Field infection of potato by the Solanum apical leaf curling virus (SALCV)

Potato plants grown from true seed were naturally infected with the Solanum apical leaf curling virus (SALCV) at the high jungle site near San Ramon, Peru. Tubers from these plants were greenhouse indexed. Symptoms of SALCV infected potato plants include apical rolling, stunting, delayed emergence, weak plants, hair sprouts, and tuber dormancy. These symptoms superficially resemble certain aspects of unusually severe current season potato leafroll virus (4) infection or those of the aster yellows and stolbur mycoplasma diseases (5). Up to 12 percent of the indexed plants were naturally infected with SALCV and SALCV was demonstrated in approximately half of the tubers that produced hair sprouts.     

The effect of soil moisture and nitrogen on yield and quality of the Russet Burbank potato

A study was conducted to obtain more information on the effects of soil moisture and nitrogen on yield and quality of the Russet Burbank potato. Total yield of tubers increased with nitrogen rates as a result of more tubers per plant and larger tubers but the percent of malformed tubers also increased. Increased nitrogen rates decreased of dry matter of tubers and increased the total amino-nitrogen content of the tubers. Placing all of the nitrogen in bands on each side of the row produced more tubers having growth cracks, culls and reduced yield of No. 1’s when compared with broadcasting. Applying a moisture stress to potato plants during the early tuber set period increased the percentage of malformed tubers having pointed stem ends, bottlenecks and dumbbell shapes; although total yield and grade of tubers were not significantly affected. Irrigating when available soil moisture was 75 or 85 percent instead of 65 percent during the growing season did not affect total yield, grade or tuber quality at the five percent probability level.     

Transmission of potato leafroll virus to or from tuber slices by aphids feeding through a membrane

Summary Eye-bearing slices, cut from healthy potato tubers and placed between Parafilm membranes, were inoculated with potato leafroll virus (PLRV) byMyzus persicae. PLRV was detected by ELISA and by transmission tests in tuber slices and in plants grown from the slices of the susceptible cv. Désirée, but not in those of the resistant cv. Arkula. These results suggest that PLRV replication and transport within tuber phloem is controlled by specific mechanisms of resistance.M. persicae was also able to acquire and transmit PLRV toPl floridana from slices cut from tubers of infected plants. The aphids effectively transmitted PLRV from slices cut from the sprouting rose end but they failed to transmit it from slices cut from the heel end of tubers.     

Cell Wall Reinforcement in the Potato Tuber Periderm After Crop Treatment with Potassium Phosphite

The potato periderm is the outer tissue of potato tubers that protects the tuber from pathogen attack, dehydration, and wounding during harvest and storage. It is of secondary origin and replaces the epidermis early during tuber development. The outer layers of the periderm consist of cells with suberized walls. Phosphite compounds (Phi) are inorganic salts from phosphorous acid, and in previous works, we demonstrated that they are effective in protecting potato plants from biotic stress caused by different pathogens and also against UV-B radiation. The aim of the present work was to study the effect of Phi on the post-harvest potato periderm structure, cell wall components, and related enzymes. In three years of field experiments, potassium phosphite (KPhi) applications were compared with an untreated control. KPhi was applied to seed tubers before planting combined with foliage application of a conventional fungicide, to seed tubers and foliage without conventional fungicide, or to seed tubers combined with foliage application of KPhi plus a conventional fungicide. Observations of periderm sections showed increases in suberin and pectin depositions in post-harvest tubers from KPhi-treated plants compared to tubers from non-treated plants. In addition, peroxidase activity increased in the periderm tissue. The activity of laccases and superoxide dismutase was measured in the protein extract of the periderm, and an increase due to KPhi treatment was detected. The results presented here suggest that early KPhi treatment to seed tubers followed by foliage treatment leads to reinforcement of the cell wall of periderm cells, which represents a benefit for future response to stresses.     

