Potato Seedlings Research Articles

Reaction of Sweet Potato Seedlings to the Russet Crack Strain of Feathery Mottle Virus

Abstract The response of 501 open-pollinated seedlings of 9 parental clones of sweet potato [Ipomoea batatas (L.) Lam.] to the severe russet crack strain of sweet potato feathery mottle virus (SRC-FMV) was evaluated under greenhouse conditions. Sixty-four percent of the seedlings showed foliar, root, or foliar/root symptoms, indicating that SRC-FMV can be sap-transmitted to seedlings. Fifty-nine percent showed foliar symptoms only. Seedlings from the parental clone with the highest percentage of symptom expression (88%) in the greenhouse were used to study the effect of selected environmental factors on foliar symptom expression. The predominant symptom was veinbanding. The percentage of plants showing symptoms varied from 0% to 46% and was influenced significantly by the interaction of light intensity × daylength × temperature.

Control of pre‐ and post‐emergence damping‐off of potato seedlings caused by Rhizoctonia solani in Peru

SUMMARYFungicide treatment of soil and true potato seed and the use of subsoil as a growth medium significantly reduced pre‐emergence damping‐off caused by Rhizoctonia solani. Attempts were made to determine safe levels of fungicides for soil and seed treatments. For seed, safe levels varied between 0–9% a.i. for pentachloronitrobenzene (PCNB) and 3‐0% a.i. for mancozeb (dithane M‐45).Fungicides only marginally reduced post‐emergence damping‐off of transplants raised from true potato seed but gave significant increase in yield. The prospects of using fungicide treatment of true seed to control damping‐off in seed beds and in direct field sowing are discussed.

Stem thinning in potato as a pre-selection index

Using the potato seedling B7906-1, stem thinning was carried out on plants having three, four, or five stems per hill. Treatments ranged from intact plants to those thinned by one, two, or three stems each. Data on the effect of stem thinning on yield and other vegetative parameters were analysed using an analysis of variance. Unlike leaf parameters, stem height and number of stolons per plant generally decreased with an increase in stem thinning. Within a control group, represented by the intact plants having the three stem densities used for treatments, the degree of association among different vegetative parameters and the measure of their contribution towards yield were determined by correlation and path coefficient analyses, respectively. Given the effect of number on weight of tubers per plant, the assessment of yield as affected by stem density treatments was confined to the former parameter. Among all parameters, number of stolons per plant was the most effective contributor to number of tubers harvested. The decrease in that parameter as a result of stem thinning, however, was not accompanied by a corresponding decrease in tuber number. The following relationship could be discerned: as number of stolons per plant decreased several stem parameters increased. Based on correlation and path analyses, it is suggested that the induced increase in number of compound leaves per stem could have compensated, directly or indirectly, for the adverse effect of stolon number on yield. Through stem density manipulation, the yield output of a variety in response to quantitatively induced, more diverse, vegetative characteristics could be evaluated.

Daminozide Protects Potato Seedlings from Metribuzin Phytotoxicity

Abstract The effect of daminozide as a plant growth retardant to protect potato seedlings from metribuzin injury was investigated. Plants of 6 potato cultivars were sprayed 42 days after planting with daminozide at 0, 2500, 5000 ppm concentrations. Four days after daminozide treatment, metribuzin at 0.56 kg/ha was applied. Within 3 days after metribuzin treatment, differences between potato cultivars in metribuzin tolerance was observed. Seven days after metribuzin application 25.2% to 42% of the control plants had more than 20% necrosis, and of this percentage, 0% to 13.9% plants were dead. Only 2.3% to 10.7% of the plants exhibited more than 20% metribuzin injury when pretreated with 2500 ppm daminozide. Potato plants treated with 5000 ppm daminozide were not damaged. The soluble solids of stem sap increased with daminozide rate. Protection from metribuzin injury in potato was associated with the increase in soluble solids in daminozide treated plants. Chemical name used: butanedioic acid mono (2, 2-dimethylhydrazide) (daminozide).

