Protein,starch, and non-protein nitrogen accumulation in high protein hybrids and low protein cultivars

Tuber protein, starch, non-protein nitrogen and percent dry matter content were measured during tuber development of four Phureja-Tuberosum-Andigena hybrids and two Tuberosum cultivars. Percentages of starch and protein in the tuber dry matter were curvilinearly related to tuber size in all six clones. The amounts of starch and protein in a tuber were linear functions of tuber size. Rates of protein accumulation in some of the hybrids were higher than those of either cultivar. Starch accumulation rates were similar among all six clones. The high protein character of at least one of the hybrids was associated with starch containing storage tissue. Differences between high and low protein clones were mainly related to quantitative differences in the subunit composition of the protein. The ratio of non-protein nitrogen to protein N was similar among the six clones. Relationships between percent dry matter and starch content were not consistent among the six clones.     

A rapid method for determining blackspot susceptibility of potato clones

Two methods of determining susceptibility of potato clones to blackspot were compared: (1) bruising by weight dropping and (2) bruising by abrasive peeling. A highly significant positive correlation was obtained between the intensity of enzymatic discoloration following abrasive peeling and the amount of blackspot that developed by weight dropping (r=0.93). Abrasive peeling was more rapid than the weight-dropping method. Tuber samples were abraded 30 sec and the amount of enzymatic discoloration evaluated after 24 hr. The need for individually bruising and hand peeling of tubers was eliminated with this method. Because of the rapidity of the abrasive peeling method, it can be used effectively in potato breeding programs to screen large numbers of clones for blackspot susceptibility. Results indicate that tuber maturity affects enzymatic discoloration and blackspot susceptibility. Immature tubers, dug while the vines are still green, are more resistant to blackspot than mature tubers. Tuber maturity therefore must be considered when screening clones for susceptibility to blackspot.     

The genetic basis for tuber greening in 24-chromosome potatoes

Greening of potato (Solarium tuberosum L.) tubers is often a problem in retail markets. An experiment was performed to study the mode of inheritance of tuber greening in 24-chromosome potatoes. Tuber greening was determined to be quantitatively inherited. Genetic and environmental variance components were calculated. Tuber greening inheritance is due to additive and epistatic effects. Epistatic effects accounted for 59% of the genetic variance. No dominance or maternal effects were observed. Narrow sense heritability was 0.27 and broad sense heritability was 0.66 after location, block, and genotype by environment interactions were removed. Broad sense heritability for tuber greening is large enough to permit effective selection against tuber greening in potato breeding programs when epistasis can be fixed.     

Growing potato plants by the water culture technique

A water culture technique was developed for the study of the nutrient requirements of the potato plant. Tuber formation was avoided by pinching off the stolons as they developed and hence vegetative growth could be studied without the complication of abnormal tuber formation in the culture solution. The K deficiency symptoms obtained by this method were essentially the same as those observed for field grown plants.     

Coastal Russet: A mid-season Russet-skinned potato cultivar

Coastal Russet (tested as B9596-2) is a clone with mid-season maturity that produces russet skin tubers that are long and slightly flattened. Tuber yields in the eastern portions of the United States have been considerably greater than for BelRus. Tubers are well-shaped, have shallow eyes, and are attractive in appearance. Tuber appearance and size make this cultivar very well suited for the tablestock market. It is not suitable for processing. Coastal Russet is highly resistant to tuber net necrosis caused by late current season infection with leafroll and is tolerant to common scab.     

Net necrosis of potato tubers associated with primary,secondary, and tertiary infection of leafroll

Tuber net necrosis, caused by leafroll virus, was found to occur as a result of primary, secondary, and tertiary infection in six clones of potato (Solanum tuberosum L.). Differences were observed between clones in their reaction to the different types of infection. In most clones there was a higher percentage of net necrosis from primary than from secondary or tertiary infection. No significant difference was observed in the severity of the net necrotic symptoms due to the different types of infection.     

