Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 7, 2010
Publication Date: August 28, 2010
Citation: Mccord, P.H., Sosinski, B.R., Haynes, K.G., Clough, M.E., Yencho, G.C. 2010. QTL mapping of internal heat necrosis in tetraploid potato. Theoretical and Applied Genetics. 122:129-142.
Interpretive Summary: Internal heat necrosis (IHN) is a physiological disorder in potato tubers that is characterized by internal dark brown patches in susceptible potato varieties. There are no visual symptoms of IHN in intact tubers; symptoms are visible only when the tuber is cut. The severity of IHN also depends on environmental factors, namely, high temperatures during the later part of the potato growing season. The most popular potato chipping variety ‘Atlantic’ is extremely susceptible to IHN. In order to develop IHN-resistant potato varieties it would be helpful to identify the genes that confer resistance to IHN. In this research we used molecular techniques to develop markers for resistance to IHN and demonstrated the usefulness of two of these markers for tracking these genes in different potato populations. This will be used by potato breeders to breed IHN resistant potato cultivars.
Internal heat necrosis (IHN) is a physiological disorder of potato tubers. We developed a linkage map of tetraploid potato using AFLP and SSR markers, and mapped QTL for mean severity and percent incidence of IHN. Phentypic data indicated that the distribution of IHN is skewed toward resistance. Late foliage maturity was slightly but significantly correlated with increased IHN symptoms. The linkage map for 'Atlantic', the IHN-susceptible parent, covered 1034.4 cM and included 13 linkage groups, and the map for B1829-5, the IHN-resistance parent, covered 940.2 cM and contained 14 linkage groups. QTL for increased resistance to IHN were located on chromosomes IV, V, and groups VII and X of 'Atlantic', and on group VII of B1829-5 in at least two of three years. The QTL explained between 4.5 and 29.4% of the variation for mean severity, and from 3.7 to 14.5% of the variation for percent incidence. Most QTL detected were dominant, and associated with decreased IHN symptoms. One SSR and 13 AFLP markers that were linked on IHN were tested in a second population. One AFLP marker was associated with decreased symptoms in both populations. The SSR marker was not associated with IHN in the second population, but was closely linked in repulsion to another marker that was associated with IHN, and had the same (negative) effect on the trait as the SSR marker did in the first population. The correlation between maturity and IHN may be partially explained by the presence of markers on chromosome V that are linked to both traits. This research will benefit potato breeders in the development of IHN-resistant potato varieties and potato geneticists and physiologists in understanding the genetic basis of resistance to internal heat necrosis.