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.     

Introgression and stabilization oferwinia tuber soft rot resistance into potato after somatic hybridization ofsolanum tuberosum ands. brevidens

Resistance to potato tuber soft rot caused byErwinia carotovora was transferred fromSolanum brevidens to the cultivated potato over the course of four backcross generations originating from a somatic hybrid. Soft rot reactions were determined via a tuber plug inoculation method developed during the course of these experiments. Soft rot resistance was highest in the somatic hybrid (only ca. 20% of tubers and plugs showed evidence of severe rotting) and lowest among progeny of control potato x potato crosses (ca. 80% of tuber plugs showed severe rot). Backcross generations involving somatic hybrids were intermediate in their reaction, and resistance stabilized to about 60% of tuber plugs showing severe rot in the BC₂ through the BC₄. Reciprocal crosses showed no difference in the inheritance of soft rot resistance, indicating that neitherS. brevidens norS. tuberosum donor cytoplasm had a significant effect on the expression of resistance. Crosses between BC₃ siblings where noS. brevidens genetic markers were detected but resistance was segregating demonstrated a dosage effect for soft rot resistance. We conclude that introgression of soft rot resistance has occurred and that at least one locus responsible for resistance inS. brevidens now resides in theS. tuberosum genome.     

Inheritance of a pectate lyase mediated soft rot resistance in crosses between transgenic potato lines of cv. désirée andS. tuberosum cultivars

Summary Expression of the pectate lyase (PL) isoenzyme 3 in transgenic potato lines of cv. Désirée mediates an enhanced resistance of tuber tissue toErwinia carotovora (Ec) soft rot due to a pre-activation of plant defence mechanisms. Therefore, theSolanum tuberosum cvs Agave and Adretta with a moderate level of soft rot resistance were crossed with such PL-expressing potato lines. The resulting progenies were assessed with respect to plant/tuber characteristics over a period of four years and then tested for PL3-expression as well as for soft rot resistance. 71% of the selected progeny lines exhibited a stable production of the PL3 enzyme. Statistical analysis revealed differences between the transgenic and the non-transgenic progeny concerning the soft rot resistance of tuber tissue. Compared with the PL-inactive progeny, extension of Ec-rotting on the wound surface of PL-transgenic potatoes was diminished on average by 51.8%. Similarly, the degree of cell lysis caused by bacterial maceration was significantly (P<0.05) reduced in tuber tissue of PL-expressing progeny lines. The latter also revealed an enhanced PPO and PAL activity in their tuber tissue indicating an active plant defence. It is concluded therefore that the PL-mediated soft rot resistance introduced into potatoes by means of molecular techniques is heritable.     

Induction of some rare somatic mutations in Solanum tuberosum L. by ionizing radiations and radiophosphorus

Summary Two mutants—the hooded-eye and eyeless—induced by 6 kR γ-rays and³²P (150μC) in theUp-to-date andKufri Sindhuri varieties of potato are described in this paper. It was observed that while the hooded-eye was more frequently induced by γ-rays,³²P had a greater tendency to induce eyeless aberrants. Certain other changes in the size and shape of tubers and tuber-skin texture in the eyeless aberrants inUp-to-date are also described. The eyeless mutants, which are incapable of propagation and obviously have no breeding or phylogenetic implications, have been termed ‘blind mutations’.

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Zusammenfassung Virusfreie Knollen der SortenUp-to-date undKufri Sindhuri wurden kurzfristig mit⁶⁰Co Gammastrahlen (6 kR) und³²P (150 μC/Knolle) entsprechend den von Jauhar und Swaminathan (1967) beschriebenen Methoden behandelt. Es entstanden verschiedenartige somatische Abweichungen. Diese umfassten Mutanten mit wulstigen Augen (Abb. 1) und augenlose Abnormit?ten (Abb. 2), die durch die beiden Mutagene mit der in Tabelle 1 angegebenen H?ufigkeit hervorgerufen wurden. Es wurde beobachtet, dass wulstigen Augen h?ufiger durch γ-Strahlen erzeugt wurden, w?hrend³²P eine gr?ssere Tendenz zeigte, augenlose Abnormit?ten auszul?sen. Bei den Mutanten mit wulstigen Augen entwickelte sich eine Haube oder eine Lappen über den Augen der Knolle. Manchmal bedecke dieser fleischige Lappen das ganze Auge. Eine Chim?re, die sowohl normale als auch anormale Knollen produzierte, wurde ebenfalls durch Gammastrahlen hervorgerufen. Die augenlosen Mutanten entwickelten keinerlei Augen; dafür entstanden oberfl?chliche Vertiefungen, die nicht in der Lage waren, einen Keim zu bilden. Es werden auch gewisse andere Ver?nderungen in Gr?sse und Form der Knollen sowie in der Textur der Schale bei den augenlosen Missbildungen der SorteUp-to-date beschrieben.