Root Protein Quantity and Quality in a Seedling Population of Sweet Potatoes

Abstract A population of 100 sweet potato seedlings from 7 parent clones was grown for one season in order to evaluate root protein quantity and quality. Protein content of the 100 seedlings ranged from 4.38% to 8.98% with a mean of 6.29%; the 7 parents ranged from 4.96% to 6.53% with a mean of 5.72%. The mean of the seedlings was not significantly different from that of the parents. The 10 seedlings with highest protein (7.40% to 8.98%) were selected for further study of protein quality. Levels of nonprotein nitrogen (NPN) in these high protein selections were not significantly different from those of the parents. The correlation between the percentage of protein and the percentage of NPN was low (r = 0.30). The amino acid pattern in the high protein selections differed significantly from the parents with lower levels of valine, cysteine, methionine, tyrosine, and phenylalanine. Trypsin inhibitor activity (TIA) levels in the selected seedlings did not vary significantly from the parents. TIA and the percentage of protein were not significantly correlated (r = 0.15). The results indicate it is possible to obtain high protein cultivars without increasing the percentages of NPN and TIA. With the exception of valine, the aromatic and sulfur-containing amino acids, the overall protein quality was not changed in the seedlings with increased protein content.

Assessment and analyses for the interpretation of potato late blight response in field studies

Potato seedlings and cultivars were successfully subjected to moderate to heavy late blight pressure in field plots to which a race complex of the pathogen was applied. Multiple assessments through the course of the epidemics revealed differences in overall disease susceptibility or resistance. Differences were also demonstrated in disease response patterns among potato lines with similar overall disease ratings. Use of principal component and cluster analyses established discrete groupings of potato lines. This provides a basis for a more objective interpretation of the results in identifying both overall disease response and pattern (slow or fast) of response of potato cultivars and breeding lines.

Título en español

Raíces de 30 cultivares y líneas, y de 310 plantas de semilla no seleccionadas de batata se evaluaron como rebanadas hervidas. Rebanadas finas de 75 selecciones de las arriba mencionadas se frieron en aceite de soya y se evaluaron como frituras. Por el color, dulzura y textura en la boca se clasificaron las 310 plantas en 25 de 27 clases teóricas. La poca dulzura estaba asociada con textura seca. La frecuencia de defectos en rebanadas hervidas se determinó. Se obtuvieron dos tipos de frituras, uno del tipo de galleta dulce y uno similar a la papa. Las características de calidad eran más o menos independientes unas de las otras y de otras características medidas. Se calcularon los coeficientes de correlación entre las evaluaciones de frituras con su sabor, fragilidad, falta de residuo de aceite y apariencia. Las altas evaluaciones no estaban correlacionadas significativamente con la dulzura. Las batatas sirven para frituras de tipo galleta dulce y tipo papa. Sin embargo, sus propiedades antes de freir no son guías confiables para lograr batatas fritas de buena calidad.

Symptomless Infection, Persistence, and Production of Pycnidia in Host and Non-Host Plants by Phomopsis batatae, Phomopsis phaseoli, and Phomopsis sojae, and the Taxonomic Implications

Phomopsis batatae, P. phaseoli, and P. sojae were able to infect, without production of obvious symptoms, seedlings of sweet potato and of 16 legumes inoculated in the greenhouse. These fungi produced pycnidia on inoculated seedlings incubated in laboratory moist chambers. Under conditions of natural infection in the field, P. sojae was recovered from stems of 14 of 21 legumes. This fungus was also isolated from seeds of cowpea and lima bean as well as from soybean, its usual host. The interpretation of these results questions the validity of regarding these anamorphs as three distinct species. Taken with the close similarity in morphology reported for these taxa in the literature and observed in my own isolates and in herbarium specimens, I conclude that these taxa are all one species, the valid name of which is Phomopsis phaseoli (Desm.) Sacc. For similar reasons, I consider the teleomorphs Diaporthe phaseolorum var. batatatis, var. phaseolorum, and var. sojae to be one and the same taxon, D. phaseolorum (Cooke & Ellis) Sacc. I believe that teleomorphic and anamorphic isolates from stem cankers and blighted tops of soybean should be provisionally called D. phaseolorum f. sp. caulivora and P. phaseoli f. sp. caulivora, respectively, until it can be demonstrated by a non-wounding technique that they can cause these pathological conditions when re-introduced into the host.

