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1.
Summary Potato clones and cultivars differ in their ability to tolerate damage by the potato cyst nematodes:G. rostochiensis andG. pallida. This paper reports a simplified field assessment whereby single, spaced plants are grown in heavily infested soils. These
trials identified those clones which are either very sensitive to damage or those that grow and yield well in the presence
of nematodes. The use of such a screening procedure in a breeding programme is discussed. 相似文献
2.
Potato seeds of 24 families consisting primarily ofSolanum tuberosum ssp.andigena with someS. vernei germplasm that were segregating for resistance to potato cyst nematodes (Globodera pallida races P4A and P5A andG. rostochiensis race R1A) were obtained from the International Potato Center. These seeds produced 468 clones with sufficient tubers for evaluation for resistance toG. pallida races P4A and P5A in pot tests at the International Potato Center. Twenty-six of these clones, selected for a high degree of resistance toG. pallida races P4A and P5A, were crossed with neotuberosum ×Solanum tuberosurn hybrids that had been selected for resistance toG. rostochiensis race R1A (golden nematode) and the viruses PVX and PVY. The resultant progenies possessed a high degree of resistance to all three races of the potato cyst nematode. From these progenies, 23 clones were selected for resistance to the three races (G. pallida P4A and P5A,G. rostochiensis R1A) of potato cyst nematodes. The better adapted clones with resistance to the 3 races of potato cyst nematodes will be used in the next cycle of back-crossing. 相似文献
3.
Summary The major geneH1 confers resistance in potatoes to the golden potato cyst nematode (Globodera rostochiensis). No direct effect of the gene on resistance to the white potato cyst nematode (G. pallida) was found, but factors increasing resistance toG. pallida were detected and it is possible that these are linked to theH1 gene. The implications of such linkage are discussed. 相似文献
4.
Summary The tolerance of and resistance toGlobodera pallida of two potato progenies which segregated for these characteristics were assessed in pots in the glasshouse. The level of
tolerance varied widely between genotypes within the progenies, with several genotypes being significantly more tolerant than
the intolerant parent. The levels of resistance and tolerance in the progenies were not significantly correlated. No indications
were obtained that the ranking of genotypes for tolerance is influenced by the density ofG. pallida in the soil. The results confirm that selection for tolerance in aG. pallida resistance breeding programme is useful and feasible. 相似文献
5.
Zusammenfassung Zur Resistenzselektion von Kartoffelgenotypen gegenGlobodera pallida (Stone) Beharens (Pa3) wurde ein monoxenischerin vitro-Test entwickelt, der die Auswertung geringer quantitativer Unterschiede in der vermutlich polygen-vererbten Resistenzreaktion
erlaubt. Hierzu wurde das aussagekr?ftigste Resistenzkriterium an 30 unterschiedlich resistenten Genotypen bestimmt. An den
anf?lligen undG. rostochiensis-resistenten Genotypen entwickelte sich immer ein h?herer Anteil Weibchen als M?nnchen, im Gegensatz zu denG. pallida-resistenten Genotypen, bei denen die M?nnchen überwogen. Eine weitere Unterteilung derG. pallida-resistenten Genotypen war durch das erh?hte Auftreten nekrotisierter Wurzelbereiche und durch Larven mit stagnierender Entwicklung
m?glich. Zur Bewertung des Einflusses der Genotypen auf die charakteristische Populationsentwicklung des Nematoden wurde ein
Schema mit vier Gruppen erstellt. Die überprüfung der untersuchten Genotypen in einem Topfkulturetest zeigte eine übereinstimmung
mit den Ergebnissen aus dem monoxenischen Resistenztests.
