Cytoplasmic substitution inSolanum. II. Tuber characteristics of reciprocal backcross progeny

Summary Recurrent backcrosses (BC) were used to introduce nuclear factors ofS. tuberosum L. ssp.tuberosum into the cytoplasm of Andean potatoesS. tuberosum ssp.andigena (Juz. and Buk.) Hawkes andS. phureja Juz. and Buk. Each generation BC was produced in reciprocal directions to test the effect of cytoplasmic substitution on yield. This report analyses tuber number, tuber weight, and tuber length of BC₂ and BC₃ substitution into ssp.andigena cytoplasm and BC₂ and BC₂ substitutions intoS. phureja cytoplasm. Direction of cross had no consistent significant effect on yield components of ssp.andigena substitution lines. InS. phureja reciprocal progenies direction of cross was responsible for significant differences of some reciprocal sets. When there were significant differences the higher yield usually occurred when ssp.tuberosum was the pistillate parent, but in some progenies when ssp.tuberosum was the pistillate parent the yield was significantly lower than in the reciprocals. It is suggested that differences between reciprocals resulted from chromosomally encoded gene action, resulting from maternal and/or paternal effects, rather than cytoplasmic factors. Authorized for publication as paper No. 7494 in the Journal Series of The Pennsylvania Agriculture Experiment Station.     

Cytoplasmic evaluations during substitution backcrossing inSolanum

Summary Sterility-resistant cytoplasmic factors ofSolanum tuberosum spp.andigena (Juz. & Buk.) Hawkes and ofSolanum phureja (Juz. & Buk.) were combined with chromosomal genes ofS. tuberosum ssp.tuberosum. Eleven morphological characters of reciprocal F₁ and BC₁ progenies were monitored to evaluate rate of progression towards characteristics occurring in the recurrent ssp.tuberosum parent. Female and male fertilities of F₁ and BC₁ populations were also evaluated. Cytoplasmic factors did not influence morphological parameters consistently, except those relating directly to fertility. Differences between reciprocal progeny depended more upon the genes of individual parents used in crosses than on cytoplasm source. No consistent reciprocal differences occurred in tuber characters and those differences which arose seem to reflect a maternal rather than a cytoplasmic influence. F₁ and BC₁ progenies containing the sterility-resistant cytoplasmic factors of ssp.andigena or ofS. phureja had higher fertility than their respective reciprocal progenies with cytoplasm of ssp.tuberosum. Pennsylvania Agricultural Experiment Station Journal Series No 6212.     

Some studies on the distribution and incidence of potato mop-top virus in Peru

Symptoms of PMTV are distributed widely in potatoes in the highlands (Andes) of Peru, but have not been found in coastal plantings; they were observed in 9 out of 22 Peruvian Departments. Incidences of over 10% of affected plants in one or more crops were found in 14 different localities. Thirteen cultivars with symptoms were observed, 9 wereSolanum tuberosum subsp.andigena Juz. & Buk., 3 were hybrids ofS. tuberosum subsp.andigena xS. tuberosum subsp.tuberosum L orS. Curtilobum Juz. & Buk. and 1 wasS. juzepczukii Buk. Symptoms were also seen in 29 clones of the potato germplasm collection of the International Potato Center. Distribution and prevalence of PMTV in Peru appear to be related to those rainfall and temperature conditions that favour its fungus vectorSpongospora subterranea (Wallr.) Lagerh.     

