Search

Interploidal hybridisation can generate changes in plant chromosome numbers, which might exert effects additional to the expected due to genome merger per se (i.e., genetic, epigenetic and phenotypic novelties).Wild potatoes are suitable to address this question in an evolutionary context. To this end, we performed genetic (AFLP and SSR), epigenetic (MSAP), and cytological comparisons in: i) natural populations of the diploid cytotype of the hybrid taxonomic species Solanum x rechei (2n=2x, 3x) and its parental species, the triploid cytotype of Solanum microdontum (2n=2x, 3x) and Solanum kurtzianum (2n=2x); and ii) newly synthesised intraploidal (2x x 2x) and interploidal (3x x 2x) S. microdontum x S. kurtzianum hybrids.Aneuploidy was detected in S. x rechei and the synthetic interploidal progeny; this phenomenon might have originated the significantly higher number of methylation changes observed in the interploidal vs. the intraploidal hybrids. The wide epigenetic variability induced by interploidal hybridisation is consistent with the novel epigenetic pattern established in S. x rechei compared to its parental species in nature.These results suggest that aneuploid potato lineages can persist throughout the short term, and possibly medium term, and that differences in parental ploidy resulting in aneuploidy are an additional source of epigenetic variation. Fil: Cara, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Ferrer, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Masuelli, Ricardo Williams. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Camadro, Elsa Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; Argentina Fil: Marfil, Carlos Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina

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 4 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. All GxG hybrids were uniformly G, but only three WxW crosses produced families that were nearly uniformly W. 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 inheritance and physiology of the greening trait, and for breeding.

The aim of this study was to assess the effect of aluminum on the in vitro activity of acid phosphatases (APases) of four potato clones, Macaca and Dakota Rose (Al-sensitive), and SMIC148-A and Solanum microdontum (Al-tolerant), grown in vitro, in hydroponics or in a greenhouse. The enzyme was assayed in vitro in the presence of 0, 1.85, 3.70, 5.55 and 7.40 mM Al. In plantlets grown in vitro, root APases were inhibited by Al in all clones, while shoot APases were inhibited by Al in S. microdontum and Dakota Rose and increased in Macaca at all Al concentrations. In plantlets grown in hydroponics, root APases increased in Macaca at 1.85 mM Al, whereas decreased at all Al levels in S. microdontum. In greenhouse plantlets, root APases decreased at 7.40 mM Al in S. microdontum and SMIC148-A, and at 3.70, 5.55 and 7.40 mM Al in Dakota Rose. Shoot APases decreased in Macaca and SMIC148-A. Conversely, in Dakota Rose, APases increased at 1.85 and 3.70 mM Al. These results show that the effect of Al toxicity on in vitro APase activity depends not only on Al availability but also on the plant organ, genetic background, and the growth conditions. Therefore, it suggests that acid phosphatases activity assessed in vitro might not be a good parameter to validate the screening for adaptation of potato clones to Al toxicity.

Systemic acquired resistance (SAR) occurs in many plant species, including potato. SAR can be induced by various signals, but also basal levels of SAR may vary between plants. In Arabidopsis mutants, basal SAR levels positively correlate with pathogen resistance. Here we test whether in 13 wild Solanum clones and five potato cultivars, basal expression levels of SAR marker genes correlate with resistance to Phytophthora infestans. Most of the examinedSolanum plants displayed significant and variable levels of race/isolate-non-specific, partial resistance to five P. infestans isolates of diverse origin. Constitutive mRNA levels of the pathogenesis-related genes PR-1, PR-2 and PR-5 in non-infected leaves varied between the Solanum clones. However, no correlation between basalPR mRNA levels and resistance was observed at the genus level. In contrast, significant correlation was found at the species level in S. arnezii × hondelmannii, S. microdontum, S. sucrense and S. tuberosum. In S. tuberosum cultivars, the levels of PR gene expression were the highest in resistant Robijn, intermediate in partially resistant Premiere, Estima and Ehud, and the lowest in susceptible Bintje. These results suggest that constitutive expression of PR genes may contribute to non-specific resistance to P. infestans inSolanum . Therefore, PR mRNAs could serve as molecular markers in potato breeding programs.