Summary A monoxenicin vitro test, which was developed for selecting resistance in potato genotypes toGlobodera pallida (Stone) Behrens, can distinguish small differences in the resistance reaction, presumed to be polygenically controlled. To establish meaningful criteria for resistance, a number of characters which could be assessed rapidly were determined (number of necrotic root areas, number of invading juveniles but not yet sexually differentiated, number of juveniles developing as males and females, number of juveniles with arrested development). Assessments were made 21, 35 and 49 days after the introduction of 1000 freshly hatched juveniles ofG. pallida Pa3- population ‘Frenswegen’ per test Petri dish. Because of differences in levels of juvenile invasion per genotype (number of necrotic root areas) and differentiated individuals (Table 1), to make genotypic comparisons, it was necessary to consider other resistance criteria along with percentage juvenilie invasion. The ratio of males to females was shown to be the most reliable criterion of resistance. There was a higher proportion of females than males on susceptible, andG. rostochiensis resistant genotypes than onG. pallida resistant genotypes on which males predominated (Table 1). A further subdivision of theG. pallida resistant genotypes was possible using the increased occurrence of necrotic root areas, and juveniles with arrested development. A scheme was constructed for rating the effect of genotypes on the characteristic development of the nematode populations. It contained four groups: susceptible reaction (Figure 1), weakly expressed resistance (Figure 2), expressed resistance (Figure 3) and strongly expressed resistance (Figure 4). Female counts from pot tests with particular genotypes were in general agreement with the results from the monoxenic resistance test (Table 1).相似文献
6.
Seeds of three progenies segregating for resistance to two pathotypes ofGlobodera rostochiensis (Rol and Ro2) and two pathotypes ofG. pallida (Pa2 and Pa3) are being released by the Cornell University Experiment Station and the USDA/ARS. This resistance is in a form suitable for North American production and was developed for use in the event that pathotypes ofG. pallida, which are prevalent in many other potato production areas of the world, are ever introduced into North America. The source of the resistance is germplasm obtained in 1984 from the International Potato Center in LaMolina, Peru. The combined resistance in this germplasm is fromS. tuberosum sspandigena andS. vernei. Resistance to PVY is also segregating in two of these progenies. 相似文献
7.
Summary Greenhouse experiments on the effects of white potato cyst nematode infestations (Globodera pallida Stone) on initial growth and development of a series of potato cultivars are compared with the results of field experiments
on sandy and sandy-peat soils on the effect of nematode density on tuber yield. A simple greenhouse test, assessing root growth
response to potato cyst nematode infection, provided a good insight into a cultivar's tolerance performance in the field early
in the growing season. As a very limited number of plants is needed for the greenhouse test, screening for tolerance can be
conducted in the early stages of a breeding programme. 相似文献
8.
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. 相似文献
9.
K. Evans 《Crop Protection》1983,2(1):97-103
Root diffusates were collected from pot-grown plants of 25 potato cultivars by leaching the soil with distilled water. The activities of the leachates collected in this way were assayed by exposing cysts of the Ro1 population of Globodera rostochiensis (Wollenweber) Behrens and the Pa3 population of G. pallida (Stone) Behrens to a geometric series of dilutions of the leachates and counting the numbers of juveniles that hatched. ‘Log activity’ values for the diffusates were computed: whereas the diffusates from most cultivars hatched G. rostochiensis well, some hatched G. pallida well and some hatched it poorly. The implications of this difference for the distribution of the two species of nematodes and for the relative tolerance of potato cultivars in the field are discussed. 相似文献
10.
Plant parasitic nematodes associated with potato feed on roots and/or tubers. About 70 species, representing 24 genera, have been reported from potato. Since nematodes attack underground plant parts, there are no reliable foliar symptoms to show that nematodes may be the major cause of poor growth and reduced tuber yields. Potato roots damaged by nematodes may show lesions, abnormal proliferation of lateral roots, emerging white females and brown cysts. Nematode attacks may render plants vulnerable to other pathogens, so disease caused by microorganisms may have nematodes as an etiological component. Therefore, nematode damage may often have been attributed to other factors. In Scandinavia, potato cyst nematodes (Globodera rostochiensis and Globodera pallida) are by far the most important nematodes on potato. In Norway, the cost of compensations schemes due to imposed statutory regulations of potato cyst nematodes may some years exceed the compensation for any other pests or diseases organism in agriculture. Other important nematodes include root lesion nematodes (Pratylenchus spp.), stubby root nematodes (Trichodorus spp. and Paratrichodorus spp.), and potato rot and stem nematodes (Ditylenchus spp.). Root knot nematode Meloidogyne hapla is considered less important. Meloidogyne chitwoodi and Meloidogyne fallax are not known to be present in Nordic countries. In the control, crop rotations using non-host crops, alternating susceptible and resistant potato cultivars, are an important control measure. However, the use of resistant potato cultivars requires knowledge of the species and pathotypes present in the field. 相似文献
11.
