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.

     

Screening tuber-bearingSolanum spp. for resistance toGlobodera rostochiensis Ro1 Woll. andG. pallida Pa2/3 stone

Summary Accessions of tuber-bearingSolanum spp. related toS. tuberosum subsp.tuberosum were obtained from the German-Dutch collection (Braunschweig, Germany) and the Inter-regional potato collection (Sturgeon Bay, USA). They were screened for resistance toG. rostochiensis Rol andG. pallida Pa2/3. Among 1567 clones from 52 accessions, 135 clones (23 accessions) were resistant toG. rostochiensis. They mainly representedS. andigena, gourlayi, spegazzinii andvernei. Among 1689 clones (74 accessions), 105 clones (32 accessions) were resistant toG. pallida. They representedS. gourlayi, spegazzinii, sparsipilum andvernei. About 25 clones were resistant to both species.     

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.     

The expression of resistance to the white potato cyst nematode (Globodera pallida) by individual potato seedlings under different inoculation treatments

Summary The resistance toGlobodera pallida of individual potato seedlings from three progenies derived fromSolanum tuberosum ssp.andigena CPC 2802 was assessed using three inoculation treatments. Plants grown from tubers from the seedlings were used to reassess resistance. All the seedling test inoculation treatments over-estimated the proportion of clones classified as resistant compared to the results from tuber-grown plants. However, the mean relative resistance of progenies estimated by both tests showed good agreement, and it is suggested that seedlings are best used for assessing the resistance of progenies of crosses to identify promising combinations rather than individual clones.     

General resistance against potato virus Y introduced into a commercial potato cultivar by genetic transformation with PVYN coat protein gene

Summary Transgenic cv. Folva potato plants expressing the coat protein gene of potato virus Y strain N (PVY^N) were produced usingAgrobacterium tumefaciens mediated transformation. Forty independent transformants were selected for resistance screening. Four clones showed complete resistance to mechanical inoculation with all the five PVY isolates tested: the PVY^N isolate from which the coat protein gene was derived, two PVY^O isolates, and two PVY^NTN isolates. Two of the fully resistant clones contained only one copy of the transgene, demonstrating that it is possible by genetic engineering to obtain highly virus resistant potato clones that can also be useful in future breeding programmes.     

Influence of storage temperature on rate of potato tuber tissue infection caused byPhytophthora infestans (mont.) de bary estimated by digital image analysis

Summary Potato tubers were inoculated with two biotypes ofPhytophthora infestans then stored at 3,7, 10 and 15°C. Image analysis quantified average reflective intensity (ARI) of diseased tissue from cut surfaces of sample tubers. Tuber tissue infection and infection rate were measured by calculating Mean ARI of samples. Average tuber tissue infection and infection rate was minimal at 3°C (P.i.-US8 orP.i.-US1). Tuber tissue infection increased at temperatures >3°C, from 220 Mean ARI seven days after inoculation (dai) to 190–150 Mean ARI 50 dai (depending on cultivar and biotype ofP. infestans). Rate of tuber tissue infection caused byP.i.-US1 at 7°C was about zero in cv. Snowden but greater than −0.2 ARI day⁻¹ (cvs Russet Burbank and Superior). Rate of late blight infection in tuber tissue generally increased with temperature from −0.2 ARI day⁻¹ (at 7°C) in all cultivars to a maximum of −0.8 ARI day⁻¹ (10°C).     

Inheritance of extreme resistance to potato virus Y in potato

Summary Segregation for extreme resistance to PVY was evaluated in progenies derived from crossing two extremely resistant potato clones with parents differing in resistance. Resistance was evaluated after mechanical inoculation with PVY^O and PVY^N, and after graft inoculation with PVY^O. Biological and serological tests (ELISA) were used for virus detection. The extreme resistance is governed by a single dominant gene, but observed segregations deviated from the expected ratios. Considerable modifying effects were detectable, depending on the potato genotype and virus isolate, for a significant excess of susceptible genotypes was observed in some progenies. Moreover, genotypes with non-parental types of resistance to PVY were observed.     