Foliar Symptoms Caused by Potato mop-top virus on Potato Plants During Vegetative Propagation in Scotland and Their Association With Tuber Yield, Spraing and Tuber Infection

The effect of foliar symptomatic infection by Potato mop-top virus (PMTV) on yield of tubers, spraing and infection in daughter tubers, and foliar symptom development and tuber infection in the following generations of propagation was investigated in commercial seed potato crops in Scotland. Six crops covering cvs Atlantic, Hermes, Nicola and Cara were studied between 2000 and 2006 by labelling paired replicates of plants with foliar symptoms and plants with no symptoms. Tubers from plants with no symptoms rarely produced plants with foliar symptoms in the following generation. Plants with no symptoms produced more infected tubers if they had been derived from plants with foliar symptoms the previous year than from plants with no symptoms. The proportion of daughter plants with foliar symptoms produced by tubers from plants with foliar symptoms in year 1 ranged from 19–41% and seemed to be associated with the severity of foliar symptoms. The detection of PMTV by ELISA in samples of leaves from plants with foliar symptoms ranged from 13% for cv. Cara to 59% for a crop of cv. Atlantic in 2004. The amounts of spraing were generally low but tended to be greater for tubers from plants with foliar symptoms than those from plants with no symptoms. These results indicate that roguing plants with foliar symptoms in seed potato crops could achieve an improvement in crop health but might be impractical when diseased plants are too prevalent.     

Effect of time of inoculation with potato leafroll virus on development of net necrosis and stem-end browning in potato tubers

The Green Mountain cultivar was used in field tests to determine the effects of inoculating potato plants at various times with the potato leafroll virus (PLRV) on development of internal necrosis of tuber tissue. Viruliferous apterae of the green peach aphid,Myzus persicae (Sulz.), were placed on each stem in all hills to be inoculated in each 3.0 m single-row plot. Planting and inoculation dates were varied in all field experiments and, in one, several vine-killing dates were also included. All harvested tubers were stored for approximately four months at 10°C to enhance development of internal necrosis prior to examination. Similar but smaller greenhouse studies involving both apterous and alate green peach aphids were also conducted using Green Mountain, Irish Cobbler, and Russet Burbank cultivars. All results showed that as inoculation was delayed relative to plant development, more net necrosis (NN) occurred. Conversely, when plants were inoculated early, stem-end browning (SEB) rather than NN predominated. A high percentage of naturally occurring SEB tubers (cv. Russet Burbank) were found by ELISA to contain PLRV. Plants produced by these tubers only rarely developed leafroll symptoms. These findings suggest a previously unsuspected causal relationship between SEB and PLRV. Implications of this apparent relationship on the epidemiology of potato leafroll in Maine are discussed.     

Influence of time of application of maleic hydrazide on the yield and quality of Russet Burbank potatoes

A three-year study in central Wisconsin with timed foliar applications of maleic hydrazide at 3 lb/A (3.36 kg/ha) resulted in an improvement in quality and a favorable alteration in the shape of tubers of the Russet Burbank potato variety. Application in early and mid-July resulted in an increase in yield of U.S. 1 tubers and reduced yield of malformed tubers. Over 40 percent fewer misshapen tubers were produced when applications of maleic hydrazide were made during July when compared with tubers from untreated plants. Applications made in midor late July resulted in tuber development with a more favorable length to diameter ratio of U. S. 1 tubers, again compared with tubers from untreated plants. Maleic hydrazide applied in early or mid-June resulted in severely reduced yield and increased incidence of misshapen tubers. When applied in July or early August, no effect on tuber specific gravity was found. Maleic hydrazide functioned as an effective sprout inhibitor on tubers from all treatment dates except when applied in early June.     

Comparative performance of different-sized seed tubers derived from true potato seed

The growth and yield of plants from different-sized seed tubers derived from true potato seed were evaluated on a per stem, per plant, and per unit area basis using either single or multiple-sprout tubers. In single-sprout tubers, haulm dry weight per stem 47 days after planting was greater in the 40–60 g tubers when compared with that in the 5–10 g or the 10–20 g tubers. This resulted in greater tuber weight per stem in the 40–60 g tubers throughout the growing season. The number of tubers per stem was not affected by seed tuber size. In multiple-sprout seed tubers of increasing size, total tuber number and total tuber weight, as well as weight of those tubers larger than 45 mm, increased on a per plant basis but decreased on a per stem basis. At different rates of planting, 1–5 g seed tubers produced smaller tubers than 5–10 g or 10–20 g seed tubers. Increased rate of planting resulted in non-significant yield increases per unit area in plots planted with 1–5 g seed tubers. The yield increases were significant when 5–10 g and 10–20 g seed tubers were planted at higher rates. The number of main stems per unit of seed tuber weight was five times greater in 1–5 g tubers compared with that in 40–60 g tubers. This resulted in low seed weights per hectare when small tubers were planted and in a high ratio of harvested to planted tuber weight.     