Summary The tolerance toGlobodera pallida of 15 potato genotypes with a high level of resistance toG. pallida was assessed by measuring their tuber yield in heavily infested fields and in nematicide treated strips in the same fields.
Tolerance was also assessed in pots in the glasshouse by measuring the total biomass after 35 and 70 days growth in heavilyG. pallida infested soil and in uninfested soil. Large differences in tolerance between the genotypes were observed. High correlations
were observed between tolerance assessments made in the field experiments and between field and pot experiments. No relationship
was found between tolerance and maturity. Shoot and root dry weight were about equally affected by the nematode. 相似文献
12.
M. S. Phillips 《Potato Research》1981,24(1):101-103
Summary The resistance expressed by progenies of potato seedlings to the white potato cyst nematode (Globodera pallida) has been assessed on bulk sowings of seedlings and on individual plants raised from tubers, and a positive correlation between
the seedling and plant tests has been established. The use of such a seedling test as an addition to other methods of screening
is discussed. 相似文献
13.
K. Scholte 《Potato Research》1990,33(2):181-190
Summary A crop rotation experiment was carried out on a light sandy soil in 1979–1986 to study the effects of the frequency of potato
cropping on yield, quality and on the occurrence of soil-borne pathogens other than potato cyst nematodes.
Tuber yield decreased markedly with increasing cropping frequency, but also depended on what crops were grown in rotation
with potato. Growth during the early part of the season, as well as the length of the growing period, were reduced in short
rotations. The fungiVerticillium dahliae andRhizoctonia solani, and root-knot nematodes (Meloidogyne spp.) were the most important yield reducing pathogens. The effects of rotation depended on the cultivar used.
The percentage of mis-shapen tubers increased with increasing cropping frequency and after application of granular nematicides,
but the incidence of common scab (Streptomyces scabies) was not affected. 相似文献
14.
Summary This paper summarizes the results, up to June 1986, of screening the Dutch-German potato collection at Braunschweig Genetic
Resources Centre (BGRC) for resistance toGlobodera pallida andG. rostochiensis virulence groups. Resistance toG. pallida was detected in 4.1 of the 78Solanum species tested. The number of accessions with a pathotype-specific high-level resistance was high but accessions with resistance
to allG. pallida andG. rostochiensis virulence groups were rare. Four accessions had a high level of resistance to all virulence groups and 26 had partial resistance.
The partially resistant genotypes differed in the average number of larvae per root and of eggs per cyst.
