Incidence, appearance and development of potato mop-top furovirus-induced spraing in potato cultivars and the influence on yield, distribution in Denmark and detection of the virus in tubers by ELISA

Summary 23 potato cultivars were grown in fields infested with potato mop-top virus and spraing was assessed on tubers at harvest and after storage. Large differences in spraing susceptibility were found between cultivars. Compared with other countries, spraing in Denmark is characterised by a high incidence at harvest, a low increase during storage and a very low proportion of superficial spraing. Decrease in spraing during storage was recorded in two cultivars. DASELISA tests for PMTV in tubers revealted a high reliability. Mapping of PMTV in important Danish potato growing areas showed that the virus is widespread. Occurrence of spraing did not influence total yield or dry matter content. Soil acidity did not influence incidence of spraing but it was more common on coarse-grained soil than on finer sandy soils. PMTV in viruliferous resting spores ofSpongospora subterranea was inactivated by heating to 90°C for 15 minutes.     

Causes of differences in growth pattern,yield and quality of potatoes (Solanum tuberosum L.) in short rotations on sandy soil as affected by crop rotation,cultivar and application of granular nematicides

Summary A crop rotation experiment was carried out on a light sandy soil in 1979–1986 to study the effects of the frequency of potato cropping on yield, quality and on the occurrence of soil-borne pathogens other than potato cyst nematodes. Tuber yield decreased markedly with increasing cropping frequency, but also depended on what crops were grown in rotation with potato. Growth during the early part of the season, as well as the length of the growing period, were reduced in short rotations. The fungiVerticillium dahliae andRhizoctonia solani, and root-knot nematodes (Meloidogyne spp.) were the most important yield reducing pathogens. The effects of rotation depended on the cultivar used. The percentage of mis-shapen tubers increased with increasing cropping frequency and after application of granular nematicides, but the incidence of common scab (Streptomyces scabies) was not affected.     

Potato viruses in China

Potato (Solanum tuberosum L.) is globally the fourth largest staple crop after rice, wheat and maize. China is the largest potato producer worldwide, accounting for 26.3% and 22.2% of the global total area and yield, respectively. Viral diseases have been a limiting factor for sustainable production of potato in China. This article provides update and comprehensive information on the most important viruses, their effect on yield and their control in China. Meristem culture is currently the most widely used technique for production of virus-free potato plants and these plants are used as nuclear stock for the production of certified seed tubers. Although a significant increase in tuber yield has been achieved using certified seed potatoes, lack of application of a national seed potato production scheme has hindered progress. Conventional breeding using virus-resistant cultivars introduced from other countries as parents has already led to the production of Chinese cultivars. Use of virus-resistant wild Solanum species and genetic transformation techniques will provide new virus-resistant varieties in the future to further enhance control of potato viruses in China.     

部分发展中国家马铃薯纺锤块茎类病毒病情况调查

马铃薯类病毒病是威胁世界马铃薯生产的主要病害之一,更影响着发展中国家马铃薯产业的发展。2008~2010年,黑龙江省农业科学院植物脱毒苗木研究所连续3年举办了马铃薯病害检测技术国际培训班,对部分发展中国家从事马铃薯工作的人员进行培训,在培训过程中进行了马铃薯类病毒方面的问卷调查,调查结果显示:这些发展中国家对马铃薯纺锤块茎类病毒比较了解,发病较重的国家不多,但总体检测水平不高,甚至不进行马铃薯类病毒的检测,多数国家不重视马铃薯纺锤块茎类病毒病的防治工作。因此,马铃薯纺锤块茎类病毒病是发展中国家的隐患。     

A glasshouse test for assessing resistance to early blight (Alternaria solani)

Summary Fourteen genotypes of potato were assessed for resistance toAlternaria solani Sor., both in the glasshouse at the Scottish Crop Research Institute in Scotland and in the field in the Negev, Israel. Glasshouse assessments agreed well with field results, identifying the most resistant and susceptible genotypes. The effects on the glasshouse test of plant age, inoculum concentration, and length of time plants were kept damp after inoculation, were examined. The best agreement with field results was shown by plants inoculated at flowering, and the best discrimination between genotypes was achieved by keeping the foliage damp for 24 h after inoculating with a spore suspension containing 2.5×10³ spores/ml.     

