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1.
Symptomatically distinct isolates of potato leaf roll virus were transmitted from White Rose to Russet Burbank potato by aphids and by grafting, from White Rose potato toP. floridana by aphids, and fromP. floridana toP. floridana by aphids. Isolates from White Rose potato generally produced stable and characteristic secondary leaf roll symptoms (but not primary leaf roll symptoms) when transmitted to Russet Burbank potato but variable symptoms when transmitted toP. floridana. Isolates from two of the latter plants with moderate and severe symptoms generally incited stable and characteristic symptoms when transmitted to otherP. floridana plants. The stable symptoms produced by each of these isolates were not modified by infestingP. floridana plants with varying numbers of viruliferous aphids. The results obtained in this study corroborate previous evidence for the existence of strains of potato leaf roll virus. It is suggested that certain White Rose potato plants contained mixtures of leaf roll virus strains. Furthermore, it is postulated that these mixtures were at least partially separated by “natural” selection following transmission toP. floridana. This mechanism provides an explanation for the stable symptoms produced by isolates transmitted fromP. floridana toP. floridana.  相似文献   

2.
On two separate occasions, some available accessions of tuber-bearingSolanum species were tested for resistance to potato viruses. Challenge inoculations were made mechanically with infective sap; and assessment was by sub-inoculation to differential host plants, supplemented by serological tests. In 1956–57, four accessions remained free from potato virus S (PVS), and nine remained free from PVM. In 1968–70, one or more clones of 11 accessions showed resistance to PVS—one of them,S. megistacrolobum, a diploid, apparently being hypersensitive. Resistance to PVX was found in seven accessions, and to PVM in two. There appeared to be resistance to the potato spindley tuber virus in five accessions.  相似文献   

3.
Summary Plants ofSolanum brevidens graft-inoculated with potato leaf roll virus (PLRV) grew vigorously and had a normal healthy appearance. Although presence of the virus was confirmed in all inoculated plants by graft tests to potato and/orDatura stramonium, recovery of PLRV fromS. brevidens PI 218228 usingPhysalis floridana and the aphidMyzus persicae was erratic and only few test seedlings became infected. Ease of recovery of the virus using aphids was not influenced by presence of a continuous graft union with infected potato. Testing ofS. brevidens PI 245763 withM. persicae was not possible due to poor aphid survival on plants of this accession.  相似文献   

4.
Tests were made on lines ofSolanum tuberosum spp.andigena to determine 1) whether resistance to potato virus Y exists in the Andigena germplasm, 2) the nature of its inheritance, and 3) the type of resistance. Results of the isolation and identification studies indicated that the pathogen involved was a common strain of potato virus Y. Under field conditions susceptible plants frequently escaped infection. However, field exposures over two seasons resulted in the same ratios as tests in which the same progenies were mechanically inoculated. Mechanical inoculation at the seedling stage proved to be a reliable means of transmission and resulted in accurate screening for resistance. Of 641 tub × tub clones tested, all were susceptible to the virus. Of 366 tub × adg clones tested, 170 were resistant and 196 were susceptible. This fits a 13:15 ratio, assuming random chromatid segregation and a single dominant gene conferring resistance. Plants that were resistant following mechanical transmission were also resistant when inoculated by aphids, indicating the reliability of mechanical transmission as a means of screening for resistance. To determine the type of resistance, top-graft and approach-graft tests were made. Failure to recover the virus from resistant plants inoculated by either grafting method suggests that immunity is the type of resistance involved.  相似文献   

5.
This study investigated the transmission efficiency of Potato leafroll virus (PLRV) by four potato colonizing aphid species, Myzus persicae, Macrosiphum euphorbiae, Aphis gossypii and Aphis fabae, reported from leaves and yellow water trap. Physalis floridana was used as a test plant for virus transmission. DAS-ELISA was used for virus screening of samples as well as virus detection on the test plant after transmission experiment. A 2-h period was sufficient for the tested aphids to acquire PLRV virions. However, a difference in the transmission potential occurred according to the aphid species. The highest potential was recorded for M. persicae and M. euphorbiae, at 90 and 80%, respectively. For the first time, the study revealed the PLRV transmission efficiency of A. fabae, estimated at 50%. The lowest potential rate of 30% was recorded for A. gossypii. This study highlights the PLRV transmission capacities of four potato colonizing aphids suspected to play a key role in the spread of PLRV in potato seed production sites.  相似文献   

