摘要:

Pathogenicity tests on potato stems were made of 133 isolates ofRhizoctonia SolaniKühn. Of these, 114 were from random sclerotia on random tubers from four fields, 13 from lesions on potato stems, and 8 from single basidiospores. A number of tests were made in the laboratory at 17° and 23 °C., in two contrasting types of artificially infested, unsterilized, virgin soil, which was maintained at optimum moisture content for disease expression.More of the isolates were pathogenic in the infertile podsol soil than in the fertile black loam. Eighteen per cent of the isolates were of virulent rank in the latter soil, in contrast to 34% of them in the former one.Indications from the study were that, under average soil conditions, approximately 20 to 50% of the isolates ofR.Solanifrom sclerotia on random tubers may be assigned to the zero and marginal classes of pathogenic rank. The data also indicated that certain isolates were inherently very deficient in pathogenicity to potato stems, while others characteristically possess a high degree of virulence. Thus, with regard to the effect of soil type and racial differences in pathogenicity, it would appear that the results of this study help to explain why the stems of a high percentage of plants from sclerotia-infested sets often escape with little or no infection under field conditions.

ISSN:1923-4287    

DOI:10.1139/cjr38c-005

出版商:NRC Research Press    

年代:1938

数据来源: NRC

摘要:

Tomatoes were grown in the greenhouse at different seasons of the year, individual fruits were picked at various stages of maturity and continuous records of their respiration obtained at 12.5 °C. It was found that the fruits of the late spring and summer went through the customary series of extensive changes in respiration rate as they ripened at the low temperature, and exhibited the lack of durability normal to this fruit. In contrast to this, the fruits of the late autumn, winter and early spring, if picked before the external appearance of red pigment, passed into a stable state in which ripening proceeded with but little change in respiration rate and with greatly enhanced duration of life at 12.5 °C.

ISSN:1923-4287    

DOI:10.1139/cjr38c-006

出版商:NRC Research Press    

年代:1938

数据来源: NRC

摘要:

A seed disease of wheat, rye, and barley, characterized by a more or less conspicuous brown or black discoloration of the kernel, particularly in the region of the embryo, frequently reduces the seed value and usually the sales value of affected grain. A comprehensive review of the relevant literature is given. The name "kernel smudge" is suggested for this disease. Two species ofAlternaria(A.tenuisandA.Peglioni) and two ofHelminthosporium(H.sativumandH.teres) are the fungi chiefly associated with it in Manitoba. The kernel smudge caused byAlternariacannot be accurately distinguished from that caused byHelminthosporium, without a laboratory examination of the seed.Extensive trials with wheat have demonstrated that theAlternariatype of kernel smudge does not affect to any marked extent seed germination, plant emergence, intensity of root rot, and yield in the subsequent crop. It was established, however, thatH.sativumdoes reduce germination, seedling emergence, and the yield, and at the same time causes an increased amount of root rot in this crop.Under Manitoba conditions infection of the kernels arises from air-borne spores which are usually deposited in the largest numbers at about the time the kernels are maturing. Contrary to some observations made elsewhere, the disease does not result in shrunken kernels; the largest kernels are frequently infected, and the small, shrunken ones usually free from the disease. Apparently the reason for this is that the large kernels force open their covering glumes, thus affording access to air-borne spores, whereas the glumes of small kernels remain closed and exclude such spores.The seed value of grain attacked by the virulent (H.sativum) type of kernel smudge was increased considerably when such grain was dusted with suitable organic mercury dusts (ethyl mercury phosphate or methyl mercury nitrate). Dusting with copper carbonate was relatively ineffective. The development of kernel smudge in the maturing crop was not prevented by dusting the growing plants with sulphur.

ISSN:1923-4287    

DOI:10.1139/cjr38c-007

出版商:NRC Research Press    

年代:1938

数据来源: NRC