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Résumé Des tubercules sans virus deUp-to-date etKufri Sindhuri ont été traités aux rayons pénétrants gamma⁶⁰Co (6 kR) et³²P (150 μC/tuber) suivant les méthodes aberrants décrites par Jauhar et Swaminathan (1967). Divers aberrants somatiques apparurent. Parmi ceux-ci des mutants avec yeux encapuchonnés (Fig. 1) et des aberrants sans yeux (Fig. 2), qui étaient induits par les deux mutgènes, à la fréquence indiquée au Tableau 1. On a observé que les yeux encapuchonnés étaient induits plus fréquemment par les rayons Y, tandis que³²P avait davantage tendance à induire des aberrants sans yeux. Chez les mutants à yeux encapuchonnés, un capuchon ou un rebord se développait sur les yeux du tubercule, quelquefois cette enveloppe charnue couvrait la totalité de l'oeil. Une plante ‘chimère’ produisant à la fois des tubercules normaux et aberrants étaits également induite par les rayons gamma. Aucun oeil ne se développait sur les aberrants sans yeux; à l'emplacement des yeux se développaient des dépressions superficielles qui ne produisaient aucun germe. Les autcurs décrivent également d'autres modifications dans la grosseur et la forme des tubercules, la texture de la peau chez les aberrants sans yeux deUp-to-date.

     

The effect of theH1 gene in potatoes,conferring resistance toGlobodera rostochiensis,on resistance toG. pallida derived fromSolanum vernei andS. tuberosum ssp.andigena CPC 2802

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.     

Transfer of PLRV resistance fromSolanum verrucosum Schlechdt to potato (S. tuberosum L.) by protoplast electrofusion

Summary Somatic fusions between an accession of the diploid wild speciesSolanum verrucosum and a dihaploid S.tuberosum genotype were produced in order to incorporate resistance to potato leafroll virus (PLRV). In total 15 somatic hybrids out of 16 regenerants were obtained. Identification of hybrids was based on additive RAPD patterns, general morphological characteristics, chromosome numbers and chloroplast counts in stomata guard cells. A field trial was performed with the hybrids, their two parents and the control cultivar Kennebec to assess field performance and phenotypic variability. Yield parameters varied considerably among somatic hybrids. Some of the hybrids gave significantly higher yields, tuber numbers and tuber weights than both parents. Pollen fertility of hybrids ranged from 19 to 77%. Twelve hybrids were found to be resistant to PLRV.     

Pre-sprouting as a Tool for Early Harvest in Organic Potato (Solanum tuberosum L.) Cultivation

Earlier harvest of potatoes (Solanum tuberosum L.) can be achieved by different pretreatments of the seed tubers. In factorial field trials in 2008–2010, two different pre-sprouting methods were evaluated: conventional pre-sprouting of tubers and pre-sprouting of tubers with stimulation of adventitious root formation (PR). The results were compared with those for untreated seed tubers stored at 4 °C until planting (control). One variety was included in three trials, and two varieties were included in one trial. The new PR method was intended to give faster development and tuber initiation than conventional pre-sprouting, which can be of value when the growing season is restricted or when early harvest is important. Plant emergence, leaf necrosis (as a measure of maturity) and incidence of late blight were assessed during the growing season. After harvest, tuber fresh weight, size and density were assessed. It was found that pre-sprouting treatments gave on average 7 days earlier emergence compared with the control. Necrosis began earlier in pre-sprouted treatments in all cases except for the late variety Sarpo Mira. In 2008 and 2009 potato late blight struck late, after onset of senescence, but in 2010 it struck earlier and the pre-sprouted treatments proved more susceptible than the control. Total tuber yield was 7–24% higher on average in all pre-sprouted treatments in the different field trials. Tests on time of harvest showed that the advantage for the pre-sprouting treatments was maintained during the season, but the difference with the control decreased with time. When the different pre-sprouted treatments were compared, the new PR method proved to be not better than conventional pre-sprouting.     

Tuber age as a contributory factor in the water relations of potato (solanum tuberosum L.)