6.
Progenies from a group of tetraploid parental clones from the USDA potato breeding program were used to investigate variation in resistance to the potato leafhopper,Empoasca fabae (Harris), and the potato flea beetle,Epitrix cucumeris (Harris). The study utilized two mating designs: i) selfing and testing both the parents and the S1 progeny; and ii) nine clones, used as males, were each crossed to three different clones, and progenies from the resulting families were tested. Statistically significant differences between families were measured in each test for both insects. Non-additive genetic variance was larger than additive genetic variance in progeny reaction to leafhopper infestation and hopperburin, but was smaller in progeny reaction to flea beetles. Environmental variation contributed heavily to the total variation of plant reaction to both insect species. Selecting individuals was indicated to be slightly more effective than selecting males on half-sib progeny performance but not as effective as selecting clones on S1 progeny performance. Because of the large environmental variance and small additive variance for both the leafhopper and flea beetle, slow progress in increasing the level of resistance to these two species in this sample population was predicted. Resistance to leafhopper infestation was genetically quite highly correlated (positive) with resistance to hopperburn, but phenotypically the correlation was considerably smaller. Negative genotypic, phenotypic, and environmental correlations between leafhopper infestation and flea beetle infestation suggest that selecting for resistance to one of these species, in the population sampled for these tests, would tend to increase susceptibility to the other.  相似文献   

7.
During 1980 and 1981 potato cultivars and breeding selections, including cultivated species and their hybrid derivatives, were evaluated for resistance to the green peach aphid (GPA),Myzus persicae (Sulzer), and to potato leafroll virus (PLRV). Criteria used were the number of aphids which colonized the clones in free choice field experiments and the number of plants derived from these experiments which showed symptoms of PLRV infection. Generally, greater resistance to GPA was found inSolarium tuberosum gp.andigena selections and hybrids than in gp.tuberosum cultivars. There were approximately fourfold differences in season-mean GPA levels among the clones tested each year. Forty-two families, representing a cross-section of the USDA breeding populations at the University of Idaho Research and Extension Center, Aberdeen, showed a similar range in colonization levels. Resistance to GPA colonization appeared to be more prevalent in gp.andigena, gp.phureja, and gp.stenotonum derivatives. There was a weak positive correlation (r2 = .34, P = .01) between foliar total glycoalkaloids and season-mean GPA colonization levels for six clones representing the range of observed resistance to GPA. Resistance to GPA colonization was apparently not directly related to resistance to PLRV infection. Katahdin, for example, was relatively susceptible to GPA colonization but very resistant to PLRV infection whereas selection A69657-4 (gp.andigena) was among the most resistant to GPA colonization but among the more susceptible to PLRV infection. Breeding for resistance to GPA colonization therefore may not be as promising for PLRV control as developing PLRV resistant cultivars.  相似文献   

8.
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.  相似文献   

9.
Summary Macrosiphum euphorbiae, collected in the field from potato plants infected with potato leafroll virus (PLRV), transmitted the virus to fewer potato plants in a field trial than did laboratory-rearedMyzus persicae. In the laboratory,M. persicae was the only efficient vector of PLRV fromPhysalis floridana seedlings, potato sprouts or excised leaves toP. floridana. Two clones ofM. euphorbiae and one clone ofAulacorthum solani transmitted PLRV from infected potato plants toNicotiana clevelandii as effeciently asM. persicae but a clone ofAphis gossypii was an inefficient PLRV vector. An isolate of PLRV, whichM. persicae transmitted inefficiently from potato toN. clevelandii, was also transmitted inefficiently byM. euphorbiae andA. solani.  相似文献   

10.
Field and greenhouse readings in Maine together with test plot readings in Florida showed the incidence of potato leafroll virus infection in 10 Kennebec seed lots from south, central and northern Aroostook County to be about 1.2%. When the seed lots were indexed by aphid transmission of the virus toPhysalis floridana Rydb. in January and July the incidence of leafroll was found to be 2% and 10% respectively. SinceP. floridana detects mild strains as well as those capable of causing visible symptoms on potato, these results indicate that mild strains are present in the Kennebec variety being grown for seed in Aroostook County. The authors indicate, however, that leafroll symptom expression inP. floridana, in many instances, was not definitive and they suggest that their data may reflect an inaccurate estimate of the prevalence of mild strains of leafroll in Maine.  相似文献   

