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1.
Summary The latent periods, wilting rates and percentages of diseased plants were analyzed for 11 carnation cultivars after root and after stem inoculation with race 2 of Fusarium oxysporum f.sp. dianth. There was no conclusive evidence for the presence of an independent extravascular resistance mechanism, except for Lena plants in which, additional to the vascular resistance components, independent root-bound factors causing retardation of the colonization and wilting process were found. A large variation was observed in the ablity of the cultivars to localize the pathogen in the vascular tissue shortly after infection of the xylem. This ability was positively correlated with the latent period, and negatively with the wilting rate and final disease index. In resistant cultivars, secondary compartmentalization of the fungus higher up in the stem was also observed. After stem inoculation, differences among the cultivars in localization ability and wilt-retarding actors could be identified at an early stage by comparing the precentages of non-colonized plants or the percentages of plants lacking vascular discolouration.  相似文献   

2.
Stem decay and root rot of Amaranthus hybridus, caused by Fusarium oxysporum is a serious threat to the commercial production of this crop in South Africa. Five Amaranthus hybridus varieties were examined in vitro for sensitivity to a culture filtrate of Fusarium oxysporum. The phytotoxicity of the culture filtrate was assessed for its inhibitory effect on callus and seeding root growth, as well as on the viability of callus cells. The five varieties exhibited a significant amount of variation in response to the culture filtrate of the pathogen. Variety 17 was the most sensitive variety in each bioassay, whereas variety 20 displayed least sensitivity to the culture filtrate. Callus of variety 20 grew well in the presence of concentrations of culture filtrate that were toxic to another four varieties and the percentage mortality of callus cells after exposure to the filtrate was also the lowest of the five varieties. Root growth of variety 20 was also least affected by exposure to the culture filtrate for up to 6 days. To our knowledge, the presence of resistance in germplasm of A. hybridus to culture filtrates of F. oxysporum has not been demonstrated before. The present study is therefore of significant value to breeding programs aimed at speedily finding amaranth cultivars that are resistant to this important pathogen. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

3.
Chickpea wilt caused by Fusarium oxysporum f. sp. ciceris is one of the major yield limiting factors in chickpea. The disease causes 10–90% yield losses annually in chickpea. Eight physiological races of the pathogen (0, 1A, 1B/C, 2, 3, 4, 5 and 6) are reported so far whereas additional races are suspected from India. The distribution pattern of these races in different parts of the world indicates regional specificity for their occurrence leading to the perception that F. oxysporum f. sp. ciceris evolved independently in different regions. Pathogen isolates also exhibit differences in disease symptoms. Races 0 and 1B/C cause yellowing syndrome whereas 1A, 2, 3, 4, 5 and 6 lead to wilting syndrome. Genetics of resistance to two races (1B/C and 6) is yet to be determined, however, for other races resistance is governed either by monogenes or oligogenes. The individual genes of oligogenic resistance mechanism delay onset of disease symptoms, a phenomenon called as late wilting. Slow wilting, i.e., slow development of disease after onset of disease symptoms also occurs in reaction to pathogen; however, its genetics are not known. Mapping of wilt resistance genes in chickpea is difficult because of minimal polymorphism; however, it has been facilitated to great extent by the development of sequence tagged microsatellite site (STMS) markers that have revealed significant interspecific and intraspecific polymorphism. Markers linked to six genes governing resistance to six races (0, 1A, 2, 3, 4 and 5) of the pathogen have been identified and their position on chickpea linkage maps elucidated. These genes lie in two separate clusters on two different chickpea linkage groups. While the gene for resistance to race 0 is situated on LG 5 of Winter et al. (Theoretical and Applied Genetics 101:1155–1163, 2000) those governing resistance to races 1A, 2, 3, 4 and 5 spanned a region of 8.2 cM on LG 2. The cluster of five resistance genes was further subdivided into two sub clusters of 2.8 cM and 2.0 cM, respectively. Map-based cloning can be used to isolate the six genes mapped so far; however, the region containing these genes needs additional markers to facilitate their isolation. Cloning of wilt resistance genes is desirable to study their evolution, mechanisms of resistance and their exploitation in wilt resistance breeding and wilt management.  相似文献   