Wild tuber-bearing species ofSolanum and incidence ofPhytophthora infestans (Mont.) de Bary on the Western slopes of the volcano Nevado de Toluca. 5. Type of resistance toP. infestans

Summary Plants of wildSolanum species (S. demissum (dms), S. verrucosum (ver), S. iopetalum (iop), S. brachycarpum (bra), and an unidentified species (unsp), from the natural habitat were inoculated in the laboratory withPhytophthora infestans race 0, to see if major genes for resistance were present, and with the most complex and aggressive race available in an attempt to reveal the level of general resistance. No plant with a susceptible reaction to race 0 was found in 120 plants ofdms, and 34 plants ofunsp. Plants with a hypersensitive reaction to race 0 and susceptible plants were found inver. When infected with a complex aggressive isolate of the fungus 73.5% of the WSS plants were susceptible. It was concluded that WSS in the area possess both complex race specific resistance and a high level of general resistance, whose effects cannot yet be separated.     

Evaluation of diploid potato clones for resistance to tuber soft rot induced by strains ofErwinia carotovora subsp.atroseptica,E. carotovora subsp.carotovora andE. chrysanthemi

Summary Tubers of clones from a diploid hybrid population ofSolanum phureja andS. stenotomum were screened for resistance to tuber soft rot caused by strains ofErwinia carotovora subsp.atroseptica (Eca),E. carotovora subsp.carotovora (Ecc) andE. chrysanthemi (Ech). Significant, positive correlations between resistance to the different strains and species were observed, indicating that screening for resistance to tuber soft rot could be accomplished by using just one of the three pathogens. Strains of Ecc and Ech were found to be much more virulent than strains of Eca. Inoculating with Ecc and Ech resulted in more distinct differences among susceptible, moderately resistant and resistant clones than inoculating with Eca.     

Combination of On-Line Solid-Phase Extraction with LC-MS for the Determination of Potentially Hazardous Glycoalkaloids in Potato Products

A simple and rapid method for the determination of naturally occurring, potentially hazardous glycoalkaloids (GAs) in potatoes and their products has been developed. The procedure is based on the on-line solid-phase extraction of the acetic acid extracts from potato products and combined with liquid chromatography (LC)-mass spectrometry (MS) in a fully automated system (Symbiosis™, Spark Holland Instruments, Emmen, The Netherlands). As sorbent material HySphere™ 18HD was used for alkaloid enrichment. GAs were eluted with the LC gradient and directly analysed by MS. Detection of the analytes was achieved in the sensitive multiple reaction monitoring mode using two characteristic ions (m/z 98 as a qualifier for GAs and m/z 868.3 as a quantifier for α-solanine or m/z 852.4 for α-chaconine). Typical validation data for method precision (v _k α-solanine = 5.3–6.5, v _k α-chaconine = 3.4–15.4), accuracy (average recovery of α-solanine = 84%, average recovery of α-chaconine = 87%) and linearity over the range from 1 to 1,000 ng ml⁻¹ (R ² = 0.9915 for α-solanine, R ² = 0.9939 for α-chaconine) with detection limits of 0.3 ng ml⁻¹ for α-chaconine and 0.5 ng ml⁻¹ for α-solanine were obtained. GA contents of commercial potato products were determined by the new on-line method and afterwards compared with those obtained with an established high-performance LC routine procedure. Better performance of the on-line procedure was obvious from the standard deviations of both methods. Other advantages included a strong reduction of overall analysis time, human intervention and solvent consumption as well as waste production. The time required for the on-line analysis was 5 min, which would allow processing of almost 100 samples in 8 h.     

