In: Phyton 56, Fasc. 1 (2016): S. 61-75 DOI: 10.12905/0380.phyton56(1)2016-0061

The Impact of Interspecific Hybridization on theChemical Compositions of Oil Pumpkin Seeds

By

Andreja Urbanek Krajnc, Ignac Janzekovic, Andreja Sober and Anton Ivancic, with 3 Figures

Key words: Oil pumpkins, Cucurbita pepo, Interspecific hybridization, Toco­pherols, Pigments, Thiols, Ascorbate.

Summary
Urbanek Krajnc A., Janzekovic I., Sober A. & Ivancic A. 2016. The impact of interspecific hybridization on the chemical compositions of oil pumpkin seeds. – Phyton (Horn, Austria) 56 (1): 61–75, with 3 figures.

The currently grown thin-coated pumpkin varieties belong to the species Cu­curbita pepo and originated from the same Styrian mutant discovered in the late 19th century. The Styrian oil pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) is economically the more important in the southern parts of Austria and the neighboring regions of Slovenia, Hungary, and Croatia. The major problems in its cultivation are viral diseases (especially the Zucchini yellow mosaic virus, ZYMV), extremely high temperatures, prolonged drought and occasionally pronounced wet periods, which may cause significant damage and severe economic losses.

In our oil pumpkin breeding program, which is based on a modified recurrent selection, we used interspecific hybridization in order to broaden the genetic base of the oil pumpkin genotypes. We involved three cultivated pumpkin species (C. argy­rosperma, C. moschata and C. pepo) and one wild (C. okeechobeensis). Normal fer­tility was restored by intercrossings, self-fertilization, and backcrosses. We consid­ered three crucial selection criteria: thin-coated seed (non lignified seed coat), bushy growth (plants with short stems) and light (white, light ocre and light yellow) fruit exterior, in order to make oil pumkins tolerant to high levels of solar radiation and high temperatures. Furthermore, the aim of the investigation was to evaluate the chemical compositions of seeds of the existing breeding materials. Interspecific hy­bridization was found to be very useful for expanding the variation range of all analyzed substances (tocopherols, pigments, ascorbate, thiols). The mean total to­copherol contents ranged between 525 and 1667 nmol/g DW, with g-tocopherol al­ways being the predominant isomer. The protochlorophyll(ide) contents ranged from 361 to 2039 mg/g DW, whereas the total carotenoids reached the value of 117 mg/g DW. The glutathione contents varied from 293 to 1908 nmol/g DW, where­as the ascorbate contents reached the value of 384 nmol/g DW. The variation ranges of most of the traits will enable breeders to conduct more rigorous selection aimed at the creation of highly productive and high quality cultivars, with the desired concentrations of antioxidants, especially tocopherols and pigments.