A Study of the Environmental Conditions Influencing the Development of Stem Rust in the Absence of an Alternate Host. IV. Overwintering of Urediniospores of Puccinia graminis tritici. V. The Period of Initial Infection of Urediniospores of Puccinia graminis tritici on Wheat. VI. Influence of Light on Infection and Subsequent Development of Urediniospores of Puccinia graminis tritici on Wheat

IV. In order to ascertain whether the urediniospores of Puccinia graminis tritici (Pers.) Erikss. and Henn. overwinter under the environmental conditions prevailing at Lincoln, Nebraska, a series of experiments was carried out extending over a period of 5 years. The results of this investigation are briefly presented. V. By the period of initial infection is meant the time required by a pathogen after it reaches a susceptible plant part to enter the tissues. To determine what the period of initial infection of urediniospores of Puccinia graminis tritici might be, experiments were undertaken during the season of 1923-24 using urediniospores of Physiologic Form XXI. VI. In order to determine the influence of light on initial infection and development of stem rust of wheat, a series of experiments were undertaken using a series of artificial light chambers. Seven-day-old seedlings of Little Club (C. I. No. 4066) were used and were inoculated with the urediniospores of Physiologic Form XXI

The Relative Susceptibility of Alfalfas to Wilt

Except for alfalfa seed originating from a few old fields of Turkestan and Ladak, all varieties and strains now grown for commercial seed production in the United States, so far tested, have proved susceptible to wilt. All seed lots tested from South America (Chile, Argentina, and Uruguay), Europe (France, Spain, Portugal, Germany, Hungary, Italy, Roumania, and Ukranian S.S.R.), Africa (Morocco, Algeria, and Abyssinia), and Asia (Palestine, Manchuria, China, Korea, and Chinese Turkestan) were found to be susceptible to wilt. All seed lots of Turkestan origin so far tested are as resistant as Hardistan, or more so. Seed samples from the following districts of Turkestan, in order of combined wilt and cold resistance, ranked thus: Khiva, Chimbai and Alma Ata, Tashkent, Samarkand, and Chardzhui. Seed from the Bukhara, Ashkhabad, and Ferghana districts while wilt resistant lacked sufficient hardiness. Similarly several seed lots from Persia and one from India, although wilt resistant, lack sufficient hardiness

The Relative Susceptibility of Alfalfas to Wilt

Except for alfalfa seed originating from a few old fields of Turkestan and Ladak, all varieties and strains now grown for commercial seed production in the United States, so far tested, have proved susceptible to wilt. All seed lots tested from South America (Chile, Argentina, and Uruguay), Europe (France, Spain, Portugal, Germany, Hungary, Italy, Roumania, and Ukranian S.S.R.), Africa (Morocco, Algeria, and Abyssinia), and Asia (Palestine, Manchuria, China, Korea, and Chinese Turkestan) were found to be susceptible to wilt. All seed lots of Turkestan origin so far tested are as resistant as Hardistan, or more so. Seed samples from the following districts of Turkestan, in order of combined wilt and cold resistance, ranked thus: Khiva, Chimbai and Alma Ata, Tashkent, Samarkand, and Chardzhui. Seed from the Bukhara, Ashkhabad, and Ferghana districts while wilt resistant lacked sufficient hardiness. Similarly several seed lots from Persia and one from India, although wilt resistant, lack sufficient hardiness

A Consideration Of The Physiology And Life History Of A Parasitic Botrytis On Pepper And Lettuce

During the autumn of 1911, while gathering the peppers (Capsicum) in the vegetable plat of the Missouri Botanical Garden, the writer observed a fungus which was appearing as a parasite on the fruits. The peduncles were covered with a dark brown mass of conidia and mycelium, which so weakened the tissues that the fruit soon fell to the ground. On opening the peppers a number of large, flat, crust-like sclerotia, 1 cm. long and .5 cm. wide, were found to fill the interior. In most cases the seeds were also covered with the crust-like masses. The conidial stage was identified as Botrytis cinerea Pers. (Botrytis vulgaris Fr.). Although Botrytis cinerea has been observed parasitic on a large number of hosts, this is the first time it has been reported as a parasite on the peppers