4份圆锥小麦-乌拉尔图小麦双二倍体的分子细胞遗传学鉴定

为了给小麦育种提供新的种质资源,对4份圆锥小麦-乌拉尔图小麦双二倍体(AABBA^uA^u)的农艺性状、染色体组成及高分子量谷蛋白亚基组成进行了鉴定。农艺性状调查结果表明,4份双二倍体的株高介于108.45~129.43 cm,分蘖数介于7.3~17.5个,穗长介于10.23~12.17 cm,小穗数介于16.26~22.06,自交结实率介于37.77%~70.46%;4份双二倍体对目前的流行条锈菌混合生理小种(条中31、条中32、条中33、条中34和水源11-4)均表现为高抗。利用寡核苷酸序列探针Oligo-pSc119.2-1、Oligo-pTa535-1、Oligo-pTa71-2、pTa-713和简单重复序列探针(AAC)5进行FISH分析,可区分出圆锥小麦-乌拉尔图小麦双二倍体的42条染色体。花粉母细胞染色体配对观察表明,在这些双二倍体的减数分裂中期I,染色体大多配对成二价体,仅有少量的单价体、三价体和四价体。SDS-PAGE分析表明,来自于乌拉尔图小麦TA#831的1Ay亚基在双二倍体Syn-TAU-2中得到了表达,但其迁移率发生了变化;来自于PI428270和PI428274的1Ax和1Ay亚基分别在双二倍体Syn-TAU-3和Syn-TAU-4中得到了表达。这些双二倍体可作为新的资源材料用于普通小麦的遗传改良。     

Resistance toErwinia carotovora subsp.atroseptica in second backcross populations of somatic hybrids betweenSolanum tuberosum andS. brevidens

Summary Eleven clones obtained from a cross between cv. Katahdin and fusion products betweenSolanum tuberosum and the non tuber-bearing speciesS. brevidens, were backcrossed again withS. tuberosum (clone AR80-127-5). Small tubers harvested from 583 seedlings of these second backcross (BC2) populations were screened for tuber tissue resistance toErwinia carotovora subsp.atroseptica under aerobic conditions. After multiplication in the field. BC2 clones again were screened for soft rot resistance under aerobic as well as anaerobic conditions. In general, the resistance of the BC2 populations was reduced in comparison with the BC1. Variation for resistance was found within the BC2 populations, but there was no correlation between the results of the three tests performed. Four BC2 populations were also screenned for resistance to blackleg in the field. Significant differences were found between populations for mean percentage of diseased plants, but these differences could not be explained by the resistance of the parental clones.     

Inheritance of resistance toFusarium sulphureum in crosses betweenS. tuberosum potato cultivars measured on field and glasshouse grown tubers

Summary Solanum tuberosum potato cultivars with differing levels of resistance to dry rot caused byFusarium sulphureum were hybridised in a half diallel crossing programme. Glasshouse grown tubers from true seedlings and field-grown tubers of the resulting progenies were assessed for their resistance toF. sulphureum. Statistical analysis revealed differences between the progenies forF. sulphureum resistance on both field and glasshouse grown tubers. On the field grown tubers, differences between progenies were due to differences in the general combining ability (GCA) of the parents. Parental phenotypes and GCA values were highly correlated. Overall. GCA was consistent for resistance or susceptibility, and glasshouse grown progenies showed a good correlation for GCA between years (r=0.85^***), and with the results of the field grown progenies (r=0.61^* in 1998 and r=0.69^** in 1999). It appears that resistance toF. sulphureum is heritable, and that this heritability is better assessed on field grown rather than glasshouse grown tubers, although the two are largely in agreement.     

Simple linear relationship between dry matter,specific gravity,and tissue specific gravity in a diploid potato breeding population

Summary Two hundred clones were randomly selected in 1988 and in 1989 from a hybrid population ofSolanum phureja andSolanum stenotomum to determine the relationship between specific gravity (SG) and percent dry matter (%DM), and between tissue specific gravity (TSG) and %DM. The objectives were: (1) to determine the dry matter prediction equation for a diploid potato population, (2) to determine whether estimates of %DM and efficiency of selection for %DM could be improved by measuring TSG, and (3) to determine the influence of year on the estimates. In 1988 the prediction equation for the relationship between %DM and SG was %DM=198.71 (SG-191.30,r=0.85. Ranges and means for the variables were: (1) %DM: 16.99–32.67, mean 25.16; (2) SG: 1.054–1.122, mean 1.089. In 1989 the relationship of %DM and SG was predicted as %DM=194.46(SG)-187.53,r=0.87; whereas the relationship of %DM and TSG was predicted as %DM=196.77(TSG)-192.91,r=0.87. Ranges and means for the variables were: (1) %DM: 10.68–34.57, mean 21.32; (2) SG: 1.030–1.122, mean 1.074; (3) TSG: 1.046–1.141, mean 1.089. Slopes were not significantly different between any of the prediction equations, but intercepts were significantly different. Estimates of %DM were not improved by measuring TSG. Year did influence the relationship between %DM and SG.     