Zusammenfassung Die Suche nach Quellen für Resistenz gegen Zystennematoden der Kartoffel,Globodera pallida undG. rostochiensis, wird bei der Stiftung für landwirtschaftliche Pflanzenzüchtung (SVP) durchgeführt. In einem kooperativen Programm werden die Neuzug?nge bei der ‘Niederl?ndisch-Deutschen Abteilung Kartoffeln der Genbank in Braunschweig’ (BGRC) in S?mlingstests intensiv auf Resistenz gegenG. pallida undG. rostochiensis in Münster (Institut für Nematologie) und in Wageningen (SVP) geprüft. Die Ergebnisse sind in den Tabellen 1, 2 und 3 zusammengefasst. Insgesamt 699 Neuzug?nge von 78Solanum-Spezies wurden auf Resistenz gegen die Virulenzgruppe Pa3 untersucht. In 260 Zug?ngen von 41Solanum-Spezies wurden resistente Genotypen beobachtet, Genotypen mit m?ssiger Resistenz (RS) in 65 Zug?ngen. Die Frequenz von Spezies mit Resistenz gegen Pa2 war ebenfalls hoch (28 von 58 Spezies). Resistenz gegen Virulenzgruppen vonG. rostochiensis wurde weniger h?ufig gefunden (Tabellen 1 und 2). Die Zahl der Zug?nge mit Resistenz gegen eine, zwei oder drei Virulenzgruppen zeigt Tabelle 3. Die H?ufigkeit von Zug?ngen mit Resistenz sowohl gegen Pa2 als auch Pa3 war hoch. Zug?nge mit kombinierter Resistenz gegen Pa2, Pa3 und Ro5 ergaben sich beiS. acaule, S. gourlayi, S. leptophyes, S. megistacrolobum, S. multidissectum, S. oplocense, S. spegazzinii, S. sucrense undS. vernei. SVP-Genotypen unter den Zug?ngen mit kombinierter Resistenz gegen die Virulenzgruppen Pa2 und Pa3 wurden zus?tzlich mit Isolaten von Pa2, Pa3, Ro1.4, Ro2.3 und Ro5 getestet. Genotypen mit Resistenz gegen eine oder mehrere Virulenzgruppen waren gegen andere Virulenzgruppen oft anf?llig. Dies deutet auf Gen-für-Gen-Verh?ltnisse hin. Nur vier Zug?nge konnten gefunden werden, die in hohem Ma?e gegen alle Virulenzgruppen Resistenz aufwiesen. Zug?nge mit partieller Resistenz gegen alle Virulenzgruppen wurden ebenfalls untersucht. Genotypen mit partieller Resistenz unterschieden sich in der durchschnittlichen Zahl von Larven pro Wurzel und von Eiern pro Zyste (Tabelle 4).
Résumé La Fondation pour l'Amélioration des Plantes Cultivées (SVP) a entrepris des recherches de sources de résistance àGlobodera pallida et àG. rostochiensis dans la collection germanonéerlandaise du centre de Ressources Génétiques de Braunschweig (BGRC). En collaboration, l'Institut für Nematologie de Münster et le SVP de Wageningen ont réalisés des tests de résistance à ces deux nématodes sur des plantules issues de graines provenant de diverses introductions. On trouvera la synthèse des résultats en tableaux 1, 2 et 3, 699 introductions appartenant à 78 espèces deSolanum ont été testées vis-à-vis de Pa3: des génotypes résistants ont été trouvés dans 260 introductions de 41 espèces deSolanum et des génotypes modérément résistants (RS) ont été trouvés dans 65 introductions. La fréquence d'espèces possédant une résistance à Pa2 est également élevéc (28 sur 58 espèces). La résistance àG. rostochiensis est trouvée plus rarement (tableaux 1 et 2). Le tableau 3 indique le nombre d'introductions possédant une résistance à un, deux ou trois groupes' de virulence. La fréquence des introductions possédant une résistance à la fois à Pa2 et à Pa3 est élevée. Des résistances à la fois à Pa2, Pa3 et Ro5 sont trouvées dans des introductions appartenant àS. acaule, S. gourlayi, S. leptophyes, S. megistacrolobum, S. multidissectum, S. oplocense, S. spegazzinii, S. sucrense etS. vernei. Ultérieurement, les génotypes combinant la résistance à Pa2 et Pa3 ont été testés au SVP vis-à vis de différentes populations de Pa2, Pa3, Ro1,4, Ro2,3 et Ro5. Souvent, les génotypes résistant au moins un groupe de virulence ne sont pas résistans aux autres groupes de virulence. Ceci montre que la résistance est basée sur une réaction gène pour gène. Un haut niveau de résistance à tous les groupes de virulence n'a été trouvé que dans quatre introductions. Des introductions possédant une résistance partielle à tous les groupes de virulence ont été trouvées. Les génotypes partiellement résistants diffèrent entre eux par le nombre moyen de larves par racine et d'oeufs par kyste.相似文献
15.
