Performance of potato (Solanum tuberosum L.) in three tropical soil families as influenced by their temperature regimes

Potato experiments (cv. Kennebec) were conducted in three tropical soil families as part of a program to determine crop production potential and land capabilities of a network of tropical soil families. Good tuber yields resulted from matching the requirements of the potato crop to land characteristics. An average yield of 32,000 kg/ha was obtained in the thixotropic, isothermic soil family of Hydric Dystrandepts in Hawaii. The results of this study indicate that with optimum plant protection year-round potato production is possible in this family of Hydric Dystrandepts under rainfed conditions. Yields of irrigated plots in the clayey, kaolinitic, isohyperthermic soil family of Tropeptic Eutrustox were 36,000 kg/ha in the winter and 25,000 kg/ ha in the summer. The results indicate that winter temperatures are nearly isothermic, and are thus suitable for potato production, in an isohyperthermic Tropeptic Eutrustox of Hawaii. No yields were obtained from plantings in the clayey, kaolinitic, isohyperthermic soil family of Typic Paleudults in Indonesia and the Philippines. Tuberization did not occur in the warm and moist environment of the Typic Paleudults. Mismatch between the temperature requirements of the potato crop and the soil temperature regime of Typic Paleudults resulted in no potatoes.     

Tolerance to potato leafhopper inSolanum tuberosum L. gp. Tuberosum clones

We identified clones inSolanum tuberosum L. gp. Tuberosum breeding populations that, although susceptible to infestation by potato leafhopper,Empoasca fabae (Harris), exhibited a tolerance which was manifested by the ability to produce higher than expected tuber yields when heavily infested with leafhoppers. Such tolerance was noted in a number of clones in varying degrees, but one, B6930-1, was exceptional. It sustained only a 19% loss in tuber yield compared to ‘Katahdin,’ a susceptible cultivar, that averaged 33% lower tuber yields under similar infestation levels. We studied the seasonal growth patterns of this clone and compared them to those of Katahdin, and B6705-10, a breeding clone with known resistance to leafhopper infestation. We found that much of B6930-l’s tolerance results from its early, vigorous vine growth and its early and rapid rate of tuber bulking, enabling this clone to escape some of the effects of leafhopper feeding, whereas Katahdin was usually just beginning to tuberize at the height of leafhopper infestation.     

Influence of plant spacing on potato (Solanum tuberosum L.) morphology,growth and yield under two contrasting environments

Summary In experiments at a temperate (43^oN) and a tropical (14^oN) location, closer plant spacing decreased stem branching, root growth, and mean tuber size but increased tuber yields per ha. Closer spacing increased plant height at the temperate site but decreased it at the tropical site where canopy cover did not reach 100%. The increased branching at the wider spacing did not compensate for fewer plants/m². Total and tuber weight per plant increased with wider spacing and was much greater under temperate than tropical conditions. Tuber yield/stem also increased with lower stem densities. Although these results provide initial data for modelling, the contrast between the two environments and interactions between spacing and cultivar suggest that further experiments need to be done with a range of cultivars at intermediate locations.     

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.     

Shoot development and flowering in potato (Solanum tuberosum L.)

Summary The shoot system of potato is a configuration of stems with terminal inflorescences. In this review, shoot development is quantified in terms of stem production, while stem development is quantified in terms of leaf and flower primordia production per stem, which are functions of the rates and the durations of primordia initiation. The effect of the position of the stem in the shoot system on number of leaves and flowers per stem is also evaluated. Flowering of individual stems is described by the ‘time to flower primordia initiation’ (expressed in number of leaves produced) and ‘flower production’ (a function of the number and the development of flower primordia). At warmer temperatures and longer daylengths the number of leaves and flower primordia per stem, and the number of stems per shoot increase by prolonging stem production and primordia development. Temperature and photoperiod also affect flower primordia survival by altering assimilate production and partitioning. The photothermal response of the number of leaves per stem is small compared to the response of stem production; at higher temperatures, flower primordia survival becomes the principal factor determining flower production. The similarity of the signals leading to flower primordia initiation and tuberization, and the relation between shoot and tuber growth are discussed.     

Genotype X environment interactions in potato (Solanum tuberosum L.)

Genotype X environment interactions were estimated for several traits in potato from a combined analysis of 11 genotypes grown at 3 locations for 2 years. Genotype X location X year and Genotype X location interactions were significant for the majority of the traits studied. Yield, reducing sugar content, dry matter content, leaf area, plant height and starch content should be tested over multiple locations and years in order to separate the genotype × environment interaction components from the total genotypic variance.     

