Species Of Botrytis Research Articles

The Perfect Stage of Botrytis cinerea

In the genus Botrytis, a number of species with well defined characters have been described and named, but one of the oldest specific names, B. cinerea Pers., has been applied to a loosely defined group of fungi, which develop the well known grayish-brown conidiophores and conidia, and large, black, flat sclerotia adhering closely to the substratum. Such forms are found on a great many plants, exhibiting various degrees of pathogenicity or living as saprophytes. Their common occurrence, widespread distribution, and often destructive effects have made them the subject of much investigation and a voluminous literature has grown up dealing with their parasitism, host range, physiology, and cytology. When these Botrytis forms are isolated, the cultures show an extraordinary range of variability in the production of sclerotia, appressoria, and conidia, in the rate of growth, and in the amount of aerial mycelium. In general, however, there is no option but to assign all these forms to the inadequately delimited species, B. cinerea Pers. and in the more recent literature one generally finds them regarded as a group, with each form being referred to as a Botrytis of the cinerea type. The literature concerning the genetic connection of species of the genera Botrytis and Sclerotinia has been reviewed by Drayton (1937). Since this was written a Sclerotinia stage has been established by Gregory (1938) for B. polyblastis Dowson. Of the five recorded cases in which a genetic connection has been demonstrated by means of cultural technique, three of them, namely, S. Ricini Godfrey, S. Porri van Beyma Thoe Kingma, and S. con-

On Botrytis Rots of stored Onions

1. The sclerotial or Botrytis rots of onions are found very often upon the stored bulbs in the central markets, as well as in the shops of greengrocers in Kyoto and Osaka. In the previous paper, the writers described the gray-mold neck rot caused by Botrytis Allii MUNN, which is most common and causes heaviest losses among them, with special reference to the morphology and the pathogenicity. of its causal fungus.2. In the present paper, the mycelial neck rot caused by Botrytis byssoidea WALKER, the small sclerotial neck rot caused by Botrytis squamosa WALKER and. also a new disease caused by an undetermined species of Botrytis were described in detail.3. Although the occurrence of these three diseases seems to be very rare in this country, they have been produced repeatedly by inoculating onion bulbs through needle wounds with mycelium from pure culture and with conidia and conidiophores which developed upon infected bulbs, upon the potato-dextrose agar or upon the sclerotia placed on the sterilized soil in the case of the hitherto undescribed disease.4. The symptoms of these diseases, as well as the morphology of their causal fungi were first described. The results of the cultural experiments carried out by the writers were then given in detail.5. It was demonstrated clearly by carefully inoculating the outer succulent scale of a bulb that the most satisfactory method of obtaining infection by B. byssoidea was of course to inject conidia into needle wounds, placing bulbs under conditions in which toorapid desiccation of the wounds is prevented. Under humid conditions and favorable temperature, invasion of the unwounded outer succulent scales has been scarcely noted in a slight degree.6. A number of experiments were made to determine the relation of temperature to infection by B. byssoidea and the rate of progress of decay. The results show that infection seems to occur in a wide range of temperature ranging from 3°C to 32°C, although the most rapid decay takes place at temperatures from 10°C to 24°C.7. Even at the most favorable conditions, the decay of onion bulbs caused by B. squamosa progressed much more slowly than in the case of other three species of Botrytis isolated from decaying onions.8. Many inoculation experiments with the undetermined species associated with onion rot were also performed by the writers. The results show that its pathogenicity seems to be as strong as to penetrate at times the unbroken cuticle of succulent scales. The most favorable temperature for the decay caused by this fungus seems to lie at approximately 24°C.9. All four species of Botrytis associated with onion rot differeach other not only in their spore-dimension, but also in their cultural characteristics especially on the plate of potato-decoction agar containing 2% dextrose.10. Inoculation experiments performed by the writers demonstrated clearly, that all the strains of Botrytis cinerea PERS. isolated from decaying fruits of strawberry and Satsuma-orange, and also from lettuce have power to infect the succulent scales of stored onions, when injected conidia together with conidiophores into needle wounds.

OBSERVATIONS ON THE SPOTTING OF TOMATO FRUITS BY BOTRYTIS GINERE A PERS.

SUMMARYCharacteristic ring‐like spots caused by Botrytis cinerea on tomato fruits are described, with observations on certain factors which influence the spotting.Evidence is presented to show that, under conditions of high humidity, Botrytis spores lying on the surface of immature fruits germinate, penetrating the epidermis, and that the spots result from the pectinase enzyme secreted by the germ tubes. With the return of drier conditions the spore‐lings die and no fungus can be isolated from mature spots.It was found that similar spots could be produced experimentally by other species of Botrytis but not with various other fungi able to attack tomatoes.The Botrytis spots are compared with aphid injury and notes are given on control.We wish to thank Mr G. Cockerham, Mr E. E. Wallace, and Dr T. Small for material of blight, and Mr W. C. Moore for records of the disease.

