Genetic marker analysis in potato for extreme resistance (Rysto) to PVY and for chip quality after long term storage at 4°C

This dissertation reports the development of genetic markers associated with extreme resistance to PVY (Rysto) and QTL referring to chip quality after long term storage at 4°C, a qualitative and a quantitatively inherited trait of the potato. The markers for extreme resistance to PVY were established within a primary dihaploid mapping population composed of 57 anther culture-derived lines from the cultivar Assia having Ry immunity from S. stoloniferum and Rx immunity. The genetic constitution of extreme resistance to PVY of Assia could be assumed as simplex (Ryryryry), which results in an approximate segregation of dihaploids ratio of 28 resistant to 29 susceptible (Ry:ry) lines. Twelve Rysto AFLP markers were selected out of 480 selective primer combinations in AFLP assays (PstI/MseI, EcoRI/MseI) using Bulk Segregant Analysis. Nineteen potato cultivars (Alwara, Arosa, Assia, Bettina, Dania, Franzi, Forelle, Hinga, Jumbo, Klepa, Kuras, Meduza, Nimfy, Oktan, Petra, Sibu, Solara, Tomba and Ute) out of 110 tested potato cultivars from Germany, The Netherlands and Poland were detected by these markers as immune to PVY in alignment with very good phenotypic resistance data. According to linkage analysis, the Rysto resistance markers are not linked to chromosome XI in contrast to a previous publication (Brigenti et al., 1997) but linked to chromosome XII based on the reference map of Milbourne et al. (1998). According to genetic pedigree analysis, these cultivars are derived from MPI breeding lines (Ross, 1986) or other sources with S. stoloniferum background. Thirteen immune potato cultivars listed by Ross were also recorded in this pedigree. Chip color tests were performed from 1998 to 2001 with 83 dihaploid lines derived from the cultivar Artis having a good chip color after long term storage at 4°C. The chip color of the Artis dihaploid population showed continuous variation and correlated highly with glucose (r=-0.67) and fructose (r=-0.73) content. An F1 backcross population mode was applied to construct 57 linkage groups covering 2085 cM. Twenty-five linkage groups covering 1379 cM could be assigned to a distinct chromosome number with 2342 AFLP, 33 SSR and 18 RFLP in a simplex manner. In addition 6 linkage groups covering 336 cM could be identified by marker alignment with the Ultra High Density map. QTL analysis revealed that QTL for chip color, glucose and fructose after long term storage at 4°C scatter over 26 linkage groups. QTL explaining over 10 % of the variability for chip color, glucose and fructose content were located on chromosomes I, IV, VII, IX, XI and XII as a result of interval mapping. Five QTL mapped on chromosomes I, IV, VII and XI explained together 58.1 % of the phenotypic variance of chip color after long term cold storage at 4°C with a significance level of p<0.0015. All five QTL for glucose content mapped on the same positions as QTL for fructose content in agreement with the correlation results. Five QTL for glucose content explaining 48.7 % represented 43.9 % of the phenotypic variance for chip color and 49.1 % for fructose content. Eight QTL for fructose content explained 49.9 % of the phenotypic variance for chip color and 60.9 % for glucose content. In addition three QTL for starch content explained together 42.83 % of the phenotypic variance and were mapped to chromosomes I, IX and LG 9. Our results in QTL analysis of dihaploids showed that the reducing sugar content contributes to the genetic variation of chip color after long term storage at 4°C. Genetische Marker fur PVY-Immunitat (Rysto) und gute Chipsqualitat nach Langzeitlagerung von Knollen bei 4°C wurden uber AFLP-Analysen an primardihaploiden Kartoffelpopulationen der Sorten Assia (Antherenkultur) bzw. Artis (Solanum-phureja-Kreuzung) etabliert. Der Rysto-Locus konnte auf Chromosom XII lokalisiert werden. Markergestutzt wurden 19 von 110 verschiedenen Kartoffelsorten als PVY-immun eingestuft. Diese 19 Sorten sind als hochresistent eingestuft und auf drei verschiedene Genquellen mit S. stoloniferum-Abstammung zuruckzufuhren. Fur die QTL-Analysen zur Chipsqualitat wurde eine Chromosomkarte mit 57 Koppelungsgruppen und einem Umfang von 2085 cM erstellt. Die ermittelten QTL fur die Einzelmerkmale Chipsfarbe und Gehalt an reduzierenden Zuckern sind uber das gesamte Genom verteilt. Funf QTL auf den Chromosomen I, IV, VII und XI erklaren die Chipsfarbe mit einem Maximum an phanotypischer Varianz von 58,1%. Die entwickelten Marker konnen zur Selektion von Zuchtmaterial herangezogen werden.