Il miglioramento genetico del pesco : nuove tipologie, extra-stagionalità e resistenza alle principali avversità

Within the goals of the modern the peach breeding industry, the search of novel fruits could take advantage of the wide diversity in flesh texture and pace of softening, e.g. melting, slow softening melting (as from ‘Big Top’ nectarine and the ‘Rich’ yellow peach series, both from Zaiger breeding program), non melting and stony hard. The traditional melting types are no more suited for the present needs of the fresh market operations, from harvest onward. Conversely, the ‘slow softening’ melting traits secure a safer handling of the fruit due to its firmer flesh, although it could reach, lately, the ‘melting’ stage of a traditional melting type. The stony hard phenotype is the only known peach not producing ethylene, that keeps a ’crunchy’ texture well behind the physiological ripening (almost three weeks on the tree); some traits are still to be improved, such as the poor ‘peach’ aroma. Furthermore, peaches with distinctive flavour could be bred by combining single Mendelian (e.g. the low acid trait described by Monet) and quantitative traits (sugars and acids), in order to select fruits featuring acidic (above 15 meq of total acidity), mild (from 11 to 15 meq) or sweet (below 10 meq) overall flavour, with tortal sugars ranging from 10 up to more than 20 °Brix. Other novel fruits could be developed by combining the ‘non bitter seed’ and the ‘soft stone’ in the very very early ripening cultivars, in order to breed an ‘all-to-eat’ fruit. Fruit brown rot from Monilinia spp. and Sharka from PPV are the major disease so far in Italy. Whyle interesting sources of resistance for brown rot were already found (e.g. ‘Contender’ yellow peach) and introgressed in the breeding stocks with very promising results, no source of resistance for PPV is known in peach. Selections from hybridization between peach and almond or P. davidiana (bringing quantitative resistance to PPV) are now employed as donor parents in a recent project funded by the Italian Ministry of Agriculture. Some results are expected in the near future, although previous work from INRA (France) with P. davidiana showed the resistance is strongly lowered by the back-cross generations required to re-gain commercial quality. Resistance to powdery mildew, altough not a major disease, is sought by employing well known sources of resistance, i.e. ‘Bolinha’ and ‘Oro A’ non melting peaches.