11.
PVA produces distinct local lesions on open leaves ofPhysalis floridana, as does PVY. But, whereas PVA induced such lesions on detached leaves, PVY did not. PVX induced similar lesions, thus the test for PVA will be most useful in work with isolated cultures of PVA or with virus tested seed lines or in screening for resistance, where PVX is absent.P. floridana plants and leaves were best held at 15 to 18 C with low light intensity (4–5 K lux). From 4–6 week old potato plants, PVA was best obtained from lower leaves, ground in 0.05 M glycine — 0.03 M phosphate buffer, pH 9.2. One leaf disc infected with PVA could be detected in a composite sample with 9 discs from healthy leaves.P. angulata andP. pubescens may also be used for diagnosis of PVA. PVY becomes systemic in these species without inducing local lesions.  相似文献   

12.
Variation in resistance to tuber damage by the tobacco flea beetle,Epitrix hirtipennis (Melsheimer) was investigated for progeny from a group of parental clones from the USDA potato breeding program. Each of nine clones, used as males, was crossed with three different clones, and the family responses were measured in field tests (Lubbock, Texas, 1967 and 1968) by counting tuber pits made by the flea beetle larvae. Statistically significant differences among families were found. The differences were due mainly to the male parents, since the male variance component, σ M 2 (0.470±0.235), was larger than the variance component of females mated to the same male, σ F(M) 2 (0.080±0.057). Theoretically, each of these components contains one-fourth of the genetic additive variance, and therefore, should be nearly equal if digenic, trigenic, and quadrigenic effects are small (and if no maternal effects are present). Apparently the male and female parents did not, in relation to the frequency of alleles controlling response to the flea beetle, represent the same genetic population. Heritability on an individual basis, calculated with 4 σ M 2 as numerator, equals 0.64±0.36; and at a 10% selection level the genetic advance value predicted for individual selection equals 1.896 SD units. If 100 males were crossed to one female each, and 20 progeny per family tested in 10 replicates, the genetic advance value predicted for selecting the best 10 males on the basis of their family performance equals 0.976 SD units. Thus individual or phenotypic selection appears to be more effective than selection based on half-sib progeny tests.  相似文献   

13.
Potato germplasm was assessed for resistance to corky ringspot disease (CRS) incited by transmission of tobacco rattle virus (TRV). TRV is transmitted by the stubby root nematode,Paratrichodorus allius, in the Pacific Northwest, and characterized by necrotic areas in the tuber. Four tests were conducted at two different problem fields in Umatilla, OR and Pasco, WA. The fields differed in the virulence of the virus isolates. Some clones and named varieties showed resistance only in the field with the relatively mild Umatilla isolate, while others remained symptomless at both sites. The host suitability of test potatoes to threeP. allius populations from the region was determined in greenhouse pot tests, and expressed as reproductive values [Rf = (final population of nematode at 55 days) / (initial population)]. TheR f values for the nematodes were not correlated with resistance ratings based on visual scoring of CRS symptoms in field grown potatoes. Thus, it appears that CRS resistance is based on reaction of potato genotypes to virus and not the vector. The availability of resistant clones inin vitro form is indicated.  相似文献   

14.
High carotenoid potato may have particular value for human health due to the antioxidant properties and the therapeutic value for eye health in patients at risk for macular degeneration. Carotenoid concentrations were determined among the progeny of a cross between two high carotenoid lines derived from diploidPapa Amarilla germplasm from South America. The total carotenoid content ranged from 82 to 2686 µg / 100 g fresh weight (FW). The higher values greatly exceeded the mid-parent value of the cross. An index for yellow tuber flesh color was determined for a subset of the progeny. A cleaved amplified polymorphic sequence (CAPS) assay was developed to distinguish the alleles of beta-carotene hydroxylase (bch) in the two high-carotenoid parents. Abch allele (denoted B) common to the high carotenoid parents co-segregated with yellow flesh in the progeny of a white-flesh x yellow-flesh cross, makingbch an excellent candidate for the classicalY locus, required for yellow tuber flesh. The same allele was also present in all other yellow-fleshed potato clones tested. Genotype atbch explained a portion of the variation of total carotenoid (R2=0.42). Clones homozygous for the B allele (BB) contained, on average, slightly more carotenoid than heterozygous Bb clones, which in turn had much more carotenoid than homozygous bb clones, suggesting a partially dominant gene model. Similarly, bb flesh was significantly less yellow than Bb and BB, the latter two being quite close. Total carotenoid varied considerably between progeny in the Bb and BB genotype categories, suggesting that variation at one or more additional loci have a significant effect on total carotenoid levels. Since the total carotenoid levels in manyPapa Amarilla cultivars and progeny are much higher than those in white- and yellow-fleshed tetraploid cultivars, it may be possible to breed for high carotenoid values in tetraploid germplasm by introducing one or more genes derived fromPapa Amarilla germplasm.  相似文献   