Planting materials for warm tropic potato production: growth and yield of transplanted seedlings or rooted cuttings and tuber materials in the field

Expansion of potato production in lowland tropical regions has been constrained by the lack of planting materials, given that adapted genotypes and suitable field management practices now exist.

The respective performance of transplanted materials (i.e., true potato seed (TPS) seedlings or rooted stem cuttings) produced in situ in the warm tropics were compared with that of genetically identical seedling tubers (tubers produced from seedlings) or seed tubers. Seed and seedling tubers had been previously produced under optimal cool conditions. Transplanted materials achieved lower maximum leaf area index than did tuber materials (1.3–2.2 vs. 2.7) but relative growth rates of cuttings and seedlings were greater. This was in part due to the greater net assimilation rate of cuttings and to greater leaf:stem ratio for both compared with plants originating from tubers. Stolon and tuber formation were greater in seed tubers than in cuttings and in seedlings versus seedling tubers. On average, seedlings produced 14 tubers per plant, apical cuttings 12, seedling tubers 8, and stem cuttings 6.

Tuber yields within a genotype were statistically similar for crops from seed tubers or cuttings and for crops from seedling tubers or seedlings. However, the proportion of marketable (i.e., > 3.5 cm diameter) tubers was approximately 12% less in the crops from seed tuber and seedlings compared with those from cuttings and seedling tubers, respectively. Within a genotype, the crop duration in the field was similar whatever the type of planting material. Maximum yields, at 23 t/ha in warm sites, were still below those of temperate potato crops, but could be achieved equally well with transplanted in situ-produced materials or imported cool-climate seed tubers.     

Effects of transitory water stress on potato tuber stem-end reducing sugar and fry color

Potatoes grown for processing in irrigated regions of the Pacific North-west sometimes develop undesirably high concentrations of reducing sugars in tuber stem ends due to hot weather and water stress during tuber development. Such tubers usually produce french fries with dark stem ends or sugar ends. In order to better quantify the relationship between water stress and stem-end sugar levels for Russet Burbank, single episodes of transitory water stress were established by delaying irrigations until soil water potentials ranging from -32 to -107 kPa were reached during early tuber bulking. To determine when the increase in reducing sugars occurred, tubers were sampled before transitory stress, at maximum stress, after stress was relieved with sprinkler irrigation, and post harvest. Reducing sugar concentrations did not increase in tuber stem ends until two weeks or longer after the plant water stress was relieved. Increased reducing sugar concentrations were positively associated with decreased soil water potential (drier soil). Tubers were sliced and fried at harvest and six weeks post-harvest. Decreasing soil water potential (drier soil) was associated with progressively darker fry colors at harvest and post harvest. Significant darkening in the average stem-end fry color light reflectance of tubers at harvest as observed at -80 kPa in 1988 and -69 kPa in 1989. The effect of imposed water stress on tuber stem-end reducing sugar concentrations was most pronounced post harvest.     

Monitoring current season potato leafroll virus movement with an immunosorbent direct tissue blotting assay

A direct tissue blotting assay (DTBA) was used to track the movement of potato leafroll virus (PLRV) from newly infected foliage to the tubers. Plant and tuber characteristics were recorded to assess plant growth stage at inoculation and PLRV effect on yield. Russet Burbank potatoes were planted at different times in 1991 and 1992 to provide plants of different maturities which were then inoculated using PLRV carrying aphids. Aphids were allowed to feed two to three days after which an insecticide was applied. Stems and tubers were tested periodically for PLRV with DTBA after inoculation. Indexed tubers were grown out and ELISA tested in the greenhouse the following winter to confirm results of summer serological tests. Plant age affected percentages more consistently than did inoculation date. When plants approximately 43 days from planting were inoculated at different dates, early inoculation produced a higher percentage of infected plants. Conversely, when plants approximately 62 days from planting were inoculated at different dates, late inoculation resulted in a higher percentage of infected plants. However, early inoculation of young plants resulted in the highest infection percentages. Tuber size and yield were negatively affected by higher percentages of leafroll regardless of the stage of growth at inoculation. DTBA is best used for detecting PLRV in foliage of plants grown from infected tubers (i.e. secondary PLRV). DTBA is less accurate for detecting primary PLRV.     