THE CHOCOLATE SPOT DISEASE OF BEANS (VICIA FABA L.) CAUSED BY BOTRYTIS CINEREA PERS

SUMMARYChocolate spot disease of broad and field beans in Britain is caused by forms of Botrytis cinerea. This disease should not be confused with the chocolate‐coloured lesions of Aphis injury, frost injury, mechanical injury, etc., and leaf spot (Cercospora Fabae and Ascochyta Fabae). All forms of Botrytis cinerea tested and some other species of Botrytis were capable of causing chocolate spot. B. cinerea will attack other species and genera of the Leguminosae, producing in some instances lesions similar to those of chocolate spot disease of beans.Chocolate spot infection is of two types, “aggressive”, causing blackening and death of part or the whole of the shoot system, and “non‐aggressive”, causing discrete or coalesced chocolate‐coloured lesions. The former type of attack is responsible for the greater part of the damage done by epidemics of the disease.Under suitable environmental conditions, there is a progressive increase in the total number of visible lesions over a period of at least 5 days after treatment with a suspension of Botrytis spores. When a dilute spore suspension is used “non‐aggressive” infection occurs. When a dense suspension is used, “progressive” infection results in “aggressive” infection: if, however, plants are removed after 24 hours to an environment unsuited to infection, the attack remains “non‐aggressive”While hyphae are abundant in the lesions of “aggressive” infection only a sparse mycelium is present in those of “non‐aggressive” infection.The maximum temperature for infection is about 30° C, the optimum about 20° C. and the minimum between +1 and ‐1° C. A water film is essential for infection, and any factors increasing the rate of evaporation of this film inhibit or decrease infection.The optimum conditions for “aggressive” infection are (a) the presence of large numbers of spores of the pathogen, (b) rain, (c) high humidity and rain to maintain the water film on the foliage for some days, (d) little or no wind and (e) a temperature between 15 and 20° C.Statistical treatment of data has established a correlation between rainfall and the severity of chocolate spot disease. Epidemics are correlated with abnormally heavy rainfall during the critical months of April, May, June and July.Spores of B. cinerea will remain viable on the leaf surface for periods of more than a month under adverse conditions.Any factor tending to weaken the crop, such as sour soil, potash and phosphate deficiency and waterlogging of the soil, renders it more liable to “aggressive” infection. In addition, chocolate spot disease appears to be favoured by a dense stand of beans and shelter from the prevailing wind.No economic method of control has been found. Care should, however, be taken to see that the crop is not weakened or in any way rendered more liable to attack.

The “Shab” disease of lavender

Summary 1. It has been shown conclusively by inoculation experiments that the primary cause of the “Shab” disease of lavender is the fungus Phoma Lavandulae Gab. Symptoms similar to those of “Shab” may, however, be due to adverse climatic and environmental factors of which the chief are frost and waterlogged soils. A species of Botrytis may also cause a die-back at times. 2. The early symptoms of the disease are that the young shoots turn yellow and wilt from about May onwards. Later the branches die back, and the disease spreads throughout the plant which ultimately dies. Pycnidia of Phoma Lavandulae are formed in great numbers on the young diseased shoots after these have been killed. 3. Infection of healthy lavender plants can take place either through or near leaf axils on young shoots in summer, or through freshly made wounds. From the points of infection the fungus grows downwards invading all the tissues, and killing the branches. Wounds are liable to invasion when freshly made at any time of the year under suitable conditions, but when more than four weeks old they appear no longer to serve as paths of infection. 4. A long period elapses between the time when a plant is inoculated and the first appearance of clear disease symptoms. During this period, which ranges from two months to a year or more, the fungus is latent within the tissues of the host. 5. The disease is spread (1) by raising plants from cuttings in which the fungus is already established, (2) by the distribution during cultural operations of branches or leaves bearing pycnidia, (3) by the distribution by wind of small particles of bark bearing pycnidia, and (4) locally by the splashing of spores from plant to plant by rain. 6. Phoma Lavandulae has been isolated repeatedly from diseased lavender plants and grown in pure culture on a variety of media. It failed to produce pycnidia except on a few media of which the chief was Dox's agar in bright sunlight. 7. Pycnospores of Phoma Lavandulae lose their viability within a few hours of being exuded from the pycnidia. On the other hand, they can remain alive within the pycnidia for long periods under a wide range of environmental conditions. 8. Whilst Phoma Lavandulae can infect most varieties of lavender the variety “Dwarf French” appears to be immune. This variety is of no use in the manufacture of perfume. Lavandula dentata is likewise immune. On the other hand, Phoma Lavandulae can grow sapro-phytically under field conditions on Chenopodium album . 9. Measures for controlling the disease based on the principles of plant sanitation have been devised and have met with considerable success wherever they have been put into operation.

