity have been analyzed to find early markers to predict graft incompatibility occurrence in peach/plum combinations (Prunus persica/Prunus spp.) at 5 months after grafting in the dormancy period. Different compatible and incompatible peach/plum grafts were grown for 5 months in a nursery. The cellular study of the graft interface revealed structural changes associated with graft incompatibility symptoms. The main structural features were cambium cell disorganization, less differentiation of vascular tissues, degeneration of phloem and xylem cells, and accumulation of phenols at the graft interface after 5 months of graft development. The peroxidase study was performed during dormancy and the vegetative growth period, and revealed a significant increase in peroxidase activity in the incompatible unions, with significant differences between compatible and incompatible grafts. Analysis of gel profiles of nonbudded rootstocks and scions revealed an anodal isoperoxidase band [relative front (Rf) = 0.48] present in scions and compatible rootstocks, and another isoperoxidase band (Rf = 0.53) only present in the incompatible rootstocks. Our results show that the analysis of cell organization to detect early structural events and the evaluation of peroxidase activity at graft unions constituted feasible and convenient methods for early diagnosis of graft incompatibility. Also, it was suggested that the presence of band Rf = 0.48 in plum rootstocks and peach cultivars could be used as a marker to predict graft compatibility for peach scions and plum rootstocks.
Sergio Jiménez, Jorge Pinochet, Anunciación Abadía, María Ángeles Moreno and Yolanda Gogorcena
The use of rootstocks tolerant to iron deficiency represents the best alternative to prevent Fe chlorosis for peach production in calcareous soils. Early detection laboratory screening procedures allow the selection of new Fe-efficient rootstock genotypes. Seventeen Prunus rootstocks were tested for root ferric chelate reductase (FC-R) enzymatic activity, leaf SPAD values, and field performance. Some rootstocks were used as a reference to compare with new Prunus selections. Micropropagated plants were grown in hydroponic culture with half-strength Hoagland's nutrient solution containing 90 μm Fe(III)-EDTA as a control treatment. Plants were transferred to iron-free fresh solutions for 4 days and were thereafter resupplied with 180 μm Fe(III)-EDTA for 1 or 2 days. In vivo FC-R activity was measured in all treatments, i.e., control, Fe-deficient, and 180 μm Fe(III)-EDTA resupplied plants. The FC-R activity after Fe resupply was higher in Fe-efficient genotypes such as AdesotoPVP, FelinemPVP, GF 677, Krymsk 86™, and PAC 9921-07 than in the controls. No induction of FC-R activity was found in other genotypes such as Barrier, Cadaman™-AvimagPVP, PAC 9907-23, and PAC 9908-02. An intermediate response was observed in GarnemPVP, Gisela 5PVP, Krymsk 1PVP, Torinel™-AvifelPVP, VSL-2™, and PAC 9904-01. According to the induction of FC-R activity after Fe resupply, genotypes were classified as tolerant, moderately tolerant, or nontolerant to iron-induced chlorosis. These results were compared with SPAD values of plants grown under controlled conditions and in the nursery. Rootstocks that show high induction of FC-R activity also showed high or very high SPAD values in the field.
Mariem Bouhadida, Juan P. Martín, Gennady Eremin, Jorge Pinochet, María Á. Moreno and Yolanda Gogorcena
Chloroplast DNA (cpDNA) in 84 Prunus L. accessions (interspecific hybrids and Prunus species) were analyzed to confirm the maternal origin of the interspecific hybrids of Prunus and to establish genetic relationships among Prunus species. The polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) method, which included amplification of cpDNA regions with three universal primer pairs (K1K2, HK, DT) and subsequent digestion with three restriction enzymes (AluI, HinfI, TaqI), revealed 33 haplotypes for the 84 accessions studied. Fourteen from these cpDNA haplotypes were shared by two or more accessions, and 19 were unique. Accessions sharing the same haplotype have maternal relationships among them, which allowed identity confirmation of maternal progenitors of Prunus interspecific hybrids in these cases. Unweighted pair group method average (UPGMA) and minimum-length spanning tree (MST) analyses were performed based on shared common fragments and the number of mutational differences among the 33 haplotypes, respectively. The cpDNA polymorphisms detected made possible the analysis of genetic relationships among the studied Prunus accessions. Most of the recovered relationships are in agreement with current taxonomic hypotheses and artificial crosses.