Summary The effect of soil pH on yield losses due to potato cyst nematodes (Globodera pallida) was investigated in experiments in the field and in a semi-controlled environment. Through annually liming a reclaimed peat
soil with about 22% organic matter, plots with pH levels of 4.5, 5.0, 5.5, 6.0 and 6.5 were obtained. In 1990 potato yields
in these plots decreased from 45 t/ha at pH 4.5 to 33 t/ha at pH 6.5, whereas the nematode densitites decreased from about
18 to 9 juveniles per g soil. In a container experiment a strong interaction was recorded between soil pH and the presence
of nematodes. Tuber yields were about 11% lower at pH 6.5 than at pH 4.5 in the absence of nematodes, but about 44% lower
when an initial population of 27 juveniles per g soil was present. 相似文献
16.
Summary Data from five long-term field experiments on sandy and sandy peat soils were analyzed for the effect of soil type on damage
caused by potato cyst nematodes to potato crops. It was shown that the water retention of the topsoil and the subsoil largely
determined the potential yield level in the different fields. According to Oostenbrink's equation the slopes of the curves
are steeper with increasing yield level, indicating that the higher the potential yield level, the higher the absolute yield
loss. However, when yield was expressed as percentage of maximum yield, yield reduction related to potato cyst nematode density
did not differ significantly, except when tolerant cultivars were grown. Increasing tolerance of cultivars to nematode damage
was reflected in less steep slopes of the yield/nematode density curves. 相似文献
17.
Zusammenfassung Durch die monoxenischein vitro-Kultivierung k?nnen geringe quantitative Unterschiede in der vermutlich polygen-vererbten Resistenzreaktion von Kartoffelgenotypen
gegenüberGlobodera pallida (Stone) Behrens (Pa3) festgestellt und für die Selektion verwendet werden. Grundvoraussetzung hierfür ist die einfache und
reproduzierbarein vitro-Kultivierung vonG. pallida. Für die Schlupfaktivierung, die Oberfl?chensterilisation und die Zugabe definierter Larvendichten wurden routinem?ssig durchführbare
Verfahren entwickelt, die einen vollst?ndigen Lebenszyklus der Nematoden unter monoxenischen Bedingungen erm?glichen. Die
aus dieserin vitro-Population gewonnenen keimfreien Zysten k?nnen für eine vereinfachte Resistenzprüfung eingesetzt werden. Die Testauswertung
orientiert sich an der Entwicklung der in die Wurzeln eingedrungenen Larven. Sie kann mit einem Stereomikroskop kontinuierlich
beobachtet werden.
Summary A monoxenicin vitro culture technique can distinguish small differences in the presumed polygenically determined resistance reactions of potato genotypes toGlobodera pallida (Stone) Behrens (Pa3) and can be used in selection. The basis for such a resistance test is the simple and reproducible cultivation ofG. pallida with the aim of achieving the complete life cycle of the nematode under monoxenic conditions. A routine practical technique was developed for hatching the juveniles in a closed system (Figure 1). This was achieved by the introduction of a hatching solution which was a mixture of root washings and 0.6 mmol l−1 picrolonic acid with a pH of 5.9 (=pH value of the nutrient agar). Using special hatching tubes the juveniles from 1000 cysts per tube could be hatched and counted within 2 or 3 days, as shown by experiment (Figure 3). Finally, the juveniles were surface sterilised in a special apparatus and distributed serially to the test genotypes (Figure 2). A density of 1000 juveniles per genotype gave the highest nematode infection (Figure 4) but allowance must be made for the surface sterilisation which in giving a high standard of asepsis killed up to 80% of the juveniles. At the same time especially vital juveniles were selected, thereby guaranteeing that the test was stringent and unequivocal. A variant of the technique used germ-free cysts which had been formed under monoxenic conditions. These were removed and crushed. The hatching effect of the genotypes' roots meant that 500 nematode eggs were sufficient for high infection. The test scores were based on the development within the roots of invading juveniles which could be observed continuously with a stereomicroscope. Males (Figure 5) and females (Figure 6) could be easily distinguished at low magnification (x10) 3–4 weeks and 4–6 weeks after the introduction of surface sterilised juveniles and monoxenically cultivated cysts respectively.相似文献
18.
