Effects of soil characteristics on the relationship between potato cyst nematodes and yield. II. Acidity (soil pH)

Summary The sandy and sandy peat soils of the northeast of The Netherlands are mineralogically very poor and acid. Independently of potato cyst nematode infestations, there is a considerable negative effect of increasing soil pH on potato tuber yield. Potato cyst nematode infections aggravate the effect of soil pH in depressing yield. It was shown that both potato cyst nematode infection and increasing soil pH values reduce the buffering capacity of the root system. Testing for yield as well as for tolerance to potato cyst nematode infection should be made at a range of soil pH values, similar to those found in the target area. This refers to active breeding programmes as well as to the selection of cultivars for yield trials.     

Relationship between potato cyst nematodes and their principal host. IV. Tolerance of potato cultivars and the effect of potato cyst nematode on initial plant growth

Summary Greenhouse experiments on the effects of white potato cyst nematode infestations (Globodera pallida Stone) on initial growth and development of a series of potato cultivars are compared with the results of field experiments on sandy and sandy-peat soils on the effect of nematode density on tuber yield. A simple greenhouse test, assessing root growth response to potato cyst nematode infection, provided a good insight into a cultivar's tolerance performance in the field early in the growing season. As a very limited number of plants is needed for the greenhouse test, screening for tolerance can be conducted in the early stages of a breeding programme.     

Relationship between potato cyst nematodes and their principal host. II. Evaluation of mathematical descriptors relating potato yield and nematode density

Summary  To describe the relationship between nematode density and yield, four equations of increasing complexity are found in the literature. They concern a linear regression curve, a log linear regression curve, a regression curve based on an exponential relation and an inverse linear regression curve. The yield to PCN density responses of these equations are shown on a linear and on a logarithmic scale. Considerable differences are shown in the way they respond to the same data. None of these equations is able to explain or forecast yield decrease caused by potato cyst nematodes.     

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.     

The use of single,spaced potato plants to assess their tolerance of damage by potato cyst nematodes

Summary Potato clones and cultivars differ in their ability to tolerate damage by the potato cyst nematodes:G. rostochiensis andG. pallida. This paper reports a simplified field assessment whereby single, spaced plants are grown in heavily infested soils. These trials identified those clones which are either very sensitive to damage or those that grow and yield well in the presence of nematodes. The use of such a screening procedure in a breeding programme is discussed.     

Effects of soil-borneRhizoctonia solani Kühn on yield and quality of ten potato cultivars

Summary The effects of soil-borneRhizoctonia solani on yield and quality of potato were studied by an extensive individual plant sampling procedure. From 1983 to 1986, stem canker and stolon pruning were examined in 10 768 plants growing on a sandy soil. Tuber yield and quality and haulm yield per plant were also recorded. The degree of attack byR. solani depended on the cropping frequency of potato. Severe and very severe stem and stolon attacks decreased fresh yield, dry matter yield and dry matter content of tubers and increased the number of deformed and small tubers, whereas the effect on haulm yield and stem number was small. Potato cultivars differed in susceptibility toR. solani, but yield response did not differ significantly between cultivars at the same levels of stem and stolon infection.     

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.     

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 effect of soil pH on yield losses caused by the potato cyst nematodeGlobodera pallida

Summary The effect of soil pH on yield losses due to potato cyst nematodes (Globodera pallida) was investigated in experiments in the field and in a semi-controlled environment. Through annually liming a reclaimed peat soil with about 22% organic matter, plots with pH levels of 4.5, 5.0, 5.5, 6.0 and 6.5 were obtained. In 1990 potato yields in these plots decreased from 45 t/ha at pH 4.5 to 33 t/ha at pH 6.5, whereas the nematode densitites decreased from about 18 to 9 juveniles per g soil. In a container experiment a strong interaction was recorded between soil pH and the presence of nematodes. Tuber yields were about 11% lower at pH 6.5 than at pH 4.5 in the absence of nematodes, but about 44% lower when an initial population of 27 juveniles per g soil was present.     

ALHAMRA,STEMSTER, SKIRZA: Three new cultivars from Caithness,Scotland

A new private potato breeding company was established in Caithness, Scotland in 1983. In August 1986 the first three potato varieties from ‘Caithness Potato Breeders Ltd.’ were accepted onto the United Kingdom National List of Potato Varieties. These three cultivars—ALHAMRA (maincrop), STEMSTER (maincrop), SKIRZA (second early), are all red-skinned and result from a cross between ‘Desiree’ and ‘Maris Piper’. All three cultivars have demonstrated high yield potential, ‘Stemster’ particularly so, and all are resistant to one pathotype of the golden (potato cyst) nematode, unlike ‘Desiree’ their red-skinned parent.     