Inheritance of tuber initiation in tuber bearingSolanum as influenced by photoperiod

Eight potato clones (three day-neutral (DN) Tuberosum, one dayneutral and four short-day (SD) Andigena) were used as parents. Eight genetic sets bearing P₁, P₂, P_1?, P_2?, F₁, F₂, BC₁, and BC₂ generations were developed. Two sets were DN×DN crosses, four SD×DN, and two SD×SD. Tuber initiation (TI) was evaluated in growth chambers with daylengths of 11, 13, and 15 hours. The stolons of each genotype were examined every eight days between the 38th and 86th day after planting. F₁ generation means from SD×DN crosses showed complete dominance of SD reaction (late TI) over DN reaction (early TI). F₁ generation means from DN × DN and SD× SD crosses showed either no dominance or a slight tendency towards the late TI parent. Within plot variances of the selfed generations suggested a variable degree of parental heterozygosity for the loci controlling TI. Andigena clones showed the greatest heterozygosity. Bell shaped frequency distributions in the segregating generations indicated that TI was under the control of several genes. It appears also that major and minor genes were involved. Broad sense heritability estimates of about 90% at 11 hours and 55% at 15 hours of daylength were computed.     

Blackspot of Russet Burbank potatoes and the carbon dioxide content of soil and tubers

These studies were designed to elucidate the influence of CO₂ on blackspot susceptibility of Russet Burbank potatoes. The influence of tuber CO₂ environment on blackspot was tested. Tubers from 1–4 and 6–8 inches deep in the soil were scored for blackspot and moisture samples were taken from their vicinity. Blackspot was worse in shallow tubers and in tubers from drier soil. Plowing under corn stover, covering the soil with plastic, and excessive irrigation failed to cause blackspot susceptible tubers. Diffusing CO₂ into the soil atmosphere under plastic sheets slightly increased the intensity of spot discoloration but the discoloration was atypical blackspot. Effects on blackspot by changing tuber gases was tested. Tubers whose gases had been evacuated and replaced by O₂, N₂, and CO₂ had lower blackspot scores than untreated tubers. Increasing the time tubers were soaked in water after gaseous evacuation reduced blackspot. Hydration consistently decreased tuber blackspot. In chemical studies, tubers were tested for blackspot and analyzed for CO₂ content. The relationship between tissue CO₂ and blackspot appeared to be inverse. Tuber CO₂ content was not influenced by time of day. Tuber blackspot scores immediately, 1, 3, and 7 hours after digging were the same, but tissue CO₂ content increased linearly with time after harvest.     

Origin and inheritance of solarmarine glycoalkaloids in commercial potato cultivars

Tuber tissues of 123 commercial cultivars were tested for their ability to synthesize solamarine glycoalkaloids. Eleven cultivars including ‘Kennebec’ and ‘White Rose’ synthesized major concentrations of solamarines, ranging between 42 and 85% of total glycoalkaloid, when tuber slices were exposed to light during wound-healing. Tuber tissues of the other 112 cultivars did not synthesize solamarines, or they synthesized only trace concentrations of these unusual glycoalkaloids. Nine of the 11 solamarine-synthesizing cultivars have a common ancestor, USDA 96-56. This parental clone synthesizes major solamarine concentrations and it also carries the R₁ gene for late blight resistance that it inherited fromSolatium demissum. Results of solamarine analyses of foliage from 47 USDA 96-56 selfed progeny suggest that this parental clone is the source of a major gene(s) for solamarines present in 9 of the commercial cultivars. However, there appeared to be an alternative source of a gene(s) for solamarines because ‘White Rose’, with onlyS. tuberosum ancestors, also synthesized major solamarine concentrations. There was no association between the R₁ gene for late blight resistance and the ability to synthesize solamarines in 31 USDA 96-56 selfed progeny that were analyzed for both characters.     

Anatomical evidence for the existence of roots on potato tubers and stolons

Roots on potato tubers and stolons displayed the normal root anatomy which consisted of a central vascular cylinder surrounded by endodermis with Casparian strips, the cortex and epidermis. Tuber roots appear to initiate from the parenchyma cells adjacent to the vascular tissue. Shoot tips were similar to normal apical meristems. These observations support our research demonstrating the growth of functional roots from potato tubers and stolons.     