The effect of short periods of shading at different stages of growth on the development of tuber number and yield

Summary Shading potato plants at the beginning of tuber initiation for a period of 12 days reduced the rate of tuber formation and growth; but after the shades were removed tuber formation continued to give more tubers and the shaded plants eventually produced 30% more tubers than the unshaded, with similar yield. Shading for 12 days during the early stages of rapid tuber bulking had no effect on tuber number or survival, though bulking rate was temporarily reduced, leading to a reduction in final yield. These number results indicate that tuber number can be influenced by the weather during the period of tuber initiation.     

Advantages of a soluble dye in blot immunobinding assays for virus detection in potatoes

Summary A technique is described in which plant sap is blotted onto small pieces (8×11 mm) of nylon membrane and virus particles bound to the paper are detected by a modification of the enzymelinked immunosorbent assay (ELISA). The detectable product of the assay is a soluble yellow dye, the absorbance of which increased with the virus content of the plant sap. Leaf or tuber sap from plants secondarily-infected with either potato leafroll virus or potato virus Y could be clearly distinguished from that of healthy plants and a majority of tubers primarily infected with PVY were also detected.     

Studies onFusarium wilt of potatoes. 2. Leaf,sprout and tuber infection in artificial inoculations

Summary In artificial inoculations it was found thatFusarium oxysporum f.sp.tuberosi is able to penetrate through potato leaves. The fungus was isolated from the stem of infected plants from all inoculated cultivars. Tubers were completely destroyed if they were inoculated before sprouting. Not any destruction was observed if inoculation was made before young sprouts are longer than 1–3 cm; plants from these sprouts were infected. Lesioned tubers were more sensitive than unlesioned ones, and tuber rot and sprout damage were increased significantly.     

Comparative field performance of potatoes from microculture

The growth and yield in the field of two cultivars of potatoes originating from three different propagation sources — tubers, microcultured shoots (microcuttings) and small tubers produced in culture (microtubers) — were analyzed. Plants originating from microculture produced only single stems emerging from the soil surface whereas tubers formed multistemmed plants. Due to vigorous branching on microcultured plants, however, vine growth appeared similar. Although the total tuber yields were the same for plants from all three propagation sources, in general microcultured plants produced smaller-sized but a greater number of tubers. Microculture is a promising method of producing high quality, certified propagules for potato production.     

Enzyme-linked immunosorbent assay (ELISA) for the detection of potato leafroll virus and potato virus Y in potato tubers after artificial break of dormancy

Summary Conditions necessary for the detection of potato leafroll virus (PLRV) and potato virus Y (PVY) in tubers from primary and secondary infected plants were investigated. Tubers were analysed before and after breaking dormancy by rindite treatment. PLRV was reliably detected indormant tubers whereas PVY was readily detected only when tubers had been rindite-treated and held for two to three weeks at 22°C and high humidity in the dark. PLRV occurred in higher concentration at the heel end than at the rose end of infected tubers and the concentration remained nearly unchanged during the experimental period of 35 days, whereas PVY was found to be more concentrated at the rose end and was rapidly accumulating in the tubers after the break of dormancy. In dormant tubers PVY concentration dropped during storage at 22°C. The use of ELISA for tuber indexing is discussed.     

A simple and rapid method for the detection of potato spindle tuber viroid (PSTVd) by RT-PCR

Summary A test procedure for PSTVd is described based on immobilisation of plant sap on filter paper, by dotting or tissue printing followed by RT-PCR. Tests were carried out using primarily and secondarily infected potato plants, primarily infected in vitro plants, and potato tubers. Print PCR was shown to be suitable for testing large samples of potato plants whereas dot PCR is recommended for in vitro plantlets and tuber tissue. Bulking one infected plant to 4 or 9 healthy plants gave reliable results with secondarily infected potato plants, but sometimes the test failed to detect PSTVd in primarily infected in vitro plants. Dotted and printed paper squares could be stored at 4°C for at least 2 weeks in Triton X-100 solution or under dry conditions. Storing at room temperature can lead to unreliable results.     

