ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024035

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

摘要:

SUMMARYOne hundred and twenty-one isolates ofPythium ultimumTrow from diseased guayule (Parthenium argentatumGray) seedlings were classified into 3 types on the basis of relative abundance of oospores and sporangia (chlamydospores) when grown on Difco cornmeal agar. Three of the isolates which produced mainly oospores were classified as type O; 71 which produced oospores and few or many sporangia were classified as type OS; and 47 which produced only sporangia were classified as type S.Twenty hyphal-tip subcultures were taken from each of 25 selected isolates. The subcultures from three O type, 11 OS type and 7 S type were similar to the parent cultures; those from 4 OS type isolates segregated into two that gave type O and type S subcultures and 2 that gave type OS and type S indicating that these four isolates were mixed cultures or were unstable as to type.In an effort to induce isolates of the S type (non-oospore formers) to produce oospores they were grown on cornmeal agar, water agar, cornmeal agar plus an extract of guayule shrub, cornmeal agar plus an extract from well-decayed leaf mold, cornmeal agar plus soil extract, and agar made from freshly grated carrots. None of these media stimulated the formation of oospores in the S type isolates.Five O type, 13 OS type and 11 S type hyphal-tip subcultures of 25 isolates were found to have very similar rates of growth on cornmeal agar at each of the following constant temperatures: 10°, 15°, 20°, 25°, 30°, 35°and 40°C. The growth rate at these temperatures was comparable to that reported (8) forPythium ultimum.The optimum temperature for mycelial growth was found to be between 25°and 30°C.Twenty-six hyphal-tip subcultures which included four O type, 13 OS type and 9 S type were tested for pathogenicity on emerging guayule seedlings in the greenhouse. All of the different types were found to be pathogenic and of comparable virulence in causing preemergence loss to guayule seedlings.In general most hyphal-tip or single-spore subcultures ofPythium ultimumisolates were stable as to type. However, one isolate, 980, readily gave rise to other types. Successive hyphal-tip transfers of a hyphal-tip subculture of 980 of the OS type gave rise to both the O and S types as well as the parent type. Three generations of single-spore (sporangium) subcultures from two isolates of the OS type were all OS type similar to the parent. Likewise one single-spore generation of two S type isolates were all of the S type.

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024036

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

摘要:

SUMMARYIn this study an ascigerous stage, originally described asSphaerella(Laestadia)RhodoraeCooke, is connected by means of pure culture methods with its pycnidial stageP. maximaEllis&Ev. and its spermagonial stageP. SaccardoiThüm. The characteristics of the perithecial stage are considered to be those of the genusGuignardiaand the nameG. Rhodorae(Cooke) comb. nov. is proposed. Synonyms are listed.P. maximais considered a distinct species and not synonymous withP. RhododendriWest, as reported by Ellis and Everhart. It is also considered distinct from the fungus determined by Tengwall asP. maximaand reported by him as the imperfect stage ofVenturia RhododendriTeng.

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024037

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024038

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024039

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

摘要:

SUMMARY1.Isolates of an intermediate nature betweenMemnoniellavon Höhnel andStachybotrysCorda have been observed.2.Stachybotrys-likeslimy heads of elliptical to oval spores andMemnoniella-likeheads of chains of spherical spores can occur on separate phialophores on the same hypha, or separately on the two phialophores of a branched phialophore.3.Single-spore isolates of cultures exhibiting this phenomenon continue to do so, whether the single spore is of the ellipticalStachybotrystype or of the sphericalMemnoniellatype.4.Isolates stable for the characters ofMemnoniella echinatafor eight years are also reported.5.The form generaMemnoniellaandStachybotrysare considered to be valid entities.

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024040

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024041

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024042

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

摘要:

SUMMARYRhizophydium ChytriomyciiandRosella Chytriomyciiare two new chytrid parasites which occur on and in the sporangia ofChytriomyces.The first parasite attacksC. hyalinusandC. aureus, while the second one is limited in host range toC. hyalinus.Extensive attempts to inoculate numerous other chytrids and larger fungi with these parasites have failed.

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024043

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor

ISSN:0027-5514    

DOI:10.1080/00275514.1946.12024044

出版商:Taylor&Francis    

年代:1946

数据来源: Taylor