Effect of crop rotation,cultivar and nematicide on growth and yield of potato (Solanum tuberosum L.) in short rotations on a marine clay soil

Summary The effects of cropping frequency on the yield of potato and on the development of soil-borne diseases was studied from 1979 to 1985 in a crop rotation experiment on a marine clay soil. Tuber yield decreased markedly with increasing cropping frequency. The yield of cv. Hertha was reduced by 27% in continuous cropping and by 15% in a wheat/potato or sugar beet/potato rotation, when compared with the rotation wheat/sugar beet/oats/potato. However, a pot experiment showed that yield depression in continuous cropping depended on the cultivar used. Crop growth declined in the second part of the growing season, and senescence accelerated as the cropping frequency increased.Verticillium dahliae was the most important yield-reducing factor. Root infection by this fungus was stimulated by the root-lesion nematodePratylenchus neglectus.     

Recent developments in potato research: scientific highlights of the EAPR conference in Sorrento, Italy, May 1999

Summary This contribution presents highlights of the oral and poster presentations in the various sessions of the 14^th Triennial Conference of the European Association for Potato Research, held in Sorrento, Italy, May 1999. It is based on the reports of the session chairpersons and the book of abstracts. The paper reports the progress made in many aspects of potato research, but also stresses the need for further collaborative work, especially in the fields of molecular physiology, marker assisted breeding, control of late blight, potato tuber moth and other pests and diseases, stress physiology and stress resistance, and sustainable cropping systems with both short and long cycle potato crops.     

Potato Ring Rot in Norway: Occurrence and Control

Potato ring rot, caused by the bacterium Clavibacter michiganensis subspecies sepedonicus, is considered to be one of the internationally most important seed potato diseases (Smith et al.; Eur J Plant Pathol 107:739–748, 2001) and has been a problem in Norwegian potato production since its first detection in 1964. Since 1965, Norway has had its own national legislation for the control of the disease. In recent years, this legislation has evolved to be more similar to the EU Commission Directive 2006/56/EC. In 1999, the Norwegian Food Safety Authority initiated an eradication program for potato ring rot with the aim of selling potatoes to other European countries. During the project period (1999–2008), efficient systems for sampling, analysis and eradication measures were built. From 1999 to 2002, the occurrence of potato ring rot in commercial potato production was monitored in all counties. Sampling was carried out according to the instructions of the Norwegian Food Safety Authority, while testing of samples was (from 2000 onwards) carried out by Bioforsk laboratories with modern serological and molecular detection methods. When ring rot was detected in a potato lot, the grower had to implement strict eradication measures. The survey was followed up with two monitoring periods, 2003–2004 and 2005–2008. During the project period, 328 cases of potato ring rot were found. The counties Hedmark, Nordland, Troms, and Tr?ndelag accounted for most of these. The main objectives of this study were to describe the occurrence of potato ring rot in Norwegian potato production and to evaluate the effectiveness of the eradication measures employed for the control of the disease. This survey showed that the overall ring rot situation did improve considerably during the project period (1999–2008), both in relation to prior periods, and when comparing the surveying and monitoring periods. Problem areas where monitoring must be continued remain.     

Grower perceptions of biotic and abiotic risks of potato production in South Africa