整薯播种对马铃薯生育及产量的影响

1979～1984年,在黑龙江省北部黑土地区气象条件、生产水平和栽培条件下,通过田间试验,研究了整薯播种对马铃薯生育和产量的影响。结果表明:整薯播种与传统习惯的切块播种相比,6年期间平产出现频率为2次,一般年份整薯播种比切块播种增产9～12%,在春旱严重的1980年,整薯播种表现出非常突出的抗旱保苗效果。在群体叶面积发展进程上,整薯播种表现早发早衰,切块播种晚发晚表,一般年份光合势前者比后者高9.6%,春旱严重的1980年高82.8%。块茎商品率以112.5克为准时,6年平均整薯播种为74.1%,切块播种为80.0%,两者相差5.9%;以50克为准时,整薯播种为97.3%,切块播种为98.2%,两者相差0.9%。     

Seed Potato Performance after Storage in Light at Elevated Temperatures

In regions with short growth seasons, it is of great importance to use potato (Solanum tuberosum L.) seed tubers with a high growth vigour and a short growth cycle. Such qualities may be obtained by treatments advancing the physiological age of the seed tubers. In this study, we have exposed tubers from four cultivars to various combinations of temperature and light conditions (green-sprouting) for 3–7 months in controlled climate. Subsequent sprout quality, seed tuber health and performance were studied in laboratory, greenhouse and field trials. Satisfactory short, sturdy and leafy sprouts were produced even after 7 months storage at 15 °C under light exposure. An assay of black scurf (Rhizoctonia solani) on the tuber skin showed that light exposure significantly reduced the occurrence compared with dark-stored tubers, while the average effect of storage temperatures was insignificant. In general, green-sprouting advanced emergence and plant growth by 1–2 weeks, and showed early tuber initiation and growth, compared to untreated material. Yields, 107 days after planting in the field trial, did not deviate significantly from untreated tubers. However, plant development at harvest was in accordance with general responses to physiological ageing of potato seed tubers, i.e. still tall and immature plants from untreated tubers, and short and mature plants from aged tubers. Results demonstrated the possibility of successful long-term storage of potato seed tubers in light at elevated temperatures and a potential for earlier harvests and higher early yields from such treatments.     

马铃薯纺锤块茎类病毒不同株系及不同接种方法对产量的影响

马铃薯纺锤块径类病毒(Potato spindle tuber viroid)是危害黑龙江省马铃薯生产的一种重要病害。为了查明不同类病毒变株对主栽品种克新1号和4号所引起的产量损失和症状反应,应用往复聚丙烯胺凝胶电泳法(Peturn-Polyacmdegel electophoresis)鉴定类病毒。试验结果表明,接种当年,接种类病毒的处理平均减产37%,按商品产量计算减产达47%。当年表现症状的植株平均为59.6%,块茎产生症状的植株平均为57.4%。用于接种的3个马铃薯纺锤块茎类病毒变株的致病力,以当地的类病毒弱系为最强,其次为北美的类病毒强系,北美的类病毒弱系的致病力较弱。类病毒对产量的影响与马铃薯品种和类病毒变株的组合有极为密切的关系。克新1号接种当地的类病毒弱系时薯块严重畸变,商品产量只为不接种对照的21%。用往复电泳法检测各个试验处理被类病毒侵柴的情况,芽接种处理,于出苗后1周即可检测到类病毒,叶接种处理,于接种后2周即能检测到类病毒。出苗后7周,植株中类病毒浓度达到高峰,随即急剧下降,到出苗后10周,大部分接种植株已检测不到类病毒。块茎直径达1厘米时,即能检测到类病毒,随着块茎膨大,类病毒浓度也相应增高,到收获前,块茎中的类病毒含量只略低于植株含类病毒高峰期的浓度。用于本试验的克新1号、4号无类病毒和主要马铃薯病毒的核心材料,在1988年已交付给省内外的良种场繁殖使用。于当年秋季抽样检测克山第二良种场连续种植二年的种薯,当年种植试管苗生产的种薯,以及试管苗等,均未检测到类病毒。