Societies and Academies

LONDON. British Mycological Society, November 20.—W. J. Dowson: An unusual species of Botrytis attacking Narcissus. The fungus is the cause of ‘fire,’ marking the leaves with one or more yellow patches. The spores of the fungus are very large, and germinate with as many as thirteen germ tubes after up to one hour in water or in dilute glycerine.—Miss A. Lorrain Smith: A new family of lichens. The lichen Cryptothecia subnidulans was described by the late Dr. Stirton, and has led to much difficulty in assigning it to a systematic position. Stirton's herbarium has revealed three additional species of the genus and two closely allied ones for which a new genus is proposed; the two genera form a family characterised by the apparently double walled ascus containing septate or muriform spores and embedded in a lax peridium of interwoven hyphae. Affinity with the fungi Myriangiales and Gymnoascales is suggested; the nearest lichen allies appear to be Thelocarpaceaa and Mycoporacea.—O. V. Darbishire: Isidia and soralia of lichens. Isidia in Peltigera prætextata develop endogenously from special hyphme which make their way to the surface, breaking through the cortex or making use of a crack. The mature isidia are very highly developed assimilators. There is a primary cortex on the upper surface with walls of wavy outline. The secondary cortex is similar to the cortex of the thallus. The gonidia are fairly closely packed towards the upper cortex with a very loose arrangement just inside the lower cortex. This cortex is of one layer of cells, with sinuate walls and interrupted here and there by pores. Soredia also have an endogenous origin. A few gonidia are gradually surrounded by the fungus and the differentiating soredium is raised to the surface of the sorial tissue, from which it becomes detached as a reproductive organ.—W. R. I. Cook: The genus Ligniera. Cross inoculations have shown that several species which have been described are merely host varieties. Infection takes place by zoospores entering root hairs. Spores serve as a resting stage and for propagation within the plant. Reduction division occurs at the formation both of spores and zoospores. Conjugation has not been seen.-W. A. Roach: On the nature of disease resistance in plants, with special reference to the wart disease of potatoes. Wart disease is an example of physiological resistance. Evidence at present suggests that immune and susceptible varieties form two distinct classes and not end members of a continuous series. The reaction towards wart disease is unaffected by grafting on either a foliage system, a root system, or of a complete plant of opposite reaction to the disease. Immunity from, or susceptibility to, wart disease is therefore probably innate to the cell and must be sought in compounds which cannot cross a graft fusion layer unchanged, and so probably cannot leave a cell. These compounds may be proteins.

ROTS OF EARLY STRAWBERRIES IN FLORIDA AND SOUTHERN CALIFORNIA

The fungi causing rots of strawberries in the southern states have been under investigation since 1915. Each season Florida strawberries have been examined either in the field or in the market by one or more of those interested in the investigation. During several seasons shipping tests were carried on, and the same fruit was examined both before and after shipment. Although there have been found on Florida strawberries fungi belonging to numerous genera, Rhizopus nigricans Ehrb. has remained the commonest and most destructive of the fungi causing decay of ripe strawberries from this region. Four months' study, January to May 15, 1920, of southern California strawberries both in the field and in the market showed a condition quite different from that in Florida. R. nigricans appeared to be of distinctly minor importance as a cause of fruit rot of strawberries; whereas a large proportion, frequently over ninety percent, of the rotten berries examined during the four months were affected with a species of Botrytis, probably Botrytis cinerea Pers. There is, then, apparently a marked difference in the relative abundance of these fungi on early strawberries in the two regions, and the probable reasons for this difference are discussed in the present paper. No one would, of course, presume to generalize from the observations of a single season, but so competent and experienced an observer as Dr. H. S. Fawcett of the Citrus Experiment Station at Riverside, California, assures the writer that the extreme prevalence of Botrytis on strawberries is a regular phenomenon of the winter season in southern California. The regions under consideration include the most southerly important strawberry shipping points on the Atlantic and Pacific seaboards. The strawberry-growing region of central Florida lies east of Tampa, Plant City and Lakeland being the chief shipping points. The southern California strawberry area lies chiefly in Los Angeles county, Gardena and Moneta being large shipping points. Attention will be confined to the early shipping season, during a portion of which these two regions usually dominate their respective markets. THE FUNGI