Seed tuber age effects on the response of potato plants (cv Alpha) to different drought stress regimes during the pre-tuberization period were evaluated. During a slow drying cycle of approximately 2 weeks’ duration, young expanding leaves on plants grown from young or old seed tubers showed no evidence of osmotic adjustment and pre-stressing the plants did not affect this situation. Pre-stressed plants from young and old tubers possessed a higher relative water content at a zero turgor potential than unstressed plants. However, tuber age did not affect significantly the relative water content at zero turgor potential. Plants derived from young seed tubers exhibited improved drought resistance such as reduced water loss from mature leaves, a larger root/shoot dry weight ratio and possible effects on root distribution in soil.     

Enhanced production of dihaploid lines via anther culture of tetraploid potato (Solanum tuberosum L. ssp.tuberosum) clones

A total of 1000 anther-derived plants was regenerated from tetraploid potato (Solanum tuberosum L.) genotypes. Capacity to undergo androgenesis was analysed in 41 potato cultivars and 7 clones grown either in the greenhouse or in the field. Of the 48 genotypes, 33 produced embryos and 23 regenerated shoots from embryos. Anther-derived plantlet production was determined in genotypes 86110, Agria, Calgary, Escort, Helios, Idole, JO 0982 JO 1432, Kainuun Musta, Kardal, KE48, Matilda, Nicola, Petra, Pito, Rustica, Stirling, Torridon, Ute, Van Gogh, Vebeca, Vento and White Lady. The highest number of shoots (24 shoots/100 anthers) was obtained from cv. Calgary, when anthers were isolated from field-grown donor plants. Incubating anthers at 28 C, rather than at 20 C or 24 C, enhanced embryo production in four genotypes tested. However, shoot production was improved only in cv. Pito cultured at 28 C. When anthers of cv. Petra were cultured at 28 C for four weeks, followed by reduction of culture temperature to 24 C, a high rate of shoot production was recorded (14 shoots/100 anthers). The ratio between dihaploids and tetraploids varied among the anther-derived plants of the different genotypes. The number of dihaploids was highest in potato clone JO1432 (100%) and in cv. Calgary (93%) and lowest in cvs. Pito (21%) and Torridon (6%).     

Effects of a mixture of NAA+BA on numbers and growth rates of tubers ofSolanum tuberosum L.

Summary A mixture of NAA at 10 mg 1¹+BA at 1 mg 1¹ caused increases in growth rates of treated tubers of potato. Sub-irrigation and foliage sprays with the same mixture caused tuber initiation and increased the growth rates of some of the tubers. In a field study substantial increases in tuber number and final tuber volume per plant were recorded.

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Zusammenfassung Die Faktoren, die die Knollenbildung und Wachstumsrate bestimmen, sind wenig bekannt. Die ?usserliche Anwendung verschiedener Wachstumsregulatoren, die getrennt auf Einzelknollen von Pflanzen, die in Spezialbeh?ltern wuchsen (Abb. 1), aufgetragen wurden, brachte wenig Ergebnisse, die kommerziell nützlich sein konnten. Eine Mischung aus NAA (10 mg/l) und BA (1 mg/l), in der selben Weise angewendet, schien jedoch das Wachstum der meisten behandelten Knollen zu f?rdern (Abb. 2). In einem 2. Versuch wurde die gleiche Mischung direkt auf ausgesuchte Knollen gegeben und es zeigte sich wieder eine Wachstumssteigerung bei einigen (Abb. 3d-f). Wurden die Wurzeln mit dieser Mischung behandelt, so beschleunigte sich das Wachstum einiger Knollen und in zwei von drei Pflanzen wurde das Wachstum des Knollenansatzes gef?rdert (Abb. 3g-j). Blattspritzungen führten zu einer starken Knollenbildung (Abb. 3k-m). In einem dritten Versuch wurden pro Woche 3 oder 7 Mal die Stengel gespritzt und das führte zu einem signifikanten Anstieg in der Knollenzahl und im Gesamtknollenvolumen/Pflanze (Tab. 2). Abweichungen von den genannten Konzentrationen oder im Verh?ltnis der beiden Wachstumsregulatoren ergaben einen Wirkungsverlust. Der Wirkungsmechanismus ist noch nicht gekl?rt.