Evolutionary pathway of T-type Chloroplast DNA in potato

Potato was domesticated in the Andes of South America. However, the presently worldwide-grown potato (Solanum tuberosum L. ssp.tuberosum, 2n=4x=48) has characteristic T-type chloroplast DNA that was introduced after late blight epidemics in the mid-19th century from the Chilean potato (2n=4x=48) grown in the southern coastal regions in Chile. Among many wild potato species, the same chloroplast DNA was found only in some populations of a diploid speciesS. tarijense Hawkes (2n=2x=24), which ranges from central Bolivia to northwest Argentina. To elucidate an evolutionary pathway of T-type chloroplast DNA fromS. tarijense to Chilean potato, 215 accessions ofS. stenotomum Juz. et Buk., considered to be the most primitive, diploid cultivated potato species, from which all the Andean cultivated species evolved, and 286 accessions of the most widely grown, Andean tetraploid cultivated speciesS. tuberosum L. ssp.andigena Hawkes (2n=4x=48) were examined in this study. No accession ofS. stenotomum had T-type chloroplast DNA, while nine accessions, mostly from northwest Argentina, ofS. tuberosum ssp.andigena had T-type chloroplast DNA. Therefore, I conclude that some populations ofS. tarijense having T-type chloroplast DNA were naturally crossed as female withS. tuberosum ssp.andigena from which the Chilean potato was selected.     

Foliage resistance toPhytophthora infestans (Mont.) de Bary in the Ecuadorian natinal collection ofSolanum phureja ssp.phureja Juz. & Buk

Summary The Ecuadorian national collection ofS. phureja ssp.phureja Juz. & Buk. was evaluated in two parts in consecutive years in the field for resistance toPhytophthora infestans (Mont.) de Bary. Levels of resistance higher than that of the moderately-resistant tetraploid control were found. Preliminary studies indicate that this resistance is a result of minor genes. Three components of resistance: lesion diameter, lesion number and latent period were all correlated with field resistance as measured by the area under the disease progress curve.     

Male sterility and 2n pollen in 4x progenies derived from 4x×2x and 4x×4x crosses in potatoes

Summary The objectives of these experiments were to evaluate male sterility (MS) and 2n pollen frequency in 77 4x×2x families and 26 4x×4x families. The 2x parents were haploid-species hybrids and the 4x parents mainly clones withS. tuberosum ssp.tuberosum (tbr) andS. tuberosum ssp.andigena (adg) in their genetic background. The female parents had different cytoplasms: adg, tbr,S. demissum (dms), andS. stoloniferum (sto). Families from female parents with adg or dms cytoplasm did not have MS plants. However, families derived from crosses of many tbr females with 2x hybrids and a 4x adg clone had a high percentage of MS plants; all the progenies from cv. Serrana (sto cytoplasm) possessed tetrad sterility. These results can be explained as due to an interaction between a dominant male sterility (Ms) gene with tbr and sto cytoplasms. Some MS 4x hybrids (tbr×adg) used as females had the Ms gene, but male fertility was restored in some plants of their progenies when they were crossed with 4x tbr clones. This indicates that some tbr clones have a fertility restorer gene (Rt). The results from both 4x×2x and 4x×4x families fit the expected ratios assuming chromatid segregation for both the Ms and Rt loci. The gene frequency of parallel spindles was estimated in the 4x population as 0.74.     

Acaphu: A tetraploid,fertile breeding line,selected from anS. acaule ×S. phureja cross

An artificial, fertile breeding line was obtained by crossingS. acaule, Bitter toS. phureja Juz et Buk. It has 2n = 48 chromosomes and was formed by fertilization ofS. acaule eggs (n = 24) andS. phureja pollen grains (2n = 24). It possesses valuable characters ofS. acaule andS. phureja combined, and is highly male and female fertile, producing abundant seed by selfing or by crossing to tetraploid, cultivated potato clones. Since it is tetraploid and easy to cross, it is expected to be more efficient for transferring valuable genes fromS. acaule to cultivars than the natural, well known, hybridogenic speciesS. ×juzepczukii (2n = 36) and S. ×curtilobum (2n = 60).     

