Seed Tubers Research Articles

Ecological interaction of a biocontrol Pseudomonas fluorescens strain producing 2,4-diacetylphloroglucinol with the soft rot potato pathogen Erwinia carotovora subsp. atroseptica

Erwinia carotovora subspecies atroseptica is the agent of soft rot of potato and causes important crop damage in Europe. Synthetic 2,4-diacetylphloroglucinol (DAPG) inhibited the growth of E. carotovora subsp. atroseptica under in vitro conditions and Pseudomonas fluorescens F113, which produces DAPG, was studied for biocontrol of E. carotovora subsp. atroseptica. Wild-type F113 (or the spontaneous rifampicin-resistant mutant F113Rif) inhibited growth of E. carotovora subsp. atroseptica on solid medium, displayed bactericidal activity towards the pathogen in liquid medium, and prevented Erwinia-mediated rotting of wounded potato tuber under in vitro conditions. F113Rif reduced the population size of E. carotovora subsp. atroseptica in soil and on potato tuber dice in competition experiments carried out with unplanted soil and soil planted with diced potato tubers, respectively. Co-inoculation of potato tuber seeds with F113Rif and E. carotovora subsp. atroseptica reduced Erwinia contamination of the seed tubers compared with single inoculation with the pathogen. F113G22 is a Tn 5:: lacZY-induced DAPG-negative biosynthetic derivative of F113 and showed no antibiosis towards E. carotovora subsp. atroseptica in vitro. In contrast to F113Rif, F113G22 did not inhibit Erwinia-mediated rotting of wounded potato tuber in vitro, did not influence survival of E. carotovora subsp. atroseptica in unplanted soil or soil planted with potato tuber dice and did not reduce Erwinia contamination of potato seed tubers. F113G22(pCU203) is a complemented derivative with restored DAPG-producing ability. F113G22(pCU203) had similar effects against E. carotovora subsp. atroseptica as F113 (or F113Rif) under in vitro conditions and in soil microcosms. The results indicate that P. fluorescens F113 is a promising biocontrol agent against the potato soft rot agent E. carotovora subsp. atroseptica and suggest that the pseudomonad's ability to produce DAPG is a key factor in its inhibition of the pathogen.

Influence of Planting Depth of the Seed Tubers on the Growth and Yield in the Cultivation of Yacon (Polymnia sonchifolia)

Tuberous roots of yacon (Polymnia sonchifolia) contain a large amount of oligofructans. So they draw great attention as a healthful diet. Processed food of tuberous roots and tea of foliages are commercially sold already. But reports on cultivation of yacon are few, influence of planting depth of seed tubers on growth and yield not yet tested. Tested were the planting depth of seed tubers in ridges 25cm high.Three planting depths: 5cm, 10cm and 15cm were tested. Each plot had three replications.Results as follows:1) Growth of main stem was least in the 5cm plot.2) Top dry weight per plant was 196.4g, 215.3g and 223.5g in 5cm, 10cm and 15cm plots respectively.3) Yield of tuberous roots per plant was 1413.0g, 1525.7g and 1269.6g in 5cm, 10cm and 15cm plots respectively. Yield of tuberous roots over 100g per plant was 970.1g, 1142.0g and 914.2g in each plots.4) Percentage of tuberous roots over 300g was least in the 15cm plot.5) Gaseous phase ratio at planting depth at harvest time was 55.08%, 47.14% and 38.17% in 5cm, 10cm and 15cm plots respectively.6) In ridges 25cm high, 10cm should be the suitable planting depth for yacon seed tubers.

Greenhouse production of potato (Solanum tuberosum L. cv. Désirée) seed tubers using in vitro plantlets and rooted cuttings in large propagation beds

Seed tuber production fromin vitro potato plantlets and cuttings was conducted in large propagation beds in a greenhouse. Propagules of wholein vitro plantlets (WIP), plantlets with apical (ACR) and lateral (LCR) cuttings removed, the rooted apical cuttings (RAC) and rooted lateral cuttings (RLC) were planted at three densities of 25, 49 and 100 plants per m2. The plantlets from which cuttings were removed (ACR and LCR) produced more tubers than the rooted cuttings (RAC and RLC); however, the most tubers were produced by WIP. RAC produced highest tuber yields followed by WIP and RLC. Intact WIP and plantlets with cuttings removed (ACR and LCR) produced twice as many tubers <40 g as those from rooted cuttings (RAC and RLC). The yield (kg/m2) as well as the number of tubers per m2 increased with the increasing planting density within the densities tested.