A method of assessing potato seedling progenies for resistance to the white potato cyst nematode

Summary The resistance expressed by progenies of potato seedlings to the white potato cyst nematode (Globodera pallida) has been assessed on bulk sowings of seedlings and on individual plants raised from tubers, and a positive correlation between the seedling and plant tests has been established. The use of such a seedling test as an addition to other methods of screening is discussed.     

Resistance to <Emphasis Type="Italic">Potato virus Y</Emphasis> in a Multitrait Potato Breeding Scheme without Direct Selection in Each Generation

In an experimental breeding scheme to improve late blight (Phytophthora infestans) and white potato cyst nematode (Globodera pallida) resistance of tetraploid potato over three generations of crossing and selection, 15 clones survived the final selection, and these were derived from 15 great-grandparents. There was no direct selection for resistance to Potato virus Y (PVY), but 14 out of the 15 great-grandparents were resistant to PVY and three had extreme resistance. Thirteen of the 15 descendants had PVY resistance and one extreme resistance. This was within the range expected for a random (unselected) sample from the genotypes of the great-grandparents. Hence, we found no evidence for any positive or negative association between PVY resistance and the attributes selected. The conclusion is that laborious selection is not required in every generation when many parents have PVY resistance, including some with more than one copy of a PVY resistance gene or resistance at more than one locus. However, in the future, determining the major virus resistance genes present in potential parents in each generation using diagnostic molecular markers would prevent susceptible × susceptible crosses being made and maximise the number of resistant × resistant ones.     

Synergistic interactions betweenRhizoctonia solani Kühn,Verticillium dahliae Kleb.,Meloidogyne spp. andPratylenchus neglectus (Rensch) Chitwood & Oteifa,in potato

Summary Samples of a sandy soil and a marine clay soil sterilized by steam were put in 55-1 containers insulated with polystyrene and placed outdoors on a brick pavement. Sandy soil was infested singly or in all possible combinations with root-knot nematodes (Meloidogyne spp.) and the fungiRhizoctonia solani andVerticillium dahliae, and the marine clay soil was infested with the root-lesion nematodePratylenchus neglectus and the same fungi to evaluate the effects of these organisms on the yield of potato. The experiments were carried out from 1983 to 1986. Tuber yield was reduced by single infestations of theMeloidogyne spp. andV. dahliae but not significantly byR. solani orP. neglectus. A three-factor interaction: nematode ×R. solani × V. dahliae was found in both experiments.R. solani andV. dahliae showed significant synergistic effects when soil was infested with theMeloidogyne spp. orP. neglectus.     

小麦品种对禾谷孢囊线虫（Heterodera avenae） 江苏沛县群体的抗性鉴定

为了筛选对禾谷孢囊线虫病(Cereal cyst nernatode,CCN)具有抗性的小麦品种,采用室内二龄幼虫接种法、网室卵接种法和田间病圃法测定了收集自5个省份的40个小麦品种对小麦孢囊线虫江苏沛县群体的抗性。室内二龄幼虫接种测定结果表明,供试材料中无免疫品种,华麦1号、温粮58和豫麦66-18系表现为高抗,扬麦13和徐麦7086表现为中抗,烟农5158表现最感病,平均单株白雌虫数达104.7个;田间病圃测定表明,上述5个品种仅华麦1号表现为抗病。网室卵接种法测定结果与室内二龄幼虫接种法及田间病圃法测定结果差异较大,显示该方法不适用小麦品种的CCN抗性鉴定。     

Monoxenischer Resistenztest für Kartoffelgenotypen gegenüber dem ZystennematodenGlobodera pallida. 1. Kultivierung der Genotypen

Zusammenfassung Zur routinem?ssigen Resistenzbestimmung von Kartoffelgenotypen gegenüberGlobodera pallida (Stone) Behrens (Pa3) wurde ein monoxenischesin vitro-Verfahren entwickelt, dessen Grundlage die keimfreie Kultivierung der Testgenotypen in einem N?hragarmedium unter definierten Bedingungen war. Dadurch konnte die vollst?ndige Entwicklung der Nematoden sowie die Dimension ihres N?hrzellensystems in den transparenten Kartoffelwurzeln kontinuierlich beobachtet werden. Der Test erm?glichte die Selektion resistenter Genotypen anhand geringer quantitativer Unterschiede in der vermutlich polygen-vererbten Resistenzreaktion. Für die Anzucht keimfreier Pflanzen aus Kartoffelsamen und- knollen wurden spezielle Verfahren entwickelt und an mehreren Genotypen geprüft. Die dabei festgestellte Variabilit?t, insbesondere bei der Wurzelbildung, erforderte für den geeigneten Zeipunkt der Nematodenzugabe die Ausarbeitung eines Wurzelboniturschemas. Die Genotypen konnten nach dem Test in T?pfen weiterkultiviert werden.

