Linnaeus, smut disease and living contagion

This paper examines the rise and fall of Carl Linnaeus's ideas on living contagion, focusing on his work with plant smut diseases. Early in his career, Linnaeus named a plant altered by anther-smut disease as a separate species, but then, probably realizing it was a diseased specimen, demoted it to a variety. He later drew direct parallels between minute insects attacking plants and infectious diseases in humans, but did not yet draw an analogy to smut diseases. After Otto von Münchhausen had sent Linnaeus the first instalment of his book Der Hausvater (1764) , Linnaeus realized smuts were contagious. He carried out his own investigations that appeared to confirm Münchhausen's conclusion that smut spores germinated to produce living and mobile animalcules. This cemented Linnaeus's view that animalcules caused contagion in human diseases, a view which he expressed forcefully, urging further studies. However, his results were questioned and discounted by others, especially John Ellis. An analysis of correspondence between Linnaeus and other microscopists shows that it is likely Linnaeus did actually see “animalcules” emerging from cereal grains. He was unaware that smut-like symptoms in wheat could also be caused by seed-gall nematodes in the genus Anguina. Linnaeus himself came to doubt the connection between fungi and contagion, and did not pursue these studies further. The presumption that Linnaeus was fanciful in his observations of animalcules may partly explain why his views had only a tangential impact on the germ-theory of disease, and why his insights remain unappreciated to this day.

Screening barnyard millet germplasm against grain smut (Ustilago panici-frumentacei Brefeld)

Barnyard millet accessions (257) were inoculated with grain smut spores at anthesis stage during 2003. Seed produced on inoculated ear heads was sown in 2005 and resulting plants evaluated for ten morphological traits and grain smut incidence. The accessions were grouped into seven groups based on origin. The lowest mean grain smut incidence was recorded for advance breeding lines, while highest mean value was observed for Uttarakhand group. Genes determining grain yield and susceptibility to grain smut were at most loosely linked as evidenced by non-significant correlations between grain smut incidence and grain yield in six out of seven groups as well as whole collection. Smut resistance along with grain yield in barnyard millet can be enhanced by adopting proper breeding strategy; therefore, in segregating generations, selection should be carried out for both characters simultaneously.

Isoenzyme analysis of teliospores from species of Anthracoidea parasitic on Carex species

The smut sori of five Anthracoidea species, A. echinospora, A. heterospora, A. buxbaumii, A. limosa, and A. paniceae, removed from infected inflorescences of 5 Carex host plant species collected from 17 natural Finnish populations, were surveyed by isozyme analysis. The protein extracts of individual sori, containing teliospores (smut spores), together with uninfected utricles, were subjected to polyacrylamide gel electrophoresis and stained for esterase and four peptidase enzymes. Single sori, representing individual infection units, were sufficient to reveal considerable esterase and peptidase isozyme activities, whereas little or no activity was seen in the control utricle extracts. High levels of genetic variation as expressed by the detection of multiple loci and allelism were recorded between species and various populations, but variation within populations was lower. Peptidase banding patterns, in particular, proved to be useful in differentiating species: A. heterospora and A. echinospora, parasitic on the same plant, were clearly distinguished by their isozyme patterns, and the three remaining smuts belonging to the subgenus Proceres could be separated from one another. One morphological character, presence of numerous thick internal swellings in the cell walls of teliospores, seemed to correlate well with banding pattern differences in A. heterospora. Key words: isozymes, electrophoresis, Anthracoidea, Carex, chemotaxonomy.

FIELD CONTROL OF LOOSE SMUT IN BARLEY WITH THE SYSTEMIC FUNGICIDES VITAVAX AND PLANTVAX

Vitavax (2,3-dihydro-5-carboxanilido-6-methyl-1,4-oxathiin) applied as a seed treatment at a rate of 113 g per 45.4 kg of barley seed gave complete control of loose smut under field conditions. The seed treatment increased yield significantly in Parkland where smut in untreated plots was 49%. In York, with 16% smut in plants grown from untreated seed, yield increases were not significant. A higher dosage (227 g) also controlled smut but appeared to cause some toxicity. Seed treatment had no apparent effect on the malting quality of the seed subsequently harvested.Plantvax (2,3-dihydro-5-carboxanilido-6-methyl-1,4-oxathiin-4,4 dioxide) applied as a soil treatment at the rates of 5.6 kg/ha and 11.2 kg/ha also resulted in effective loose smut control in York barley but did not result in increased yield. There were indications that yield was depressed at the higher rate in York and at both rates in the variety Herta.There were also indications that treatments with either chemical had a slight effect on height, date of maturity, weight per hectoliter and 1,000-kernel weight. Seed treatment at planting time did not prevent infection of barley florets by loose smut spores 55 to 60 days after planting.

Sphacelotheca cruenta. [Descriptions of Fungi and Bacteria].

A description is provided for Sphacelotheca cruenta. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Sorghum bicolor (S. vulgare) (sorghum), S. sudanense (Sudan grass), S. halepense (lohnson grass), and other Sorghum spp., and (in India, fide Chona & Munjal; 31: 400) Saccharum officinarum (sugarcane). DISEASE: Loose smut of sorghum. In addition to the grain being replaced by smut spores the plants are markedly stunted and their forage value reduced while infected heads are looser, bushier and darker green than healthy ones due to hypertrophy of the glumes; for further details see Tarr, 1962. GEOGRAPHICAL DISTRIBUTION: Africa, Asia, Europe, N., C. and S. America; see CMI Map 408, 1965. TRANSMISSION: Infection of the seedlings occurs from seed contaminated with spores (Noble et al, An annotated list of seed-borne diseases, 1958, p. 66). Spores remain viable for four years in the laboratory but as they germinate readily in water soil transmission is unimportant. Spread within the crop by floral infection by air-borne spores has been observed.

STUDIES ON THE INHERITANCE OF COVERED SMUT REACTION, LEMMA COLOR, AWN DEVELOPMENT AND RACHILLA PUBESCENCE IN OATS

An oat cross, Black Mesdag × Victory, was studied genetically for covered smut reaction, lemma color, awn development and rachilla pubescence. Only the F3 was studied for reaction to the covered smut fungus, Ustilago levis (K. and S.) Magn. Prior to sowing, the caryopses were dehulled and inoculated with smut spores. Hybrid susceptibility (up to 95%) corresponded with that of Victory, the non-resistant parent. Segregation among F3 families occurred in the ratio 4 immune: 9 moderately resistant: 3 susceptible. It is concluded that smut resistance is conditioned by two genetic factors: a dominant factor, which when homozygous gives high resistance or immunity, and a less potent supplementary factor.Both the F2 and F3 were studied for the grain characters mentioned. Each of these characters was found to be controlled by two genetic factors. F2 segregation ratios were as follows:—lemma color, 12 black: 3 gray: 1 white; awn development, 12 strong: 3 intermediate: 1 weak; rachilla pubescence, 12 long: 3 short: 1 glabrous. The F3 gave good substantiation of the F2 ratios except in the case of awn development where fairly wide deviations from the expected occurred, due, it is believed, to environmental influences.No correlations between smut reaction and grain characters were found. Association between rachilla and callus pubescence was observed; but this is not believed to be due, necessarily, to a genetic linkage.Homozygous strains combining smut immunity with agronomically desirable grain characters were obtained.