The control of silver scurf and development of thiabendazole resistance inHelminthosporium solani as affected by the rate of fungicide applied to potato seed tubers

Seed tubers were immersed in suspensions of thiabendazole (Storite) or thiabendazole plus imazalil (Extratect) at different concentrations and planted in a field experiment. During the following 2 years samples of the produce were planted after treatment with the same fungicide formulation used on the seed.

Use of true potato seed in the tropics: Potentials and realities

Abstract In the tropics, the high costs and limited availability of high quality tuber seed are the major constraints for successful potato production. In the last fifteen years or so, true potato seed (TPS) has emerged as one alternative with exceptional potential for eliminating many of the problems associated with tuber seeds. The technology has generated greater expectation and many local potato programs are already using TPS within their propagation programs. Yet, given the level of expertise needed to manage TPS‐based potato production, it is not clear whether TPS can be successfully used at the farmer level. This paper reviews key features of the TPS technology and assesses the performance of TPS at various locations in the tropics.

388 EFFECTS OF DEHAULMING ON CANOPY GROWTH AND TUBER YIELD OF `YUKON GOLD'

Seed tubers of `Yukon Gold' (Solanum tuberosum L.) exhibit strong apical dominance, resulting in relatively poor stem emergence. Cutting seed tubers to overcome apical dominance in `Yukon Gold' results in irregular, uneven stem emergence. In 1992 and 1993, experiments were conducted to evaluate the effects of dehaulming (excising stems to ground level after field emergence) whole, cross- and longitudinal-cut seed tubers of `Yukon Gold' on canopy growth and tuber yield. For all seed piece types, dehaulming during the first week of field emergence produced uniform plant stands and increased yields of U.S. no. 1 tubers by 16 and 42% and large tubers (&gt; 6.4 cm dia.) by 340 and 64% in 1992 and 1993, respectively. Our data indicate that tuber bulking rate was increased by dehaulming. The possible causes and implications of increased tuber bulking rates in dehaulmed potato plants are discussed.

Advancing growth vigor of seed potatoes by a haulm application of gibberellic acid and storage temperature regimes

Seed tubers that are planted soon after their harvest give low yields because of dormancy and low growth vigor. In the research reported in this paper, we investigated the advancing effect of a haulm application of gibberellic acid (750 g GA/ha) 6 days before haulm pulling and its interaction with storage temperature regimes on the growth vigor of immaturely harvested seed tubers of three cultivars. The effects on tuber yield were also examined in one experiment. The storage regimes were: 18 C continuously, hot pre-treatments of different duration (different periods at 28 C and subsequently 18 C) and a cold pre-treatment (20 days at 2 C and subsequently 18 C).

Fungicide treatment of seed tubers infected with thiabendazole-resistantHelminthosporium solani andPolyscytalum pustulans for controlling silver scurf and skin spot on stored progeny tubers

Seed tubers, cv. Desiree, derived from stocks treated annually with thiabendazole were infected with thiabendazole-resistant strains ofHelminthosporium solani andPolyscytalum pustulans. Samples of seed tubers were either untreated or immersed for 5 min in fungicide suspensions of thiabendazole, imazalil or thiabendazole plus imazalil and planted on four farms in 1988 and 1989. After harvest, tuber samples from each treatment were treated with thiabendazole and stored for 6 months.