4.
Banana and plantain are among the most important food crops in developing countries but production is threatened by increasing virulent forms of Fusarium oxysporum f. sp. cubense. Chemical control is not economically effective and,therefore, breeding programs are necessary. Traditional field studies of new genotype resistance to this disease are time-consuming and destructive. Therefore,we developed a rapid and non-destructive procedure to differentiate field-grown banana resistant from susceptible clones. This procedure implicates application of culture filtrates of Fusarium oxysporum f. sp. cubense race 1 onto banana leaves. The relationship between duration of the fungal in vitro incubation, and the fungal culture fresh mass, the culture filtrate absorbency, and the Gross Michel (susceptible cultivar)leaf lesion area (after application of the culture filtrate) were similar and at 24day-incubation the highest values of the recorded indicators were observed. A comparison between Gross Michel and FHIA-01(resistant) was also performed. The most relevant differences between cultivars were observed at 48 hours after application of the culture filtrate, and in the middle-aged leaves. The position of the culture filtrate application in the leaf limb (distal, middle, proximal) was not determinant. A wider comparison among banana cultivars confirmed previous results informed by other researchers using different systems to study this plant-fungus interaction. Such a confirmation validates the effectiveness of the procedure described here to select rapid and non-destructively banana resistance to this disease at field level. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

5.
Fusarium basal plate rot (FBR), caused by Fusarium oxysporum f. sp. cepae, is an important soil-borne disease of onions worldwide. The causal organism infects the basal stem plate of the bulb and eventually kills the entire plant through degradation of the basal plate. F. o. f. sp.cepae infections in dormant bulbs during storage allow secondary infections to occur. The primary method of infection by F. o. f. sp. cepaeis through direct penetration of the basal stem plate. Infection can also occur through wounded tissue particularly roots and basal portions of bulb scales. The most cost-effective methods of control are crop rotation and host plant resistance. Current research suggests that a single gene, two genes, or multiple genes govern resistance to FBR. Breeding programs have successfully used screening procedures to develop intermediate- and long-day, FBR-resistant cultivars. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

6.
Inheritance of zucchini yellow mosaic virus resistance in Cucumis melo L.   总被引：4，自引：0，他引：4  
M. Pitrat  H. Lecoq 《Euphytica》1984,33(1):57-61
Summary Resistance to zucchini yellow mosaic virus has been found in the muskmelon line PI 414723 from India. This resistance is effective against the ZYMV strains E15 and 1318 belonging respectively to the NF and F pathotypes. Resistance to E15 (no vein clearing and yellowing symptoms) is governed by one dominant gene (symbol Zym) according to segregations observed in F1, F2 and BC1 progenies. This gene is epistatic dominant over Fn, which induces wilting and necrosis after inoculation with F pathotype. Linkage studies suggest that Zym inherits independently from Fom-1, Fom-2, Vat, Wmv and Fn but is linked with a (13.1 ±2.4 units).  相似文献   

7.
Summary Immature bulbs were used in two screening trials to identify daffodil genotypes resistant to basal rot disease caused by Fusarium oxysporum f. sp. narcissi. Progenies, having at least one parent with some resistance, were grown in compost infested with chlamydospores of the fungal pathogen, and survivors were recovered at final harvest. Survival rates were very low when one-year old bulbs were used; the greater survival of two-and three-year old bulbs indicates that resistance increased with bulb age. Selection pressure was influenced by inoculum concentration in the compost. Continuous variation of percentage bulb survival between progenies suggests a polygenic mode of inheritance; there was no evidence of maternal inheritance. Parental general combining ability (GCA) was highly significant and accounted for much of the difference in bulb survival between progenies, but non-additive parental effects were also apparent. GCA rankings in the two trials were similar and reflected the resistance of parental cultivars in the field. A three-dimensional graphing procedure was devised to depict goodness of fit of progeny data to the additive model.  相似文献   