The objective of this study was to evaluate the effects of aluminum (Al) on the zinc (Zn), manganese (Mn), iron (Fe) and copper (Cu) concentrations in four potato clones (Macaca and Dakota Rose: both Al-sensitive clones; and SMIC148-A and Solanum microdontum: both Al-tolerant-clones), grown in a nutrient solution (pH 4.00) with 0, 50, 100, 150 and 200mg Al L-1. Root Zn and Fe concentrations decreased linearly with the increase of Al levels in Macaca, SMIC148-A and Dakota Rose and increased linearly in S. microdontum. Shoot Zn concentration showed a quadratic relationship with Al in S. microdontum and SMIC148-A, but a curvilinear response in Dakota Rose. Shoot Fe concentration showed a quadratic relationship with Al in S. microdontum, SMIC148-A and Dakota Rose. Root Mn concentration decreased linearly in Macaca and SMIC148-A, and increased linearly in S. microdontum with Al levels. Mn concentration showed a quadratic relationship with Al in roots of Dakota Rose and in shoot of SMIC148-A, and increased curvilinearly with Al levels in shoot of Dakota Rose. In shoot, there was no alteration in Zn, Fe and Mn in Macaca and Mn concentration in S. microdontum. Roots and shoot Cu concentration increased linearly in Dakota Rose, and showed quadratic relationship with Al in Macaca. Roots Cu concentration showed a quadratic relationship with Al levels in S. microdontum and SMIC148-A. Shoot Cu concentration increased linearly in S. microdontum, and decreased linearly in SMIC148-A. Therefore, the excessive Al accumulation affected the uptake and distribution of Zn, Fe, Mn and Cu in roots and shoot of potato clones.The response of shoot Cu concentration to Al was less altered in the Al-tolerant clones than was in Al-sensitive clones. Aluminum tolerance in S. microdontum may be connected with greater levels of Zn, Fe and Mn in the roots.