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%).     

High temperature storage of potato (Solanum tuberosum L.) for processing — a feasibility study

Tubers of three potato cultivars were stored at room temperature (20–39°C, 30–75% RH), under an insulated storage run on passive evaporative cooling (16–30°C, 70–90% RH) and a refrigerated storage (2–4°C, 90–95% RH) for 14 weeks and studied periodically for storage losses, reducing sugar content and dry matter percent of tubers, in order to explore the possibility of storing potatoes for processing at higher temperatures. Physiological losses in tubers remained less than 10% until 12 weeks of storage under evaporatively cooled storage. Reducing sugar contents increased by only 52.4–242.1% in tubers stored in evaporatively cooled storage as compared to 90.5–484.2% increase in tubers stored in refrigerated storage until 14 weeks. Potatoes stored in evaporatively cooled store were more suitable for processing into chips and french fries due to lower physiological losses and lower reducing sugar content of tubers.     

Optimizing the propagation of potato (Solanum tuberosum L.) by stem cuttings

Stem cuttings from potato plants are frequently used in multiplication programs for disease-free cultivars. The survival of these leafy cuttings is often very poor, and thus various techniques were investigated which were designed to increase rooting and cutting survival. Stock plants of cultivars “Caribe,” “Jemseg,” “Keswick,” “Russet Burbank,” “Sable,” “Sebago” and “Shepody” were grown in the greenhouse under long days. Promoting growth of the axillary shoots was successfully achieved by shading the shoot apex with aluminum foil. Trimming the outer leaves of the cuttings was deleterious to both survival and rooting. A rooting hormone improved root initiation and development, and the use of shade cloth or intermittent mist increased survival by reducing wilting. A rooting substrate of vermiculite: perlite (1:1) provided sufficient aeration, support and drainage for the cuttings. Antitranspirants sprayed on the stock plants prior to the excision of cuttings and also on the excised cuttings did not improve rooting or survival. The addition of activated charcoal (1% w:w) increased rooting of the cuttings and improved vigor of potted plants obtained from the cuttings.     

Suppression of marker genes in sequentially transformed potato (Solanum tuberosum L.)

Transgenic potato lines were developed from the advanced selection, ND860-2, by sequential transformation usingAgrobacterium tumefaciens and two different constructs. Five doubly-transformed lines were utilized to study gene expression of the first construct. Three doubly-transformed lines had less NPT II antigen than the singly-transformed counterpart from which each was derived. GUS activity was reduced in all doubly-transformed lines compared to their singly-transformed original genotypes. Therefore, NPT II and GUS genes in the first construct were suppressed to varying degrees by a second construct. Further investigations into this important subject will be necessary to enable multiple transformations with genes of agronomic interest.     

Water relations of the potato (Solanum tuberosum L.) cultivars Raritan and Shepody

Physiological responses to drought stress were evaluated in the potato cultivars Raritan and Shepody. Under well-watered conditions, Raritan exhibited a higher transpiration rate than Shepody. This higher rate could be related to a lower calculated stomatal resistance on abaxial leaf surfaces. Under drought stress conditions, Raritan consistently demonstrated superior performance over Shepody in the following areas: leaf water retention, epicuticular wax levels, desiccation tolerance and root growth. The estimated relative water content at a leaf water potential of-1.0 MPa was higher for Raritan than Shepody regardless of leaf age and may indicate a greater drought resistance in the former cultivar.     

Molecular analysis of genetic variation in potato (Solarium tuberosum L.). I. German cultivars and advanced clones

Summary The genetic variation of 69 potato cultivars and advanced clones from a commercial German breeding programme were analysed by using 6 AFLP primer combinations or 26 microsatellite (SSR) primer pairs. Available pedigree information was reflected in genetic distances. Cluster and principal coordinate analysis showed clear patterns of related genotypes with slight differences dependent on the marker system used. AFLP analysis, in particular, differentiated groups based on their genetic background: Clones with common ancestors separated from unrelated cultivars. A minimum of 150 polymorphic markers were necessary to obtain reliable results. Diversity index, effective multiplex ratio, and the resulting marker index were calculated for both marker systems. Their use for parent selection is discussed in relation to achieving maximum heterosis.     

