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11.
Patterns of shoot elongation of 2-yr seedlings from native North American populations of ponderosa pine and Douglas-fir were compared to those of Argentine land races originating from unknown provenances. The comparisons were conducted in Moscow, Idaho (USA), and suggested that the ponderosa pine land race was descended from a California provenance at low or middle elevations but that the growth potential of the land race was only mediocre in comparison to eight native populations. The Douglas-fir land race exhibited a relatively high growth potential in comparison to 19 native provenances and undoubtedly originated from a mild coastal environment. The results provide concrete recommendations for upgrading the growth potential of the Argentine land races by importing germ plasm of specific provenances. 相似文献
12.
13.
J. A. Lane T. H. M. Moore D. V. Child K. F. Cardwell B. B. Singh J. A. Bailey 《Euphytica》1993,72(3):183-188
An in vitro growth system was used to determine the virulence of two samples of Striga gesnerioides from Zakpota in southern Benin. Cowpea variety B301, previously considered resistant to all races of S. gesnerioides, was susceptible to both samples of the parasite. Two other cowpea varieties, 58–57 and IT81D-994, were totally resistant. Resistance in 58–57 was associated with a hypersensitive necrosis of infected roots, whilst IT81D-994 supported production of small S. gesnerioides tubercles with stems which failed to develop. Striga gesnerioides from southern Benin is the fourth race of the parasite to be identified, and the first with virulence on variety B301. The implications for breeding cowpeas with resistance to S. gesnerioides are discussed.Abbreviations IITA
International Institute of Tropical Agriculture
- LARS
Long Ashton Research Station
- SAFGRAD
Semi-Arid Food Grain Research and Development 相似文献
14.
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
15.
Effect of plant density on selection for seed yield in two population types of Phaseolus vulgaris L.
Summary Pedigree selection for seed yield, using early generation yield tests, was practiced from the F2 to F7 in two populations of common bean (Phaseolus vulgaris L.) in three plant densities: 66, 133, and 266 thousand plants ha-1 at CIAT-Palmira, Colombia. The six highest yielding lines selected from each plant-density, along with 13 parents, were evaluated in a 7×7 lattice design with three replications at the three densities utilized for selection, and at 399,000 plants ha-1 in 1988 and 1989.Based on the mean performance of selected lines and the mean of the parents, selection for seed yield was effective in all densities in both populations. However, none of the lines selected from the population within the race Mesoamerica (TC 4673) significantly outyielded their best parent under any plant density. The highest yielding lines selected from the interracial population (TR 4635) outyielded their best parent irrespective of the plant-density used for selection. The highest yielding line originated from the highest density used for selection. Low density was neither good for selection nor for evaluation and identification of high-yielding cultivars of common bean. There was no significant difference between the mean yield of lines selected at the intermediate and high population densities. The effects of plant density, year, and their interactions were significant for seed yield. 相似文献
16.
Petra Scheewe 《Euphytica》1994,77(1-2):25-29
Summary The fungusPhytophthora fragariae Hickman is the causal agent of red stele disease in strawberry (Fragaria × ananassa), this being a major disease in many areas with cool and moist conditions. Success of resistance breeding can be nullified
by the appearence of specific races of the fungus capable of overcoming the introduced resistance. In some countries (USA,
UK, Japan and Canada) races were identified by using a differential set of strawberry cultivars. The absence of an international
standard differential set and the use of different test methods make a comparison of the identified races difficult or even
lead to contradictory results for one variety/race combination. The aim of this study was to obtain information about the
spectrum of pathogenic races in Germany as a basic contribution to research on resistance breeding against the fungus. The
susceptibility of different strawberry cultivars to German isolates ofP. fragariae was evaluated. The inoculation was done by modifying a method described by Milholland et al. (1989). Rootedin vitro plants, four weeks after transferring them to the soil, were used for the investigation. Inoculation was done with a zoospore
suspension of defined concentration. Up to now three German isolates, G-1, G-2, and G-3, can be separated by their ability
to infect and produce oospores in the roots of the strawberry cultivars ‘Senga Sengana’, either ‘Saladin’, ‘Redgauntlet’ or
‘Climax’ andFragaria chiloensis clone ‘YaquinaB’. These results confirm the existence of pathogenic races ofP. fragariae in Germany and should be taken into consideration for resistance breeding against the fungus. 相似文献
17.
袁景顺 《河北农业大学学报》1994,17(3):85-88
根据全国统一的8个寄主鉴定结果,仍以叶1(26),叶2(360)和洛10小种群为主要优势小种(群)。在洛10小种中仍以361,261,363和377出现频率较高。近年来,叶1,叶2出现频率在逐年增长,叶3在下降。用新鉴别寄主鉴定的小种,以V1,9-12,15-16;V1,9-12,15-16;V1,9-16;V1,9-12,14-16;V1,9-13;15-16出现频率较高。用毒力频率分析,IRN66—331,Redman6068,百农3217和丰抗13抗性较好,而东方红3号,丰产3号等品种高度感病,能侵染洛10品种小种在逐年上升,毒力频率均达83.33%。这为抗锈育种寻找抗源提出了新的要求。 相似文献
18.
番茄叶霉病侵染机制及抗性机理研究进展 总被引:2,自引:0,他引:2
WANG Xiaoyan WANG Bingliang 《长江蔬菜》2008,(10)
番茄叶霉病是由Cladosporium fulvum(Cook)Ciferrd引起的一种世界性病害。自从20世纪80年代以来,随着保护地番茄面积的扩大,该病的危害也越来越严重,成为了番茄生产上的重要叶部病害,严重影响番茄产量和品质。综述了近年来在番茄叶霉病侵染机制、生理小种的分化和抗病性机制方面的研究进展,并对其抗性研究前景进行了展望。 相似文献
19.
A total of 404 isolates of Xanthomonas campestris pv. vesicatoria , obtained from Capsicum chinense cv. West Indian Red grown in Barbados and Grenada, were differentiated into pathogenic races, and of these, 96 were tested also for selected taxonomic group phenotypes. The response of C. chinense to infection by several X. campestris pv. vesicatoria races and the contribution of races isolated from this cultivar to severity of bacterial spot of bell pepper and tomato were also investigated. P4T2, P5T2 and P6T2 were the predominant races of X. campestris pv. vesicatoria isolated from C. chinense grown in Grenada, whereas nine races (T1, P4, P6, P0T2, P1T2, P4T1, P4T2, P6T1 and P6T2) were isolated in Barbados. Race P4T2 comprised 46.0 and 71.4% of the isolates from Barbados and Grenada, respectively. The 96 isolates, all of which overcame resistance conferred by the gene Bs2 , shared taxonomic group B strain characteristics, including the presence of the β-protein band, positive amylolytic activity and inability to oxidize cis -aconitate. The C. chinense cv. West Indian Red was susceptible only to races of X. campestris pv. vesicatoria that can overcome Bs2 gene resistance. Of six such races identified in Barbados, only P4T1, P4T2 and P6T1 affected bacterial spot-susceptible bell pepper or tomato in the field, and they amounted to only 1.5–2.1% of each sample of isolates from these plant species. Moreover, they were confined to the smallest bacterial spot lesions. Bell pepper was most severely affected by combinations of races T1 with P3T2 and T2 with P0T1, and tomato by race T1 only and combinations of races P0T1 with P0T2 and P1T1 with P1T0, all of which prevailed in the field despite selection against them by C. chinense cv. West Indian Red. 相似文献
20.