Seed protein variation within accessions of wild and cultivated potato species and inbredSolanum chacoense

Summary Soluble proteins in seed potato were analyzed by electrophoresis (PAGE). The Index of Variation (IV) was calculated in order to estimate variation within each accession of wild and cultivated potato species andS. chacoense selfed lines. Seeds of 34 accessions representing 14 species from six taxonomic series were analyzed. The IV ofS. chacoense selfed lines decreased from 47.7 in the S₂ to 12.9 in the S₇ generation. The average IV for the self-incompatible diploid species was 41.2, whereas that of the selfcompatible diploid species,S. polyadenium, was 21.3. TetraploidS. tuberosum ssp.andigena andS. sucrense had an average IV of 62.2, which is much higher than that observed in any other diploid species. The naturally selfing speciesS. acaule (4x), and its colchicine-doubled derivative (8x), showed very low variation (IV=7.5). The IV appears to reflect heterozygosity and is affected by the breeding mode and the genetic constitution of diploid parents for derived polyploids.     

Pollen-pistil incompatibility in a diploid hybrid potato population with cultivated and wild germplasm

The basis of low seed set was investigated in a diploid hybrid population with germplasm from the cultivated speciesSolanum tuberosum spp.tuberosum andS. tuberosum ssp.phureja and the wild speciesS. chacoense. Controlled crosses were performed following an incomplete diallel mating design which included the hybrid population and the parental species. Pollen grain germination and pollen tube growth were observed with fluorescence microscopy in 174 intrapopulation and interspecific combinations of genotypes. Fifty percent of the combinations of genotypes within the hybrid population and 46% of those between this population and the parental species were incompatible; overall, 71% of the interspecific combinations of genotypes were compatible when plants of the hybrid population were used as females, vs. 5% when used as males. Although the site of reaction could vary in a given intrapopulation or interspecific cross with the combinations of genotypes, pollen tube inhibition occurred in the first third of the style in 42% of them. Since the gene pool of the hybrid population had been widened with germplasm from other geographic areas and the genotypes ofS. tuberosum ssp.tuberosum, S. chacoense andS. tuberosum ssp.phureja used in this study were not the ones involved in the original crosses, it is concluded that the S-locus is not controlling the incompatibility reaction but rather that a cross-incompatibility system, possibly governed by more than one locus, is acting.     

Component analysis of general resistance toPhytophthora infestans in clones from the Colombian potato collection

Summary Studies on the level of resistance to entrance and resistance to invasion within leaves indicated that the best genotypes in the Colombian material reached the level of cv. Record. No significant differences in resistance were found betweenS. tuberosum ssp.andigena andS. phureja clones. Resistance to entrance and resistance to invasion were correlated.

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Zusammenfassung Von 29 S?mlingen, die aus Selbstbefruchtung von 12 verschiedenen Klonen hervorgingen, wurden zwischen ein und fünfzehn Pflanzen auf Resistanz gegen das Eindringen und auf Resistenz gegen das Ausbreiten derPhytophthora infestans ins Blattwerk untersucht (Tablle 1). Die beiden Komponenten der Blattresistenz waren korreliert (r=0,63^***, Abb. 1). Keine signifikanten Unterschiede wurden im Ausmass der Blattresistenz zwischen den Klonen vonS. tuberosum ssp.andigena undS. phureja gefunden. Ein Vergleich mit den Feldresistenz-Standards zeigte, dass nur die besten Genotypen der kolumbianischen Kollektion den von der Sorte Record erbrachten mittleren Resistenzgrad erreichten (Tabelle 2).

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Résumé Une à quinze plantes, issues de 29 plants provenant de l'auto-pollinisation de 12 cl?nes différents ont été testées pour leur résistance à l'invasion du feuillage (tableau 1). Les 2 composants de la résistance foliaire sont corrélés (r=0,63^***, fig. 1). Aucune différence significative n'a été trouvée dans les niveaux de résistance foliaire entre les cl?nes deS. tuberosum ssp.andigena etS. phureja. Une comparaison avec les témoins de référence résistants au champ indique que seulement les meilleurs génotypes des collectes de Colombie atteignent le niveau moyen de résistance de la variété Record (tableau 2).