8.
When challenged with Fusarium oxysporum f. sp. vasinfectum (Fov) from vegetative compatibility groups (VCGs) 01111 and 01112 in glasshouse tests, Gossypium australe Mueller and Gossypium sturtianum Willis accessions showed a variety of disease responses ranging from highly resistant to highly susceptible. Under high disease pressure G. sturtianum accession Gos-5275 was significantly more resistant than the commercial G. hirsutum cultivars that are designated standards for Fusarium resistance by Australian cotton breeders. Under low disease pressure G. sturtianum accession Gos-5250 was more susceptible than a highly susceptible commercial cultivar. A series of glasshouse tests was performed at two locations (Indooroopilly, QLD. and Canberra, ACT), and under low and high disease pressure. In these tests, a hexaploid cross (Gos-5271) generated from a Fusarium-resistant G. sturtianum (Gos-5275) and a Fusarium-susceptible G. hirsutum L. (CPI-138969) was significantly more resistant to Fusarium wilt than its G. hirsutum parent. Thus G. sturtianum, with a diploid genome and a range of responses to Fov challenge, has the potential to provide the basis for the elucidation of the genetic basis of resistance to Fusarium wilt in cotton species. In addition, resistant accessions of G. sturtianum are identified as a potential source of Fusarium wilt resistance genes for cotton breeding. In the glasshouse tests used to assess the resistance of various Gossypium accessions to Fusarium wilt disease, the scoring of vascular browning was found to give a more reliable indication of disease severity than the scoring of foliar symptoms. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

9.
Summary Potato plantlets derived from in vitro propagation of three cultivars known for their field resistance (Cruza 148 and BR-63.65) or susceptibility (Désirée) to Pseudomonas solanacearum E.F. Smith were artificially inoculated under controlled conditions. The aim of this work was to determine the optimal inoculum concentration and the best observation period in which the cultivars would show different reactions to bacterial infection as expected on the basis of their field performance.A suitable statistical analysis of disease indices is proposed to distinguish between resistant and susceptible responses, with a particular care for the applicative needs and a univocal interpretation of the results. In order to evaluate the significance of sources of variation related to the observed mean differences, the analysis of variance and a convenient clustering procedure of disease index means were applied.The statistical analysis revealed that, under our conditions, an inoculum concentration of 5×106 cfu/plant was suitable for separating resistant from susceptible responses, in accordance with the reactions already observed in field experiments by other authors. Also, differences among the three cultivars were best observed nine to twelve days after inoculation with the pathogen.  相似文献   

10.
Summary Calli of resistant, intermediary and susceptible wheat (Triticum aestivum L.) varieties were selected using culture filtrates of Fusarium graminearum and F. culmorum and the regenerants were evaluated for resistance up to R3. Czapek-Dox broth medium was inoculated with mycelia of Fusarium isolates and incubated for 2–6 weeks. Filtrates were added to MS callus growing medium, then 5 weeks-old calli were transferred onto this medium (MST) for 4–5 weeks. MST containing 30% filtrate was found to be suitable for selection. Resistant calli were transferred again to fresh MST for further two selection cycles. The surviving calli produced less fertile regenerated lines (R0) than the non-selected ones. Among 18 R1 lines tested for Fusarium-resistance in the seedling stage by artificial inoculation in the greenhouse, two (11.1%) were significantly more resistant, one (5.6%) was more susceptible than the original cultivar and the rest (83.3%) behaved similarly to the donor plants. Among unselected R3 lines of three varieties, practically the same number of resistant plants were found as among the related selected ones. When the R3 selfed generations obtained through double-layer and culture filtrate selection techniques were tested for Fusarium-resistance, 35.7% of the lines were found to be more resistant than the original cultivars, none was more susceptible and 64.3% had a reaction similar to that of the source materials. Thus, inheritance of the disease reaction was not stable in all cases. Success of in vitro selection for Fusarium-resistance depended also on the genotype, and toxin analysis showed that although being effective, the selective media contained deoxynivalenol only exceptionally. In selecting wheat for Fusarium-resistance in vitro, the culture filtrate technique proved better than the double-layer procedure.  相似文献   