Sangre selection studies: I. Selection and comparative trials

Seventeen clonal selections of Sangre were made from a tuber-unit seed lot planted at the San Luis Valley Research Center in 1982. Seven selections had typical vine size and 10 had larger vine size than the standard cultivar. Progeny of each selection were increased and observed in 1983. During the three-year interval from 1984–1986 comparative performance trials were conducted. All clones selected for larger vines were significantly taller and later maturing than the standard. Clones 10 and 11 also had significantly greater total yields and clones 10, 11, and 14 had significantly greater U.S. No. 1 yields. Tuber shape of these clones was comparable to the standard. Results indicate that improvement may be made in the Sangre cultivar through clonal selection.     

Influence of temperature and length of storage on resistance of potato to tuber rot induced byErwinia chrysanthemi

Tubers of 11 clones ofSolanum tuberosum subsp.andigena (andigena) and 12 cultivars ofS. tuberosum subsp.tuberosum (tuberosum) were inoculated with water suspensions (5.5 × 10⁴ 5.5 × 10⁵, 5.5 × 10⁶ CFU/ml) ofErwinia chrysanthemi. Tubers were inoculated immediately after harvest and after 6 and 16 wk of storage at 4 and 23°C. Tuber rot incidence in andigena and tuberosum increased as inoculum concentration increased. Based on tuber rot severity, clones of andigena were classified as resistant, intermediate, or susceptible and cultivars of tuberosum were classified as intermediate or susceptible. Rot severity increased in all tubers stored at 4°C and in tubers of tuberosum stored at 23°C; rot did not increase in tubers of andigena stored at 23°C. Electrolyte leakage (EL), total sugars (TS), reducing sugars (RS), non-reducing sugars (NRS) and dry matter (DM) were determined in non-inoculated tubers. There was a significant positive correlation between the rate of EL, concentration of RS and tuber rot in andigena and tuberosum. Tuber rot and DM were negatively correlated in tubers of andigena; but they were not correlated in tuberosum. Clones of andigena with low EL, TS, RS, and high DM were resistant to tuber rot, and the incidence of tuber rot in these clones was much less influenced by temperature and length of storage. The influence of temperature and length of storage on susceptibility toE. chrysanthemi may be explained by increased cell membrane permeability; increased leakage of accumulated sugars in potatoes stored at 4°C could favor bacterial proliferation resulting in more disease.     

Inheritance of tuber traits from phureja in diploid phureja - Tuberosum hybrids

Heterosis and combining ability for tuber number, average tuber weight, and total yield were evaluated in Phureja - haploid Tuberosum diploid hybrids. Heterosis estimates suggest dominance for high tuber number and low average tuber weight in Phureja. Total yield of the hybrid population exceeded the high parent. The higher-yielding segment of hybrids had a significantly higher number of smaller tubers per plant. Breeding value could be improved by attaining high yield with a lower number of larger tubers per plant. General combining ability was the only significant source of variation for tuber number and average tuber weight indicating high heritability. Phenotypic recurrent selection should be an effective approach to manipulating these traits. General and specific combining ability were significant for total yield. Full exploitation of genetic variance for yield will require test-crossing.     

Updated listing of potato species names,abbreviations and taxonomic status

Tuber-bearingSolanum species described since 1753 are listed alphabetically. A three-letter abbreviation for numerous species not included in Simmonds (1963) are proposed. Some pertinent taxonomic notes are provided for all species names. The systems of classification proposed by S.M. Bukasov, D.S. Correll, J.G. Hawkes, and C.M. Ochoa have been used to determine the current taxonomic status of each species.     

A Study of the relationship of late blight resistance to glycoalkaloid content in fifteen potato clones

Tuber glycoalkaloid (TGA) content, leaf glycoalkaloid (LGA) content, and the level of multigenic resistance to late blight were determined for 15 potato clones. There was no association between the level of blight resistance and the TGA or LGA contents in these clones. However, TGA and LGA contents were highly correlated. The genotypic correlation coefficient between TGA and LGA contents for the 15 clones was 0.82 (SE = 0.115). TGA contents from blight-infected plants were not significantly higher than TGA contents from healthy (fungicide-protected) plants. The results indicate that breeders should be able to select for multigenic late blight resistance withohut increasing TGA contents of clones in their breeding programs.     

