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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
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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
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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
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Summary A reliable impression of the resistance of lettuce plants to the leaf aphid Myzus persicae can be obtained via aphid honeydew production. Under controlled temperatures, the number of honeydew droplets produced by these aphids per plant in 180 minutes with five plants per genotype offers a good criterion of this resistance. 相似文献
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Summary Potato (Solanum tuberosum L.) cultivars were grown in pots and containers under a rain shelter to examine differences in stomatal conductance, water-use
efficiency, and carbon isotope fractionation. Conductance was measured on abaxial leaf surfaces with a steady state diffusion
porometer. Carbon isotopic analyses were made with an isotope ratio mass spectrometer. Water-use efficiency (WUE) was obtained
by dividing total dry matter production by cumulative transpiration.
Significant genetic variation was observed for each trait. WUE was positively related to carbon isotope fractionation (13∈) and was inversely related to stomatal conductance. Carbon isotope analysis and porometry show potential as indirect screening
methods to identify genetic differences in water-use efficiency. 相似文献
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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
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Summary The inheritance of nitrate content in lettuce was analysed using 16 F2 populations and three F3 populations. Frequency distributions of nitrate content in F2 and F3 populations were unimodal and symmetrical, indicating a quantitative inheritance. Both significant positive and negative deviations of the F2 mean from the mid-parent value were found, indicating dominance or epistasis. Deviations towards low nitrate content were more frequent than deviations in the other direction. Estimates of heritabilities for nitrate content in the F2 populations ranged from 18% to 69% and were in most cases above 50%. Crosses between low nitrate cultivars did not have lower estimates of heritability in the F2 than crosses between cultivars with larger differences in nitrate content. In one case a genotype x experiment interaction for nitrate content of parental cultivars was found.Three F3 populations of crosses between cultivars with low nitrate content were analysed. Estimates of heritabilities for F3 line means ranged from 78% to 91% and estimates of the genetic standard deviation of nitrate content in unselected advanced generations ranged from 0.24–0.33 g kg–1. The estimates of heritabilities and of genetic variation in advanced generations offer good prospects of selection of low nitrate genotypes in lettuce. A comparison of efficiency of selection in the F2 generation and F3 line selection is made. 相似文献
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Reni Chaerani Remmelt Groenwold Piet Stam Roeland E. Voorrips 《Journal of General Plant Pathology》2007,73(2):96-103
A droplet inoculation method was used for evaluation of tomato resistance to early blight, a destructive foliar disease of
tomato caused by Alternaria solani (Ellis and Martin) Sorauer. In this test method, leaflets are inoculated with small droplets of a spore suspension in either
water or a 0.1% agar solution. Early blight resistance was evaluated based on lesion size. The droplet method better discriminated
the level of resistance (P < 0.001) for a range of spore densities in comparison with the more commonly used spray inoculation method. Lesions generated
by droplet inoculation at 7 days after inoculation ranged from small flecks to almost complete blight with an exponential-like
distribution of lesion sizes. Significant correlations (r = 0.52, 0.58, and 0.63, P < 0.001) were observed across three glasshouse tests of 54 accessions including wild species using the droplet method. The
most resistant accessions included wild species: one accession of Solanum arcanum, three accessions of Solanum peruvianum, one accession of Solanum neorickii, and one of Solanum chilense. Solanum pennellii and Solanum pimpinellifolium accessions were susceptible, whereas Solanum habrochaites and Solanum lycopersicum accessions ranged from susceptible to moderately resistant. The droplet test method is simple to apply, offers a fine discrimination
of early blight resistance levels, and allows objective evaluation. 相似文献
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Summary Colchicine treatments of 13 lettuce cultivars for production of polyploid lettuce also resulted in rapid growing diploid mutants. 相似文献