Effect of inoculum source on root and tuber infection by potato blemish disease fungi

The incidence of potato pathogens on healthy roots of micropropagated (MP) and seed tuber (ST) plants was examined on successive dates during the growing season in two field experiments. Microplants were grown in a glasshouse for 4–5 weeks in perlite or peal‐based substrates, and exposed or not to natural inoculum before planting in the field. The seed tubers originated from stocks of visually clean or moderately blemished tubers and were surface‐sterilized or not before planting. Polyscytalum pustulans and Helminthosporium solani only infected roots of ST plants and inoculated MP plants. The incidence of P. pustulans was affected by seed tuber‐borne inoculum and, in I year, by the substrate. H. solani was detected infrequently on roots. Rhizoctonia solani was present at low frequencies in most root samples, and more ST than MP plant roots were colonized; there were no substrate effects. In 1 year, increased inoculum levels increased root infection, but only in MP roots. Colletotrichum coccodes occurred at high frequencies and was most common in roots of ST plants. Progeny tubers showed some treatment effects when tested in September and after storage for 6 months, but there were no consistent relationships between root and progeny tuber infection.

Rapid multiplication of potatoes: Influence of environment and management on growth of juvenile apical cuttings

Seed tubers are costly and often unavailable in the warm tropics. Alternative methods of growing potatoes include the use of cuttings. Vigorous mother plants are needed to produce large quantities of cuttings particularly under warmer temperatures. This paper reports the influence of temperature, media fertility and hormones on the growth of apical cuttings and their subsequent productivity as mother plants in Vietnam. Subsoil or sand and dried sieved cow manure at a ratio of 1:3 was best for rooting and establishing cuttings as mother plants under high temperatures (minimum/maximum of 23.7/31°C). Weekly foliar sprays of diluted Knop’s media or complete NPK improved growth of rooted cuttings. Mother plants produced the greatest number of cuttings at the mid and high elevation locations (800 and 1300 m above sea level) where it is possible throughout the year. At the lowland site, temperatures went beyond the critical level from April to October for mother plant survival and apical cutting production. Kinetin or GA3 did not significantly improve cutting production while their combination did improve productivity compared to the control. Mother plants were generally productive for four months after their establishment.

The influence of host resistance and climate on the initial appearance of foliar late blight of potato from infected seed tubers

Seed tubers of susceptible and moderately resistant cultivars were inoculated withPhytophthora infestans and planted in a field in four trials over three years. After emergence, the foliage was periodically examined for late blight lesions. For the four trials, blight was first observed 9, 5,4, and 4 days after the accumulation of 18 severity values supporting the use of severity values for the prediction of initial appearance of blight as used in Blitecast. The first observance of blight followed a period of consecutive days which were favorable for blight development and ranged from 17 to 46 days after median emergence. Lesions were observed on foliage of the susceptible cultivars before detection on moderately resistant cultivars for three out of four trials. We conclude that late blight will usually, but not always, appear in susceptible cultivars before it appears in moderately resistant ones.

Potato ( Solanum spp.) in an isohyperthermic environment IV. Effects of cutting seed tubers

Seed tubers are the largest potato-production cost in the warm tropics. Cutting the tubers into small seed-pieces is one way to reduce this expense. Seed-tuber cutting was evaluated in seven experiments with five cultivars (evaluated in one or more experiments) in The Philippines. Cut seed-pieces produced equal or greater yields compared to whole seed tubers at similar seed rates (t ha −1). With the cv. Cosima, seed rates from 0.8 to 3.9 t ha −1 (whole or cut) gave yields between 21 and 27 t ha −1. Lowering seed rates to 0.4 t ha −1 by cutting into small seed-pieces increased yield per unit seed weight planted (highest ratio was 44:1). Cutting resulted in many more stems per unit weight of seed planted, particularly for cultivars with long dormancy (up to 100% increase). Seed-curing for 5 days before planting was essential for cv. P-7 but only slightly advantageous for Cosima. Benomyl or sodium-hypocholorite treatments did not improve suberization or plant growth. Suberization was rapid under the high temperatures ( x ̄ = 25° C ) of our study. Seed cutting is feasible in reducing seed rates and for more effective use of large, expensive seed tubers.

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.

