Daughter Tubers Research Articles

Evidence for persistent, symptomless infection of some potato cultivars with tobacco rattle virus

Infection with an M-type (particle producing) isolate of tobacco rattle virus (TRV) was detected in leaves and/or roots of some plants from 11 of 13 potato cultivars grown in soil containing viruliferous trichodorid nematodes. Virus was detected in tubers of 8 of 13 cultivars, although only two (Pentland Dell and Maris Bard) developed spraing symptoms. Six cultivars (Arran Consul, Home Guard, King Edward, Romano, Sante and Wilja) were infected with TRV without developing spraing symptoms. Plants grown from virus-containing, symptomless tubers became systemically infected with M-type TRV and produced symptomless infected daughter tubers. Virus was maintained through three generations of vegetative propagation, and the plants were sources for acquisition of the virus by trichodorid nematodes. Distribution of virus in both spraing-affected and symptomless tubers was erratic. Movement of symptomlessly infected seed tubers may be a means of dissemination of the virus and of its introduction to previously unaffected sites.

High level of resistance in potato to potato mop-top virus induced by transformation with the coat protein gene

Transgenic plants of potato cvs Saturna and Pentland Marble expressing the potato mop-top virus (PMTV) coat protein (CP) gene were produced. Plants contained transgene RNA transcript and CP. In resistance tests made in a screenhouse, plants were grown in pots containing field soil infested with viruliferous Spongospora subterranea (the vector of PMTV). PMTV infection of the daughter tubers was determined by ELISA; 10% and 17%, respectively, of tubers from non-transformed control plants of Saturna and Pentland Marble became infected. However, tubers from six transgenic Saturna lines were immune to PMTV infection, and only one transgenic Pentland Marble tuber of 261 tested from four lines was infected. Spraing symptoms were not seen in any Saturna tubers, but less than 1% of transgenic Pentland Marble tubers developed symptoms compared to 12% of those from control Pentland Marble plants.

The infection of potatoes byPhytophthora infestans during simulated washing and its control using a hot water treatment

A single blighted tuber released on average 1.39 mg ofP. infestans mycelia and sporangia during simulated washing. In subsequent experiments up to 100% of tubers were infected when healthy tubers were washed in a suspension ofP. infestans equivalent to a concentration of 1.65 μg ml−1, i.e. that calculated to be in a commercial washing plant after washing a potato stock with approximately 1% of tubers infected with blight for 4 hours. Immature tubers were more prone to infection during washing than mature tubers. Damaging tubers, irrespective of their maturity, increased the incidence of tuber infection. The viability ofP. infestans isolates was significantly reduced byin vitro immersion in water at 44°C for 5 minutes. The infection of daughter tubers dipped in a suspension ofP. infestans for 3 minutes was prevented when the suspension temperature was 44°C. There was no indication of tuber damage at this temperature.

Effects of planting density, stem pruning treatments, and shade on secondary tuber development in Sandersonia aurantiaca

The effects of three plant densities (128, 256, and 384 tubers/m2), three stem pruning treatments, and shading on tuber weight and incidence of secondary tuber production in Sandersonia aurantiaca (Hook.) were assessed in a factorial experiment. Pruning treatments were an unpruned control, a single cut just below the lowest flower at early flowering, and a multiple cut treatment (as per single cut treatment plus 25% more stem removed every 2 weeks). Tuber weight and secondary tuber formation were significantly affected by both plant density and stem pruning treatments, but not by shading. Averaged across all pruning treatments secondary tuber formation was reduced from 25.7 to 0.6% with increasing plant densities. Mean daughter tuber weight, including the weight of tubers with attached secondary tubers, was also reduced with increasing plant density (11.4, 7.9, 6.5 g) and with increasing severity of pruning treatments (11.1, 8.4, 6.2 g). However, the effect of stem pruning on secondary tuber formation was much less than that of plant density. Only at the lowest density of 128 tubers/m2 were there significant responses, with secondary tuber formation declining from 33.7 to 15.5% with increasing severity of pruning. Increasing the plant density from 128 to 256 tubers/m2 reduced secondary tuber formation to a low level (3.2 cf. with 33.7%) on unpruned stems, without affecting the daughter tuber weight (10.5 versus 10.7 g). Such cultural practices show great promise for controlling secondary tuber formation during commercial tuber production.