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Résumé Les facteurs qui contr?lent la tubérisation et la croissance des tubercules ne sont pas très bien compris. Plusieurs substances régulatrices de la croissance ont été appliquées seules sur des tubercules de plantes cultivées dans des unités spéciales (fig. 1), mais peu d'information commercialement utilisable n'a p? en être tiré. Toutefois, un mélange de NAA (10 mg 1¹) plus BA (1 mg 1¹) appliqué de la même fa?on semble stimuler la croissance de la plupart des tubercules traités (fig. 2). Dans une seconde expérimentation, des applications du même mélange, faites encore directement sur les tubercules sélectionnés, favorisent la croissance de certains d'entre eux. Appliqué sur les racines, le mélange favorise la croissance de quelques tubercules ainsi que le début de tubérisation sur deux ou trois plantes (fig. 3g-j). Pulvérisé sur le feuillage, le mélange provoque une importante tubérisation (fig. 3k-m). Dans une troisième expérimentation en plein champ, la pulvérisation sur le feuillage trois à des accroissements significatifs du nombre de tubercules (tableau 2). Lorsqu'on s'écarte des concentrations établies ou du rapport des deux substances de croissance, ces effets disparaissent. Les mécanismes impliqués ne sont pas compris.

     

Restriction fragment length polymorphism inSolanum spp for the construction of a genetic map ofSolanum tuberosum L.: a preliminary study

Summary When using two restriction enzymes and DNA probes from different sources, high levels of restriction fragment length polymorphism (RFLP) were observed in Southern blot hybridisation experiments, among 6 di(ha)ploid genotypes ofSolanum tuberosum and some closely related species. In 3 F1 sample populations of 14 individuals each, both heterozygosity and segregation of hybridisation patterns were observed. The non-radioactive biotin-dUTP/SA-AP method for DNA detection on Southern blots proved to be satisfactory and reliable.     

Aspects of fusion combining ability of dihaploidSolanum tuberosum L.: influence of the cytoplasm

Summary Creation from 4x hybrid clones from protoplast fusion of 2x clones of potato was evaluated. Besides combined nuclear genomes, composition of the cytoplasm significantly influenced the phenotypic traits of hybrid clones. To ascertain the influence of parental cytoplasm on the success of protoplast fusion and regeneration of hybrid plants, data from 74 fusion combinations of 50 dihaploid clones were analyzed. The majority of dihaploid breeding clones belonged to the cytoplasm types Wα, Tβ and Wγ. When the closely related mt types α, β and γ were used, fusion combinations had a better combining ability compared with more distantly related cytoplasms δ and ⃛. Fusions containing the same mitochondrial type (homofusions) were not superior to closely related mitochondrial types. However, homofusions of cytoplasm type Wα yielded significantly more hybrids than homofusions of type Tβ. In general, parental cytoplasm types had little impact on the fusion combining behaviour. Thus the cytoplasm type of the fusion parents is not a suitable marker for predicting the combining ability in protoplast fusion experiments.     

Relationships between numbers of main stems and yield components of potato (Solanum tuberosum L. cv. Erntestolz) as influenced by different daylengths

Summary The relationshops between numbers of main stems and some measures of growth and yield, as well as total tuber yield, were examined for potatoes grown under different daylengths. Leaf area, tuber number and tuber yield per plant increased significantly with increasing daylength and number of main stems. Numbers of main stems and leaf area were correlated positively with tuber number and tuber yield and negatively with average tuber weight. The correlations were stronger with stem number than with leaf area and were differently affected by daylength. Standard regression coefficients indicated that stem number has strong positive and negative relationships with tuber number and average tuber weight, respectively. Since tuber number was a better determinant of yeild than average tuber weight, the final relationship between the numbers of main stems and tuber yield remained positive for all daylengths. Determinants that will best explain variation in tuber total yield, tuber number, and average tuber weight are suggested.     

The degree of starch phosphorylation as influenced by phosphate deprivation of potato (Solanum tuberosum L.) plants

Summary The levels of starch phosphorylation in potato tubers were investigated in relation to fertilization with phosphorus (P) of field-grown and greenhouse-grown plants. The field-grown plants received 0, 15 or 30 kg P ha⁻¹. Starch from plants grown without P-fertilizer contained 15.6 nmol P (mg starch)⁻¹ whereas starch from plants grown with 30 kg P ha⁻¹ contained 20.6 nmol P (mg starch)⁻¹. The greenhouse-grown plants were cultured in inert media and received nutrient solutions containing 0, 3, 12 or 24 mg P l⁻¹, respectively. Plants grown with no P-fertilizer produced tuber starch with phosphorylation levels reduced to approximately 30% of the level found in plants grown with an ample supply of P. Thus, the level of starch phosphorylation can be modified by limiting the P-supply through the root system. Application of foliar P-fertilizer to the greenhouse-grown plants had no significant effect on the phosphorylation of the tuber starch.     

