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961.
962.
Simon R. Leather 《Integrated Pest Management Reviews》1996,1(3):163-180
The ecological implications of insect resistance in conifers are rarely discussed. It is however a fairly straightforward plant-insect interaction and should be treated as such, making use of the increasing amount of information in this field. Work on tree breeding is usually carried out by silviculturalists who, not surprisingly, rarely consider the insect component of the environment in which the treess are growing. In all fairness, it must be stated that many entomologists, fail to consider the plant component of the interaction. Clonal forestry will almost certainly result in the loss of genetic variability. The use of clonal material has already been cited as a possible source for the diminution of the resistance against pests and diseases and if particular resistance mechanisms against forest pests are sought in the future the reduction in genetic material caused by clonal selection could have serious consequences. The ethics of clonal forestry have been questioned as have the ethics of biotechnological advances in the area of recombinant DNA molecules. The potential of both these techniques should be publicized and brought to the attention of the general public and the scientific community at large and evaluated. To improve our forest environment and to protect the environment as a whole, entomologists, geneticists, physiologists and silviculturalists must work together to produce better trees that require little, if any, chemical aid, be it insecticides, herbicides, fungicides or fertilizers. An increasing awareness of the environmental problems generated by large-scale insecticide applications to forest plantations, coupled with an increasingly chemophobic work-force and the difficulty in obtaining pesticide registration for use in forest environments, means that the forest industry world-wide must look to the use of integrated control measures with more diligence than has been shown in the past. Many recent outbreaks of pests and diseases have been linked with particular seed origins of tree crops. Host plant resistance as part of a suite of other proposed integrated control tools is thus an obvious candidate for development. Despite this, scientists concerned with tree improvement continue to select largely for silvicultural traits rather than for resistance to pests and disease. The different avenues open to plant breeders are examined and the potential of breeding trees resistant to insect attack highlighted. Using resistant trees as part of an integrated pest management system has five very important properties. Firstly, there is no additional pest control cost to the grower, secondly, it operates at all levels of insect incidence and not just when the pest is at high population levels, thirdly, it reduces the insect population cumulatively, fourthly it avoids toxic residues and environmental pollution and, finally, it usually interacts well with the other integrated pest management strategies in existence. 相似文献
963.
P. Castagnone-Sereno M. Bongiovanni A. Palloix A. Dalmasso 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(6):585-590
Experiments were designed to analyze the relationships between the root-knot nematodeMeloidogyne incognita and resistant tomato and pepper genotypes. From a natural avirulent isolate, near-isogenic nematode lineages were selected with virulence either against the tomatoMi resistance gene or the pepperMe3 resistance gene. Despite the drastic selection pressure used, nematodes appeared unable to overcome the pepperMe1 gene, therefore suggesting some differences in the resistance conferred byMe1 andMe3 in this species. Nematodes virulent onMi-resistant tomatoes were not able to reproduce onMe1-resistant nor onMe3-resistant peppers, and nematodes virulent onMe3-resistant peppers were not able to reproduce onMi-resistant tomatoes nor onMe1-resistant peppers. These results clearly demonstrate the specificity ofM. incognita virulence against resistance genes from both tomato and pepper, and indirectly suggest that gene-for-gene relationships could occur between these two solanaceous crops and the nematode. 相似文献
964.
Catherine Grondeau Alexandre Mabiala Rachid Ait-Oumeziane Régine Samson 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(4):353-363
Pseudomonas syringae pv.pisi, pea bacterial blight agent, is seed-transmitted. Some aspects of its life cycle and its biology were investigated. The colonization of pea plants obtained from naturally infected seeds was studied in natural conditions while high populations of bacteria developed on plants showing no symptoms. Two streptomycin-resistant mutants were used to study the epiphytic life of the pathogen. Populations were monitored in different host-parasite compatibilities. When race 2 or race 6 of the pathogen was surface-inoculated on susceptible cultivars, a decrease of population size was observed during the following one to three days but was followed by an increase to levels 1000 times greater than the initial number detected, without symptoms for most of the plants. When race 2 was surface-inoculated on resistant genotypes or race 6 on non-host plants, bacteria did not multiply but population levels slightly decreased.Pseudomonas syringae pv.pisi shows a resident phase and its development is race-specific. Weeds collected in naturally contaminated pea fields, diseased or not, often harboured the pathogen but with levels smaller than those observed on peas. Pea crop debris and volunteers kept high levels of bacteria for at least eight months after the harvest of a diseased crop. As long as two pea crops are not grown one after the other in the same field, it is unlikely that debris and volunteers will act as an important inoculum source. The development of this pathogen during the growing season is considered as an important parameter to take into account for controlling the disease through seed health testing. 相似文献
965.