Canopy Light Distribution, Photosynthesis and Tuber Yield of Eddoe Plant Characterized by Clipping and Non-Clipping of Daughter Tuber Leaves

The effects of clipping of daughter tuber leaves of eddoe plants (Colocasia esculenta Schott, var. antiquorum Hubbard, cv. Uhan) on dry matter production, canopy photosynthesis and tuber yield were investigated. The clipping of daughter tuber leaves resulted in different vertical canopy structure and different light distribution within the canopy. In the row-base of the non-clipped plot, relative light intensity was 10% lower than in the clipped plot. In the non-clipped plot, net photosynthetic rate of eddoe plant reached 4.9g CO2 m-2 h-1, while in the clipped plot, it reached only 2.7g CO2 m-2 h-1. The non-clipped plot attained a total tuber yield of 1844g m-2 but the clipped plot reduced tuber yield approximately by 25%. We presume that the canopy of the non-clipped plot intercepted more light due to higher LAI (leaf area index) than the clipped plants. The higher LAI and higher light interception of non-clipped plants resulted in higher photosynthesis and higher dry matter production and hence higher tuber yield than in the clipped plot.The present experiment concluded that daughter tuber leaves have a great contribution to the canopy photosynthesis and to promoting thickening growth of tuber. Therefore, it would be better not to clip daughter tuber leaves for obtaining higher tuber yield.

The resistance of potato plants toErwinia carotovora subsp.atroseptica in relation to their calcium and magnesium content

The effect of adding gypsum (CaSO4) to growing media on the resistance toErwinia carotovora subsp.atroseptica (van Hall) Dye of potato (Solanum tuberosum L.) stems and mother and daughter tubers was examined in field and glasshouse experiments. The decayin situ of inoculated mother tubers from field plots treated before planting with gypsum was significantly delayed compared with tubers sampled from non-amended plots. Blackleg development was also significantly delayed in the gypsum-amended plots; however, for both mother tubers and stems the increased resistance associated with the application of gypsum later disappeared. Stem resistance tended to be related to tissue calcium and magnesium concentrations which were higher in plots treated with gypsum than in untreated plots. Daughter tubers produced in plots amended with gypsum generally contained a higher concentration of calcium in their cortex and were more resistant to decay byE. carotovora subsp.atroseptica but the effect was not consistent.

Soil survival and thiabendazole sensitivity ofHelminthosporium solani isolates from Alberta, Canada

Survival of the pathogen causing silver scurf of potato (Helminthosporium solani) in Alberta soils was studied by evaluatingH. solani infection in the progeny ofH. solani-free nuclear seed potato tubers planted in fields where potatoes had never been grown or were grown 1, 2, 3, or 4 years previously. Daughter tubers from all the fields developed silver scurf lesions, andH. solani was isolated from infected tubers. This is the first report of survival ofH. solani in Alberta soils. Soil-borne inoculum appears to have a role in the epidemiology of the disease and in the introduction of the pathogen into silver scurf-free potato seed stock. Of 31 plant species tested, only potato was found to be a host ofH. solani. Most of theH. solani isolates from north central Alberta were more sensitive to thiabendazole than those from southern Alberta, where thiabendazole is much more commonly used.

Translocation and mechanical spread of a Minnesota isolate of potato virus S in potatoes

Potato cultivars Norland, Kennebec, and Russet Burbank were inoculated with a Minnesota isolate of potato virus S (PVS) in the field. The incidence of secondary infection, measured by enzyme-linked immunosorbent assay (ELISA), indicated that significantly more PVS infection occurred in Russet Burbank than Norland or Kennebec, and that Norland had significantly more infection than Kennebec (P≤ 0.01). Mature plant resistance was not observed. Rapid reinfection of PVS-free seedlots resulted from inoculum point-sources when routine cultivation practices were followed. Reinfection rates were significantly greater for seedlots grown at Grand Forks, ND, when compared with seedlots grown at Becker, MN, during both years of the study (P≤ 0.01). After two years in the field, reinfection rates for Norland (71.8%) and Russet Burbank (73.0%) did not differ significantly, but were significantly greater than the reinfection rate for Kennebec (29.5%) (P≤ 0.01). In greenhouse-grown plants, PVS moved out of rub-inoculated leaves within 24 hr, however, 13 and 20 days were required before PVS was detected with ELISA in foliage above and below the inoculated leaf, respectively. The frequency of PVS detection was significantly greater in foliage above the inoculated leaf compared to foliage below the inoculated leaf (P≤ 0.05). Translocation of PVS from inoculated leaves to daughter tubers occurred within 13 days for Russet Burbank and Norland and within 20 days for Kennebec.

