Molecular mapping of the potato virus Y resistance gene Rysto in potato

Ry _sto is a dominant gene which confers resistance to potato virus Y (PVY) in potato. We have used bulked segregant analysis of an F₁ tetraploid potato population to identify three AFLP markers linked to and on either side of Ry _sto . The tomato homologue of one of these AFLP markers was assigned to linkage group XI by analysis of an F₂ mapping population of tomato, suggesting that Ry _sto is also on chromosome XI of the potato genome. This map position was confirmed by the demonstration that Ry _sto was linked to markers which had been previously mapped to chromosome XI of the potato genome. Four additional AFLP markers were identified that were closely linked to Ry _sto in a population of 360 segregating progeny of a potato cross between a resistant (Ry _sto ) and a susceptible parent. Two of these markers were on either side of Ry _sto , separated by only a single recombination event. The other two markers co-segregated with Ry _sto . Received: 29 July 1996 / Accepted: 30 August 1996     

Behavior of potato gametoclonal plants against the necrotic strain of potato Y potyvirus

A total of 59 Solanum tuberosum androgenetic plants have been obtained through anther culture, 47 of which derived from a tetraploid clone, seven from a diploid hybrid, and five from an anther-derived clone. About two thirds of the anther-derived plants were dihaploids, a few were monohaploids (5.08%) or aneuploids (6.78%), whereas the tetraploid genotype generated about a third of tetraploids. Seven hundred twenty seven R₁ plants arisen from tubers of the androgenetic potatoes were mechanically inoculated with the necrotic strain of the potato Y potyvirus (PVY^N) and grown in a glasshouse. Fifty days after inoculation, the presence of PVY^N in R₁ plants was detected by DAS-ELISA (Double Autibody Sandwich). Only three plants (0.4%) of genotype H2-258 exhibited local necrotic symptoms (hypersensitivity reaction) suggesting the presence of the N _y gene, and this extreme resistance is epistatic to hypersensitive resistance. The immunity (R _y-gene) to PVY^N was retained through anther culturing and present at all levels of ploidy. The pattern of segregation for immunity was differentiated according to the ploidy level of the anther-derived plants. This changed segregation pattern may be due to a loss of resistance during the culturing, when an endoreduplication has taken place or to the possible regeneration from Second-division restituted unreduced microspores. Anyway, this segregation pattern must be taken into account when gametoclones are used in genetic studies. Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 4, pp. 572–578. The text was submitted by the authors in English.     

用马铃薯人工饲养马铃薯块茎蛾的方法

介绍一种马铃薯块茎蛾Phthorimaeaoperculella的室内人工饲养方法。在人工养虫室内用 1 0 %的蜂蜜水喂养成虫 ,用滤纸收集卵块 ,幼虫在薯块上饲养 ,化蛹于牛皮纸卷成的纸筒中 ,饲养结果发现马铃薯块茎蛾完成 1代大约需要 35～ 4 6d ,室内连续饲养块茎蛾 3代 ,卵的孵化率、幼虫化蛹率、成虫羽化率均在 90 %以上。     

Role of the methionine cycle in the temperature-sensitive responses of potato plants to potato virus Y

Plant–virus interactions are greatly influenced by environmental factors such as temperatures. In virus-infected plants, enhanced temperature is frequently associated with more severe symptoms and higher virus content. However, the mechanisms involved in such regulatory effects remain largely uncharacterized. To provide more insight into the mechanisms whereby temperature regulates plant–virus interactions, we analysed changes in the proteome of potato cv. Chicago plants infected with potato virus Y (PVY) at normal (22 °C) and elevated temperature (28 °C), which is known to significantly increase plant susceptibility to the virus. One of the most intriguing findings is that the main enzymes of the methionine cycle (MTC) were down-regulated at the higher but not at normal temperatures. With good agreement, we found that higher temperature conditions triggered consistent and concerted changes in the level of MTC metabolites, suggesting that the enhanced susceptibility of potato plants to PVY at 28 °C may at least be partially orchestrated by the down-regulation of MTC enzymes and concomitant cycle perturbation. In line with this, foliar treatment of these plants with methionine restored accumulation of MTC metabolites and subverted the susceptibility to PVY at elevated temperature. These data are discussed in the context of the major function of the MTC in transmethylation processes.     