15.
Samples of 4285 individuals from a hybridSolanum phureja Juz. et Buk. —S. stenotomum Juz. (Phu-Stn) and 105 individuals ofSolanum phureja (Phu) diploid potato populations were twice inoculated with potato virus Y strain “o” (PVY°) using the air brush technique. After discarding seedlings with PVY visual symptoms both in the greenhouse and in the field, 1508 seedlings were judged to be resistant to PVY° (35.2%). Only 5.7% of the Phu seedlings were PVY° resistant compared to 35.2% of the Phu-Stn seedlings. At harvest, a mild selection pressure for yield and tuber appearance was applied and 602 Phu-Stn clones were chosen for further evaluation. Selected clones were re-evaluated for PVY° resistance in the greenhouse. Clones were mechanically inoculated twice with PVY°. Clones susceptible to PVY° were determined by visual observations, ELISA (Enzyme-linked immunosorbent assay) tests, grafting of tobacco PVY° infected shoots on potato clones, and infectivity tests usingNicotiana tabacum as a PVY° plant indicator. In the process, 224 clones were found to be extreme resistant to infection by PVY°, with an overall frequency for PVY° extreme resistance of 5.2%. In another experiment, the first year Phu-Stn PVY° resistant clones (554 clones) were mechanically inoculated twice with “common” strain of potato virus X (PVX). Similarly, we discarded clones susceptible to PVX by combining visual evaluation and ELISA with PVX re-inoculation of negative clones and an infectivity test, usingGomphrena globosa as a PVX plant indicator. After this process, seven extreme resistant and eight resistant clones to infection by PVX were found; the overall frequency of PVX extreme resistance was 1.3%. Five clones were extreme resistant to both PVY° and PVX.  相似文献   

16.
Potato virus Y (PVY) is a major pathogen of potato and transmitted non-persistently by aphids. Aphis fabae is the main vector of PVY in the High Grade Seed Potato Production Area (HG area) in Finland, where the number of aphids and infection pressure with PVY are rather low, but problems with PVY occur in PVY-susceptible cultivars. The aim of the study was to test straw mulch, mineral oil, birch extract, and insecticides for control of PVY in small-scale field experiments and, additionally, at farm level in growers’ fields in the HG area of Finland. The insecticide esfenvalerate reduced the incidence of PVY in the progeny tubers by 29% in one of the 3 years, whereas other chemical treatments or birch extract had no significant effect on PVY incidence. Spraying foliage with mineral oil (Sunoco 11 E/3) reduced the incidence of PVY in 2 years by 43 to 58%, respectively. Straw mulch spread to the field at the time of plant emergence reduced PVY incidence in all 3 years by 50–70%. At farm level, straw mulch reduced the incidence of PVY in the progeny tubers by 25–47%, respectively, in both years tested; however, combining application of straw mulch and mineral oil did not further reduce incidence of PVY. Successful control of PVY in the HG area of Finland using straw mulch may be explained by transmission of PVY early in the growing season at the time of plant emergence and the relatively low number of vector aphids.  相似文献   