     

Use of RAPD markers in potato genetics: Segregations in diploid and tetraploid families

The objective of the present study was to evaluate random amplified polymorphic DNA (RAPD) as a source of markers for use in investigations in potato genetics. Segregation of 18 loci in diploidSolanum goniocalyx xS. phureja and 12 loci in tetraploidS. tuberosum ssp.tuberosum ×S. tuberosum ssp.andigena families fitted Mendelian and tetrasomic ratios, respectively. Eight loci in the diploid progeny were arranged in three linkage groups. Segregations of these markers fitting expected ratios indicate that they can be effectively used in potato genetics, breeding and evolution.     

Relative Braunfäuleresistenz beiSolanum tuberosum ssp.andigena

Zusammenfassung Ergebnisse systematischer Prüfung auf relative Resistenz der Knollen von 1274 Herkünften der ssp.andigena (adg) genenüberPhytophthora infestans werden mitgeteilt. Die Methode des Kn?llchenstestes erm?glichte dabei das Eindringen des Pilzes direkt ins Knollenmark oder über die intakte Schale. Nur etwa 1% der Herkünfte enthielt einen Anteil von >25% Idiotypen mit gutem Resistenzniveau. Eine Analyse der Fundorte ergab keine Anhaltspunkte für die gezielte Suche von Resistenzquellen. Ergebnisse aus der züchterischen Nutzung von adg betreffen die ph?notypische Resistenz der Nachkommen und weitere Merkmale.

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Summary Results are reported of late blight resistance inS. tuberosum ssp.andigena (adg) and its use in breeding. Tests were carried out on material of the gene bank in Gross Lüsewitz (GLKS). Seedlings were cultivated under glass cover in a 6-years test period. To examine tuber resistance toPhytophthora infestans the following test was set up: 2–5 tubers per idiotype, up to 8 idiotypes per accession and year of test were taken and 1274 different accessions were examined with an average number of 23 idiotypes and 59 tubers from each. Inoculation was made by fresh deep cuts to the pith and by subsequent immersion in a solution of zoospores, 6–9×10⁴ ml⁻¹ with a mixture of the pathotypes (1.2.3.4.5.7.10.11, 1.2.3.4.7.8.10 and 1.2.3.4) at a temperature of 16–18°C and at an air humidity of >90%. Evaluation of the presence of aerial mycelium and browning after 7 days allowed the calculation of a resistance score (B_K): grade 9 (highly resistant) to grade 1 (highly susceptible). The mean values derived from the accessions (Fig. 1) revealed that a medium level of susceptibility is dominating and that they rarely exceed average levels of cultivars. Approximately 1% of the accessions contained ≥25% of idiotypes with B_K ≥6 and these may be interesting for breeding purposes. Table 1 shows the analysis of accessions with the most favourable mean values. Geographic evaluation did not yield indications for a more purposeful search for sources of resistance, since detailed reports on find-spots were missing (Table 2). Combination tests withPhytophthora-resistant genes of adg for crosses of adg withS. demissum (dms) andS. stoloniferum (sto) proved to be more useful as they partly showed good heritable resistance to haulm and tuber infection ofP. infestans (Table 3). The problem of the possible role of unknown r-genes is discussed. Only a few crosses with ssp.tuberosum (tbr) generated a progeny with sufficient resistance. Selection from such progeny over several years resulted after the second year in rejections, mainly because of susceptibility for viruses, too small tubers and lack of flowering (Table 4). Results of varietal research of the former German Democratic Republic proved that with the use of suitable parents in breeding for nematode resistance,Phytophthora susceptibility from adg could be balanced off (Table 5). The cultivar Auralia is a good example of the importance of adg in achieving a high level of resistance to late blight.

     

Disease resistance inSolanum phureja and diploid and tetraploidS. tuberosum × S. phureja hybrids

Summary DiploidSolanum phureja, diploid and tetraploidS. tuberosum × S. phureja hybrid, and tetraploidS. tuberosum backcross clones were assessed for resistance to commercially important diseases. There was a reduction in the expression ofS. phureja characteristics with increasing dosage ofS. tuberosum genetic material. The generally high resistance of theS. phureja group to common scab, potato leafroll virus and potato virus Y decreased, while resistance to gangrene, foliage and tuber blight tended to increase. Resistance genes were probably well dispersed throughout theS. phureja genotype so that many were lost on hybridisation, butS. phureja could be a useful source of scab and virus resistance in the production ofS. tuberosum cultivars.     

