摘要:

Helminthosporium sativum,Fusarium culmorum,Ophiobolus graminis,Leptosphaeria herpotrichoides,Wojnowicia graminis,Erysiphe graminis,Tilletia caries, andTilletia foetensreadily overwinter under natural conditions at Edmonton, Alberta, Canada. The first five of these overwinter at Edmonton in both spore and vegetative stages and are highly resistant to cold. Even in a non-hardened condition several of them survived severe frost. Young germ tubes ofH.sativumfor instance continued growth after being frozen solid overnight. Fresh agar cultures ofH.sativum,F.culmorumandO.graminisgrew vigorously after exposure to sub-zero temperatures. Agar cultures ofH.sativumandF.culmorumwere viable after a 17-day exposure to temperatures ranging from about 0° F. to —50° F.Conidia ofH.sativumproved less resistant to freezing and thawing than to continuous freezing. They survived longer than conidia ofF.culmorumandF.graminearum. Mycelia of all foot-rot fungi grown on sterilized barley seeds were viable in one case after three months of continuous freezing, and in another after 40 alternate freezings and thawings.H.sativumandF.culmorumgrowing in soil survived 61 alternate freezings and thawings.H.sativum,F.culmorum and L.herpotrichoides, retained their viability more readily on the soil surface than when buried at depths of from 2 to 12 in. Well aerated soil seemed to favor the survival ofH.sativum, although other factors besides aeration probably are involved. Strains ofH.sativumfrom high latitudes were not better adapted to low temperatures than strains from lower latitudes.The bunt fungi,T.cariesandT.foetens, are shown to be capable of overwintering at Edmonton in the form of mycelia in winter wheat. Infection of winter wheat from soil-borne spores may occur in western Canada, but in these experiments soil-borne spores did not survive to infect wheat in the spring.Erysiphe graminisoverwinters in the perithecial stage at Edmonton. In the studies made, ascospores were differentiated in the spring, when favorable conditions prevailed and before the first infections of winter wheat were observed.

ISSN:1923-4287    

DOI:10.1139/cjr37c-041

出版商:NRC Research Press    

年代:1937

数据来源: NRC

摘要:

About the time of full bloom, many epidermal cells divide by a tangential wall. Later in June all the epidermal cells become vacuolated and some divide again by tangential walls forming a layer varying from two to four cells thick. Early in July a cambium is initiated in the innermost cells of epidermal origin. This cambium is very active and immediately gives off cells which differentiate into cork. Non-russeted portions may have either a very thick convoluted cuticle or a double layer of cuticle. The development of the periderm and the histology of the mature protective layers are illustrated by fifteen figures.

ISSN:1923-4287    

DOI:10.1139/cjr37c-042

出版商:NRC Research Press    

年代:1937

数据来源: NRC

摘要:

Fifteen officially graded samples of frosted wheat were collected from each of grades No. 3 Northern to No. 6, for 1930, 1931, 1932 and 1933, and 20 samples from each of these grades in 1934 and 1935. Physical classification of the kernels in each sample showed that the present system of grading is efficiently applied. While this system usually gives grades of frosted wheat, the averages of which fall in the right order with respect to combined milling and baking quality, it fails to give close indication of the baking quality, particularly of individual samples.A statistical examination of the relation between quality characteristics and grading factors showed that milling quality is closely related to the percentages of immature and heavily frosted kernels and also to the weight per measured bushel. Baking quality is not closely related to any of the grading factors now in use. Protein content is the best single index of baking quality, and the relation is improved if the percentages of immature and heavily frosted kernels are taken into account. The quality decreases more or less uniformly over the entire protein range with increasing percentages of immature kernels, but the presence of heavily frosted kernels is related to greater quality decreases in low protein samples than in high protein samples. The correlation between yield of straight flour and loaf volume facilitates simultaneous evaluation of milling and baking quality in grading. The application of these findings to practical grading is discussed.

ISSN:1923-4287    

DOI:10.1139/cjr37c-043

出版商:NRC Research Press    

年代:1937

数据来源: NRC