Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/30/2010
Publication Date: 2/1/2011
Citation: Cai, X., Spooner, D.M., Groves, R., Schramm, S., Jansky, S.H. 2011. A Test of Taxonomic and Biogeographic Predictivity: Resistance to Potato Virus Y in Wild Relatives of the Cultivated Potato. Phytopathology. 101(2):205-212. Interpretive Summary: It is commonly believed that if resistance to a disease is identified in a wild crop species, then resistance is also likely to be found in close relatives of that species. This concept guides breeders in the search for new sources of disease resistance. Similarly, information about the habitat in which a species is found may provide value in predicting the source of new resistance genes. This study was carried out to determine whether taxonomic or biogeographic data can be used to predict the distribution of genes for resistance to potato virus Y. There was no consistent association between potato virus Y resistance and taxonomic treatments of species. However, there was a much higher than expected proportion of resistant plants in accessions collected at elevations below 2100m. This relationship may be related to the distribution of aphids, which act as vectors for PVY. A search of low elevation species populations may reveal new sources of PVY resistance genes.
Technical Abstract: A major justification for taxonomic research is its assumed ability to predict the presence of traits in a group for which the trait has been observed in a representative subset of the group. Such predictors are regularly used by breeders interested in choosing potential sources of disease and pest resistant germplasm for cultivar improvement. We have previously undertaken a series of studies of resistance to white mold, early blight, Colorado potato beetle and soft rot to determine whether we can predict the distribution of valuable genes in wild Solanum species based on taxonomic or biogeographic data. In this study, we evaluated potato virus Y resistance using 135 accessions of 36 ingroup (sect. Petota) and two outgroup (sect. Etuberosum). Species and individual accessions with high proportions of plants with resistance to potato virus Y have been identified in this study, but tremendous variation for resistance to potato virus Y was found within and among species. There is no consistent association between potato virus Y resistance and taxonomic series (based on an intuitive interpretation of morphological data), clades (based on a cladistic analysis of plastid DNA data), ploidy, and breeding system. However, the correlation coefficient between endosperm balance number (EBN) and PVY resistance was -0.22 (P=0.01). The five species with the highest percentage of resistant plants were 1 EBN. A Chi-square test indicated that the 1 EBN species contain a higher percentage of resistant plants than expected based on the frequency of resistant plants (P=0.0012). Our study identified new germplasm with resistance to the potato virus Y, S. albornozii, S. andreanum, S. bukasovii, S. bulbocastanum, S. cardiophyllum, S. hjertingii, S. iopetalum, S. jamesii, S. kurtzianum, S. paucijugum, S. pinnatisectum, and S. schenckii. The correlation between resistance and elevation was high (-0.41) and significant (P<0.0001). A Chi-square analysis revealed that there was a much higher than expected proportion of resistant plants in accessions collected at elevations below 2100m ('2 = 20.4, P=0.000006). This relationship may be related to the distribution of aphids, which act as vectors for PVY.