Cucurbit Genetics Cooperative Report 22:5354 (article 19) 1999
Disease Resistance of cucurbita pepo and C. maxima Genetic Resources
Eva Kristkova
Research Institute of Crop Production Praha, Division of Genetics and Plant Breeding, Department of Gene Bank, Slechtitelu 11, 783 71 Olomouc, Czech Republic
Ales Lebeda
Palacky University, Faculty of science, Department of Botany, Slechtitelu 11, 783 71 Olomouc, Czech Republic
Introduction. A collection of genetic resources of Cucurbita pepo and Cucurbita maxima was evaluated for resistance to the most important viral and fungal pathogens of cucurbitaceous vegetables in the Czech Republic.
Methods. The set of more than 400 accessions (PI), kindly provided by gene banks in ames and Geneva (USA), included local cultivars and landraces from around the world.
This collection has been evaluated for resistance to the cucumber mosaic cucumovirus (CMV) (3), watermelon mosaic potyvirus2 (WMV2) (2) and powdery mildew of cucurbits ({PM) (1). A group of selected accessions previously reported as highly resistant to CMV and WMV2 were screened for resistance to the zucchini yellow mosaic potyvirus (ZYMV) (4).
The screening for resistance to the viruses was carried out under controlled conditions in a growth chamber or glasshouse after an artificial inoculation. Local Czech isolates of viruses were used. The resistance to powdery mildew was evaluated under field conditions of natural infection of Erysiphe cichoracearum and Sphaerotheca fuliginea. the infection degree was based on the visual evaluation of symptoms on host plants and in some cases, the presence of virus was controlled by DASELISA.
Results. In spite of a relatively high susceptibility of both Cucurbita species to all above mentioned pathogens in general, a large variation of resistance within individual accessions was found. the genotypes with the highest level of resistance to CMV, WMV2 and PM are listed in the Table 1.
The C. maxima species can be considered as more resistant to CMV, WMV2, and PM as compared to the C. pepo response to these pathogens. No accession was found to be resistant to all pathogens under study (CMV, WMV2 and PM) (1,2,3). The C. pepo accession PI 518687 could be used for WMV2 and PM resistance breeding (1,3). The C. maxima accession PI 500483 expressed a promising level of resistance to CMV and WMV2, similarly as four other C. maxima accessions ({O 295342, PI 368572, PI 458691 and PI 265557) (2,3). Unfortunately, all accessions under study were highly susceptible to ZYMV (4).
Table 1. Cucurbita pepo and Cucurbita maxima accessions ({POI number and/Origin/) with high level of resistance to the cucumber mosaic cucumovirus (CMV), watermelon mosaic potyvirus2 (WMV2) and powdery mildew of cucurbita (PM  Erysiphe cichoracearum, Sphaerotheca fuliginea).
CMV 
C. pepo 
PI 438699 / Mexico/ 
C. maxima 
PI 176530 /Turkey/, PI 177891 /Turkey/, PI 265555 /Turkey/, PI295342 / Australia/, PI 368564 / Yugoslavia/. PI 368572 Yugoslavia/, PI 372458 /Yugoslavia/, PI 458685 /Argentina/, PI458691 Argentina/, PI 458693 /Argentina/, PI 482466 /Zimbabwe/, PI 490352 /Burkina/, PI 500483 /Zambia/. 
WMV2 
C. pepo 
PI 184745/Austria/, PI 265550 /Argentina/, PI 368570 /Yugoslavia, PI 379291 /Yugoslavia/, PI 458672 /Argentina/, PI 458662 /Argentina/, PI 458661 / Argentina/, PI 458709 /Argentina/, PI 500483 /Zambia/. PI 419081 /China/ 
PM 
C. pepo 
PI 176536 /Turkey/, PI 518687 /USA/, I 38700 /Mexico/, PI 442300 /Mexico/, PI 357937 /Yugoslavia/, PI 442296 /Mexico/, PI 507888 /Hungary/, PI 438823 /Mexico/, PI 442292/Mexico/ 
C. maxima 
PI 458674 /Argentina/, PI 458673 / Argentina/, PI 458675 /Argentina /, /, PI 135370 /Afghanistan/, PI 137866 /Iran/, PI 165027/Turkey/PI 166046 /India/, PI 169404 /Turkey/ 
Literature Cited
 Kristikova, E. and A. Lebeda. 1997. Variation in field resistance of Cucurbita pepo L. PI accessions to the powdery mildew of cucurbita. In: Kobza el al. (eds.) Biology and Technological Development in Horticulture, Proceedings of an International Horticultural Conference, 912 September, Lednice na Morave, Czech Republic, p.331.
 Kristikova, E. and A. Lebeda. 1998. Variation in response of Cucurbita spp. to watermelon mosaic virus2 (WMV2) infection .In Recent Advances in Vegetable Virus Research, Proc. Ninth Conference of the ISHS VVWG, 2227 August, Torino, Italy, pp. 7275.
 Lebeda, A. and E. Krostikova. 1996. resistance of Cucurbita pepo and Cucurbita maxima germplasms to cucumber mosaic virus. Genet. Res. Crop. Evol. 43:461469.
 Lebeda, A., E. Kristikova, S. Kozelska, M. Jokes and J. Rodova. 1998. Response of Cucurbita pepo and Cucurbita maxima genotypes to Czech isolate of zucchini yellow mosaic virus. In:: Recent Advan.in Veget. Virus Res., Proc. of Ninth Conf. of the ISHSVVWG. 2227. August, Torino, Italy, p. 76.