普通小麦/山羊草属间杂交F_1的形态学及细胞遗传学研究

为了解普通小麦与山羊草属的杂交F1代的育性、细胞遗传学表现及育种利用潜力,以普通小麦7182和丰优1718为母本,分别以卵穗山羊草SY163和离果山羊草SY119为父本进行杂交,对杂交F1代的生育特性、染色体构型、田间条锈病抗性、F1自交和回交结实性等进行了分析。结果表明,F1代植株生长势较强,株型倾向母本,成熟期穗子易断,壳硬;杂交F1代高度不育,花粉可育率1.26%~3.54%,回交结实率2.08%~5.26%,仅普通小麦/卵穗山羊草自交结实,但结实率最高仅为0.25%。7182/SY163、7182/SY119、丰优1718/SY163、丰优1718/SY119杂交F1代花粉母细胞减数分裂中期I的染色体构型平均分别为31.11I+1.90II+0.03III、20.04I+7.45II+0.02III、30.08I+2.40II+0.04III、22.37I+6.30II+0.01III,说明普通小麦与2种山羊草杂交亲和性差,且可交配性主要由山羊草基因决定。田间条锈病抗性鉴定结果显示,F1代均对条锈菌混合小种高抗或免疫,这对于丰富小麦抗病基因资源有重要意义。     

Molecular Mapping of Sterility QTLs qSS-3, qSS-6a and qSS-7 as Single Mendelian Factors via NIL strategy

Hybrid sterility between Oryza glaberrima and O. sativa seriously hampers the introgression of favorable genes from each other. In order to further understand this issue, identification and isolation of hybrid sterility QTLs as single Mendelian factors are an effective strategy. A genetic map was constructed using a BC₁F₁ population derived from a cross between an O. sativa japonica cultivar and an O. glaberrima accession. Four main-effect QTLs for pollen sterility were detected in the BC₁F₁. Five BC₈F₁ advanced backcross populations were developed via successive backcrosses based on phenotype and molecular selections. The BC₈F₁ populations showed bimodal distribution for pollen fertility and could be classified into semi-sterile and fertile types, fitting single Mendilian factor inheritance ratios. Three QTLs detected in the BC₁F₁ corresponding to qSS-3, qSS-6a and qSS-7 were mapped on chromosomes 6, 3 and 7, respectively, as single Mendilian factors.     

The geographical distribution,inheritance and pest-resisting properties of sticky-tipped foliar hairs on potato species

Summary Near Cochabamba in Bolivia, plants ofSolanum berthaultii with sticky-tipped foliar hairs only have been collected but further south near Sucre, both sticky-tipped and pointed-tipped forms of this species and ofS. tarijense occur. Further south still, in Tarija, and in the border region of Argentina, only pointed-tippedS. tarijense has been collected but at Salta sticky-tippedS. tarijense has been found. InS. tarijense andS. herthaultii, the presence of sticky-tipped hairs (for which an aqueous fluoroscein solution is a selective stain) on adult foliage is controlled by a single dominant gene: plants with this character were more resistant to the aphidMyzus persicae and to the miteTetranychus urticae, and trapped more of the thripsThrips tabaci. In addition to the dominant gene, at least one set of recessive genes was needed for the full expression of this character in crosses withS. phureja and withS. tuberosum ev. Pentland Crown.T. urticae were trapped on second-generationS. tuberosum × berthaultii with this type of hair. Part of this work was done at the International Potato Center (CIP), Apartado 5969, Lima, Peru.     