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

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.

Effect of selecting potato seedlings under maritime conditions on the performance of the first clonal generation under Prairie conditions

The Agriculture Canada Potato Breeding Program in New Brunswick is the source of new germplasm for co-operative breeding projects in other regions of Canada. Selection under maritime conditions in early clonal generations is conducted at Fredericton, New Brunswick prior to shipment of seedlings to these projects. An evaluation of this system was required with the advent of a new breeding project at the Lethbridge Research Station, Alberta, in 1979 for the Prairie region of Canada. Two groups of first field generation seedlings obtained from the Fredericton breeding program were compared in Alberta. One group was composed of seedlings obtained at random and the second of seedlings obtained through the normal selection procedures used at Fredericton. Ten crosses were sampled in 1979 and twelve in 1980. Results of the study provide evidence that pre-selection in the first clonal generation at Fredericton significantly (P < 0.05) improves the maturity, yield, and tuber traits of these seedlings grown in Alberta, yet does not cause a major reduction in the variability of traits.

Effect of potato seed tuber glycoalkaloid content on subsequent infection byRhizoctonia solani

Since glycoalkaloids have been shown to have fungitoxic properties, it is important to know what impact this might have on potato plant breeding programs which select for low levels of total glycoalkaloids (TGA) in the tuber. Potato clones with TGA levels ranging between 1.6 and 32.8 mg/100 g fresh tissue were planted in two trials to evaluate the relationship between seed tuber TGA and incidence ofRhizoctonia solani infection in the developing plant. An inoculation procedure was followed in the greenhouse and field to establish uniform infection of potato seedlings. Plants were examined for lesion development on stems and stolons and assigned disease ratings. In the field, yield of malformed tubers was recorded and included in the overall disease ratings. The results reported herein indicate that TGA levels in the seed tuber are unrelated to the severity ofR. solani infection in the seedling.

Selection of first-year potato seedlings for resistance to potato leaf roll virus

In families obtained from crossing pairs of parents with high resistance to potato leaf roll virus (PLRV), individual clones differ greatly in their level of resistance. Inoculation of first-year seedlings was effective in selecting more resistant families, but it was not so effective in selecting more resistant individual clones.

Assessing potato seedling progenies for resistance to the white potato cyst-nematode

SUMMARYA bulk seedling test is described which can be applied shortly after completion of a crossing programme. The test assesses resistance to G. pallida in progeny derived from crossing programmes involving S. luberosum, S. vernei and S. tuberosum spp. andigena. It provides good estimates of both the mean level of resistance within progenies and the breeding value of the parents. The test was applied to a crossing schedule involving a half-diallel and a North Carolina 2 design utilizing a range of material. The results and their implications are discussed.

Tests for transmission of four potato viruses through potato true seed

SUMMARYThe Andean potato calico strain of tobacco ringspot virus (TRSV‐Ca) was detected in 2–9% of potato seedlings grown from true seed from plants of cv. Cara and clone G5998(6) infected with TRSV‐Ca. Similarly, a potato isolate of the oca strain of arracacha virus B (AVB‐O) was detected in 4–12% of progeny seedlings of cv. Cara and clone D42/8 infected with AVB‐O. Potato virus T (PVT) passed through 33–59% of seed from PVT‐infected cv. Cara, but only 0–2% infection was detected in seedlings from seed of PVT‐infected clone D42/8. By contrast, no infection was detected in seedlings grown from seed from plants of G5998(6), D42/8 or cv. Cara infected with Andean potato latent virus strains Hu (APLV‐Hu) or Caj (APLV‐Caj), although both strains passed through seed of Nicotiana clevelandii.AVB‐O, PVT and TRSV‐Ca were detected in all tests of pollen from flowers of infected potato plants, but APLV‐Hu and APLV‐Caj were detected less frequently. AVB‐O and PVT were transmitted through 2% and 8% respectively, of seed from healthy potato plants pollinated with pollen from infected plants. However, no transmission through seed was detected when pollen from TRSV‐Ca infected plants was used. None of the four viruses were transmitted to healthy potato plants pollinated with pollen from infected plants.APLV‐Hu caused exceptionally severe symptoms in the cv. Cara plants used for seed production, but the Bolivian strain of PVT induced only mild symptoms rather than the severe systemic necrosis previously reported for the type of strain of PVT in this cultivar. No symptoms developed in potato seedlings infected with TRSV‐Ca, AVB‐O or PVT through the seed.

