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Downy mildew on lettuce is currently controlled using host resistance genes (Dm genes) that confer race-specific resistance in seedlings. Field resistance (FR) that is active in adult plants but not seedlings was identified in the cvs. Grand Rapids and Iceberg. The goal of our study was to evaluate the utility of Grand Rapids as a source of novel Bremia resistance alleles, particularly in comparison with Iceberg. To measure FR, downy mildew symptoms were evaluated following natural infection in field experiments. The responses of Grand Rapids and Iceberg were similar in many respects. Although both cultivars had a small percentage of plants exhibiting disease symptoms, the average disease ratings were as low as for cultivars with effective Dm genes. We observed no evidence for race specificity. FR was effective over 3 years of our study, despite documented variation within pathogen populations. Both cultivars lacked all known seedling resistance genes except Dm13, which was not responsible for the resistance observed in field experiments. Similar segregation of FR was observed in F2 populations for both Grand Rapids and Iceberg. The presence of highly susceptible families within Grand Rapids × Iceberg populations suggested the presence of at least one unique resistance allele in each cultivar. Preliminary genetic analysis of FR from Grand Rapids revealed a high estimate of narrow-sense heritability that suggested simple inheritance, but single gene models did not fit the observed data. Our results suggest that Grand Rapids may represent an underutilized resource for controlling downy mildew in lettuce. 相似文献
3.
Brigitte Maisonneuve Marie Christine Chupeau Yannick Bellec Yves Chupeau 《Euphytica》1955,85(1-3):281-285
Summary Various genes for disease resistance identified in wild Lactuca are difficult, even impossible to exploit in lettuce breeding, due to sexual incompatibility between L. sativa and wild Lactuca sp. We adapted two cellular biology techniques to overcome these interspecific barriers: in vitro embryo rescue and protoplast fusion. In vitro rescue of immature embryos was used successfully for sexual hybridization between L. sativa and L. virosa. Vigorous hybrid plants were produced between L. sativa and seven accessions of L. virosa. Protoplast fusion permitted the regeneration of somatic hybrids between L. sativa and either L. tatarica or L. perennis. Hybrids between L. sativa and L. tatarica were backcrossed to L. sativa. 相似文献
4.
Summary After steam sterilizing of certain glasshouse soils a surplus of exchangeable manganese (SEM) occurs. Great differences exist between lettuce genotypes for sensitivity to SEM.Research on the inheritance of insensitivity was carried out by intererossing five lettuce genotypes: Lactuca sativa cys. Neptune (sensitive). Plenos. Troppo and Celtuce (all insensitive) and an accession of L. scrriola (insensitive). From analysing various populations (as F1's. F2's and B1's) it appeared that different numbers of genes for insensitivity were present in the parents varying from one gene in Plenos and Troppo, two genes in L. serriola to possibly four genes in Celtuce. Genes in the three first mentioned parents were linked in repulsion phase and a chromosome map for these genes was made. 相似文献
5.
Summary Many lettuce cultivars (Lactuca sativa L.) with high resistance to lettuce root aphid (Pemphigus bursarius L.) also carried the gene Dm-6 for specific resistance to downy mildew (Bremia lactucae
Regel). This suggests the possibility of linkage between this gene and root aphid resistance. The origin of this association is discussed. 相似文献
6.
