Seedborne transmission of Zucchini yellow mosaic virus and Cucumber mosaic virus in Styrian Hulless group of Cucurbita pepo.

A total of 62 seed lots originating from hulless pumpkin fruit exhibiting typical symptoms of ZYMV infection were tested in insect-free greenhouses in three consecutive years. Of those, 25 seed lots showed seedborne virus transmission that ranged from 0.29 to 15.34 % of the seeds. In total 19997 seeds were sowed, 16039 plants were monitored and 225 plants were seedborne virus infected. Of those, 166 had ZYMV and 59 had mixed infection of ZYMV and CMV as identified by ELISA serological tests, by indicator plants or by RT-PCR. The average rate of seedborne transmission of ZYMV was 1.4 %. Coat protein gene of CMV and ZYMV were characterized and compared. INTRODUCTION Zucchini yellow mosaic virus (ZYMV) was first identified in northern Italy. Soon after, it was identified in areas throughout the world where cucurbits are cultivated, including Mediterranean countries, Japan, Germany, Central Europe, China, Chile, Australia, Mexico, Mauritius, Canada and the USA (Desbiez and Lecoq 1997; Greber et al. 1987; Nameth et al. 1986; Prieto et al. 2001; Robinson et al. 1993; Sammons et al. 1989; Tobias et al. 1996). This relatively new, but aggressive virus (member of the potyvirus group) has spread rapidly throughout the world, suggesting an efficient transmission from plant to plant by several aphid species in a nonpersistent manner (Lisa and Lecoq 1984) and long distance distribution via infected seeds (Davis and Mizuki 1986; Schrinjwerkers et al. 1991; Fletcher et al. 2000). The efficient intercontinental spread of the virus can be explained by international trading of infected seeds. However, the rate of disease transmission via seed is low and difficult to prove (Provvidenti and Robinson 1987; Gleason and Provvidenti 1990; Robinson et al. 1993). There is some evidence for seed transmission in the case of zucchini (Davis and Mizuki 1986; Schrinjwerkers et al. 1991), buttercup squash (Fletcher et al. 2000) and hulless oilseed pumpkin (Tobias and Kovacs 2001). This work focused on studying the seedborne virus transmission on hulless oilseed Cucurbitaceae 2008, Proceedings of the IX EUCARPIA meeting on genetics and breeding of Cucurbitaceae (Pitrat M, ed), INRA, Avignon (France), May 21-24, 2008