A method of assessing potato seedling progenies for resistance to the white potato cyst nematode

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.

Screening for resistance against the wart fungusSynchytrium endobioticum in potato seedlings with a modified Spieckermann method

The Spieckermann method of testing potatoes for resistance against potato wart (Synchytrium endobioticum (Schilb.) Perc.) was modified by using the plant growth regulator Cycocel to cause early initiation of tubers from potato seedlings and to allow maintenance of the plants in small containers (e.g. ‘Jiffy pellets’) until symptom expression. Less space, time and much less inoculum are needed in comparison with the original method.

A rapid technique for assessing the resistance of families of potato seedlings to potato leaf roll virus

A technique is described by which families of potato seedlings can be rapidly screened for resistance to potato leaf roll virus (PLRV) in the greenhouse with a minimum expenditure of labour and bench space. Seed of different families was sown in rows in four replicated blocks and the seedlings produced were exposed to viruliferousMyzus persicae when very young. Symptoms resembling those typical of secondary infection with PLRV developed within a few weks and families with few affected seedlings compared with the susceptible control were classed as resistant. Tests done at different times with similar sets of families gave similar results. Applying infectiveM. persicae by shaking heavily colonised potato shoots above the seedlings was more effective and far less time consuming than transferring them individually by hand using a fine paint brush.

Transmission of potato virus Y byRhopalosiphum padi L.

Winged forms ofRhopalosiphum padi were shown to transmit PVY but they were not efficient vectors as only ca 3% of the test plants (potato seedlings) became infected when inoculated with from 5 to 20 aphids per plant.

Effect of Seedling Age, Environmental Temperature, and Foliar Total Glycoalkaloids on Resistance of Five Solanum Genotypes to the Potato Leafhopper 12

Potato seedlings were evaluated at 2, 3, and 4 wk of age for resistance to Empoasca fabae (Harris) using glasshouse methods. The relative resistance rankings of seedling-stage plants, as measured by nymphal survival and plant injury, were similar to those obtained by field assessment of mature plants in earlier studies. Resistance of the wild, diploid species, Solanum pampasense Hawkes, was detectable in seedlings as young as 2 wk of age. Depending on the growth stage, foliage of S. pampasense seedlings contained 3–14 times the levels of total glycoalkaloids as that of the susceptible cultivar, ‘Katahdin’, suggesting involvement of these steroidal glycosides in potato leafhopper resistance. For mature plants, use of a fluctuating 25°/l5°C temperature regime provided a wider range in expression of resistance between clones than did a constant 25°C regime.

Solanum demissum P.I. 230579, a True seed diagnostic host for potato virus Y

Seedlings ofSolarium demissum P.I. 230579 in the 5-to 10-leaf stage growing under 18-hour days and at 20 to 24°C developed dark, irregular, slightly elongated local lesions 3 to 5 days following inoculation with any one of three strains of potato virus Y (PVY). Local lesions did not develop after similar inoculations with any one of two or more strains each of potato viruses A, M, S, X, or spindle tuber and a single strain each of potato calico and potato yellow dwarf. Inoculations from diseased specimens infected with PVY plus potato viruses A, M, S, and X, singly or in some combinations did not affect the efficiency of P.I. 230579 in detecting PVY in the mixed infections. Plants of P.I. 230579 developed significant numbers of local lesions from PVY inoculations at temperatures from 16 to 27°C and at inoculum dilutions through 1:100. Excised individual leaves of P.I. 230579 can be used to detect PVY. Leaves of plants exposed to air pollutants are unsuitable for assay purposes.S. demissum P.I. 230579 is homozygous for the local reaction to isolates of PVY and is a valuable aid for indexing aphid or mechanically inoculated potato clones or seedlings for resistance to the virus. It is a superior diagnostic host for differentiating PVY from other viruses commonly found in potatoes in the United States.