11.
Summary Shoot tip cultures from banana clones susceptible and resistant to Fusarium oxysporum f. sp. cubense (FOC) race 1 and race 4 were grown in vitro in the presence of different concentrations of fusaric acid and fungal crude filtrates or inoculated with a conidial suspension of FOC to assess correlation between in vivo and in vitro behaviour. Explants were susceptible to both filtrate and fusaric acid irrespective to their known field resistance/susceptibility response. No clear linkage between in vivo and in vitro behaviour was observed and our results suggest that the use of crude filtrate or non-host specific toxin (fusaric acid) in a screening programme for selecting a novel resistant genotype of Musa to FOC is not feasible. When peroxidase activity was used as a parameter to discriminate between sesceptibility and tolerance, results were in good agreement with field response of host plant to pathogens. Early enzymatic activity increased in the incompatible host-pathogen interaction but not in the compatible interaction.Abbreviations IBA Indolebutyric acid - 2iP 6-dimethylallylamino-purine - VCG Vegetative Compatibility Group - FOC Fusarium oxysporum f. sp. cubense - IEF isoelectrofocusing  相似文献   

12.
Elizabeth Keep 《Euphytica》1985,34(3):801-809
Summary Established Western European black currant cultivars are susceptible to Dasyneura tetensi but the Scandinavian Sunderbyn II, Kangosfors and Hedda, and 10 out of 33 Russian cultivars showed very slight or no leaf symptoms of midge attack in the field.Of species within the black currant Section Eucoreosma, Ribes dikuscha, R. pauciflorum (probably=syn R. ussuriense), and R. americanum were not attacked, but an accession of R. bracteosum proved very susceptible. Species within other sections of the genus were not attacked.A strong dominant resistance gene in R. dikuscha, designated Dt, appeared to be linked with (a) gene(s) controlling resistance to American gooseberry mildew, Sphaerotheca mors-uvae. Resistance in Sunderbyn II and, probably, in R. pauciflorumwas oligogenic and dominant.  相似文献   

13.
S. M. Ali  B. Sharma  M. J. Ambrose 《Euphytica》1993,73(1-2):115-126
The economic importance and current progress made in studies of the host-parasite relationship and identification of sources of resistance and breeding strategies of some important biotic diseases of pea are reviewed in this paper. The root rot complex caused by Rhizoctonia solani, Fusarium solani, Aphanomyces euteiches, Pythium ultimum and Fusarium oxysporum f. sp. pisi, race 1 and 2 has been reported from all commercial pea growing areas of the world. Adequate sources of resistance have been identified and there has been impressive success in the control of the Fusarium wilt pathogen following the introduction of wilt-resistant cultivars. Leaf and stem diseases of pea caused by the Ascochyta complex, Peronospora viciae and Erysiphe pisi are prevalent in most temperate pea growing regions of the world. Several sources of resistance are available, some of which are surprisingly durable. The biochemical genetic parameters of phenolic content used for assaying resistance to Erysiphe pisi offers an alternative method of evaluating breeding material. Wild relatives of pea (Pisum fulvum and P. humile) are valuable additional sources of genetic variation and provide good sources of resistance to pests and diseases. In temperate rainfed pea growing areas of southern Australia, pea seed yield is more closely related to dry matter production than harvest index. Tall and leafy cultivars proved more productive than afila types.  相似文献   