The objective of this study was to evaluate the effects of aluminum (Al) on the zinc (Zn), manganese (Mn), iron (Fe) and copper (Cu) concentrations in four potato clones (Macaca and Dakota Rose: both Al-sensitive clones; and SMIC148-A and Solanum microdontum: both Al-tolerant-clones), grown in a nutrient solution (pH 4.00) with 0, 50, 100, 150 and 200mg Al L-1. Root Zn and Fe concentrations decreased linearly with the increase of Al levels in Macaca, SMIC148-A and Dakota Rose and increased linearly in S. microdontum. Shoot Zn concentration showed a quadratic relationship with Al in S. microdontum and SMIC148-A, but a curvilinear response in Dakota Rose. Shoot Fe concentration showed a quadratic relationship with Al in S. microdontum, SMIC148-A and Dakota Rose. Root Mn concentration decreased linearly in Macaca and SMIC148-A, and increased linearly in S. microdontum with Al levels. Mn concentration showed a quadratic relationship with Al in roots of Dakota Rose and in shoot of SMIC148-A, and increased curvilinearly with Al levels in shoot of Dakota Rose. In shoot, there was no alteration in Zn, Fe and Mn in Macaca and Mn concentration in S. microdontum. Roots and shoot Cu concentration increased linearly in Dakota Rose, and showed quadratic relationship with Al in Macaca. Roots Cu concentration showed a quadratic relationship with Al levels in S. microdontum and SMIC148-A. Shoot Cu concentration increased linearly in S. microdontum, and decreased linearly in SMIC148-A. Therefore, the excessive Al accumulation affected the uptake and distribution of Zn, Fe, Mn and Cu in roots and shoot of potato clones.The response of shoot Cu concentration to Al was less altered in the Al-tolerant clones than was in Al-sensitive clones. Aluminum tolerance in S. microdontum may be connected with greater levels of Zn, Fe and Mn in the roots. O objetivo deste estudo foi caracterizar o efeito do alumínio (Al) na concentração de zinco (Zn), manganês (Mn), ferro (Fe) e cobre (Cu) em quatro clones de batata (Macaca e Dakota Rose: sensíveis ao Al; e SMIC148-A e Solanum microdontum: tolerantes ao Al) crescendo em solução nutritiva (pH 4,0) com 0, 50, 100, 150 e 200mg Al L-1. A concentração de Zn e Fe em raízes diminuiu linearmente com o aumento dos níveis de Al nos clones Macaca, SMIC148-A e Dakota Rose e aumentou linearmente em S. microdontum. Na parte aérea, a concentração de Zn mostrou resposta quadrática ao Al em S. microdontum e SMIC148-A, enquanto no clone Dakota Rose houve uma resposta cúbica. Nos clones S. microdontum, SMIC148-A e Dakota Rose, a concentração de Fe mostrou resposta quadrática ao Al. A concentração de Mn em raízes diminuiu linearmente em relação ao Al nos clones Macaca e SMIC148-A e aumentou linearmente em S. microdontum. Para Dakota Rose e SMIC148-A, a concentração de Mn mostrou uma resposta quadrática em relação ao Al em raízes e parte aérea. A concentração de Mn na parte aérea aumentou de forma cúbica com os níveis de Al no clone Dakota Rose. Na parte aérea, não houve alteração na concentração de Zn e Fe na Macaca e de Mn nos clones Macaca e S. microdontum. Em raízes e na parte aérea, a concentração de Cu aumentou linearmente no clone Dakota Rose e mostrou resposta quadrática no clone Macaca. A concentração de Cu mostrou resposta quadrática com os níveis de Al em raízes dos clones S. microdontum e SMIC148-A. Na parte aérea, a concentração de Cu aumentou linearmente no clone S. microdontum e diminuiu linearmente no clone SMIC148-A com o aumento nos níveis de Al. Portanto, a acumulação excessiva de Al afetou negativamente a absorção e a distribuição de Zn, Fe, Mn e Cu nas raízes e na parte aérea dos clones de batata. A resposta da concentração de Cu na parte aérea ao Al foi menos alterada nos clones Al-tolerantes que naqueles Al-sensíveis. A tolerância ao Al em S. microdontum pode estar conectada com os maiores níveis de Zn, Fe e Mn nas raízes.