Effects of fungicides on the growth and conidial germination of Colletotrichum coccodes and on the development of black dot disease of potatoes

SUMMARYThe effects of 10 fungicides on the growth of Colletotrichum coccodes in agar culture and on the germination of conidia was investigated. In field experiments in 1990 and 1991 the extent to which treating black dot‐affected potato seed tubers with fungicides affected the development of the disease on stem bases, roots and tubers was assessed. Black dot was also assessed on plants from field trials in 1990 which were designed to investigate the efficacy of the soil sterilant 1,3‐dichloropropene (Telone) and two nematicides, aldicarb (Temik) and ethoprophos (Mocap).Prochloraz and fenpiclonil were the most effective fungicides in decreasing the size of C. coccodes colonies on agar. Imazalil, propiconazole and dichlorophen were also effective, but at higher concentrations, whereas tolclofos‐methyl, thiabendazole and benomyl were only moderately effective. Resistant sectors developed from inhibited colonies on agar containing fenpiclonil and tolclofos‐methyl. Conidial germination was prevented at 1 mg/litre fenpiclonil and 5 mg/ litre dichlorophen; imazalil, benomyl and thiabendazole were also moderately effective.Fenpiclonil and propiconazole seed tuber treatments consistently decreased black dot infection on roots, stem bases and daughter tubers early in the season, but only fenpiclonil decreased disease on tubers at harvest in October. Propiconazole also delayed emergence and decreased stem numbers. Soil treatment with 1,3‐dichloropropene, aldicarb or ethoprophos had no effect on black dot but Rhizoctonia solani tuber infection and black scurf were increased.

Assessment of tuber storage and sprouting treatments forSandersonia aurantiaca

Abstract Temperatures of 3–5°C were suitable for the long‐term storage of sandersonia tubers. Tubers sprouted during storage at 10°C, but no sprouting occurred with up to 202 days of storage at 3–5°C. Tuber viability and subsequent sprouting were less after storage at 1°C than following 3–5°C storage temperatures. Sprouting temperatures of 20–26°C gave high sprouting percentages following long‐term storage. Tubers failed to sprout at 35°C and sprouting percentages were lower at 30°C than 20–25°C following longer storage durations (>60 days). Storage duration, storage temperatures, and sprouting temperatures influenced the time from storage removal to sprouting, storage removal to stem harvest, stem size, and daughter tuber weight. Stem length declined with increasing storage duration of 110–171 days, but was slightly greater after 202 days of storage than after 171 days. Possible reasons for these plant responses are outlined. Daughter tuber weight declined with storage duration and was less following a sprouting temperature of 20°C than 23–26°C.

Effects of wounding fungicide-treated potato seed tubers on silver scurf disease on daughter tubers at harvest

Silver scurf on daughter tubers at harvest was decreased by treating seed tubers with imazalil or thiabendazole in March but significantly increased when the treated tubers were wounded the day before planting in May. The disease was also increased by wounding seed tubers not treated with fungicide. Black dot was decreased by seed treatment with imazalil but was not affected by wounding.

Resistance to potato leaf roll virus multiplication in potato is under major gene control

The concentration of potato leaf roll virus (PLRV), as measured by a quantitative enzyme-linked immunosorbent assay, in the foliage of potato plants (Solanum tuberosum) of cv 'Maris Piper' with secondary infection was 2900 ng/g leaf, whereas in clones G7445(1) and G7032(5) it was 180 ng/g leaf and 120 ng/g leaf, respectively. To examine the genetic control of resistance to PLRV multiplication, reciprocal crosses were made between the susceptible cultivar 'Maris Piper' and the two resistant clones, and the three parents were selfed. Seedling progenies of these families were grown to generate tubers of individual genotypes (clones). Clonally propagated plants were graft-inoculated, and their daughter tubers were collected and used to grow plants with secondary infection in which PLRV concentration was estimated. The expression of resistance to PLRV multiplication had a bimodal distribution in progenies from crosses between 'Maris Piper' and either resistant clone, and also in progeny from selfing the resistant parents, with genotypes segregating into high and low virus titre groups. Only the progeny obtained from selfing 'Maris Piper' did not segregate, all genotypes being susceptible to PLRV multiplication. The pattern of segregation obtained from these progenies fits more closely with the genetical hypothesis that resistance to PLRV multiplication is controlled by two unlinked dominant complementary genes, both of which are required for resistance, than with the simpler hypothesis that resistance is conferred by a single dominant gene, as published previously.