In an experimental breeding scheme to improve late blight (Phytophthora infestans) and white potato cyst nematode (Globodera pallida) resistance of tetraploid potato over three generations of crossing and selection, 15 clones survived the final selection,
and these were derived from 15 great-grandparents. There was no direct selection for resistance to Potato virus Y (PVY), but 14 out of the 15 great-grandparents were resistant to PVY and three had extreme resistance. Thirteen of the 15
descendants had PVY resistance and one extreme resistance. This was within the range expected for a random (unselected) sample
from the genotypes of the great-grandparents. Hence, we found no evidence for any positive or negative association between
PVY resistance and the attributes selected. The conclusion is that laborious selection is not required in every generation
when many parents have PVY resistance, including some with more than one copy of a PVY resistance gene or resistance at more
than one locus. However, in the future, determining the major virus resistance genes present in potential parents in each
generation using diagnostic molecular markers would prevent susceptible × susceptible crosses being made and maximise the
number of resistant × resistant ones. 相似文献
19.
SeveralSolatium tuberosum clones were tested for resistance to the reniform nematode,Rotylenchulus reniformis. Commercial cultivars La Rouge and possibly Red La Soda had high levels of resistance to the reniform nematode.R. reniformis resistance was found to exist independently of the H1, H2, or H3 genes for resistance to races of potato cyst nematodes,Globodera rostochiensis andG. pallida. In addition to reniform nematode resistance, B7642-2, B7154-8 and B7680-6 contained the H1 gene and breeding linePI 377741 contains the H1 and H2 gene for potato cyst nematode resistance. Over a three month period reniform nematode counts were significantly lower in pots where resistant varieties were grown. 相似文献
20.
Summary Diploid potato clones (dihaploid x wild species hybrids) and their colchicine doubled, tetraploid counterparts were compared
for resistance to eelworm (Globodera rostochiensis andG. pallida) and for pollen ‘stainability’ as an indicator of viability. The responses due to doubling were not uniform. For eelworm
resistance, three of the five clone pairs showed no differences; in one pair the tetraploid was significantly more susceptible
to one pathotype but not to two others and in the remaining pair, the tetraploid was significantly more susceptible to both
pathotypes used. In eleven of fourteen pairs tested for pollen ‘stainability’, the tetraploid had significantly less ‘good’
pollen. In one case, the tetraploid had significantly more ‘good’ pollen. Generally there was sufficient ‘good’ pollen to
allow further crossing at the tetraploid level.
Zusammenfassung Fünf diploide Kartoffelklone, Kreuzungen zwischen anf?lligen Dihaploiden und nematodenresistenten Vermehrungen vonSolanum spegazzinii, S. vernei und einer nicht-beschriebenen, mitS. sparsipilum verwandten peruanischen Art, wurden hinsichtlich ihrer Resistenz mit ihren Colchicin-verdoppelten Gegenstükken verglichen. Tabelle 1 zeigt die verwendeten Nematoden-Populationen (Globodera rostochiensis undG. pallida) zusammen mit der Anzahl gebildeter Zysten. Die Reaktionen gegenüber Verdopplung waren nicht einheitlich; drei der fünf Klonpaare zeigten keine Unterschiede, bei einem der Paare war der tetraploide Teil signifikant anf?lliger gegen einen der Pathotypen, aber nicht gegen zwei andere, und beim letzten Paar war der tetraploide Teil gegen beide verwendeten Pathotypen signifikant anf?lliger. Obwohl die tetraploiden Pflanzen generell ein etwas gr?sseres Wurzelsystem entwickelten als die diploiden und eine gr?ssere Oberfl?che für die Einwirkung der Nematodenlarven