J. E. Van Den Ende 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(4):227-236
A greenhouse screening method for resistance to ringspot (Mycosphaerella brassicicola) inBrassica oleracea is described. High infection levels were achieved by spraying young plants by mycelial inoculum enriched with 3% sucrose. The screening method was tested on three Brussels sprouts, three cabbage and three cauliflower cultivars, with known reactions to ringspot in the field. Resistance was expressed both in cotyledons and true leaves by a lower number of lesions than the susceptible control and/or by hypersensitive reactions. Results of the seedling tests reflected differences in resistance in the field. Under controlled conditions the new test can be applied year-round to young plants, thus accelerating selection procedures. 相似文献
966.
Surveys of cereal diseases and pests in the Netherlands. 4. Occurrence of powdery mildew and rusts in winter wheat 总被引:1,自引:0,他引:1
R. A. Daamen R. W. Stubbs W. Stol 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(5):301-312
Results of annual surveys of winter wheat fields from 1974 to 1986 were compiled to describe epidemics of powdery mildew and rusts in relation to weather and cultivar resistance.An average of 29 and 70% of fields were infected by powdery mildew in May and July, respectively. Mildew prevalence in May was positively correlated with average temperature in October and with average temperature over the months December, January, February and March. In addition, it was correlated negatively with the average grade of mildew resistance of the cultivars sown each year. Prevalence of mildew in July did not show consistent correlations with weather characteristics nor with mildew prevalence in May.Yellow rust was usually not detected in May and on average 18% of the fields was infected in July. The occurrence of yellow rust decreased after 1977, when the farmers adopted cultivars resistant or moderately resistant to yellow rust.Brown rust was usually not detected in May, while in July on average 48% of the fields was infected. Brown rust intensity in July was high in years with a high March temperature and high precipitation during April and May.Black rust was rare in the Netherlands, with 3 and 1% of the fields infected in July 1977 and 1981, respectively. 相似文献
967.
968.
Genetics of resistance to soybean cyst nematode (SCN), Heterodera glycines Ichinohe is very complex. Crosses involving PI 437654, which is resistant to all races of cyst nematodes with other sources of resistance (Peking, PI 88788, and PI 90763) indicated that resistance to race 3 was controlled by four genes, two of which were dominant resistance genes and the other two were recessive resistance genes. For race 5, a four gene model with two recessive and two dominant resistance genes in epistasis has been proposed. For race 14, the results suggested a three gene model with one dominant and two recessive alleles. Several other plant introductions have been isolated which have different genes conditioning resistance. Most of the currently grown soybean varieties derived resistance from Peking and/or PI 88788. Resistance to SCN in these soybean varieties has broken down because of the emergence of several new races and populations of SCN. The use of PI 437654 or Hartwig and other plant introductions with different genes for resistance will broaden genetic diversity and stabilize yield. 相似文献
969.
C. El Modafar A. Clérivet A. Vigouroux J. J. Macheix 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(5):503-509
Inoculation of leaves of resistantPlatanus occidentalis and susceptiblePlatanus acerifolia leaves withCeratocystis fimbriata f. sp.platani, the canker stain disease agent, induced foliar necrosis and biosynthesis of two phytoalexins, scopoletin and umbelliferone. Foliar symptoms keep localized and accumulation of coumarin phytoalexins was rapid for incompatible interactions. Necrosis spread widely and accumulation of these phenolic compounds was much later and lower for compatible interactions. The differential response could be used in a genetic improvement program for resistance against canker stain. 相似文献
970.
Chrysantus N. Akem 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(2):183-187
Soybean cultivar Samsoy 1, and the breeding lines TGx 849-313D and TGx 996-26E, grown in a field with a heavy epidemic of frogeye leaf spot caused byCercospora sojina, were treated with double foliar applications of the fungicide benomyl. The treatments were made using four application schedules at six different growth stages, starting from V3 (fully developed leaves, beginning with trifoliate nodes) to R5 (beginning seed_, to determine the effect of the fungucide timing on frogeye leaf spot severity, soybean grain yield and grain quality. Generally, applications at R1 (beginning bloom) and R3 (beginning pod) significantly (P<-0.05) reduced disease severity in the 2 susceptible genotypes, Samsoy 1 and TGx 849-313D. Plot yields of these genotypes were also significantly greater than the untreated controls when the fungicide applications were made at R1 and R3. There was no significant difference in diseave severity or grain yield, between the untreated control and the different times of application, on the resistant genotype TGx 996-26E. Improved seed germination and lower levels of seed infection byC. sojina occurred for all fungicide timings in the susceptible genotypes. The results suggest that fungicide spraying initiated at R1 and followed up at R3 is most effective in frogeye leaf spot control and can also result in higher grain yields, than applications made earlier or later in the season. Control of frogeye leaf spot, however, is best achieved by growing resistant cultivars. 相似文献