Sources of parthenocarpy for Zucchini breeding: relationship with ethylene production and sensitivity

Euphytica (2014) 200:349362 DOI 10.1007/s10681-014-1155-8

Sources of parthenocarpy for Zucchini breeding: relationship with ethylene production and sensitivity

Cecilia Martnez Susana Manzano

Zoraida Megas Dolores Garrido Beln Pic

Manuel Jamilena

Received: 16 January 2014 / Accepted: 15 May 2014 / Published online: 6 June 2014 Springer Science+Business Media Dordrecht 2014

Abstract Parthenocarpy is becoming an essential trait for off-season greenhouse production of Zucchini squash. Given that winter conditions promote a reduction in the number of male owers and in the activity of pollinators, the application of synthetic auxins is currently the most widespread method to induce fruit set. We have evaluated the parthenocarpic tendency of 48 long-fruited accessions of Cucurbita pepo spp. pepo, from morpho-types Zucchini, Vegetable marrow and Cocozelle, including 45 traditional cultivars and 3 commercial hybrids, with the goal of identifying new sources of parthenocarpy for breeding programs. After the rst screening, 20 selected accessions were evaluated for the growth rate of unpollinated fruit. Twelve of the selected accessions identied as either strongly parthenocarpic or non-parthenocarpic, were compared for fruit rate growth, ethylene production and

ethylene sensitivity. Apart from the three control hybrids, the fastest parthenocarpic fruit growth was observed in CpCAL112, CM-37, E-27, PI261610, and V-185. The source of the parthenocarpy of some of these accessions differs from that of the hybrids as it was not associated with the conversion of female into bisexual owers or with the so-called fruits with attached owers syndrome, which is an undesirable trait in current parthenocarpic hybrids. The alternative sources of parthenocarpy may be of great importance in current Zucchini breeding programs. We also demonstrate that the parthenocarpy of these accessions is associated with downregulation of ethylene production in unpollinated fruits during the rst days post anthesis (DPA). In non-parthenocarpic accessions, unpollinated fruits boosted ethylene production at 3 DPA, concomitantly with fruit abortion and senescence, while in parthenocarpic accessions, fruits produced little ethylene at 3 DPA. Therefore, ethylene production in ovaries/fruits at 3 DPA can be used as a marker to identify and select parthenocarpy in Zucchini squash. However, in the cultivars tested here, ethylene production and sensitivity in vegetative organs and in male owers earlier than 3 PDA do not appear well associated with parthenocarpy.

Keywords Cucurbita pepo Parthenocarpy

Andromonoecy Ethylene production

Ethylene sensitivity

C. Martnez...