boten, liess sich der Schluss ziehen, dass dies nur geringe Auswirkung auf die Feststellbarkeit von Unterschieden zwischen Vertretern der Ploidiepaare hatte. Die Zahl der Eier pro Zyste wurde durch die Resistenz der Pflanzen im Testmaterial nicht beeinflusst. Die Ergebnisse deuten auf gleiche oder niedrigere Grade der Nematodenresistenz durch die Colchicin-Verdopplung. Allerdings deutet die Uneinheitlichkeit der Reaktion darauf hin, dass die Produktion einiger ‘verdoppelter’ Klone mit erh?hter Resistenz doch nicht ganz auszuschliessen ist. Colchicinverdoppelte Klone mit Resistenz im Duplex-Stadium dürften hohen potentiellen Wert als Eltern für weitere Züchtungen auf tetraploidem Niveau haben, vorausgesetzt sie behalten ausreichende Fertilit?t bei. Pollen-‘F?rbbarkeit’ als Indikator der m?nnlichen Fertilit?t wurde in einem gr?sseren Umfang bei Ploidiepaaren, von denen die meistenS. acaule und/oderS. stoloniferum in der Elternschaft hatten, untersucht. Die Ergebnisse zeigt Tabelle 2. In 11 von 14 Paaren hatten die Tetraploiden signifikant weniger ‘gute’ Pollen, in einem Falle signifikant mehr. Generell waren ausreichend ‘gute’ Pollen vorhanden, um weitere Kreuzungen auf tetraploider Ebene zu gestatten. Die Rückkehr auf die tetraploide Ebene via Colchicin-Verdopplung l?sst deshalb einen hohen Anteil verwertbarer Elternlinien für die Erzeugung nematodenresistenter St?mme erwarten.
Résumé Cinq cl?nes diplo?des obtenus par croisement entre dihaplo?des sensibles aux nématodes et résistants, issus deS. spegazzinii, S. vernei et d'une espèce péruvienne non décrite associée àS. sparsipilum, ont été comparés, pour leur résistance, avec leurs homologues tétraplo?des. Les populations de nématodes (Globodera rostochiensis etG. pallida) qui ont été utilisés sont présentées dans le tableau 1 avec le nombre de kystes nouvellement formés. La réponse donnée par le doublement des chromosomes n'a pas été uniforme; trois des cinq cl?nes n'ont pas montré de différences avec leurs homologues diplo?des; dans un cas le tétraplo?de a été significativement plus sensible à un pathotype mais pas aux deux autres et dans le dernier cas, le tétraplo?de a été significativement plus sensible aux deux pathotypes utilisés. Bien que les plantes tétraplo?des développent généralement un système radiculaire légèrement plus important et présentent une plus grande surface à l'infection par les larves de nématodes que les diplo?des, on conclut que cela a eu peu d'effet au niveau des différences observées entre les deux types de plo?die. Le nombre d'oeufs par kyste n'a pas été affecté sur les plantes résistantes, dans le matériel testé. Ces résultats suggèrent que des degrés similaires ou moindre de résistance aux nématodes peuvent résulter du doublement chromosomique d? à l'effet de la colchicine. Cependant, la non uniformité des réponses fait en sorte que la création de quelques cl?nes tétraplo?des résistants aux nématodes pourrait se faire. De tels cl?nes, ayant des gènes de résistance au niveau duplex, auraient une grande valeur potentielle comme parents pour les hybridations futures au stade tétraplo?de s'ils gardent une fertilité suffisante. La coloration du pollen comme indicateur de fertilité male a été étudiée sur une large gamme de plo?die doublée ayantS. acaule et/ouS. stoloniferum dans la parenté. Les résultats de ces tests sont donnés dans le tableau 2. Dans onze des quatorze paires comparées le tétraplo?de a eu un pollen significativement moins bon que le diplo?de. Dans un cas le tétraplo?de a présenté un pollen significativement meilleur. Cela parait suffisant pour prendre en considération le croisement au niveau tétraplo?de. Par le retour au state tétraplo?de sous l'effet de la colchicine ont peut s'attendre à obtenir de fortes proportions de géniteur valables pour la création de variétés résistantes aux nématodes.相似文献