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Title: Variation for tuber greening in the diploid wild potato Solanum microdontum

Author
item Bamberg, John
item MOEHNINSI, M - University Of Idaho
item Navarre, Duroy - Roy
item SURIANO, J - University Of Wisconsin

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2015
Publication Date: 5/1/2015
Citation: Bamberg, J., Moehninsi, M., Navarre, R., Suriano, J. 2015. Variation for tuber greening in the diploid wild potato Solanum microdontum. American Journal of Potato Research. 92(3):435-443.

Interpretive Summary: Potato is the most important vegetable crop in the US and world, but could be improved in many ways. Stocks in the US Potato Genebank have a great breadth of genetic diversity for traits, so provide opportunities for genetic improvement that may not exist in the potato crop breeding genepool. One such trait is the greening of potato tubers when they are exposed to light, either if they are not covered by soil in the field or when displayed by grocers. This causes a great deal of economic loss, since green tubers are not acceptable for fresh or processed eating. We found that the wild potato species S. microdontum varies greatly for greening. Tubers of some plants did not get green at all after light exposure that caused other plants' tubers to get very green. These extreme types should be very useful to studying the genetics and physiology of tuber greening, as well as for breeding the non-greening trait into new cultivars.

Technical Abstract: Greening of the tuber skin is an undesirable defect in fresh and processed potato. Tubers of 92 Solanum microdontum families represented by 12 individuals each were generated in the winter greenhouse in 2009-2010. These were evaluated in two trials of family bulks after four days of exposure to 200 ft candles of fluorescent white light at room temperature, similar to that observed in local grocery stores, and according to preliminary tests, able to turn some microdontum tubers very green. A qualitative score of green (G) or white (W) was assigned to each tuber. Tubers of about 10 % of families were scored as mostly W. In comparison, when 185 named Solanum tuberosum cultivars were illuminated in the same way, none from Europe or North America scored W. Two replicates of G and W individual tubers were selected from a variety of microdontum families and planted to create a new clonal generation of tubers. Those second generation daughter tubers showed a response to illumination which was consistent with that of the previous clonal generation. Finally, W and G clones were selected and mated to test heredity. All GxG hybrids were uniformly G, but only three WxW crosses produced families that were nearly uniformly W, suggesting W is recessive. Thus some selections were shown to have consistent non-greening over trials spaced in time, over a clonal generation, and, when crossed together produced pure non-greening progeny. On the other hand, several very green selections similarly were consistently very green over time, clonal regeneration, and intermating. Tests of tuber tissue for glycoalkaloids showed that some illuminated clones neither green nor accumulate glycoalkaloids. These materials would make good models for further study of genetics and physiology of the greening trait, and for breeding.