Control of skin spot and silver scurf on stored cv. King Edward potatoes by chemical and non‐chemical methods

SummaryIn 3 years, seed tubers of cv. King Edward were planted in field experiments and diseases assessed on the daughter tubers after storage for 24–26 wk. In 1991 and 1992, the seed tubers were treated with a mixture of thiabendazole and imazalil at two rates. Tubers were harvested on several dates from late August to early October and dried under different conditions before storage.In 1990, silver scurf after storage was decreased equally by dry curing for 2 wk and windrowing for 2 h whereas skin spot was decreased most by dry curing, and these effects were greater the earlier tubers were harvested. In 1991, dry curing for 2 wk decreased skin spot and silver scurf more than dry curing for 1 wk, and skin spot was slightly decreased by windrowing for 2 h; windrowing improved the control of both diseases when tubers were subsequently dry cured. In 1991 and 1992 fungicide treatment of seed tubers greatly decreased skin spot after storage and was also effective against silver scurf, but increased black dot when tubers were harvested in September or October.Skin spot was controlled equally well by the two rates of fungicide but silver scurf was less well controlled when the dose was decreased by 75%. It is suggested that amounts of fungicide applied to seed tubers could be decreased provided that the efficiency of application is improved and that crops are harvested early and dried before storage.

Resistance to potato leafroll luteovirus can be greatly improved by combining two independent types of heritable resistance

SummaryTwelve potato clones were exposed to infection by aphids with potato leafroll luteovirus (PLRV) in three field trials in order to assess their resistance to infection. Up to 92% of the plants of some clones became infected, although other clones were relatively resistant to infection and one clone remained virus‐free in all three trials. The resistance of the same 12 clones to PLRV multiplication was assessed in glasshouse‐grown plant: lants were graft‐inoculated and their daughter tubers were used to grow plants with secondary infection. High concentrations of PLRV were found in some clones (c. 1700 ng/g leaf) while in others much less virus accumulated (as little as 60 ng/g leaf). However, clones in which little virus accumulated were not necessarily those which were most resistant to infection in the field, and there was no association between the two types of resistance. Nevertheless, both types of resistance were found in some clones. The clone G8107(1), which remained virus‐free in all the field exposure trials, was also the most resistant to PLRV multiplication. The combination of these two types of resistance in cultivars should help to eliminate the spread of PLRV in crops.

The susceptibility of tubers of potato cultivars to black dot (Colletotrichum coccodes (Walk.) Hughes)

SummaryIn experiments with commercial seed of different cultivars at Rothamsted and Woburn, Bedfordshire in 1985 – 88 the severity of black dot on daughter tubers at harvest differed between cultivars. The disease was most severe on Desiree tubers. Amounts of disease were similar at both sites in 1986 – 88 but in 1985 it was more severe at Woburn than at Rothamsted.Disease‐free seed of 12 (1987) or 15 (1988) cultivars were planted in experiments at Rothamsted (inoculated with Colletotrichum coccodes or not) and at Mepal, Cambridgeshire (not inoculated) and black dot assessed at harvest in October 1987 and in September and October 1988. There were significant differences in the amount of disease on different cultivars and the order of severity was similar at the two sites, on the two harvest dates in 1988 and in both years. Desiree, Maris Piper, Maris Peer and Record were amongst those cultivars severely affected whereas Cara, Pentland Crown and Romano were least affected.Skin discoloration caused by black dot was more noticeable on white‐skinned than red‐skinned cultivars and was severe on the Dutch cultivars Estima, Marfona, Santé and Wilja.