Growers' surveys took place in all sixteen potato growing regions of South Africa in 2013 and 2014. The agro-ecological climate of these regions is diverse and potato is produced in rainy or dry seasons, in winter or summer seasons, or year round. Growers were asked how often in ten years crops suffered more than 25% yield losses due to extreme weather events related to precipitation events such as hail, floods and droughts, and to temperature-related events such as frost and heat waves. Simultaneously they were asked their opinion about occurrence and severity of diseases caused by potato viruses, fungi and bacteria and pests such as nematodes, tuber moths, aphids and leaf miners. Weather related hazards resulted in losses over 25% virtually each year in the Gauteng growing region due to hail, frosts and floods; losses occurred less than once every five years, for example due to extremely high temperatures, in the Sandveld area where growers take a risk by producing potatoes in hot summers. Regarding the biotic factors, every pest or pathogen assessed was reported to occur on at least one farm in each growing region. Countrywide the lowest frequency of 50% was recorded for powdery scab whereas the insects tuber moths, leaf miners and aphids were reported most frequently, by between 88% and 98% of the growers. The complex of silver scurf and black dot resulted in the greatest yield losses in all growing regions, followed closely by tuber moth, early blight and the blackleg/soft rot disease complex. Yield losses due to potato virus Y, potato leaf roll virus and aphids were not reported as being very severe. When the growers' perceptions of severity of biotic factors were accumulated, significant differences between the regions appeared, with the Eastern Cape most prone with an accumulated score of 700 due to an array of pests and diseases, and the North–West with a score of only 50 mainly attributed to root knot nematodes. Growers were also asked how frequently biocides were applied to potato to control soil-borne organisms (nematicide and seed treatment), foliar fungi or insects. There were no significant correlations between frequency of biocide applications and severity of the disease as reflected in yield losses, most likely because growers use biocide applications as insurance against pests and diseases. This is common among crop farmers around the world. Although potato production in South Africa appears to carry more risks than production elsewhere, South African commercial potato growers are economically competitive when compared to growers in other areas of the globe, with comparable planting conditions and risks.     

Integrated pest management of potato tuber moth in field and storage

Summary The potato tuber moth (PTM),Phthorimaea operculella (Zeller), is one of the most damaging pests of potatoes in field and storage. Tuber moth is active throughout the year in North Africa but is most active from late April to early August. Many cultural practices that are used by farmers to improve the yield and quality of potato can also limit the development of the potato tuber moth and minimise damage to tubers. As the farmers gain more experience with both agronomic practices and chemical insecticides, they are likely to rely more heavily on cultural practices and less on insecticides to manage PTM. Measures which could keep PTM damages in rustic and diffuse light stores to a minimum are discussed. Ideally, there is need to integrate pest management in potato fields and stores. PTM control in stores was found to be more effective if infestation in fields was kept to a minimum. Low infestation at harvest and rapid handling of the potatoes going into store established good initial storage conditions and decreased the likelihood of post-harvest losses. Biological insecticides in particular were more effective in preventing losses by insects in stores in cases where the initial level of infestation was relatively low.     

Applied Biotechnology to Combat Late Blight in Potato Caused by <Emphasis Type="Italic">Phytophthora Infestans</Emphasis>

Potato is an important crop, grown worldwide. It suffers from many pests and diseases among which late blight, caused by the oomycete Phytophthora infestans, is the worst. The disease is still causing major damage in many potato production areas and control is only possible by applying fungicides frequently. The knowledge on the molecular biology and genetics of the interaction between the plant and the oomycete is developing rapidly. These are relevant fields of study, currently dominated by the discovery of many resistance genes and numerous effector proteins and the analysis of their specific mode of action. These studies may yield essential information needed for the development of durable resistance. The long-term and worldwide effort to breed for resistance so far has had little effect. A novel breeding approach may change this. It is based on cisgenic modification (CM) consisting of marker-free pyramiding of several resistance genes and their spatial and temporal deployment yielding dynamic varieties that contain potato genes only. It is envisioned that this CM approach with potato’s own genes will not only prove societally acceptable but may also result in simplifications in the legislation on use of the CM approach. Various parties in the potato research arena intend to cooperate in this novel approach in a number of developing countries where potato substantially contributes to food security. The use of resources such as land, water and energy improves when the effect of late blight is markedly reduced.     

Breeding and physiological aspects of potato cultivation in the Mediterranean region

Summary In the Mediterranean area the potato is a very important crop and can be cultivated throughout the year. However, tuber yields are generally much lower than those in Northern European countries. This is because the environmental and agro-economic conditions are different from those of Northern countries where most cultivars were developed. We feel that the objective for the “new Mediterranean potato” must be the availability of potato cultivars for each environment and for each planting season. Breeding programmes should focus on improving potato production within a specific agro-ecological Mediterranean area rather than improving crop production across areas. This paper reports aspects of potato breeding and physiology related to resistance to stress conditions in the Mediterranean area, with particular emphasis given to resistance to abiotic (heat, drought and frost) as well as biotic stresses. We also discuss the potential to produce seed tubers suitable for potato cultivation in the Mediterranean area.     