Numerous pathogens can infect potato, but late blight (Phytophthora infestans (Mont.) de Bary) and potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida are most damaging. Several species of root knot nematodes (RKN) are an emerging threat. Breeders have successfully deployed disease resistance genes (R-genes) to protect potato from diseases, starting from the first half of the 20th century. DNA markers facilitate the introgression of R-genes and enable the pyramiding of multiple R-genes in a potato cultivar. Pyramiding may improve the level of resistance, the resistance spectrum and the durability of the resistance. In this thesis, the experimental work is described in four chapters. Two chapters focus on the identification, mapping and characterisation of late blight and nematode resistance genes. The other two chapters focus on the pyramiding of R-genes to achieve something more in terms of resistance than was offered by the individual R-genes. In Chapter 2, a locus involved in late blight resistance, derived from Solanum microdontum, was identified and characterised. The resistance is associated with a hypersensitive response and results in a delay of infection of about 1-2 weeks. Both a quantitative as well as a qualitative genetic approach was used, based on data from a field assay. QTL analysis identified a QTL on chromosome 4. A qualitative genetic analysis resulted in the positioning of this locus on the short arm of chromosome 4. This position coincides with a conserved Phytophthora R-gene cluster which includes R2, R2-like, RPi-blb3 and RPi-abpt. This strongly suggests that RPi-mcd1 is the fifth R-gene of this NBS-LRR cluster. In Chapter 3, two resistance genes, RPi-mcd1 and RPi-ber, introgressed from the wild tuber bearing potato species S. microdontum and S. berthaultii were combined in a segregating diploid S. tuberosum population. Individual genotypes from this segregating population were classified into four groups by means of flanking molecular markers; carrying no R-gene, with only RPi-mcd1, with only RPi-ber, and a group with the pyramided RPi-mcd1 and RPi-ber. The levels of resistance between the groups were compared in a field experiment in 2007. The group with RPi-mcd1 showed a significant delay to reach 50% infection of the leaf area of three days. The group with RPi-ber showed a delay of three weeks. The resistance level in the pyramid group suggested an additive effect of RPi-mcd1 with RPi-ber. This result suggests that potato breeding can benefit from combining individual R-genes. In Chapter 4, a resistance to G. pallida Rookmaker (Pa3), originating from wild species S. tarijense was identified by QTL analysis. The resistance could largely be ascribed to one major QTL. GpaXIltar explained 81.3 % of the phenotypic variance in the disease test and mapped to the long arm of chromosome 11. Another minor QTL explained 5.3 % of the phenotypic variance and mapped to the long arm of chromosome 9. Clones containing both QTL showed no lower cyst counts than clones with only GpaXIltar. After Mendelising the phenotypic data, GpaXIltar could be more precisely mapped near markers GP163 and FEN427 thus anchoring GpaXIltar to a region with a known R-gene cluster containing virus and nematode resistance genes. In Chapter 5, a study is described that tests if pyramiding of two resistance genes against the root knot nematode Meloidogyne hapla, RMh-tar and RMh-chcA , will result in improved, or even an absolute level of resistance. RMh-tar and RMh-chcA, introgressed from the wild tuber bearing potato species Solanum tarijense and S. chacoense were combined in a segregating diploid S. tuberosum population. With the aid of markers, descendants from this segregating population were classified into four groups, carrying no R-gene, with only RMh-tar, with only RMh-chcA, and a group with the pyramided RMh-tar and RMh-chcA. Upon inoculation with M. hapla isolate Bovensmilde, the group containing only RMh-chcA showed a decline of 88 % in average developed egg masses compared to the group without RMh-chcA and RMh-tar. The group of genotypes containing only RMh-tar, but not RMh-chcA, showed a decline of 55% in developed egg masses compared to the group without RMh-chcA and RMh-tar. The effect of both loci, RMh-tar and RMh-chcA combined, did not further reduce the number of egg masses compared to the level of RMh-chcA alone. The study presented in this thesis shows that marker assisted selection is a very powerful method and sometimes the only way to screen for the presence of certain genes. It furthermore shows that pyramiding different resistance genes, even with minor effects, can result in plants with an increased level of resistance.