Factors affecting the development of spraing in potato tubers infected with potato mop-top virus

A larger proportion of tubers of Arran Pilot potato growing at the surface of soil infested with potato mop-top virus (PMTV) showed spraing symptoms (brown rings) at harvest than of tubers from below the surface. Infected tubers with or without spraing developed a spraing ring when stored in darkness, first for 1–2 wk at 18 d?C and then for 1–2 wk at any constant temperature between 5 and 13 d?C. Only a faint surface ring developed when either of these periods was decreased to 1 day; 4-day periods were needed to induce distinct symptoms. Internal tuber symptoms developed more slowly than surface symptoms, and their formation was favoured by cutting the tubers in half. Additional pigmented surface rings were produced outside the first ring by successive cycles of treatment at 18 and 9d?. Spraing did not develop when the first stage of treatment was at 22–25d?, when the tubers were kept first at 10d? and then at 5d?, when the treatment at 5–13d? preceded that at 18d?, or when the tubers were kept at constant temperatures ranging from 5 to 25d?. When tubers of six potato varieties were grown in PMTV-infested soil and then stored at temperatures designed to induce symptoms, the varieties known to be the most susceptible in the field were those which had the greatest tendency to develop spraing during storage. When infected tubers were exposed to light, typical spraing symptoms were not induced, but greening of the tuber surface was much delayed in localized ring-shaped areas, so that pale weals appeared. Spraing symptoms were produced, in favourable conditions, by the reaction of cells at the periphery of the PMTV-invaded zone. Internal spraing did not prevent PMTV invading tissue outside the brown arcs; its rate of spread was about 10 μm/h at 14–18d?.     

Effects of Zygorrhynchus moelleri on the growth of potato and reproduction of potato cyst nematodes

Laboratory, pot and field experiments investigated the effects of the fungus Zygorrhynchus moelleri on the growth of potato and on the reproduction of the potato cyst nematodes (PCN), Globodera pallida and G rostochiensis. Preliminary laboratory tests showed that Z. moelleri growth was favoured by temperatures and pH ranges commonly present in field soils. The fungus colonised potato roots in vitro and in compost or field soil. It also stimulated in vitro root growth of three potato cultivars. In pot experiments Z. moelleri stimulated potato growth, particularly in the presence of PCN attack. In field plots infested with a mixture of G pallida and G. rostochiensis, tuber yields were not increased after application of the fungus but, in G pallida‐infested plots, yields were significantly increased after drills were inoculated with Z. moelleri. The application of Z. moelleri had no apparent effects on nematode reproduction. Factors influencing the interactions between Z. moelleri, potato and potato cyst nematodes are discussed and the potential role of the fungus as a plant growth promoter in organic potato production considered.     

Application of enzyme-linked immunosorbent assay to the detection of potato leafroll virus in potato tubers

Factors affecting the detection of potato leafroll virus (PLRV) by enzyme-linked immunosorbent assay (ELISA) in tubers of field-grown potato plants with primary or secondary infection were studied. The reactions of extracts of virus-free potato tubers were minimised by pre-incubating the extracts at room temperature and by careful choice of the dilution of enzyme-conjugated globulin. PLRV was reliably detected in tubers produced by secondarily infected plants of all six cultivars tested. PLRV concentration was greater in heel-end than in rose-end vascular tissue of recently harvested tubers but increased in rose-end tissue when tubers stored at 4°C for at least 5 months were placed at 15–24°C for 2 wk. PLRV occurred at greater concentration in tubers from plants of cv. Maris Piper with natural or experimentally induced primary infection than in tubers from secondarily infected plants; again PLRV concentration was greater in heel-end than in rose-end vascular tissue. Plants whose shoots were infected earliest in the growing season were invaded systemically and produced the greatest proportion of infected tubers; plants infected late in the season also produced infected tubers but PLRV was not detected in their shoot tops. PLRV concentration in tubers from the earliest-infected plants was less than in tubers from later-infected plants. PLRV was detected reliably by ELISA in tubers from progenies that were totally infected but was not detected in all infected tubers from partially infected progenies. ELISA is suitable as a routine method of indexing tubers for PLRV, although the virus will not be detected in all infected tubers produced by plants to which it is transmitted late in the growing season.     

