Evaluation of Selected Cucurbitaceous Vegetables for Resistance to Zucchini yellow mosaic virus

Zucchini yellow mosaic virus (ZYMV) causes considerable losses of cucurbitaceous vegetables grown nearly all over the world; indeed, the commonly planted cultivars are highly susceptible to ZYMV. In all, 3 cultivars of American and 8 of European summer squash (Cucurbita pepo), and 6 Japanese and 21 European cucumber lines (Cucumis sativus), including both slicing and pickling species, were selected for the evaluation of their resistance to the most virulent Czech strain, ZYMV-H (GenBank accession number DQ144054). Butternut squash (Cucurbita moschata) ‘Menina 15’, Chinese slicing cucumber ‘Taichung Mou Gua-1’ (TMG-1), and watermelon (Citrullus lanatus) accession PI 595203 were included in the experiment, because they were reported to be resistant to ZYMV. The tested plants were mechanically inoculated by ZYMV-H and their resistance was assessed through a comparison of the relative virus protein concentrations and visual symptoms. Butternut squash Menina 15, Chinese slicing cucumber TMG-1, Japanese slicing cucumber breeds ‘G22' and ‘A192-18’, and watermelon PI 595203 were evaluated as immune: the virus concentration in their leaves was zero, as verified by polymerase chain reaction. American summer squash ‘Cougar’ and Japanese slicing cucumber breeds ‘A202-18’, ‘R10’, and ‘S93-18’ were clearly resistant, because the virus multiplied at a low rate in these plants. The remaining tested cultivars were tolerant or susceptible to ZYMV.

Relative concentration of Apple mosaic virus coat protein in different parts of apple tree

The optimal conditions for detecting <I>Apple mosaic virus</I> were assessed by determining relative concentrations of viral coat protein in different tissues (leaves, flower petals, dormant buds, and phloem) in five selected symptomless <I>Apple mosaic virus</I>-infected apple trees of two cultivars at different terms during the vegetation period. Relative concentrations of <I>Apple mosaic viru</I> were calculated as the reciprocal value of the <I>Apple mosaic virus</I> coat protein titer determined by ELISA. The highest relative virus concentration and therefore the highest reliability of virus detection was obtained with young leaves in April before flowering. The reliability of the detection was proved by repeating tests of 80 apple trees of four cultivars in the two subsequent years. The presence of <I>Apple mosaic virus</I> was tested in young apple leaves before flowering taken from 472 apple trees from selected orchards of the Czech Republic. The association of the outcome with climate is also discussed.

Seasonal variation in Blueberry scorch virus concentration in highbush blueberry and implications for disease monitoring and management

Seasonal variation in relativeBlueberry scorch virus(BlScV) concentration was determined for three infected highbush blueberry,Vaccinium corymbosum, cultivars in a commercial field in southwestern British Columbia, Canada. Relative virus concentration per g of infected blueberry flower clusters and leaf terminal tissue varied during the season with significant cultivar-by-time interactions. Flower clusters had the highest BlScV concentration per g of tissue and could be collected in early May for disease surveys. Timing of leaf sample collection for BlScV surveys, transmission studies and virus purification should be based on studies of temporal variation in BlScV concentration for the principal cultivars in a production area.