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Issue Environ. Biosafety Res.
Volume 3, Number 1, January-March 2004
Page(s) 17 - 28
DOI 10.1051/ebr:2004004

Environ. Biosafety Res. 3 (2004) 17-28
DOI: 10.1051/ebr:2004004

Comparative fitness of a wild squash species and three generations of hybrids between wild × virus-resistant transgenic squash

Marc Fuchs1, Ellen M. Chirco2, Jim R. Mcferson3 and Dennis Gonsalves1

1  Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA
2  Department of Horticultural Sciences, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA
3  Plant Genetic Resources, USDA-ARS, Cornell University, Geneva, NY 14456, USA

(Received August 25, 2003; accepted December 15, 2003.)

Abstract We compared some fitness components of the wild squash species Cucurbita pepo spp. ovifera var. texana (C. texana) and three generations of hybrids (F1, BC1, and BC2) between C. texana and commercial transgenic squash CZW-3 over three consecutive years under field conditions of low (LDP) and high disease pressure (HDP) by Cucumber mosaic virus (CMV), Zucchini yellow mosaic virus (ZYMV) and Watermelon mosaic virus (WMV). Transgenic squash CZW-3 expresses the coat protein (CP) genes of CMV, ZYMV, and WMV, and is resistant to these three aphid-borne viruses. Across all HDP trials, transgenic BC1 and BC2 hybrids expressing the three CP genes grew more vigorously, displayed resistance to CMV, ZYMV, and WMV, and produced a greater number of mature fruits and viable seeds than nontransgenic hybrid segregants and C. texana. Transgenic F1 hybrids behaved similarly to BC1 and BC2 hybrids but grew less vigorously than C. texana. In contrast, across all LDP trials, C. texana outperformed the transgenic and nontransgenic hybrid segregants. Further, only one back cross was necessary to recover individuals with most of the C. texana characteristics and yet maintain virus resistance. Our data suggest that C. texana acquiring CP transgenes upon hybridization and introgression could have a selective advantage if CMV, ZYMV, and WMV are severely limiting the growth and reproductibility of wild squash populations.


Key words: Key words: Risk assessment / gene flow / transgenic squash CZW-3 / Cucurbita texana / hybrids / fitness evaluation / selection pressure / Cucumber mosaic virus / Zucchini yellow mosaic virus / Watermelon mosaic virus / virus resistance

Corresponding author: Marc Fuchs fuchs@colmar.inra.fr

© ISBR, EDP Sciences 2004


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