14.
Summary In vitro tillers of over 1000 genotypes from nine contrasting Lolium perenne cultivars were cultured on various media containing the synthetic cytokinin, 6-benzylaminopurine (BAP), in order to determine the effect on tillering. The cultures were assessed after seven weeks for survival, tiller production, size and vigour. Added auxins 2,4-dichlorophenoxyacetic acid (2,4-D) and -napthaleneacetic acid (NAA) had no consistent beneficial effects.A significant relationship was found between in vitro tiller production and cultivar heading date. Genotypes of early-heading, less persistent cultivars produced more tillers than genotypes from late heading more persistent cultivars. This was consistent with the generally higher in vitro tiller production in the biennial species Lolium multiflorum cultured on similar media.  相似文献   

15.
Summary For genetic analysis of head blight in winter rye (Secale cereale) caused by Fusarium culmorum, six homozygous inbred lines from the Petkus gene pool were crossed in all combinations to obtain 15 diallel F1 crosses and the corresponding 15 F2 crosses. These materials and 10 additional inbreds were artificially inoculated in a 2-year field experiment. The inbreds were also tested with F. graminearum in a separate sub-experiment.Single disease rating, average disease rating, and yield components (grain-weight per spike, 1000-grain weight, kernel number per spike) relative to the non-inoculated treatment were significantly affected by Fusarium head blight in all material groups. The relative grain weight per spike ranged from 26% to 88%. Significant genotypic and genotype x year interaction variances were found throughout. Heritabilities were highest for homogeneous inbreds (h2=0.6–0.8) and lowest for heterogeneous F2 crosses (h2=0.4–0.6). Disease rating and relative grain-weight per spike were highly correlated for the inbreds and F2 crosses (r0.7, P0.01), but lower for the F1 crosses (r0.6, P0.05). Inter-annual correlation coefficients for disease ratings and relative grain-weight per spike ranged from r0.7 (inbreds) to r0.5 (F2 crosses). The diallel analysis showed significant GCA effects only for relative 1000-grain weight in 1990, but significant SCA and SCAx year interaction variances for most traits. The resistances of 16 inbreds to F. culmorum and F. graminearum were tightly associated for all traits (r=0.96–0.97, P0.01).In conclusion, only slow progress can be expected from selecting for Fusarium head blight resistance in rye due to the limited amount of additive genetic variance and the great improtance of environmental factors.  相似文献   

16.
Summary A simultaneous analysis of the virulence of races 1, 2 and 4 of Fusarium oxysporum f.sp. dianthi to a series of nine carnation cultivars revealed the presence of different interactions between races and cultivars, as well as differences in pathogenesis between race 1 on the one hand and race 2 and 4 on the other.The most common race 2 induced typical symptoms of Fusarium wilt in all susceptible cultivars. The cultivars showed considerable variation in resistance to race 2. Only Novada remained free of external symptoms throughout the experiment. In diseased plants of all cultivars studied, infected vascular tissue was white with dark brown margins, and heavy degradation of the cell walls and xylem parenchyma cells had occurred. All Dutch isolates corresponded with race 2.Race 4 induced wilt symptoms similar to those induced by race 2, and there was a similar variation in resistance to race 2 and 4 in the cultivars. On average, the race 4 isolates were less aggressive than those of race 2. Compared with race 2, there was evidence of some genotype × race interactions: Pallas proved to be considerably more susceptible, and Lena more resistant to race 4 than to race 2. The isolates of race 4 induced a nistopathology similar to that induced by race 2, but with less vascular browning.Race 1 induced atypical but severe wilt symptoms and unusual vascular discoloration in Elsy, Niky and Sam's Pride only. The vascular tissue in these cultivars turned pale brown; in spite of heavy colonization of these tissues virtually no degradation of cell walls was observed. All other cultivars tested proved virtually resistant to race 1, providing further evidence for genotype × race interactions.Within races, limited but statistically significant genotype × isolate interactions were found as well, in particular within race 4. These are tentatively attributed to independent variation of two (or more) resistance components.  相似文献   