A Research Delusion

With the administrative heads of many of our educational institutions demanding a doctorate of every member of the permanent staff, as it is supposed to be a prerogative for research, and the issuing of a list of titles published each year by their staff, the urge for so-called research, namely, a list of titles, goes madly on. In fact publication sometimes becomes a sort of self-defense, for the absence of any titles over a brief period of years stamps one either as lacking the ability of doing research or inefficient. Likewise, such a policy has permeated the staff, so that their interest is centered in output rather than in quality. This is just another characteristic symptom of megalomania, so prevalent in our day in most lines of endeavor. I think that on an occasion of this kind a brief period can be profitably spent in analyzing the present tendency in research in order that we may have a better understanding of what actually constitutes research

A Study of the Environmental Conditions Influencing the Development of Stem Rust in the Absence of an Alternate Host. III. Further Studies of the Viability of Urediniospores of Puccinia graminis tritici

1. The influence of relative humidity and temperature on the viability of the urediniospores of two Physiologic Forms of Puccinia graminis tritici has been determined. 2. The same general relation between the viability of the urediniospores and the relative humidity and temperature was found, namely, that the lower the temperature the longer the spores retained their viability at all relative humidities, while at any stated temperature the spores were viable the longest at the medium humidities. 3. Urediniospores of Physiologic Form XXI held at 49.0 per cent relative humidity and maintained at a temperature of 5° C. when tested for germination at the end of 1 year yielded 30 per cent germination and produced a heavy infection on 2 out of 12 plants. 4. The application of this method for the storing of rust material for long periods is discussed

A Research Delusion

With the administrative heads of many of our educational institutions demanding a doctorate of every member of the permanent staff, as it is supposed to be a prerogative for research, and the issuing of a list of titles published each year by their staff, the urge for so-called research, namely, a list of titles, goes madly on. In fact publication sometimes becomes a sort of self-defense, for the absence of any titles over a brief period of years stamps one either as lacking the ability of doing research or inefficient. Likewise, such a policy has permeated the staff, so that their interest is centered in output rather than in quality. This is just another characteristic symptom of megalomania, so prevalent in our day in most lines of endeavor. I think that on an occasion of this kind a brief period can be profitably spent in analyzing the present tendency in research in order that we may have a better understanding of what actually constitutes research

A Study of the Environmental Conditions Influencing the Development of Stem Rust in the Absence of an Alternate Host. I. The Viability of the Urediniospores of Puccinia graminis tritici Form III

No exact data are at hand regarding the influence of temperature and relative humidity on the viability of the urediniospores of stem rust under controlled conditions. 1. The influence of relative humidity on the viability of the urediniospores of Puccinia graminis tritici Form III is very pronounced and closely associated with temperature. 2. At high relative humidities, depending somewhat on the temperature, the percentage of germination is low and the period over which the spores are viable is very short. 3. The same relation exists at the low relative humidities except that it is not so pronounced and is more variable. 4. The highest percentage of germination and the longest viable period of the spores occur at the medium relative humidities. High temperatures lower the percentage of germination and shorten the viable period while at low temperatures the opposite occurs, at the medium relative humidities

SOURCES OF AMYLASE-PRODUCING BACTERIA

In the search for bacteria possessing high amylolytic activity, some thousand or more isolates were screened on soluble starch agar and the extent of their activities determined qualitatively by the loss of medium response to Lugol\u27s iodine solution. The selected isolates were then grown on a liquid wheat bran medium and the resulting starch-dextrinizing activity measured quantitatively. No attempt was made to determine the properties of the various amylases. The primary purpose of this report is to point out the original sources from which the isolates were made and to correlate the nature of the substrates with the extent of amylase production by the bacteria