Searching for resistance to ZYMV among Cucurbita maxima cultivars

J. Svoboda, L. Leisova-Svobodova, P. Kominek
Fruits of the winter squash Cucurbita maxima Duchesne with orange flesh are very popular for their wide use in cooking and high carotene content. Commonly planted cultivars are highly susceptible to Zucchini yellow mosaic virus (ZYMV). Fruits from infected plants are dark green-spotted, and their shelf life is shortened. The most effective way to protect them against ZYMV is growing resistant cultivars. Seeds from 23 cultivars and new breeding lines of C. maxima were gathered. Their level of resistance to ZYMV was evaluated by a comparison of the relative virus concentrations in plants after mechanical inoculation with the highly virulent Czech ZYMV-H strain and by evaluation of symptoms. The relative concentration of ZYMV protein in the leaves was calculated from the virus titer determined by ELISA. The results demonstrated that squashes ‘Invincible F1’ and ‘Star 7026 F1’ are highly resistant to ZYMV – the virus concentration in their leaves was below detection limit, and there were no ZYMV symptoms on their leaves and fruits. However, a biological test and electron microscopy proved the presence of ZYMV in the plants. This means that the virus multiplied in these plants at a low rate. Other winter squashes ‘Amord F1’, ‘Grey Queen’ and the new breeding line 322/17 were assessed as moderately resistant. The rest of the evaluated cultivars were tolerant or susceptible to ZYMV. An experiment crossing ‘Invincible F1’ with the popular susceptible winter squash ‘Hokkaido’ was performed. The progenies showed that the resistance of the parental plants is coded recessively in the genome. The results are further discussed.
Svoboda, J., Leisova-Svobodova, L. and Kominek, P. (2020). Searching for resistance to ZYMV among Cucurbita maxima cultivars. Acta Hortic. 1294, 239-244
DOI: 10.17660/ActaHortic.2020.1294.30
winter squash, Invincible, Star, virus titer, electron microscopy

Acta Horticulturae