Evidence that resistance to potato leafroll virus accumulation in tetraploidsolarium tuberosum L. is controlled by one or few major genes that are not complementary

Summary Previous investigations into the inheritance of resistance to accumulation of potato leafroll virus indicated a dominant major-gene effect, but the segregation ratios in progenies of crosses were a closer fit to a model involving two complementary genes (both required for resistance and one present in the susceptible parent cultivar, Maris Piper) than to a single gene model. In this study, we tested the complementary gene hypothesis by backcrossing susceptible segregants from one of these progenies to their susceptible parent, Maris Piper. No resistant segregants were found in the five backcross progenies examined, so the complementary gene hypothesis was not supported. There was significant variation between susceptible progeny-members in these backcrosses. The progeny of another, highly resistant parent clone, G. 8107(1), selfed, was also examined: all members were resistant. Whilst there is evidently a dominant major-gene effect involved, this is not the whole picture and there are other unidentified genetic effects.     

栽培甜菜和白花甜菜种间杂交后代无融合生殖的观察

栽培甜菜和白花甜菜杂交获得的Ｆ＿１代以栽培甜菜连续回交产生了Ｂ＿１Ｆ＿２代和Ｂ＿２Ｆ＿３代￣［４］．在Ｂ＿２Ｆ＿３代中，２ｎ＝２７的植株达３０．１９％，推测其中大多数染色体组仍为ＶＶＣ。具有ＶＶＣ染色体组的核型中，含９个白花甜菜校长的染色体和１８个较短的栽培甜菜染色体，差别明显，易于区分。我们通过对Ｂ＿１Ｆ＿２（Ｂ１４，２ｎ＝２７）和Ｂ＿２Ｆ－３（２ｎ＝２７）植株间形态特征相似性比较、两个世代植株有丝分裂特异核型比较、两类植株减粉分裂行为比较、过氧化物酶和酯酶同工酶酶谱相似性比较，有力地证明了栽培甜菜和白花甜菜种间杂交后代中，从Ｂ＿１Ｆ＿２（Ｂ１４）到Ｂ＿２Ｆ＿３之间传递上存在着无融合生殖现象。     

Molecular analysis of genetic variation in potato (Solarium tuberosum L.). II. International cultivar spectrum

Summary Seventy-five commercial potato cultivars orginating from North America, Europe and Japan were analysed using AFLP and SSR markers to assess their genetic relationships. Results of cluster and principal coordinate analysis reflect in most cases known pedigree information. Independent of the marker system used it was possible to identify groups based on their geographical descent. Cultivars from Central and East Europe formed two overlapping pools. An Anglo-American gene pool was also identified. Additionally, principal coordinate analysis based on AFLP data uncovered that this pool is subdivided in two groups. One group is more closely related to the European pools and dominated by cultivars with immediate background of cv. Kathadin. Japanese cultivars gave no distinct cluster.     

甘蓝型油菜DH群体抗裂角性的遗传分析

提高抗裂角性是培育适合机械化收获油菜品种的基本要求。为了明确油菜抗裂角性的遗传规律,本研究利用抗裂角性差异显著的两个甘蓝型油菜品系配制杂交组合,通过小孢子培养构建了一个双单倍体(doubled haploid,DH)群体。采用随机碰撞法对该群体进行连续两年的抗裂角性鉴定,并利用植物数量性状的主基因+多基因混合遗传模型及偏度和峰度分析对抗裂角性进行遗传分析。结果表明,甘蓝型油菜的抗裂角性受3对主基因+多基因控制,涉及的基因数目为8~10对,存在基因的加性效应及基因间的互补作用;两年试验中抗裂角性的主基因遗传率均大于85.00%,主基因遗传率较高,表明该性状主要受主基因控制,受其它微效多基因及环境的影响有限。因此,在油菜抗裂角性遗传改良中,应通过杂交聚合不同抗性等级材料中的主效抗裂角基因,在早期世代加强对抗性的选择,并可以忽略环境因素的影响。     

Detection of ribosomal RNA genes by chemiluminescence inSolanum tuberosum L.: a rapid and non-radioactive technique for the characterisation of potato germplasm

Summary The characterisation of potato germplasm is important for the exploitation of this crop, and DNA techniques are playing an increasingly important role as valuable tools in the evaluation of agronomic characters. The rapid, non-radioactive detection of the ribosomal RNA gene fragments which identify restriction fragment length polymorphisms (RFLPs) in two cultivars ofSolanum tuberosum L. is described.