The effect of storage conditions on subsequent field performance of potato seed tubers in Tunisia

Seed tubers of four cultivars were grown under similar conditions and harvested simulataneously. They were stored in traditional dark storage, diffused-light storage, or cold storage, and with combinations of these three methods for 150 or 230 days beginning in the hot, dry summer period. The effect of storage conditions on emergence, stem and tuber number, tuber size distribution and yield is discussed. Results suggest an optimal combination of storage method, cultivar choice, and sprout management practices may be achieved to obviate the need for cold storage in warm climates. Emergence and yield were consistently good for the 150-day storage period when traditional storage was followed by diffused-light storage. The sam technology gave promising results for the 230-day period with cultivars Claustar or Desiree when seed was desprouted prior to planting.

Effects of silver scurf (Helminthosporium solani) on seed potatoes

Seed tubers with severe (80–100% of surface affected) or slight (less than 20% of surface affected) silver scurf were selected from commercial stocks and planted at Rothamsted in 1979–81. Severely affected seed lost more weight (13%) than slightly affected seed (8%) during storage on trays, and produced more but smaller sprouts. Ground cover, leaf area and tuber yields were decreased by severe infection for up to 7 weeks after planting but thereafter effects of seed infection were non-significant. In two years, tubers produced from seed with severe silver scurf had less infection than those from slightly affected seed, but in 1980 most disease developed on tubers from seed with severe infection.

Soil and Seed Tubers as Sources of Inoculum ofErwinia carotovorapv.carotovorafor Stem Soft Rot of Potatoes

Soil and Seed Tubers as Sources of Inoculum of<i>Erwinia carotovora</i>pv.<i>carotovora</i>for Stem Soft Rot of Potatoes

Reduction of Yield Depressions in High Frequency Potato Cropping Soil after Seed Tuber Treatments with Antagonistic Fluorescent Pseudomonas spp.

AbstractSevere yield depressions observed in high frequency potato cropping caused by microbial factors other than eelworms or known pathogens (narrow rotation effect) were reproduced in pot experiments. Total plant weight in a soil continuously cropped with potatoes was only 69% of that in a similar soil continuously cropped with wheat. Tuber weight in potato‐soil was only 13 % and number of tubers only 10% of that in wheat‐soil. Seed tuber treatment with cell suspensions of fluorescent antagonistic pseudomonads in carboxymethylcellulose (CMC) raised tuber yield in potato‐soil up to 70% (550 % increase), number of tubers up to 93% (934 % increase) and total plant weight up to 90% (31 % increase) as compared with CMC‐treatment in wheat‐soil. Antagonistic fluorescent Pseudomonas isolates WCS 365, WCS 358 and WCS 374 producing mainly siderophores, with little or no production of other inhibitory substances, were more effective in diminishing the narrow rotation effect than the isolates that produced mainly inhibitory substances of different nature.

Tetrazolium tests as indicators of tuber physiological age and yield potential

Seed tubers were treated by incubation of cut surfaces in solutions of 0.5%, 2,3,5-triphenyl tetrazolium chloride (TZ) for 30 or 90 min. Reaction rate, measured as change in surface reflectance (R/hr) and distance of transport in vascular tissue (mm/hr), were significantly correlated with tuber aging due to time (1, 2, 3 years) or temperature treatments and with sprout number per tuber. TZ results were significantly correlated with yield of U.S. no. 1 tubers in field tests. It was proposed that TZ be used in seed tuber testing and as a cytochemical probe in physiological studies.

The quality of seed tubers multiplied in the Golan Heights for the spring season in Israel

Seed tubers grown in the northern mountain region — the Golan Heights — were as productive as imported seed tubers. In cvs. Blanka and Desiree, both the locally grown and the imported seed tubers were similar when yield components and tuber fresh weight are considered. In Up-to-Date, the locally grown seeds produced higher yields of marketable tubers (over 60 g/tuber) than those imported. Desiree seed tubers grown for two generations in the Golan Heights did not differ significantly in their productivity as compared with common Golan seeds and with imported ones. Seed tubers harvested from plots which were protected by means of white coarse nets and weekly sprays with insecticides, were virtually virus-free and were used for growing commercial seeds in the Golan. The use of this method for seed multiplication is suggested.

Rhizoctonia Disease of Potato: Effect on Yield and Control by Seed Tuber Treatment

Rhizoctonia Disease of Potato: Effect on Yield and Control by Seed Tuber Treatment