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Open Access Highly Accessed Research article

Allopolyploidy and the evolution of plant virus resistance

John Gottula1*, Ramsey Lewis2, Seiya Saito3 and Marc Fuchs1

Author Affiliations

1 Department of Plant Pathology and Plant-Microbe Biology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA

2 Department of Crop Science, North Carolina State University, 4310 Williams Hall Campus, Box 7620, Raleigh, NC 27695-7620, USA

3 Kearney Agricultural Research Center, University of California, Parlier, CA 93648, USA

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BMC Evolutionary Biology 2014, 14:149  doi:10.1186/1471-2148-14-149

Published: 3 July 2014

Abstract

Background

The relationship between allopolyploidy and plant virus resistance is poorly understood. To determine the relationship of plant evolutionary history and basal virus resistance, a panel of Nicotiana species from diverse geographic regions and ploidy levels was assessed for resistance to non-coevolved viruses from the genus Nepovirus, family Secoviridae. The heritability of resistance was tested in a panel of synthetic allopolyploids. Leaves of different positions on each inoculated plant were tested for virus presence and a subset of plants was re-inoculated and assessed for systemic recovery.

Results

Depending on the host-virus combination, plants displayed immunity, susceptibility or intermediate levels of resistance. Synthetic allopolyploids showed an incompletely dominant resistance phenotype and manifested systemic recovery. Plant ploidy was weakly negatively correlated with virus resistance in Nicotiana species, but this trend did not hold when synthetic allopolyploids were taken into account. Furthermore, a relationship between resistance and geographical origin was observed.

Conclusion

The gradients of resistance and virulence corresponded to a modified matching allele model of resistance. Intermediate resistance responses of allopolyploids corresponded with a model of multi-allelic additive resistance. The variable virus resistance of extant allopolyploids suggested that selection-based mechanisms surpass ploidy with respect to evolution of basal resistance to viruses.

Keywords:
Allopolyploidy; Grapevine fanleaf virus (GFLV); Nepovirus; Nicotiana; Resistance; Susceptibility; Tomato ringspot virus (ToRSV)