Numerous pathogens can infect potato, but late blight (Phytophthora infestans (Mont.) de Bary) and potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida are most damaging. Several species of root knot nematodes (RKN) are an emerging threat. Breeders have successfully deployed disease resistance genes (R-genes) to protect potato from diseases, starting from the first half of the 20th century. DNA markers facilitate the introgression of R-genes and enable the pyramiding of multiple R-genes in a potato cultivar. Pyramiding may improve the level of resistance, the resistance spectrum and the durability of the resistance. In this thesis, the experimental work is described in four chapters. Two chapters focus on the identification, mapping and characterisation of late blight and nematode resistance genes. The other two chapters focus on the pyramiding of R-genes to achieve something more in terms of resistance than was offered by the individual R-genes. In Chapter 2, a locus involved in late blight resistance, derived from Solanum microdontum, was identified and characterised. The resistance is associated with a hypersensitive response and results in a delay of infection of about 1-2 weeks. Both a quantitative as well as a qualitative genetic approach was used, based on data from a field assay. QTL analysis identified a QTL on chromosome 4. A qualitative genetic analysis resulted in the positioning of this locus on the short arm of chromosome 4. This position coincides with a conserved Phytophthora R-gene cluster which includes R2, R2-like, RPi-blb3 and RPi-abpt. This strongly suggests that RPi-mcd1 is the fifth R-gene of this NBS-LRR cluster. In Chapter 3, two resistance genes, RPi-mcd1 and RPi-ber, introgressed from the wild tuber bearing potato species S. microdontum and S. berthaultii were combined in a segregating diploid S. tuberosum population. Individual genotypes from this segregating population were classified into four groups by means of flanking molecular markers; carrying no R-gene, with only RPi-mcd1, with only RPi-ber, and a group with the pyramided RPi-mcd1 and RPi-ber. The levels of resistance between the groups were compared in a field experiment in 2007. The group with RPi-mcd1 showed a significant delay to reach 50% infection of the leaf area of three days. The group with RPi-ber showed a delay of three weeks. The resistance level in the pyramid group suggested an additive effect of RPi-mcd1 with RPi-ber. This result suggests that potato breeding can benefit from combining individual R-genes. In Chapter 4, a resistance to G. pallida Rookmaker (Pa3), originating from wild species S. tarijense was identified by QTL analysis. The resistance could largely be ascribed to one major QTL. GpaXIltar explained 81.3 % of the phenotypic variance in the disease test and mapped to the long arm of chromosome 11. Another minor QTL explained 5.3 % of the phenotypic variance and mapped to the long arm of chromosome 9. Clones containing both QTL showed no lower cyst counts than clones with only GpaXIltar. After Mendelising the phenotypic data, GpaXIltar could be more precisely mapped near markers GP163 and FEN427 thus anchoring GpaXIltar to a region with a known R-gene cluster containing virus and nematode resistance genes. In Chapter 5, a study is described that tests if pyramiding of two resistance genes against the root knot nematode Meloidogyne hapla, RMh-tar and RMh-chcA , will result in improved, or even an absolute level of resistance. RMh-tar and RMh-chcA, introgressed from the wild tuber bearing potato species Solanum tarijense and S. chacoense were combined in a segregating diploid S. tuberosum population. With the aid of markers, descendants from this segregating population were classified into four groups, carrying no R-gene, with only RMh-tar, with only RMh-chcA, and a group with the pyramided RMh-tar and RMh-chcA. Upon inoculation with M. hapla isolate Bovensmilde, the group containing only RMh-chcA showed a decline of 88 % in average developed egg masses compared to the group without RMh-chcA and RMh-tar. The group of genotypes containing only RMh-tar, but not RMh-chcA, showed a decline of 55% in developed egg masses compared to the group without RMh-chcA and RMh-tar. The effect of both loci, RMh-tar and RMh-chcA combined, did not further reduce the number of egg masses compared to the level of RMh-chcA alone. The study presented in this thesis shows that marker assisted selection is a very powerful method and sometimes the only way to screen for the presence of certain genes. It furthermore shows that pyramiding different resistance genes, even with minor effects, can result in plants with an increased level of resistance.

Current taxonomic interpretations of Solanum microdontum BITTER partition the species into two or three infraspecific taxa, variously recognized as subspecies or varieties. The present study reexamines these taxa using morphological data from four individuals each of 69 accessions from most of the range of the species, planted in a common field plot. Our results show that the character states used to recognize infraspecific taxa in S. microdontum often vary within accessions and have no correlation with geography. We conclude that past hypotheses have used typological concepts and that infraspecific taxa are not warranted. This study questions other hypotheses of infraspecific taxa in sect. Petota. Solanum microdontum BITTER is a highly variable species distributed from northern Bolivia (La Paz Prov.) to northwestern Argentina (La Rioja Prov.). It is a member of sect. Petota, a group of 232 species (as interpreted by HAWKES 1990) related to the cultivated potato. The species is self-incompatible and diploid (2n = 2x = 24), except for some scattered triploid cytotypes in the southern part of the range in Argentina (OKADA 1981). Many populations of S. microdontum are distinguished by entire leaves, but intra- and interpopulational variability encompasses morpho- types with pinnately-dissected leaves more similar to those of other wild species. This variability has been partitioned into six species, three subspecies, and six varieties, but current classifications reduce this variability to one species with two subspecies: subsp, microdontum and subsp, gigantophyllum (BITTER) HAWKES & HJERT. (HAWKES 1990; Table 1) or three varieties, vat. microdontum, var. metrio- phyllum BITTER, and var. montepuncoense OCHOA (OCHOA 1990). Var. microdontum and var. metriophyllum are equivalent nomenclaturally to subsp, mierodontum and subsp, gigantophyllum, respectively; var. montepuncoense is distinct, and is a possible interspecific hybrid (see below). This study investigates the morphological and geographical patterns of variability in S. microdontum to find if infraspecific taxa are warranted.