P.R. Ellis S.J. McClement P.L. Saw K. Phelps W.E. Vice N.B. Kift D. Astley D.A.C. Pink 《Euphytica》2002,125(3):305-315
In a series of glasshouse and laboratory experiments, lettuce varieties and wild Lactuca species were screened for resistance to the lettuce root aphid, Pemphigus bursarius (Ron.). Several new sources of resistance to P. bursarius development and survival were identified. Extremely high levels of resistance were found in the wild species L. saligna, L. perennis and L. virosa. Resistance was also identified in the lettuce variety Grand Rapids. This resistance is controlled by one or two genes. At
least one of these genes is not allelic to the existing Lra gene. Grand Rapids therefore represents a new source of resistance to P. bursarius.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Summary Six lettuce lines, representing two types of resistance to the green peach aphid, Myzus persicae, and a control line with high susceptibility to M. persicae were tested for resistance to six different clones of Myzus persicae and two clones of the potato aphid, Macrosiphum euphorbiae.The clones of M. persicae showed very different levels of aggressiveness on lettuce: two had a high level of reproduction, two had an intermediate level and two were poorly adapted to lettuce as a host. Differences between lettuce lines in aphid reproduction increased with increasing aggressiveness of the aphid clone, which means that aggressive clones are most effective for selection purposes. No evidence was found for clone-specific plant genotype reactions, meaning that lines resistant to one clone will also be resistant to other clones of M. persicae, allthough not neccessarily at the same level. The lettuce lines selected for partial resistance to the aggressive clone WMp1 were completely or almost completely resistant to less aggresive clones.No differences in level of reproduction were found between the two clones of M. euphorbiae and no relation was observed between resistance to M. persicae and M. euphorbiae, indicating the species-specific character of resistance to leaf aphids in lettuce. 相似文献
8.
Summary Eighty-one accessions of three Lactuca species which showed no recognisable race specific resistance to Bremia lactucae when tested in the laboratory as seedlings, exhibited different degrees of susceptibility when exposed to natural field infection. As a group, crisp genotypes had less mildew and a slower rate of disease development than other types of lettuce. Wild forms of Lactuca sativa and Lactuca serriola were particularly susceptible. In a further trial, the low field susceptibility of three lettuce cultivars (Iceberg, Batavia blonde de Paris and Grand Rapids) was confirmed. Disease development on cv. Iceberg was compared to that on the highly susceptible cv. Hilde in experiments where the two cultivars were grown either in close proximity or in isolation. The absolute level of attack on cv. Iceberg depended upon disease pressure and differences between the two types only became apparent approximately 8 wk after sowing. 相似文献
9.
Summary The genetics of partial resistance of lettuce to Myzus persicae was studied using F1 and F2 generations of two crosses between a susceptible and partially resistant accession (Norden x Batacer and Liba x Norden) and three crosses in which both parents were partially resistant (Batavia la Brillante x Batacer, Batacer x Liba and CGN4741 x Batacer). Partial resistance to M. persicae inherited quantitatively, without important dominance effects. Only in the cross Batacer x Liba were significant departures of the F1 and F2 from the midparent found, which were probably caused by epistatic effects. Reciprocal F1s had similar resistance levels, indicating the absence of cytoplasmic or other maternal effects. Estimates of broad-sense heritability ranged from 0.34 to 0.61. The results indicated that lines with an improved resistance level can be obtained from crosses between partially resistant accessions, preferably by line selection or the application of indirect marker aided selection.Abbreviations PR
partial resistance, partially resistant
- S
susceptibility, susceptible 相似文献
10.
Summary The inheritance of resistance to Nasonovia ribis nigri in L. sativa was investigated. Parents and F1 and F2 populations from crosses between the susceptible cultivar Ravel and two resistant breeding lines were tested. In both breeding lines one dominant gene appeared responsible for resistance. 相似文献
11.
Summary Twenty-one accessions of 3 wild Lactuca species which could be hybridised with L. sativa, the cultivated lettuce, were inoculated at different stages of plant development with 3 multivirulent isolates of Bremia lactucae. Nineteen sources of resistance to B. lactucae, not attributable to the previously recognised resistance factors 1–11 were identified. Two lines of L. serriola showed similar resistance patterns as lines carrying R11. The resistance of some accession was incomplete particularly at the seedling stage and this phenomenon may be race specific.Tests on segregating F2 populations of crosses between 2 different L. serriola accessions and L. sativa cultivars showed that the resistance in one line (LSE/18) appears to be inherited as a single dominant gene, which is sometimes incomplete in expression and allelic to either Dm6 or R7. The segregation patterns for resistance in PI 281876 did not give readily interpretable ratios.To assess the frequency of occurrence in B. lactucae populations of virulence factors to overcome this novel resistance, 11 of the novel sources of resistance were inoculated with numerous collections of the pathogen from the UK, Czechoslovakia and elsewhere and found to show a high level of resistance. 相似文献
12.