Transgenic-Bt potato plant resistance to the colorado potato beetle affect the aphid parasitoid Aphidius nigripes

Using the biotechnological plant resistance for herbivore control with less reliance on chemicals in integrated pest management (IPM) programs critically depends on predictable interactions with no-target organisms of various trophic levels. Plant resistance to insect pests based on recombinant Bacillus thuringiensis could interfere with natural enemies of non target pests. Performance of the potato aphid parasitoid Aphidius nigripes was studied on the 'Superior-BT line transgenic for the CryllIA toxin of B. thuringiensis, resistance to the Colorado potato beetle; and none transformed 'Superior' line which served as control. Parasitoid survival was significantly lower on the 'Superior-BT' line compared to control. Adult females were largest on 'Superior' and smallest on BT potatoes. This difference was reflected on parasitoid fecundity, which was lowest on 'Superior-BT', and highest on Superior. The results indicate that factor of potato resistance to the Colorado potato beetle affected the fitness of a parasitold of the aphid Macrosiphum euphorbiae, a secondary pest of potato. The effects on the parasitoid were complex but were generally interpretable in terms of host aphid quality variation among potato lines used as food by the aphids during parasitoid development.     

Mapping of resistance to the potato cyst nematode Globodera rostochiensis from the wild potato species Solanum vernei

A population of diploid potato (Solanum tuberosum) was used for the genetic analysis and mapping of a locus for resistance to the potato cyst nematode Globodera rostochiensis, introgressed from the wild potato species Solanum vernei. Resistance tests of 108 genotypes of a F₁ population revealed the presence of a single locus with a dominant allele for resistance to G. rostochiensis pathotype Ro1. This locus, designated GroV1, was located on chromosome 5 with RFLP markers. Fine-mapping was performed with RAPD and SCAR markers. The GroV1 locus was found in the same region of the potato genome as the S. tuberosum ssp. andigena H1 nematode resistance locus. Both resistance loci could not excluded to be allelic. The identification of markers flanking the GroV1 locus offers a valuable strategy for marker-assisted selection for introgression of this nematode resistance.Abbreviations BSA bulked segregant analysis - RAPD random-amplified polymorphic DNA - RFLP restriction fragment length polymorphism - SCAR sequence-characterized amplified region     

Restricted multiplication of potato leafroll virus in resistant potato genotypes

Plants of a range of potato genotypes differing in rating for field resistance to potato leafroll virus (PLRV) were inoculated with the virus by grafting or by aphids (Myzus persicae). Plants of all genotypes tested became infected by each inoculation method and PLRV was detected by ELISA in the upper leaves of all genotypes within 26 days after grafting. Most genotypes with high resistance ratings developed only mild primary and secondary symptoms whereas those with low resistance ratings developed more pronounced symptoms. However, one genotype (G7461(4)) with a high resistance rating was very severely affected. The concentrations attained by PLRV in genotypes with high resistance ratings were only 1–10% of those in genotypes with low resistance ratings. These differences in virus concentration were found in young leaves of plants with primary or secondary infection, whether inoculated by grafting or by aphids and whether grown in the glasshouse or the field. In older leaves, differences in virus concentration between genotypes were at least as pronounced as those in younger leaves. In contrast, PLRV concentration in vascular tissue at the heel end of tubers of plants with primary infection was similar for all the genotypes tested. Although low PLRV concentration was consistently associated with high resistance rating it is not the only form of resistance to PLRV occurring in potato.     

Dynamics and management of the white potato cyst nematode Globodera pallida in commercial potato crops

Eight trials were conducted in commercial potato fields infested with the white potato cyst nematode (wPCN, Globodera pallida) and one in a field infested with the yellow PCN (yPCN, Globodera rostochiensis). Our aims were to produce data to validate and refine a computer‐based program (The Model) for the long‐term management of PCN, to determine nematicide effectiveness and to assess rates of PCN population decline between potato crops. Prior to planting, each farmer applied an overall nematicide treatment to his field, except for ten untreated plots that were widely spaced to encompass a range of PCN population densities. Each untreated plot was paired with a similar plot in the adjacent treated area and all plots were intensively sampled for PCN population densities at planting (P_i) and again at harvest (P_f) when tuber yields were determined. Four trials were re‐sampled 2–4 years later to determine PCN population decline rates. Regressions that form the basis of ‘The Model’ and described the relationship between P_i and tuber yield and PCN population density at harvest were fitted to the results from both the untreated and nematicide treated plots. These regressions also enabled us to estimate the yield potential at each site in the absence of PCN and showed that nematicide treatment generally did not increase yield potential and that both tuber yield and PCN multiplication decreased with increasing P_i. However, there were major differences between sites and cultivars. When untreated, the yield of cv. Maris Piper was hardly affected in a highly organic soil with P_i > 200 eggs g^?1 whereas the yield of partially resistant cv. Santé was decreased from a potential of c. 60 t ha^?1 to c. 20 t ha^?1 in a light silt with P_i = 20 egg g^?1 soil. Similarly, untreated wPCN multiplication rates at a low P_i ranged from 46‐fold to >100‐fold. Nematicide effectiveness was estimated from the regressions and, at several sites, yield was decreased despite nematicide treatment. Control of wPCN multiplication was even poorer. In only two of seven trials planted with susceptible cultivars was more than 50% control achieved – maximum populations in treated plots usually exceeded 250 eggs g^?1. Partially resistant Santé decreased the multiplication rate of wPCN in the two trials where it was planted. An alternative analysis using Genstat indicated that The Model tended to underestimate the maximum multiplication rate and overestimate the maximum population density. When four sites were re‐sampled 2–4 years after harvest the populations of wPCN had declined by between 15% and 33.5% per annum with a mean of 26% per annum. Modelling indicated that rotations longer than 8 years were required to control wPCN unless other effective control measures, such as growing a partially resistant cultivar, were used.     