Cryotherapy of Potato Shoot Tips for Efficient Elimination of Potato Leafroll Virus (PLRV) and Potato Virus Y (PVY)

Viral diseases constitute a major constraint to high yield and high quality production of potato. Potato leafroll virus (PLRV) and Potato virus Y (PVY) are among the most damaging potato viruses and are prevalent in most potato growing areas. In the present study, attempts were made to eliminate PLRV and PVY by three cryogenic protocols, i.e., encapsulation-dehydration, encapsulation-vitrification and droplet. Results showed that both PLRV and PVY could be efficiently eliminated by cryogenic treatments with 83–86% and 91–95% of frequencies of virus-free plantlets obtained for the former and latter, respectively. Frequencies of virus-free plantlets produced by cryogenic treatments were higher than those by meristem culture (56% for PLRV and 62% for PVY) and thermotherapy (50% for PLRV and 65% for PVY), and similar to those by thermotherapy followed by meristem culture (90% for PLRV and 93% for PVY). Survival (75–85%) and regrowth (83–89%) from cryo-treated shoot tips were higher than those from meristem culture (50–55%) and thermotherapy followed by meristem culture (40–50%), but similar to those from thermotherapy (80–87%). The morphology of the plantlets regenerated from cryo-treated shoot tips was similar to that of non-treated plantlets. Thus, cryotherapy would provide an alternative method for efficient elimination of potato viruses, and can be simultaneously used for long-term storage of potato germplasm and for production of virus-free plants.     

Breeding potato cultivars with tubers resistant toPhytophthora infestans

Summary Available information has been reviewed on tuber resistance toP. infestans, its inheritance and breeding procedures used to obtain potato cultivars superior in this character. P. infestans is worldwide the most destructive potato pathogen. Tuber resistance is an essential component of potato resistance as this pathogen is often responsible for tuber rot in storage, and infected tubers of susceptible cultivars provide an important way for its overwintering. In Europe many cultivars and advanced breeders selections have been obtained with tuber resistance toP. infestans, but in the last decades no progress is noted in the mean level of this resistance in cultivars. The expression of tuber resistance depends to a large extent on testing conditions and therefore it can be difficult to evaluate. Consequently making progress in breeding is not easy, and also cultivar assessment data from various countries sometimes differ considerably. It is concluded from published data that it should be easier to make progress in breeding potato cultivars with resistant tubers if more attention is paid to combining the various types of resistance which are already known, and if the genetic determination of durable resistance toP. infestans is better understood. Professor Dr. K.M. Świeżyński passed away on 27th July 2000     

马铃薯晚疫病和早疫病田间主要识别特征及病原学研究

马铃薯是我国粮食生产体系中十分重要的粮食作物。近年来,马铃薯病害的发生流行逐年加重,已成为限制我国马铃薯产业健康发展的主要障碍之一。马铃薯晚疫病和早疫病是马铃薯种植过程中危害最为严重的2种病害,该文总结了马铃薯晚疫病和早疫病田间主要识别特征、病原菌特征及生物学特性,为2种马铃薯病害的综合防控提供理论基础及技术参考。     

Inheritance of extreme resistance to potato virus Y in potato

Summary Segregation for extreme resistance to PVY was evaluated in progenies derived from crossing two extremely resistant potato clones with parents differing in resistance. Resistance was evaluated after mechanical inoculation with PVY^O and PVY^N, and after graft inoculation with PVY^O. Biological and serological tests (ELISA) were used for virus detection. The extreme resistance is governed by a single dominant gene, but observed segregations deviated from the expected ratios. Considerable modifying effects were detectable, depending on the potato genotype and virus isolate, for a significant excess of susceptible genotypes was observed in some progenies. Moreover, genotypes with non-parental types of resistance to PVY were observed.     

Production and use of seedling tubers from true potato seed (TPS) for potato cultivation in Italy

Summary The effect of varying plant population on the production of tubers from potato seedlings was investigated during 1992 and 1993 using three different plant densities: 35, 70, 100 plants/m². Increasing the plant population significantly increased the number of tubers produced, but no significant difference was found between the plant densities of 70 and 100 plants/m². The seedling tubers produced in nursery beds were tested in the field for ware potato production using different sized tubers. The best performances were obtained using tubers 30–40 mm. Significant differences were evident among the 7 true potato seed (TPS) families used, but data grouped by type of cross did not indicate any significant difference between 4X×4X and 4X×2X crossing groups.     