Summary Interspecific crosses were carried out between the three Lactuca species L. virosa, L. serriola and L. sativa to transfer resistance to the leaf aphid Nasonovia ribis nigri from L. virosa to the cultivated lettuce. L. sativa, L. serriola was used as an intermediate parent between the other two species. Many irregularities were observed in the interspecific hybrids, ranging from premature dying of F1 plants resulting from a kind of bastard necrosis till complete male and female sterility and deviating microsporogenesis. Using in vitro culture and after several backcrosses male and female fertile plants were obtained with a L. sativa habit and with resistance to the leaf aphid. 相似文献
13.
Summary A total of 1789 accessions of several lettuce collections was screened to find new major gene resistance to the downy mildew fungus Bremia lactucae Regel. The accessions belonged to the species Lactuca sativa (N=1288), L. serriola (N=399), L. saligna (N=52) and L. virosa (N=50). A total of 20 races of B. lactucae were used, 14 of which were NL-races, isolated from cultivated lettuce in the Netherlands. The other six races were isolated from wild L. serriola in Czechoslovakia. The accessions were initially screened with two races: NL1 and NL3. Accessions with resistance to one or both of these races were tested with the other races. Phenotypes with new resistance were found in accessions of all four Lactuca species. Of L. sativa, four accessions were found with resistance phenotypes that could not be explained by combinations of known major genes. Many accessions of L. serriola had resistance phenotypes that indicated the presence of unknown resistance genes. All interactions between accessions of L. saligna and races of B. lactucae were incompatible in leaf disc tests, except for four accessions, which showed some sporulation with race NL6. Several accessions of L. virosa were resistant to all races used. Other accessions of L. virosa gave a race-specific interaction with B. lactucae. 相似文献
14.
Summary Three lines of lettuce with resistance to Nasonovia ribisnigri, based on the dominant Nr-gene, and four lines selected for partial resistance to Myzus persicae were tested against three species of leaf aphid: N. ribisnigri, M. persicae and Macrosiphum euphorbiae. The effect of the Nr-gene was also studied in a segregating F2 population.In the material tested, resistance to N. ribisnigri was exclusively based on the Nr-gene, lines selected only for resistance to M. persicae showed no resistance to N. ribisnigri. The Nr-gene also induces partial resistance to M. persicae, but the level of this resistance is influenced by other genes, because the lines with Nr-gene differed significantly from each other for reproduction of M. persicae. The Nr-gene had no effect on the resistance of lettuce to M. euphorbiae.In lines with the Nr-gene, levels of resistance to M. persicae and to M. euphorbiae were correlated, suggesting that the resistance may be determined by the same genes. The Nr-line with highest resistance to M. persicae was comparable for this characteristic to the lines selected for resistance to M. persicae.The cultivars Taiwan and Ravel possess a resistance factor to M. euphorbiae that has no effect on M. persicae or N. ribisnigri. Lines selected for resistance to M. persicae also showed partial resistance to M. euphorbiae. Based on the present results no conclusions can be drawn whether this resistance is based on the same genes that provide resistance to M. persicae, or on a resistance factor comparable to that found in Taiwan and Ravel. 相似文献
15.
Resistance to the southern root-knot nematode Meloidogyne incognita Chitwood would be an important attribute of lettuce Lactuca sativa L. cultivars adapted to both protected and field cultivation in tropical regions. `Grand Rapids' and a few other cultivars
are reported to be resistant to this nematode. In this paper, we studied the inheritance of the resistant reaction of `Grand
Rapids' (P2) in a cross with a standard nematode-susceptible cultivar Regma-71 (P1). F1(Regina-71 × Grand Rapids) and F2 seed were obtained, and inoculated along with the parental cultivars with different races of M. incognita to evaluate nematode resistance. Broad sense heritability estimates for the number of galls and of egg masses per root system,
gall size and gall index were generally in the order of 0.5 or higher. Class distributions of these variables over generations
P1, P2, F1 and F2 were in agreement with simulated theoretical distributions based on monogenic inheritance models. F3 families were obtained from randomly sampled F2 plants and tested for reaction to the nematode. The frequency ratio of homozygous resistant, segregating and homozygous susceptible
F3 families did not differ from the 1:2:1 ratio expected from monogenic inheritance. M. incognita resistance appears to be under control of a single gene locus. The Grand Rapids allele (for which the symbol Me is proposed) is responsible for the resistant reaction, and shows high (though incomplete) penetrance, variable expressivity
and predominantly additive gene action.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Summary More than 200 accessions of three wildLactuca species were screened in the laboratory for race-specific resistance toBremia lactucae. Only a fewLactuca entries showed resistance both as seedlings and in a leaf disc test. Accessions ofL. serriola andL. sativa had a low degree of resistance. The best entries were also compared under field conditions. TheL. saligna entries were totally free from disease in the field test. High resistance was also recorded in a fewL. serriola entries and in lettuce cultivars such as Saffier and Mariska. 相似文献
17.
