摘要:

Fifty-five species of weeds and seven of cultivated plants were collected from root rot areas in strawberry plantations and found to be infected withPratylenchus penetrans(Cobb 1917) Filip. & Stek. 1941. Perennial plant species with soft-textured roots contained larger populations ofP. penetransand had more extensive root necrosis than those plant species with hard-textured roots.

ISSN:0008-4026    

DOI:10.1139/b60-027

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

The lethal and mutagenic effect of ultraviolet light on two isolates ofCochliobolus sativuswas studied. Conidia of a dark-spored strain were considerably more resistant to high doses of radiation than those of a white-spored strain. Ultraviolet radiation increased the frequency of mutation in the fungus. Mutants were recovered that differed from their parents in degree of sporulation, rate of growth, pigmentation, amount of aerial mycelium, topography and consistency of colony, and pathogenicity to wheat seedlings. Tetrads from crosses between weakly and highly pathogenic strains indicated that pathogenicity was not a clearly segregating character.

ISSN:0008-4026    

DOI:10.1139/b60-028

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Field populations of the large raspberry aphid,Amphorophora rubi(Kalt.), were observed for 4 years on 13 varieties of raspberry. Lloyd George and St. Walfried were immune, Malling Enterprise and Malling Promise were resistant, and the remainder were susceptible to infestation. Each variety was naturally infected with black raspberry necrosis virus. Vector studies demonstrated that this virus was acquired with difficulty from the immune varieties and also from the susceptible variety St. Regis, but was readily acquired from the remaining 10 varieties.

ISSN:0008-4026    

DOI:10.1139/b60-029

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Seeds of wheat sown in soils of subgermination moisture content sometimes decay and die. The critical moisture content at which maximum seed decay occurs is at a level approximately equal to one-half the difference between air-dry soil and soil moist enough for seed to germinate. The relationship apparently holds irrespective of soil type, even though the actual moisture percentage of different soil types at the critical level is quite distinct. “Dry” soil as used in these studies refers to air-dry soil with 8% moisture added. The subsequent germination of wheat was reduced after 3 days' incubation in “dry” soil at 30 °C, and 14–20 days at 5 °C. Germinability was reduced in strongly saline soil. Different samples of wheat varied greatly in germinability after incubation in “dry” soil. Sterilizing the “dry” soil did not change its effect on germination of various seed lots.Much of the variation in loss of germinability was correlated with thresher injuries to the seed coat. Wheat, rye, and hull-less varieties of oats and barley, especially with seeds of more than standard weight per bushel, are susceptible to thresher injury. Growth cracks, sprouting, and frost injury all affect germination adversely. Cereal seeds with hulls, or with high moisture content, or below standard weight, or of small size, and wheat without projecting embryos, are less susceptible to thresher injury, and to consequent reduction of germinability.The “field” fungiAlternariasp. andHelminthosporiumspp. grew out of cereal seeds plated on potato-sucrose agar or moistened filter paper and from germinated seeds grown in “moist” soil. After incubation in “dry” soil germinating seeds gave rise toAlternaria, but not toHelminthosporiumspp. The non-germinating seeds from “dry” soil were infected by “storage” fungi, e.g.Penicillium,Aspergillus,Rhizopus, andMucor. The “storage” fungi do not usually infect cereal seeds sown in “moist” soil, but in “dry” soil both sound and injured seed can be infected. The infection of sound seed is slow, permitting the seed to germinate, but injured seed is infected rapidly and does not germinate. The “storage” fungi invade seeds already infected by “field” fungi and inhibit the growth of the latter.All samples of treated and untreated wheat seed sown in “moist” soil gave good germination. After incubation in “dry” soil the germination of treated seed was fair to good, and of untreated seed was poor to good. Treatment with formalin before incubation in “dry” soil doubled the germination; treatment with Ceresan M, Half-ounce Leytosan, and a water soak trebled germination compared with the untreated check. However, the best treatment in “dry” soil gave 31% less germination than the untreated check sown in “moist” soil. Under “dry” soil conditions a sound seed coat appears to provide better protection against seed-decaying organisms than any seed treatment tested.