The male fertility of primary and further generation dihaploids ofSolanum tuberosum

Summary Male sterility in dihaploids ofSolanum tuberosum is often a barrier to their utilization in breeding and genetical studies. Although the male fertility of primary dihaploids (obtained directly from tetraploids) was generally low, a few were produced by the author which produced seed when used as pollen parents on female fertile dihaploids. The population of further generation dihaploids (from dihaploid intercrosses) produced from the showed a marked improvement in male fertility. Comparative data from measurements of different aspects of male fertility in dihaploids are presented. These showed that the weight of pollen per anther, the percentage of (iodine) stainable pollen and the number of seeds per berry were greater in further generation dihaploids than in primary dihaploids. It is suggested that interspecific crosses using dihaploids are not necessarily useful for increasing male fertility in diploid potatoes. The advantages of breeding at the diploid level withinS. tuberosum are discussed. Rare male-fertile dihaploids could be used to generate diploids with a high frequency of male fertility. These could then be used to cross with any other flowering dihaploids to combine characters at the diploid level, so exploiting the simpler genetic ratios associated with disomic inheritance.     

Crossability of some green-peach-aphid-resistant tuber-bearing solanums,potential bridging species,andSolanum tuberosum ssptuberosum

Blue light fluorescence microscopy was found to be a quick and easy procedure for assessing pollen tube development in interspecific pollinations ofSolanum. Based on penetration of pollen tubes to the base of the style, several combinations of green-peach-aphid-resistant species and potential bridging species to S.tuberosum ssp.tuberosum should be considered for embryo culture. Sterile or highly infertile hybrids were obtained between green-peach-aphid-resistantS. tuquerrense andS. tuberosum ssp.tuberosum and are described. Slightly fertile hybrids were obtained betweenS. tuquerrense andS. polytrichon, a species compatible withS. tuberosum ssp.tuberosum.     

T-type chloroplast DNA inSolarium tuberosum L. ssp.tuberosum was conferred from some populations ofS. tarijense Hawkes

The highly heterozygous and tetraploid nature of potato (Solanum tuberosum L. ssp.tuberosum) has hampered discovery of its wild ancestral species. Chloroplast DNA is a very reliable indicator to trace maternal ancestry of crops. Most of the common potato (grown worldwide) has unique, T-type chloroplast DNA derived from Chilean cultivated potato (both areS. tuberosum ssp.tuberosum). Analyzing seven different chloroplast DNA markers, I found all the T-type accessions of cultivated potatoes shared the same chloroplast DNA haplotype only with some accessions ofS. tarijense Hawkes and its derived hybrids. Thus, I conclude that some populations ofS. tarijense acted as the maternal ancestor of potato.     

Germplasm transfer from the wild tetraploid speciesSolanum acaule bitt. to the cultivated potato,S. tuberosum L. using 2N eggs

Solanum acaule Bitt. (acl ¹, 2n=4x=48 and 2n=6x=72) is a wild potato species in which resistance to adverse biotic and abiotic agents has been found. The tetraploid subspeciesacaule andaemulans cannot be easily crossed with the common potato,S. tuberosum L. Grouptuberosum (tbr, 2n=4x=48) because the development of the endosperm in the hybrid seed is abnormal. Since 4xacl behaves as a diploid in intra and interploidy crosses, it was postulated that the hybridization barrier withtbr could be overcome if the wild species produced 2n gametes. One hundred and ninety-seven plants of 4xacl (22 introductions) were screened for pollen of heterogeneous size; only two plants produced this type of pollen, with 3% and 5% of pollen in the large class, respectively. On the other hand, 427 plants (47 introductions) were screened for 2n eggs through controlled crosses withtbr. Forty-one plants (13 introductions) produced 219 berries of which 46 contained at least one plump seed. Seed from berries with low seed set gave rise to hexaploid hybrids possibly through the functioning of 2n eggs from 4xacl. A sample of these hybrids was successfully backcrossed as female parents totbr, giving rise to 5x BC₁ progenies. These BC₁ progenies could be easily back-crossed totbr, yielding tetraploid or near tetraploid BC₂ plants.