Breeding for postharvest cold tolerance in zucchini squash

摘要

Tolerance to postharvest chilling injury (PCI) is an extremely important trait in current zucchini breeding programs, especially for productions that are export-orientated and require therefore refrigerated transport and storage. In the search for newsources of tolerance to PCI, we have screened more than 100 accessions of Cucurbita pepo, which had elongated fruit and belonged to morphotypes Zucchini, Vegetable Marrow and Coccozelle. The fruit of the 20 most promising accessions and 5 commercial hybrids was stored for 7 and 14 days at 4°C, and evaluated mainly for PCI, but also for fruit weight loss, and ethylene production. We found that the fruit from commercial hybrids and most of the accessions was very sensitive to cold storage, losing its marketable value after 7 days of storage at 4°C. The fruit of three accessions, CpCAL003, CpCALOSl and CpCAL053, however, showed the lowest PCI index and fruit weight loss in two successive trials, indicating that they were highly tolerant to PCI. We tested the inheritance of PCI tolerance in CpCAL003, and the potential use of this in zucchini breeding programs, by crossing the identified tolerant accession with the cold sensitive CpCAL112, and by evaluating the Fj and F2 progenies, as well as the two backcrossing populations BC, and BC>, The results indicate that he PCI tolerance of i CpCAL003 is not a monogenic Mendelian trait, but rather a complex polygenic quantitative trait. The lower PCI and fruit weight loss in the fruit of some segregating plants in F2, BCi and BC2 indicated, however, that this trait could be selected and introgressed in modern hybrid cultivars of zucchini. Moreover, we found that the production of cold-induced ethylene was correlated with PCI and fruit weight loss not only inthe different analyzed accessions, but also in the segregating populations (Fz, BCi and BC2), demonstrating that that ethylene production can be used as a marker for the selection of PCI tolerance in the present-day zucchini breeding programs.