Effects of a mixed-isolate mycorrhizal inoculum on the potato – potato cyst nematode interaction

Inoculation of microplants of potato cv. Golden Wonder with Vaminoc, a mycorrhizal inoculum of three arbuscular mycorrhizal fungi (Glomus spp.), resulted in an increase in in‐sand hatch of Globodera pallida, but not G. rostochiensis, within 2 weeks. By this time, mycorrhized plants also supported a larger number of feeding nematodes of both PCN species (50% higher for G. rostochiensis) than did non‐mycorrhized plants, with a higher proportion of the G. pallida population being fertilised females than for G. rostochiensis. After 12 weeks, the multiplication rate of G. rostochiensis on mycorrhized plants was significantly greater than on non‐mycorrhized plants, whereas no such difference was observed for G. pallida. The principal component of PCN multiplication affected by mycorrhization was increased cyst number per plant from 6 to 12 weeks. Over this period, there was no increase in cyst number per plant for either PCN species on non‐mycorrhized plants, whereas the value increased on mycorrhized plants for both G. rostochiensis (by almost 200%) and G. pallida (57%). Mycorrhization resulted in significant increases in the root and shoot dry weights of plants grown in the absence of PCN. Although mycorrhized plants carried a larger PCN burden than non‐mycorrhized plants when grown on PCN‐infested medium, as a result of the increased PCN multiplication rate, they produced larger root systems than did nonmycorrhized plants, suggesting increased tolerance to PCN of the mycorrhized plants, particularly to G. rostochiensis. Of morphological characters investigated in the absence of PCN, only stem height (increased) was significantly affected by mycorrhization. Colonisation by mycorrhizal fungi resulted in increased tuber yield both in the absence (significant increase) and presence (non significant) of PCN, as a result of increased tuber number per plant. These results are discussed in the light of the possible use of AMF as part of an integrated PCN management plan.     

Factors affecting the detection of potato leafroll virus in potato foliage by enzyme-linked immunosorbent assay

Using antiserum globulins that reacted only weakly with plant materials, potato leafroll virus (PLRV) at 10 ng/ml was detected consistently by enzyme-linked immunosorbent assay (ELISA). The reaction with PLRV particles was slightly impaired in potato leaf extracts that were diluted less than 10^-1 but not at greater dilutions. Antiserum globulins that reacted more strongly with plant materials could be used satisfactorily for coating microtitre plates but were unsuitable for conjugating with enzyme. The detection end-point of PLRV, in leaf sap of potato cv. Cara plants grown from infected tubers in the glasshouse, was about 10^-2 and the virus was reliably detected in extracts of composite samples of one infected and 15 virus-free leaves. PLRV concentration was much less in extracts of roots or stolons than in leaf extracts. The virus was detected in infected leaves of all 27 cultivars tested. PLRV was readily detectable 2 wk before symptoms of secondary infection developed in field-grown plants of cv. Cara and Maris Piper and remained so for at least 5 wk. Its concentration was slightly greater in old than in young leaves and was similar to that in glasshouse-grown plants. In field-grown plants of cv. Maris Piper with primary infection, PLRV was detected in tip leaves 21–42 days after lower leaves were inoculated by aphids; in some shoots it later reached a concentration, in tip leaves, similar to that in leaves with secondary infection. Symptoms of primary infection developed in the young leaves of some infected shoots but were inconspicuous and were not observed until at least a week after PLRV was detected by ELISA.