The role of soil, seed-potato tuber and haulm in the transmission of Phoma foveata from infected seed to daughter tubers

Infestation of ridge soil by Phoma foveata was examined over 4 years by collecting soil samples at various distances from seed tubers which were either naturally infected or inoculated with a distinctive strain. Samples were taken on four occasions during each growing season. Infestation was greatest immediately around the tuber and was largely confined to a distance of 15 cm until haulm destruction, after which P. foveata was detected more widely in the soil. The effects of various seed-tuber and haulm treatments on the incidence of daughter-tuber contamination by P. foveata were assessed over 5 years. Removing the infected seed tuber at emergence significantly (P < 0.05) reduced the contamination at haulm destruction of daughter tubers harvested by hand in only 1 out of 4years. In all years, tuber contamination was much less(P < 0.05) when stems were pulled and removed than when they were desiccated by applying diquat dibromide. The incidence of tuber contamination did not increase between haulm destruction and harvest when stems were pulled and removed. In another experiment, tuber contamination increased linearly with the delay in pulling haulms after applying diquat dibromide. Cutting and removal of stems tended to reduce gangrene contamination, relative to the desiccation of stems by applying diquat dibromide, in all years where the seed tuber had been removed, but in only 2 out of 5 years where the tuber was present.

Contamination of seed potato tubers grown from stem cutting or microplant‐derived tubers by Phoma foveata and Polyscytalum pustulans in Scotland: the influence of site and fungicide treatment at harvest

SummaryA survey was made over 5 years of the incidence of contamination by Phoma foveata and Polyscytalum pustulans on 3‐year‐old virus‐tested stem cutting (VTSC) stocks assessed on three occasions during the storage season, and on their daughter tubers at five farms. The contamination occurring on plants grown in small plots from stem‐cutting/microplant tubers was also assessed at the farms.Fungicide treatment soon after harvest reduced the incidence of both pathogens, especially P. pustulans. Tuber contamination was similar for samples collected after fungicide treatment and before planting. The incidence of contamination on daughter tubers, relative to that on the untreated mother tubers, was less with P. foveata but was similar or greater with P. pustulans. Contamination by both pathogens varied between farms and was reflected in the degree of contamination occurring on daughter tubers from stem‐cutting/microplant tubers.The incidence of P. foveata on stems, soil and tubers of seed stocks classified at Foundation Stock grade from various regions of Scotland was assessed over 2 years. The incidence of tuber contamination was correlated (P &lt; 0.05) with the amount of tuber‐borne soil contamination for all comparisons, but was correlated with stem inoculum in only 7 out of 13 comparisons. The largest amounts of stem inoculum of P. foveata were found in stocks in Aberdeenshire.These results are discussed in relation to the spread of both pathogens to healthy VTSC stocks.

Untersuchungen zur Durchseuchung einer Kartoffelnachkommenschaft mit dem Erreger der Bakterienringfäule, Clavibacter michiganensis subsp. sepedonicus, bei wiederholtem Nachbau