Assessment of the field resistance of potato genotypes with major gene resistance to late blight (Phytophthora infestans (Mont.) de Bary) using inoculum comprised of two complementary races of the fungus

Summary Two races ofPhytophthora infestans, differing in virulence against four major (R) genes for resistance, were used to assess the field resistance of differential (R) genotypes, both singly and mixed together in equal proportions. The mixed inoculum led to an over-estimation of the foliage resistance of genotypes with which only one of the races was compatible, by up to two scoring categories of a 1–9 scale in field trials and, to a lesser extent, in glasshouse tests depending on the differential and the test. Assessment of tuber resistance was not significantly affected. The R₁₀ and R₂ differentials showed a higher level of field resistance in the foliage and tubers, respectively, than the other genotypes. It is concluded that assessments of genotypes which may possess R genes, using mixed inoculum, should be interpreted with caution, and apparent high levels of field resistance confirmed through genetic studies of the inheritance of the resistance.     

Antioxidant Activities of Four Edible Seaweeds from the Southern Coast of Thailand

The aqueous extracts of four marine algae, Caulerpa racemosa var. macrophysa, Gracilaria tenuistipitata var. tenuistipitata, Sargassum sp., and Ulva lactuca, from the coastal areas in Southern Thailand, were prepared by boiling dried seaweed powder in water for 3 h, and by autoclaving each sample at 120 °C for 3 h. They were then freeze-dried and evaluated for their antioxidant activities using DPPH (1, 1-diphenyl-2-picrylhydrazyl), hydroxyl radical (OH^•) and superoxide anion (O₂^•−) scavenging assays. Boiling extracts of the seaweeds, except C. racemosa, were found to have higher total phenolic contents (TPC) than those obtained from the autoclave method. The antioxidant results also showed that O₂^•− scavenging activity existed only in the boiling extracts of C. racemosa, G. tenuistipitata, and U. lactuca. In DPPH and OH^• assays, however, almost all the boiling extracts were less active than the autoclave ones. Among the four alga species, Sargassum sp. was the most active. Both extracts of this seaweed had the highest TPC and also displayed the strongest DPPH^• and OH^• inhibitory activities. A strong positive-correlation between the antioxidant potency and TPC of the autoclave extracts was found, while for the boiling extracts such relation was very weak. This result thus reflected that in addition to the phenolic compounds, there might be some other active components present in these extracts involved in the antioxidant activity.     

Frühselektion auf relative Krautfäuleresistenz an Sämlingen der Kartoffel und deren spätere Kraut- und Braunfäuleresistenz

Zusammenfassung Im Gew?chshaus wurden 838 hoch krautf?uleanf?llige bis hoch resistente Kartoffelidiotypen als S?mling auf relative Krautf?uleresistenz (KR_G), als Einzelstaude und A-Klon im Scheibentest auf relative Braunf?uleresistenz (B_S) und als A-Klon auf relative Krautf?uleresistenz im Feld (KR_F) untersucht. Durch rechtzeitiges Abschneiden am Stengelgrund überlebten auch stark befallene S?mlinge. Bei scharfer S?mlingsselektion (KR_G≥8 behalten) blieben 24% der Ausgangszahl erhalten, aber nur 52% der vorhandenen resistenten Idiotypen mit KR_F≥5 und B_S≥6,4. Wurden nur S?mlinge mit KR_G≥7 behalten, so gingen immer noch 8% der sp?ter erkennbaren Resistenztr?ger für Kraut- und Braunf?ule verloren, jedoch ergab sich eine Einschr?nkung des Zuchtmaterials durch die Frühselektion auf 57% der Ausgangszahl. Es kam starke ontogene Pr?disposition des Krautes sowohl in Richtung erh?hter Anf?lligkeit als auch erh?hter Resistenz vor. Neunundrei?ig Braunf?uleresistenztr?ger waren als S?mling hoch krautf?uleanf?llig. Scharfe Selektion der S?mling ist unangemessen. Für die Sortenauslese wird die Frühselektion auf Krautf?uleresistenz nicht empfohlen.