17.
A seedling inoculation technique for screening potato progenies for resistance toPseudomonas solanacearum was devised, and the effect of certain treatment variables on efficiency of the technique was determined. Concentration of inoculum and age of seedlings were critical factors; with very young seedlings (16 days old) or low concentration of inoculum (105 cells/ml for isolate K-60) many seedlings escaped infection. With older seedlings (25 days old) and high concentrations of inoculum (109 cells/ml), very few or none of the seedlings survived. Inocula containing mixtures of the most virulent isolates, such as S-207, S-213, and S-123, even at relatively low populations (ca. 105 cells/ml), killed most of the susceptible seedlings. In the standard procedure, true seed was sown in rows 3.2 cm apart in 50 x 35 cm flats and seedlings were grown for 20 days in a growth room at 22 C and a 14-hr photoperiod. For inoculation, 5 liters of a cell suspension of two pathogenic isolates ofP. solanacearum (S-207 and S-213, or S-207 and S-123) were added to each flat, and roots were cut immediately with a knife run between and across the rows of seedlings. Inoculated seedlings were incubated in a growth room at 28 C for 2 weeks, and survivors then were moved to the greenhouse for propagation. Stem inoculation of 20 clones derived from plants that survived the standard procedures showed that 16 of them had clear-cut resistance to the bacterium. Tests with 39 hybrid families from crosses of resistant clones with susceptible Mexican and Colombian cultivars showed a relatively high survival rate in progeny from crosses involving three specific resistant parents.  相似文献   

18.
As part of the International Potato Center’s (CIP) virus resistance breeding strategy, a group of 182 selected clones from intercrosses among duplex Potato Virus Y (PVY) immune progenitors derived fromSolanum tuberosum ssp.andigena (i.e., YYyy × YYyy) was sampled. These clones were test-crossed to the PVY susceptible tester 377964.5 (yyyy) to search for triplex (YYYy) and quadruplex (YYYY) PVY immune potato progenitors. Seedlings of each test-crossed progeny were screened for PVY immunity. Genetic analysis of observed ratios for immunity-susceptibility showed that two of the 182 clones segregated as triplex under the assumption of a random chromatid segregation model. The double reduction coefficient, α, and its standard error were estimated from the experimental data, and had values of 0.1566 and 0.0186 respectively. These results indicated that crossovers take place during meiosis between the locus and the centromere, permitting sister chromatids to migrate to the same pole producing a random chromatid segregation. In the population evaluated, no clone was identified as a quadruplex. The two triplex PVY immune genotypes will produce about 96% of progenies with PVY immunity when mated to PVY susceptible advanced clones or varieties. These progenitors have the potential to provide a durable PVY genetic control and diminish the present impact of this virus on the potato crop. Also, immunity to PVY will significantly simplify the seed production process.  相似文献   

19.
When five varieties of virus-free potatoes were introduced and multiplied for three years at an elite seed farm in Prince Edward Island where virus-infected potatoes were also grown, approximatly 10% of each variety became infected with both potato virs S (PVS) and potato virus X (PVX). However, when eight varieties of similar stocks were multiplied for 2 years at private farms in the absence of virus-infected potatoes, all remained free from PVX. Four of the varieties also remained free from PVS and four became infected with amounts of less than 5%. In other tests on these stocks, no potato virus Y (PVY) was detected. Post harvest tuber testing onNicotiana debneyi Domin. was found to be more reliable in detecting recent infections of PVS than foliage tests done during the growing season. This was so whether the foliage tests were done on the indicator plant, serologically or doubly-tested by both methods.  相似文献   

20.
The level ofFusarium dry-rot resistance found in important potato varieties has been improved with agronomically acceptableSolanum tuberosum genotypes. Three breeding selections, A74114-4, A76260-16, and BR6316-7 were highly resistant to the two commonFusarium dry-rot species (F. roseum Lk ex Fr. f. sp.sambucinum [Fs], andF. solani var.coeruleum (Sacc), Booth [Fc]). Resistance was determined separately for each of these species. Resistance to Fs was genetically distinct from resistance to Fc since there was no correlation between Fs and Fc reaction for 180 progeny clones from six crosses representing all combinations of resistance. Resistance to each of theseFusarium species was readily transmitted to progeny. Seventy-five percent of the progeny from resistant X resistant parents were also resistant to Fs, while 95% of the progeny from susceptible X susceptible parents were susceptible. Mixed infections withErwinia atroseptica and eitherFusarium species resulted in a qualitative change from a resistant reaction to a susceptible reaction. Bacterial interaction withFusarium spp. is, therefore, an important consideration in determining storage-rot resistance.  相似文献   

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