The transmission of potato ring rot caused by Clavibacter michiganensis subsp. sepedonicus from plant tubers inoculated to daughter tubers and the incidence in progenies of this material in the following 5 cultivation years were studied. In first year potato plants inoculated and cultivated in a plastic house remained symptomless. However, in the next springtime 5.3. (cv. “Fringilla”) untill 9.3% (cv. “Astilla”) of the stored tubers showed typical ring rot symptoms (discoloration and maceration of the vessel zone of tubers). Plant tubers germinated in light or in darkness did not differ in their susceptibility. By gram staining, serological analysis (agargel diffusion technique) and bioassay (inoculation of Solanum melongena plants) it could be demonstrated, that nearly 50% of the tubers became latently infected by the ring rot pathogen. The continued cultivation of this tuber material in the field showed in the first two years (1980, 1981) only a low portion of tubers with ring rot symptoms (dependent on the varities tested from 0.8–5.2%). In 3 and 4th cultivation year (1982, 1983) the percentage of incidence increased to 4.3–14.8%. In the last year of cultivation (1984) 5.3–7.6% of the tubers with typical symptoms could be found, that was a similar portion like in 1982. No correlation between the occurrence of black leg in the crop (caused by Erwinia carotovora subsp. atroseptica) and the incidence of ring rot was to state. In der vorliegenden Arbeit wird die Übertragung der Bakterienringfäule (Erreger: Clavibacter michiganensis subsp. sepedonicus) von künstlich infizierten Pflanzkartoffeln auf die Tochterknollen und der akute Befall in Nachkommenschaften aus diesem Material in 5 aufeinander folgenden Anbaujahren analysiert. Im 1. Anbaujahr (Folienhaus) waren keine Krankheitserscheinungen zu beobachten; erst im Frühjahr des Folgejahres zeigten 5,3 (Sorte „Fringilla“) bis 9,3% („Astilla“) der eingelagerten Knollen typische Ringfäulesymptome (Verfärbung und Mazeration des Gefäßbündelringes). Bei Licht oder im Dunkeln gekeimte Pflanzkartoffeln ließen keine signifikanten Unterschiede in ihrer Anfälligkeit erkennen. Mit Hilfe der Gramfärbung und einer serologischen Analyse (Agargel-Diffusionstest) sowie im Biotest (Inokulation von Eierfruchtpflanzen) konnte nachgewiesen werden, daß ca. 50% der Knollen latent mit dem Ringfäuleerreger verseucht waren. Der nachfolgende Anbau dieses Knollenmaterials im Freiland führte in den ersten beiden Jahren (1980, 1981) nur zu einem geringen akuten Befall des Erntegutes (je nach Sorte 0,8–5,2%). Im 3. und 4. Nachbaujahr (1982,1983) erhöhte sich dieser Anteil auf 4,3–14,8%. Im letzten Anbaujahr (1984) lag der Befall bei 5,3–7,6% und damit etwa ebenso hoch wie im 3. (1982). Zwischen dem Auftreten der Schwarzbeinigkeit im Bestand (Erreger: Erwinia carotovora subsp. atroseptica) und dem Befall mit der Bakterienringfäule war keine Korrelation nachweisbar.

Potato growth and tuber production as affected by inoculation of cut and whole seed withRhizoctonia solani (AG 3) and the use of seed treatment fungicides

A potato seed tuber inoculation technique forRhizoctonia solant resulted in consistent field study results and demonstrated a reduction of about 15% in early plant vigor ratings 30 days after planting. Plant stands were generally unaffected by the introduced pathogen presence around the potato seed. After 45–60 days’ growth, inoculated seed had significant increases in the number of weak plants compared to the uninoculated seed. The impact ofR. solani on daughter tuber production included significant total yield losses in two of three years and seed inoculation increased the severity of black scurf on daughter tubers with significant differences occurring two of four years. Use of whole seed resulted in similar early plant vigor losses as was found for cut seed but inoculated, whole seed treatments had fewer weak plants and less yield loss than inoculated, cut seed treatments. Pre-planting seed treatment fungicide applications resulted in a few significant differences in plant growth and yield depending on the fungicide used. Black scurf incidences on daughter tubers were generally reduced but significant differences were more frequent for whole than cut seed treatments. However, none of the commercially available seed treatment fungicides provided consistent disease control. Aspects of disease incidence, development and control for potato production conditions in the northeastern region are also discussed.

Effects of potato leafroll virus on the crop processes leading to tuber yield in potato cultivars which differ in tolerance of infection

SUMMARYThe effects of infection with potato leafroll virus (PLRV) on the four crop processes leading to tuber fresh weight yield were examined in field plots of four cultivars (Montana, Pentland Crown, Maris Piper and King Edward) differing in tolerance to infection. Averaged across cultivars, infection decreased yield by 50%. This decrease was equally due to less light (total solar radiation) being intercepted, a lower efficiency with which intercepted light was converted into dry weight, and a smaller proportion of dry weight being partitioned to tubers. Dry matter content of the tubers was also diminished but to a lesser extent. The main difference between the cultivars in their response to infection was in the partitioning of dry weight. In Montana and Pentland Crown, harvest index was decreased by 15% in infected plants, whereas in the less tolerant cultivars, Maris Piper and King Edward, it was decreased by 25%. The decline in photosynthetic performance of Montana, a cultivar with slightly earlier maturity than the other three, was delayed in PLRV‐infected plants. Effects on number of daughter tubers essentially reflected those on yield to the extent that average tuber weight did not change in Maris Piper, was one third less in King Edward, and the change was intermediate in Montana and Pentland Crown.