Vine pulling as a means of top killing potatoes

Vine pulling as a means of top killing potatoes was evaluated by measuring tuber discolouration, desiccation of stems and leaves, stems missed and rerooted, and tubers exposed during pulling. Tuber discolouration ratings determined for potatoes that had been top killed in mid-August by chemical desiccant, rotobeating or vine pulling, remained low during the four-year study except in 1978 with the chemical desiccant. Machine pulling evaluations indicated effective vine kill to be rated at 89–99% for leaves and 79–98% for stems with several cultivars of potatoes. A number of stems rerooted which reduced the vine kill ratings.     

Shoot formation in potato tuber discs in tissue culture

Tuber discs of potato (Solanum tuberosum) growing on a modified Murashige and Skoog medium produced callus and embryoid bodies but failed to form shoots. However, if 0.4 ppm of 6-benzylaminopurine was added to the basal medium, shoots became visible seven weeks after inoculation.     

Potato leaf and tuber water potential measurements with a pressure chamber

The use of a pressure chamber for measurements of water potential of potato (Solatium tuberosum L.) in leaves and tubers is described. For satisfactory results, evaporation from samples must be prevented prior to and during measurements, and samples must be measured quickly following detachment. Tubers were suspended in the chamber by their rhizomes for water potential measurements. Tuber water potentials appeared too low (dry) when rates of pressurization exceeded 0.05 bar sec¹ as the balancing pressure was approached (within 2 bars). Variations in measurements associated with the rhizome length, and with lack of equilibrium within the tuber, are discussed. Field measurements showed that under moderate to high transpiration, there was no simple relationship between leaf and tuber water potentials. In wet soil, tubers were wetter than leaves throughout the day. In dry soil, tuber potentials became as dry as those of leaves by the afternoon. Factors contributing to this changing pattern are discussed.     

Some anatomical and physiological potato tuber characteristics and their relationship to hollow heart

The inception site of hollow heart (HH) and possible relationships between HH and physiological or anatomical characteristics of tubers were investigated. Scanning electron micrographs revealed cells at the site of HH inception were physically rather than enzymatically degraded. Transmission electron micrographs of tuber pith cells from non hollow (NH) tubers showed cell wall and cytoplasm width varied among cultivars but were not related to HH resistance. Water potential of NH tuber tissues at the pith, bud, center and stem end of 3 cultivars and one selection varying in resistance to HH was determined. Although the water potential gradually became less negative as tubers advanced in maturity, no differences were found in water potential between pith cells in various parts of tubers or among cultivars. Tuber pith cells increased in size concomitant with tuber growth. In all tubers pith cells were largest in the center and stem end and smallest in the bud end, but differences in mean pith cell size among cultivars were not related to HH susceptibility. However, within a cultivar the bud, center, and stem end pith cells of HH tubers were all smaller than the corresponding pith cells from similarly sized NH tubers.     

Weight loss of potatoes as affected by age,temperature, relative humidity and air velocity

The factors affecting potato tuber weight loss were studied by suspending individual tubers of Kennebec, Red Pontiac, and Norgold Russet potatoes in chambers where temperature, relative humidity, and air flow past the tubers could be controlled. The results of a regression analysis indicated that the age of the tubers closely followed by temperature was most highly correlated to weight loss. Tuber weight and relative humidity were next and about equally correlated with weight loss. Air velocity had the lowest correlation coefficient Prediction equations for predicting the weight loss of the potato tubers as a function of the various environmental and potato tuber variables were developed from a step-wise regression analysis program. The standard error for these regression equations was about ±1.5% weight loss from the predicted value The weight loss of the tubers in this experiment are likely higher than bulk stored potatoes because of the greater surface area exposed to air flow. Also, other than temperature, the other variables (air velocity, relative humidity, and potato weight) were relatively uncontrolled and therefore had high variations. A plot of weight loss versus time indicates a non-linear response with greater variation as time increases.