ISSN:0008-4026    

DOI:10.1139/b60-030

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

A study along a line NNE. from the metal smelter at Falconbridge, Ontario, reveals that strong sulphate accumulation in the surface soil occurs only within about one mile of the chimneys emitting sulphur dioxide pollution while effects upon the soil drainage waters are marked to a distance of nearly two miles, and still clearly evident 10 or more miles away. The number of species present in the flora declines sharply within about four miles of the smelter, but certain species (e.g.Pinus strobus,Vaccinium myrtilloides) disappear at much greater distances. Among the most tolerant species areAcer rubrum,Quercus rubra,Sambucus pubens, andPolygonum cilinode.

ISSN:0008-4026    

DOI:10.1139/b60-031

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Concentration of chlorophyll per unit area of land surface was measured for six forests and 13 native and managed herbaceous stands in central Minnesota. Chlorophyll samples were extracted in acetone and in ethyl ether, and spectro-photometric analysis made of chlorophyllaandbcontent. Wet and ovendry weights of the aboveground crop were determined.A highly significant correlation was found between the dry weight of the aboveground crop of the annual herbaceous stands and the chlorophyll content of these stands. All stable natural herbaceous stands had an approximately similar ratio of chlorophyll to the dry weight of aboveground parts.Chlorophyll content in grams per square meter of land surface along an upland gradient from field crop through native communities of increasing age or successional development or both wasZea mays(2.7),Soja max(0.9), younger to older successional stages of old field (0.3 to 0.6), native prairie (0.7), xeric (more open) savanna (0.6), mesic (less open) savanna (1.0), conifer–hardwood forest (3.1). Chlorophyll content for a pond hydrosere from theNymphaea odoratamargin throughCarex lasiocarpamat toChamaedaphne calyculatashrub andLarix laricinaforest increased from 0.3 to 1.4 g/m2. Values for a younger and olderPopulus tremuloideslowland grove were 1.7 and 5.9 and for aTyphamarsh were 4.6 g/m2.These data showed a tendency for later successional stages to exceed earlier stages, for some lowland stands to exceed upland stands, for forest to exceed herbaceous communities on a given moisture level, and for field crops to exceed prairie and old field. The upland old field to forest sequence and the lowlandNymphaeatoLarixsequence had similar chlorophyll contents for a given stage of successional development. There was a highly significant positive correlation between chlorophyll content and height of the arboreal stands, and a significant positive correlation between chlorophyll content and herbaceous stand height.A significant difference in chlorophyll content was found between all stands with three or more sample plots, except those with closely correspondent mean values. The maximum difference between stands was twentyfold, which does not support previous studies which have suggested a similarity of chlorophyll content in diverse communities.Chlorophyll concentrations and wet and dry weights per various plant parts are presented for the seven tree samples, and the presence of chlorophyll in other than leaf parts emphasized.

ISSN:0008-4026    

DOI:10.1139/b60-032

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

The results of chromosome studies of five species of mosses from the Mont Tremblant area of Quebec are presented. The chromosome numbers of two species,Plagiothecium roeseanum(Hampe) B.S.G., with the numbern = 20, andPolytrichum ohioenseRen. & Card., with the numbern = 14, are reported for the first time. Both species are established tetraploids with no evidence of chromosome irregularities in meiosis. Chromosome numbers reported for the other three species are as follows:Dicranum rugosum(Hoffm.) Brid.,n = 12;Dicranum scopariumHedw.,n = 12; andPlagiothecium denticulatumHedw.,n = 20. The population ofD. rugosumthat was studied did not possess small precociously separating bivalents as have been reported for European populations. The close resemblance of the chromosome complements ofP. denticulatumandP. roeseanumis in line with the close taxonomic relationship between the two species. Cytotaxonomic implications are discussed under each species.