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Summary The reliability of blight resistance assessments made at the seedling stage and subsequent loss of tuber blight resistance were studied in 838 seedlings with different relative resistance to foliage blight. The criteria were assessed after Darsow (1989) in a field experiment in which the effect of maturity class was largely eliminated. Seedlings with 4–6 developed leaves were inoculated in the glasshouse with 3–3.5×10⁵ zoospores of a mixture of pathotypes. Multiple assessments (NB 9=high resistance, 1=greatest susceptibility) and immediate removal of shoots at the stem base allowed those forms most susceptible to foliage blight to be regenerated for testing in subsequent years (single plants, A-clone). Table 1 gives the crosses, scores for resistance of the parents and the numbers of seedlings tested per progeny. The percentage distribution of foliage blight resistance in the field (KR_F) related to that of the seedlings (KR_G) is given in Fig. 1. Potato plants which were very susceptible at the seedling stage could nevertheless grow in the field and exhibit good foliage blight resistance. The reverse was also observed. The distribution after weak selection for the development of blight on the seedling in the field is given in Table 2. There was an unavoidable loss of 10% and 14% in those rotted seedlings that possessed foliage and tuber blight resistance respectively (Table 3). High tuber blight resistance (B_S) occurred in all classes of seedlings with foliage blight resistance; likewise susceptibility to tuber blight occurred in seedlings with foliage blight resistance. From seedlings with KR_G≥7, 204 out of a total of 222 retained their genotypes with KR_F≥5 and B_S≥6.4. A reduction of 43% in the final number of seedlings was accompanied by a loss of 8% of those that possessed combined resistance. Of the seedlings which had been harvested and pre-tested, 277 out of 481 later had insufficient levels of resistance. Early selection will only be advantageous by careful selection of progenies with increased levels of resistance. The interaction of resistance with environment and developmental stage does not at present commend the application of this approach to varietal breeding.

     

Detecting resistance to the root-knot nematodesMeloidogyne hapla andM. chitwoodi in potato and wildSolanum spp.

Summary Various methods of screening for resistance to root-knot nematodes were compared and evaluated. Seedling populations ofSolanum spp., grown in clay pots and plastic tubes with silver sand and inoculated with juveniles ofMeloidogyne chitwoodi andM. hapla, showed large differences in the number of egg masses on roots 7 weeks after inoculation. The differences were reproducible when re-testing was done with cuttings and plants from tubers. No resistance toMeloidogyne spp. was observed with ten potato cultivars when grown in clay pots, plastic tobes or closed containers. Plants from tubers in growth pouches developed a large two-dimensional root system, and after inoculation with juveniles the infection process could be observed over 8 weeks. A method of infecting potato tuber tissue withMeloidogyne is described, using tuber slices in Petri dishes as a potential screening test for tuber resistance.     

Naturally occurring viral infections inSolanum brevidens andS. fernandezianum

Summary Two species of wild potato,S. brevidens andS. fernandezianum, were surveyed for six potato-infecting viruses in their natural habitats in the Puerto Montt Region and Robinson Crusoe Island of Chile, respectively. Potato viruses S (PVS), M (PVM) and X (PVX) and potato yellowing virus (PYV) were found in some clones of the Chilean Potato Germplasm Collection, whereas only one population ofS. brevidens out of six was virus-infected, namely by PVS. The cultivated potatoes on Robinson Crusoe Island were infected by PVS, PVM and PVX and infested byAulacorthum solani andMyzus persicae, whereasS. fernandezianum was infected by PYV and infested byA. circumflexum, A. solani andAphis spp.