---

Summary A monoxenic resistance test for routine use was developed to determine the resistance of potato genotypes to the cyst nematodeGlobodera pallida (Stone) Behrens. The basis of the procedure is the aseptic cultivation of the genotypes under test in a nutrient medium in defined conditions. It was possible with it to observe invasion, the development of the nematodes, as well as the dimensions of their feeding cells in the transparent potato roots. Small, quantitative differences, due presumably to the polygenically determined resistance reactions of the genotypes, could be distinguished, and selection for resistance was feasible. For routine trials special procedures were developed using surface sterilisation of potato seed and etiolated sprouts which gave high levels of sterility. The genotypes from seeds could be tested directly, but those from etiolated sprouts had to be prepared by stem cutting. A root system was obtained which correlated with known ratings. Each genotype established from seed and etiolated shoots, developed at different rates, as did their root systems, and no definite timespan could be set before nematode introduction. Growing the cultivars under light before the test resulted in faster root development (Table 2), and a higher nematode infestation than in darkness (Figure 4). The time for nematode inoculation was determined by a rating system based on the location of the perimeter of the root system (Figure 5). In this way physiological factors and the individual growth rate of each genotype were allowed for, with the aim of assessing possibly high levels of nematode infection. At the end of the test the seedling genotypes can be removed from sterile culture and grown on in pots. Where genotypes form minitubers (Table 1) it is possible to proceed early to the next stage in cultivation or to store them trouble-free.

     

Assessment of new potato cultivars in Europe: a survey

Summary In 1994, a postal questionnaire was sent to 41 institutes in 27 countries to obtain information on the national potato cultivar testing programmes in Europe. Responses were received from 19 countries. Foliage, tuber and yield characteristics were assessed in all countries but the number of sites and replicated varied considerably between the countries. Cooking and taste qualities were measured in most countries using relatively simple methods but processing characteristics were tested less commonly. Susceptibility to the most common diseases, i.e. late blight, common scab, leafroll and PVY^o, was assessed in over 75% of the countries while resistance to another 21 disease and 4 potato cyst nematode pathotypes was assessed by various countries, depending on their national importance. Many of the assessments were based on records of natural infection although controlled inoculation tests were done more frequently for the more important diseases.     

The effect of chloride fertilization on blackspot susceptibility and other quality characteristics and on yield of potato

Summary Trials were carried out in two years on a sandy loam and on a heavy clay soil with two cultivars to examine the potential of chloride fertilization as a tool to reduce blackspot susceptibility of potatoes and to investigate other effects on yield and quality. Blackspot susceptibility was significantly reduced in cv. Marijke, but not in cv. Bintje as a result of increasing doses of applied chloride from 0 to 400 kg ha1. Dry matter concentration, assessed as under-water weight, was reduced by chloride in both cultivars at the two locations. Fry colour of French fries was improved by chloride. Applying 400 kg ha⁻¹ Cl⁻ to both soil types decreased net tuber yield >35 mm of cv. Bintje but not of cv. Marijke. Chloride caused slower emergence, retarded crop development and less stems per plant on the sandy loam soil but not on the heavy clay soil.     

Fingerprinting Indian potato cultivars by random amplified polymorphic DNA (RAPD) markers

Summary Random amplified polymorphic DNA markers were used to distinguish and characterize 20 Indian potato cultivars. A total of 198 scorable fragments were amplified using 10 random primers, only two of which were monomorphic. Similarity values among the cultivars ranged from 0.33 to 0.80. A primer having resolving power above 7.4 was sufficient to distinguish all 20 cultivars. Wide variations in band profiles were observed when the same template DNA was amplified using Taq DNA polymerase from four different sources. No significant difference in profile complexity was observed at 40°C annealing temperature with a primer having 70% GC content. Prior restriction of template DNA resulted in band profiles whose complexity was similar to or higher than that of unrestricted template. However, multiplex RAPD with cleaved template DNA could not increase fingerprint complexity. Publication No. 1666, CPRI. Shimla     

甘南农牧过渡区燕麦田孢囊线虫的发生与分布

为明确孢囊线虫在高寒、高海拔区的发生与分布情况,2015年8月,采用Z字型取样法,对甘南农牧过渡区10个乡镇燕麦田的80份根际土样进行了孢囊线虫调查。80份土样中孢囊线虫平均检出率为87.5%,夏河县的达菱乡、达麦乡、唐嘎尔乡与那吾乡,卓尼县杓哇乡及临潭县冶力关镇土样的检出率均达100%;夏河县王格尔塘镇最低,为60%。海拔高度不同,孢囊线虫的分布不同,在海拔2 501~2 800m的区域土样中,孢囊线虫检出率最高,为100%,在海拔3 101~3 500m区域检出率最低,为58.3%。燕麦田间孢囊线虫密度平均为3.7个·100g~(-1)土,其中卓尼县杓哇乡的密度最高,为14.4个·100g~(-1)土,夏河县王格尔塘镇和临潭县冶力关镇的最低,为1.1个·100g~(-1)土。通过形态学特征鉴定,此区的孢囊线虫为燕麦孢囊线虫(Heterodera avenae)。