ISSN:0008-4026    

DOI:10.1139/b60-033

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Eleven aphid species commonly found on rosaceous plants were tested as vectors of eight strawberry viruses.Amphorophora rubi(Kalt.),Aphis rubifolii(Thomas),Aulacorthum solani(Kalt.),Macrosiphum rosae(L.),Myzus ascalonicusDoncaster,M.ornatusLaing,M. persicae(Sulz.),Pentatrichopus fragaefolii(Cock.),P. tetrarhodus(Walk.), andP.thomasiRis Lambers transmitted the vein banding virus from one or both of two sources.P. fragaefolii,P. tetrarhodus, andP. thomasitransmitted mild mottle, while onlyP. fragaefoliiandP. thomasitransmitted curly-dwarf mottle.M. rosaetransmitted vein banding and possibly mild yellow edge.Aphis forbesiWeed failed to transmit any of the viruses tested. None of the species tested transmitted witches’ broom, crinkle, or strawberry latent-A virus.

ISSN:0008-4026    

DOI:10.1139/b60-034

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

Young winter rye seedlings, grown and hardened at 1° or 1.5 °C in the dark, developed a high level of cold hardiness at two stages prior to emergence of the first leaf. The first maximum occurred when coleoptiles were less than about 1 mm in length and was followed by a decrease in hardiness. A second and higher maximum occurred when coleoptiles were about 15–30 mm in length (5 weeks at 1.5 °C; 7 weeks at 1 °C) and it was followed by a rapid decrease in hardiness beginning at about the time the leaf broke through the coleoptile. Genetic differences corresponding with those obtained in the field were established by hardening seedlings for 7 weeks at 1 °C and exposure to −15 °C for 16 hours or by hardening for 5 weeks at 1.5 °C and exposure to −14 °C for 16 hours. The use of a lower (−4 °C) hardening temperature resulted in a large increase in cold hardiness at the younger stages of development but little or no increase where seedlings had already reached a maximum of hardiness from exposure to 1.5 °C for 5 weeks. Satisfactory genetic differences were not determined by exposure to −14 °C for 16 hours after hardening at −4 °C. In general the response to hardening of young winter rye seedlings was similar to that found with winter wheat.

ISSN:0008-4026    

DOI:10.1139/b60-035

出版商:NRC Research Press    

年代:1960

数据来源: NRC

摘要:

The data accumulated over the past 30 years from the classification of some half a million plants are presented. It is shown that the mapping of chromosome 2, the former linkage group 1, presents many difficulties because of the lethal nature ofWo, and the reduced viability ofro,dv, andm. The problem of classification ofo,bk, andms10also presents difficulties. The examination of the monogenic ratios shows many of them to be disturbed because of lethality, viability, and misclassification, but these causes do not account for all the discrepancies. In the case ofWoandawthere are large excesses of the dominant class; this evidence along with data from anomalous recombination values indicates a chromosomal abnormality. It is suggested that this abnormality is a duplication which in some stocks gives twoWoloci about 25% apart, and twoawless than 40% apart, and also involves the loci ofMeandCu.The recombination values indicate that the map isdv3 m2 d4 p10 aw(psoro) 13 Me(Cubk) 4Wo2 ms105 s. The five genes within the brackets are in the positions indicated but the recombination values within each bracket are not known. While this linear order gives the best synthesis of the 61 recombination values, it also reveals several exceptions. Theawpsandawovalues which should be less than 10% are 40%, andps owhich should be 3% is 26%. Significant differences of more than 10% are also registered between sets of data for the same pair of genes; this is another indication of chromosomal changes. The findings presented here should furnish a framework for more critical examination of specific sections of this linkage group.

ISSN:0008-4026    

DOI:10.1139/b60-036

出版商:NRC Research Press    

年代:1960

数据来源: NRC