Summary Thirty-five rice (Oryza sativa L.) varieties, including 18 japonica, 5 javanica and 12 indica subspecies and 12 lettuce (Lactuca sativa L.) varieties were identified taxonomically, using PCR with originally designed 21 RAPD (Random Amplified Polymorphic DNA) primers and 8 sequence-specific primers, used for amplifying four specific DNA fragments. Use of these primers revealed polymorphisms among varieties in rice and lettuce and facilitates DNA fingerprinting. Dendrograms of both species based on polymorphisms were constructed and genetical relationships were established. In rice, half the number of amplified bands were polymorphic and almost all varieties differentiated. However, differentiation of minor genetic alterations among somaclonal variants or mutants and their mother varieties was not feasible. In L. sativa, 47% of the amplified fragments were polymorphic and all 12 varieties were differentiated. Some of the PCR fragments were variety or type specific, which could be used for indicators for type-selection. The dendrogram obtained showed differentiated clusters of crisphead, leaf and butterhead type, findings in good accord with the classification based on the genetic background. 相似文献
18.
J. T. Fletcher 《Euphytica》1992,63(1-2):33-49
Summary Cultivars of tomatoes, cucumbers, lettuce and peppers have been bred for resistance to one or more pathogens. Some tomato and cucumber cultivars have resistance to a wide range of diseases. Resistance has been transient in many cases and a succession of cultivars with new genes or new combinations of resistance genes has been necessary to maintain control. There has been a number of notable exceptions and these have included durable resistance to such pathogens asFulvia fulva and tomato mosaic virus. With lettuce the resistance situation is complicated by the occurrence of fungicide resistant pathotypes. There are no strains ofAgaricus bisporus purposely bred for disease resistance.In protected flower crops only resistance to Fusarium wilt in carnations has been purposely bred but differences in disease resistance are apparent in cultivars of many ornamental crops. This is particularly so in chrysanthemums where there are cultivars with resistance to many of the major pathogens. Similar situations occur with other flower crops and pot plants. Cultivars of some species have not been systematically investigated for resistance.The need for genetic resistance will increase with the further reduction, in the limits on pesticide use and an increasing public awareness and importance of pesticide pollution.ADAS is an executive agency of the Ministry of Agiculture, Fisheries and Food and the Welsh Office. 相似文献
19.
J. W. Maxon Smith 《Euphytica》1979,28(2):351-359
Summary A commercial formulation of triforine1, a systemic fungicide not normally used on lettuce, induced marked phytotoxicity on certain cultivars. The phytotoxic agent was found to be triforine and not one of the other components of the formulation.Test crosses between resistant and susceptible cultivars have shown that resistance is recessive and determined by a single major gene for which the symbol tr is proposed. The character is unlikely to be of much significance in lettuce crop protection but is potentially useful in genetic studies and for the production of hybrid lettuce seed. 相似文献
20.
Summary Nitrate content was measured in 135 genotypes of cultivated lettuce (Lactuca sativa L.) and 21 genotypes of wildLactuca spp. grown in two experiments. In Experiment 1 plants were grown on nutrient film. In Experiment 2 plants were grown in large pots of potting soil. Within cultivated lettuce five plant types were distinguished and within each of them genotypes were found with low nitrate content. The coefficient of variation in the experiment with plants growing in large pots was not larger than in the experiment with plants growing on nutrient film. In butterhead genotypes nitrate content was negatively correlated with dry matter content and positively with plant fresh weight. 相似文献