Disease resistance inSolanum phureja and diploid and tetraploidS. tuberosum × S. phureja hybrids

Summary DiploidSolanum phureja, diploid and tetraploidS. tuberosum × S. phureja hybrid, and tetraploidS. tuberosum backcross clones were assessed for resistance to commercially important diseases. There was a reduction in the expression ofS. phureja characteristics with increasing dosage ofS. tuberosum genetic material. The generally high resistance of theS. phureja group to common scab, potato leafroll virus and potato virus Y decreased, while resistance to gangrene, foliage and tuber blight tended to increase. Resistance genes were probably well dispersed throughout theS. phureja genotype so that many were lost on hybridisation, butS. phureja could be a useful source of scab and virus resistance in the production ofS. tuberosum cultivars.     

Fertilizer management impacts on stand establishment, disease, and yield of Irish potato

Summary Excessive fertilizer application in North Carolina, USA results in high residual soil levels of P, K and total soluble salts in potato fields. Our objectives were to determine the salt sensitivity of three common cultivars (Atlantic. Snowden and Superior), and the effects of planting density and fertilization on stand establishment, soilborne disease, and yield. Greenhouse results suggest that potato growth and emergence, but not shoot initation, are reduced by high salinity. On a Portsmouth fine sandy loam, high fertilizer rates did not reduce stands of cv. Atlantic in the field in 1996 or 1997. Excess N resulted in moreRhizoctonia stem canker in 1996, and lower yields at the lower planting density in 1997. Yield compensation for reduced plant density occurred in 1997 at the lower N rates (56 and 112 kg N ha⁻¹) and at the high PK rate (49 kg P and 139 kg K ha⁻¹).     

The potato genetic resources held in trust by the International Potato Center (CIP) in Peru

Summary Potatoes account for about half of the world's annual output of all roots and tubers, and since the early 1960s, the increase in area planted in developing countries has been higher than for any other major food crop. Annual world production currently totals 274 million tons on 18 million hectares, with China and India accounting for 22 percent of this total. In less than a generation, most of the world's potatoes will be harvested in Asia. Africa, or Latin America, where the potato is becoming an increasingly important source of food and its cultivation provides rural employment and income for the growing population. The rapid emergence of processing facilities for the fast food industry, and the indirect influence of improved rice and wheat irrigation systems have also contributed to the expansion of potato production in Asia. The demand is strongest for processing quality potatoes that supply the fast food chains in large urban concentrations where processed potato products fetch top prices. Such increasing demand is putting strong pressure on national and international breeding institutions to produce high quality processing varieties well adapted to the wide array of agro-ecological conditions, in South East Asia in particular. The lack of adequate seed systems in this region is the single most important impediment to the expansion of the cultivation of the crop. Unfavourable agro-ecological conditions interfere with the production of high quality seed in most Asian potato growing areas, and the availability of high quality seed of the right quantity at the right time remains the most consequential bottleneck to efficient potato production. The seed issue is also the principal problem of potato cultivation in the traditional potato growing areas of Central and Eastern Europe. A review of “the development of integrated systems for large scale propagation of elite plants using in vitro techniques” with specific focus on “potato seed production by tissue culture” is therefore very timely. It provides a platform for analysis and discussion of solutions for some of the most common seed problems facing the potato industry in many parts of the word. All efforts to improve the potato crop and to solve the associated seed problems begin with the right choice and use of the available genetic resources. Resistance to certain pests and diseases has a direct bearing on the success of a seed program. Multiple virus resistance, in particular, would ensure a halt to seed degeneration caused by an accumulation of viruses and thus greatly prolong the ability of seed producers and ware potato growing farmers to grow their crops at great economic benefit. This paper will therefore deal with the current status of the World Potato Collection held in trust by the International Potato Center (CIP) in Peru by presenting up-to-date information on its classification, phytosanitary status and availability of the genetic material and its evaluation data to the breeders worldwide.