Cryopreservation of in vitro-grown meristems of potato (Solanum tuberosum L.) by encapsulation-vitrification

Summary Alginate coated meristems from in vitro-grown axillary buds of potato (Solanum tuberosum L.) were successfully cryopreserved by vitrification. Excised meristems were precultured on sucrose-enriched MS medium and then encapsulated. To induce dehydration tolerance (osmotolerance), encapsulated meristems were treated with a mixture of 2 M glycerol plus 0.6 M sucrose for 90 min. These encapsulated meristems were dehydrated with a highly concentrated vitrification solution (PVS2 solution) for 3 hr at 0°C prior to a plunge into liquid nitrogen. Successfully vitrified meristems developed shoots within 3 weeks after plating without intermediary callus formation. The average rate of shoot formation amounted to nearly 70%. No difference was observed in RAPD analysis using 17 primers between cryopreserved and non-treated plantlets. The cryogenic protocol was successfully applied to 14 cultivars. It was also confirmed that the encapsulated vitrified meristems produced much greater shoot formation than the encapsulated dried meristems. Thus, the encapsulation vitrification protocol appears promising for cryopreservation of potato germplasm.     

Plant regeneration from cell suspension culture of potato (Solanum tuberosum L.)

In the present study, for callus production leaf and stem segments of potato cultivar White Desiree were cultured on MS medium supplemented with 2,4-D, NAA and Kinetin (callus production medium). Calli then were transferred in the same liquid medium for cell suspension production. In the next step cell suspensions were transferred back to the callus production medium. Finally, calli derived from cell suspension were cultured on 6 different shoot initiation media (S1-S6). However, on S6 medium with combination of GA3 and BAP more than 80% of the calli produced shoot buds and shoots. Fully grown shoots then were rooted and produced whole plants. Chromosome and morphological analysis showed no somaclonal variation among regenerated plants.     

Effects of temperature and photoperiod on early growth and final number of tubers in potato (Solanum tuberosum L.)

Summary A phytotron experiment with all combinations of two photoperiod (12 or 18 h) and four temperature (18/12, 22/16, 26/20 or 30/24 °C; 12h/12h) treatments was carried out to analyse quantitative effects on early tuber growth, dry-matter partitioning and number of tubers of two cultivars. Higher temperatures and longer photoperiod delayed the onset of expolinear tuber growth and the onset of linear tuber bulking. Higher temperatures also gave lower absolute tuber growth rates. Photoperiod did not affect absolute tuber growth rate at lower temperatures. Higher temperature and longer photoperiod gave lower relative rates of partitioning of dry matter to the tubers. Differences between treatments in numbers of tubers initiated were inconsistent. This quantitative analysis of the effects of temperature and photoperiod on characteristics of tuber growth should prove useful in potato modelling.     

Cost efficient potato (Solarium tuberosum L.) cultivar identification by microsatellite amplification

Potato cultivar identification is of great importance for seed production, germplasm management and breeders’ right protection. This study identified four SSRs necessary to discriminate between 37 commercially important potato (Solarium tuberosum L.) cultivars from INTA and other origins, frequently used in Argentina and neighbouring countries. Their PIC values ranged from 0.63 to 0.73 and separation was performed using high resolution agarose gel electrophoresis. The clear patterns obtained and the low cost and simplicity of the technique makes it an ideal tool for routine and effective potato cultivar identification.     

A rapid screening technique for drought resistance in potato (Solanum tuberosum L.)

Summary The reduction in growth in the dark of leaf dises floated over polyethylene glycol 6000 solution of water potential −0.4 MPa, relative to the growth of similar leaf dises floated over water for the same period, varied in the range 10–87% in 28 genotypes. The growth reductions in the genotypes tested were in general agreement with what is known about their drought resistance. Publication No. 906, Central Potato Research Institute, Simla.     

Varietal and environmental effect on the glycoalkaloid content of potato (Solanum tuberosum L.)

The tubers of 14 potato varieties were analysed for glycoalkaloids. The level of glycoalkaloids in tubers of all the varieties analysed are within the safe limits for human consumption. The peels of tuber contained about 60–70% of the total glycoalkaloids present in the whole tuber. The levels of glycoalkaloids in leaves and tubers were correlated (r=0.865). There was a significant increase in the content of glycoalkaloids in peels of tubers exposed to sunlight. Glycoalkaloid contents increased at the rate of 1.9mg/100g fresh weight per day in peels of Kufri Jyoti tubers exposed to diffused sunlight.