17.
Summary The bean weevil Acanthoscelides obtectus, is an important storage pest of common beans in Latin America and Africa. A few wild bean accessions from Mexico have been identified as highly resistant to the weevil. One accession, G 12952, was crossed to two susceptible bean cultivars differing in seed size. Reciprocal F1 and F2 individual seed were evaluated for days to adult emergence (DAE) and emerged adult weight. Maternally inherited seed size affected resistance measurements only in the F1 reciprocal crosses, however, the overall resistance level of the F1 was more similar to that of the susceptible cultivars. The F2 showed a continuous, but skewed distribution from low to high DAE. Very few F2 individuals had the resistance level of G 12952. When the frequency distributions were divided into discrete categories based on parental response, resistance was found to be inherited as two recessive complementary genes. The F3 generation showed an overall lowering of resistance levels compared to their original F2 evaluations. However, none of the lines classified as resistant (50 DAE) in the F2, fell into the susceptible category in the F3, indicating that the resistant genotypes were relatively stable as expected with recessively inherited traits. Modifying genes from the commercial parents may be responsible for general lowering of resistance. Seed size was negatively correlated with adult weight but not with DAE. The unique resistance of the wild bean accessions is discussed in relation to its inheritance. The results and obstacles encountered in the A. obtectus breeding program at CIAT are described.  相似文献   

18.
Summary Calluses of spring and winter wheats (Triticum aestivum L.) were selected for Fusarium resistance in vitro, using the double-layer culture technique. Potato-dextrose agar medium in vials was inoculated with mycelia of Fusarium graminearum and F. culmorum. After one week, fungal cells were killed by autoclaving and the agar medium containing the thermostable toxic metabolites was overlayered with MS callus-growing medium. Later, wheat calluses were placed on the upper medium for 4–5 weeks, and from the surviving calluses plants were regenerated. R2 seedling populations from self-fertilized R1 plants of 4 varieties were tested for Fusarium resistance by artificial infections in the greenhouse, and 3% of the regenerated R2 plants have been found to be more resistant than the original cultivars.  相似文献   

19.
Summary The feeding, fecundity, mortality and rate of development of Liriomyza trifolii (Burgess) on 12 cultivars of Dendranthema grandiflora (Tzvel.) (Syn. Chrysanthemum morifolium (Ramat.)) were determined in no choice experiments. Number of feeding punctures, number of eggs laid and total number of larvae varied between cultivars but these characters were not strongly associated with leafminer population increase. Good indicators of host plant resistance were larval mortality, number of pupae and duration of the larval period. Of these three, larval mortality which could be as high as 98% was most suitable.Based on life history data it was predicted that Liriomyza trifolii cannot survive on the resistant cultivar Penny Lane. This prediction was verified experimentally.  相似文献   

20.
Summary Phenotypic stability of bacterial leaf spot resistance in peach (Prunus persica (L.) Batsch) regenerants, either selected at the cellular level for insensitivity to a toxic culture filtrate of Xanthomonas campestris pv. pruni or screened at the whole plant level for resistance to X. campestris pv. pruni, was investigated. A detached-leaf bioassay was used to evaluate the original regenerants again after three years in the greenhouse and also after a two to three year cycle of tissue culture propagation. Peach trees derived through micropropagation from the original regenerants were also evaluated after one to three years growth in the field. Although leaf spot resistance was retained in some regenerants over time in the greenhouse, following in vitro propagation, and under field conditions, resistance was either lost or not expressed in others. Regenerants # 19-1 and #156-6, derived from embryo callus of bacterial spot susceptible Sunhigh, were significantly more resistant than Sunhigh. High levels of resistance were exhibited in greenhouse plants and field-grown trees of regenerant #122-1, derived from embryo callus of moderately resistant Redhaven. This research provides additional evidence that selecting or screening for somaclonal variants with disease resistance is a feasible approach to obtaining peach trees with increased levels of bacterial spot resistance.Abbreviations TC Tissue-Cultured - TF Toxic culture Filtrate  相似文献   

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